#1231 Michael Gurven - Seven Decades: How We Evolved to Live Longer

00:00 Ricardo Lopes: Hello, everyone. Welcome to a new episode of the Dissenter. I'm your host, as always, Ricardo Lops, and today I'm joined by a return guest, Doctor Michael Gervin. He's a professor in the Department of Anthropology at the University of California, Santa Barbara. He's also part of the Integrative Anthropological Sciences Unit and also associate. Director of the evolutionary Anthropology and Biodemography Research Group there and today we're going to talk about his book Seven Decades How we evolved to Live Longer and it's a very nice cover and nice book. So Doctor Gervin, welcome back to the show. It's always a pleasure to talk with you.

00:40 Michael Gurven: Yeah, thank you so much for having me on. Uh, YOU know, I, I thought we last talked a few years ago and then you tell me it was 6 years ago, so I don't know, time is flying by.

00:52 Ricardo Lopes: Yeah, I mean, 6 years ago, I also had a completely different haircut, so, you know.

00:59 Michael Gurven: Hey, you still have hair, that's the important part.

01:03 Ricardo Lopes: Uh, OK, yeah, I, I guess so. I guess so. OK, so, uh, to get into the topic, because it's very interesting that last time, uh, I asked, we have a long interview and I asked you about your research, but we didn't touch, if I remember correctly, on the topic of longevity. So what got you interested in studying that?

01:27 Michael Gurven: Yeah, uh, I was trying to remember what we actually did talk about. I think it was more about social behavior and cooperation, um, and so, yeah, you know, it's actually not that a distant, you know, cry from, from thinking about cooperation just because, you know, humans are so social, and one of the ways we're even able to make it to, you know, through childhood, much less to adulthood. IS through, you know, interdependence, relying on other people. Um, THERE'S so many different things that kind of, uh, make you unable to, you know, get up and walk, uh, that make you sick, that make you not feel that great that day. And if we didn't have other people to help take care of us, um, we wouldn't make it. So this relationship just between cooperation and thinking about health, aging, and longevity. It was kind of a shoo-in, you know, and it was always sort of in the back of my mind starting some of the work in, in Paraguay, but, uh, especially once I started doing some work in Bolivia, uh, thinking about aging, thinking about longevity, um, and yeah, that was basically what kind of got me started over, was was like maybe 25 years ago or so, yeah.

02:45 Ricardo Lopes: OK, so I imagine that if we were to pick up a random person on the street and ask them, OK, so who do you think studies longevity? I guess that most people would say doctors, probably. But I mean, you're an anthropologist, so how do you study longevity as an anthropologist?

03:06 Michael Gurven: Yeah, good question. Um, And it also is why, you know, I was trying to situate this even with, with the book, right? There's, there's no shortage of books out there on health, fitness, aging, uh, you know, and many of them, you know, definitely take different tacks than I do, like they're You know, a kind of checklist of things you could do to improve your life, to help live longer, uh, and it helps having an MD to make that, you know, more credible. Uh, AND then other folks are, you know, the molecular biologists that are sort of on the forefront to thinking about different, you know, molecular pathways that, um, can be altered in ways that can slow aging processes, and it's like, yeah, what do I have to contribute? And so, yeah, that's where I think what was interesting, you know, I didn't really go into this thinking like, you know, I'm a longevity researcher, but it was just by, by kind of working, you know, that, that stereotype joke about Uh, the drunk kind of looking under the, the spotlight for their, for their keys, yet, you know, their keys are on the other side of the room, but you're just looking where the spotlight is. And so I do think that, you know, there's a lot of great work out there on aging and longevity, uh, focused on people just like you and me. Um, AND so my approach was just like, well, if we look To other populations, um, around the world, uh, that haven't been really studied, uh, let alone just the basic fact that, you know, the kinds of populations I'm working with are the kinds of populations, the kinds of environments, the kinds of lifestyles that we've had up until just, you know, not too long ago. Uh, CERTAINLY, there could be something learned from all of that. And, and so that's been, that's been my approach and, and, you know, it started off with a couple. You know, obvious things, right? Like, uh, it's easy to focus on disease, perhaps than just thinking about aging and longevity a little bit large. So just the very fact that if we looked at people's hearts, if we looked at their brains and focused on heart disease, focused on diabetes, focused on Alzheimer's disease, uh, if we're finding that certain populations around the world just don't suffer from these diseases or suffer very minimally, That has huge implications for thinking about aging and longevity, uh, that we never would have known or thought about if we hadn't really stepped outside of the normal kind of biomedical circuit to the kinds of populations that anthropologists, you know, this is more their, their bread and butter. So I would say, you know, as an anthropologist, what I had to contribute was one, kind of looking and studying where most people are not. Uh, BUT then also I think taking as an evolutionary anthropologist in particular, taking a broader perspective on uh the history of our species, right? And so thinking about lifespan, longevity, and aging, not so much from a, like a clinical perspective, right, but from an evolutionary perspective where even just the basic idea. Maximizing lifespan is not a goal of evolution, natural selection, right? That, that, that, you know, that's something that we want for ourselves, but if we understand biology, then we can get a different perspective. So yeah, that was also, I would say something that I had to contribute that uh many other folks involved in the aging lifespan arena uh are not.

06:49 Ricardo Lopes: And how is old age defined? Because I think that this question will be important for when later we talked about how we actually evolved to live around 70 years and why we have uh post reproductive uh lifespan and all of that. So how do you define old age?

07:13 Michael Gurven: Yeah, so I talked about this a little bit in the book, right? Where certainly the people I work with, you know, if they don't know their age, and you don't have numbers beyond like 7, then maybe you don't age, right? You just, if you can't identify it, it doesn't happen. Um. But, you know, of course, obviously that, you know, that sounds silly to even suggest, but it's not, the one aspect of it that might be true is, it's hard to obsess over your age, like the number, if, it's not, if it's just not something that's salient in your, in your life. Like, no one like looms with dread when they're approaching their 40th birthday or their 50th birthday or their 60th cause they wouldn't really know that that particular milestone is happening. And so I think, you know, people around the world. Sort of defined old age, you know, in a way that just seems a bit more practical, right? Um. Something somewhat functional when you can no longer do certain things that you're, you know, used to doing, you can't see quite as well as you used to, uh, you have trouble moving around, um, you know, these are the ways that people have, you know, defined kind of old age in terms of, I think, functionality and, you know, and I think that sort of underlies a lot of the Cultural dialogue now about, you know, you're only as old as you feel, that, uh, you know, 40 is the new 30, 50 is the new 40, where, you know, if, if we're able to actually be in the, the kind of shape at 50, that maybe we would have been, you know, 100 years ago when we were 40. Then yeah, in a, in a way, you have kind of delayed aging a bit, and, and we should think about it in, in those particular terms. So yeah, so I, I kind of take a more holistic kind of view about What is old age. Um, NOW, certainly when you're doing studies, it's hard to take that kind of holistic view and, and for practical purposes, I still think it's instructive to say, all right, amongst people aged 60 and over or age 65 and over, you know, let's look at their health or let's look at certain characteristics and You know, whether or not a 60, that even at age 65, some people are gonna feel a lot younger are gonna be a lot healthier than, than other folks, um, and that's part of the thing that's just really interesting and exciting to try to understand, you know, why, why does the variability, it just increases with age, right? Everyone age 20 is probably in reasonably decent shape regardless of how much they're exercising or not. Uh, YOU know, let alone, let's leave the Olympic athletes out of that. But, you know, by 65, there's just huge range of variability in people's health and condition.

10:08 Ricardo Lopes: Yeah, I guess that's an interesting point to make here as well is that, uh, I mean, you know, of course, much more about this than I do, but uh there are at least some traditional societies where people don't count time the way we do, or, I mean, of course, they are aware of the passage of time. But they possibly don't even have the notion of a year, so I mean, they, they don't know they are, or, or, or, or they don't even care if they are 40 years old, 50 years old, 60 years old, and, and I mean, of course, the point I'm making here is not to say that because they don't have the The same notions of time that we have that they are uh uncivilized or something like that because those are not really scientific terms and uh but I mean they have a different way of noticing the passage of time than we do,

11:09 Michael Gurven: right? Yeah, and I think. Yeah, so aside from how you're feeling in your own health and condition, you can also think about just in terms of life stage. So, you know, if you have children, then, you know, maybe that puts you in a different category, uh, and then certainly by the time your children have children and you're a grandparent, it's like, oh, now I feel old. But, you know, again, that, that's relative because in a lot of places, you know, if you're having your, your child, your first child at age 18, then And your children have their first children at 18, then by the time you're still in your mid-30s, you know, you're a grandparent, and by the time you're in your 50s, you know, you're a great grandparent. So, uh, again, you know, it, it's sort of relevant, but it's not, it can't cleanly be defined old age, you know, specifically, uh, as that.

12:05 Ricardo Lopes: And so what is life expectancy, because we use this term a lot, but what actually is life expectancy and what kinds of information can we get from it?

12:18 Michael Gurven: Yeah, good. So I think. When people think about lifespan, it's probably the most common thing to, to come to mind that we think about the life expectancy of a and life expectancy is of a population, right, not really of a person. But we, we, what we ascribe it to a person. So if the life expectancy in the US, for example, is like 78, then we do think that on average a person born will live about 78 years. So the expectancy part means it's, it's an average, right? And that, and, and that's all it is. It's so it's the average lifespan in a population, um, but it's a bit deceptive, right, because Imagine, imagine there's 100 people, and everyone born lives to age 50. And so, the average there is the same as everyone's lifespan, and so the average life expectancy would be 50. And in that case, it represents everyone in the population. But you can also have a life expectancy of 50 where half the people live to 100.5 the people, you know, die right after they're born. And so the average there is also gonna be 50 because half the people live to 100.5 the people kind of died at birth. But in that particular case, no one lived to 50, right? They either died right after birth or they lived 100 years. So this is where a life expectancy sometimes Uh, can be quite distant from the, the lived years of the majority of people in the population. And so, you know, I introduced this in the book because we're so used to hearing that life expectancy in the past, and life expectancy in groups like hunter-gatherers, you know, was low. That, you know, it was in the, in the 30s, sometimes even in the 20s, uh, and on good, on a good day, maybe in the 40s, but what that doesn't mean, it doesn't refer to that first example that everyone lived to their 30s and then they died, but it's more like the second example that there's such a huge concentration of deaths early in life, that first year of life is the most dangerous. Uh, AND then even to age 5, you know, over a quarter of births of people born wouldn't make it to their 5th birthday. Uh, SOMETIMES that can be, you know, even higher, like 30, 35%. So when you take that into account, then it actually turns out on the other side, there's lots of people making it into adulthood and well into adulthood. So if you're able to make it past that. That gauntlet, that first, say, 15 years of life, so you're kind of close to being an adult, then there's actually a good chance that you make it to your 40s, 50s, 60s, and even into your 70s. And so, you know, hence that's, you know, the, the title of the book. Um, I'm glad you had a copy with you. I had to look for mine to find it. Um, BUT this idea that We've lived to 7 decades in the past. And that that's actually, uh, if you do look into adulthood, the sort of average lifespan in adulthood. For those who make it to adulthood is in that kind of 6 to 7 decades range. I have to always be careful now when I say that because, uh, you know, uh, I did that and my son was like, did you say 67 decades? I don't know if it's in Portugal, but uh Uh, I was in Malaysia a couple of months ago and I heard people doing the 6/7 thing, so it's global.

16:15 Ricardo Lopes: Yeah, yeah, I think so. Uh, I, I mean, do you think that we should also clarify when we talk about life expectancy, uh, whether we're talking about life, life expectancy at birth or life expectancy after people reach a particular age?

16:35 Michael Gurven: Yeah, I think, and that's a good, that's a good question to ask. Uh, I, I recently, uh, recently wrote an op ed about this, um, because I do think sometimes when people think about like the tech bros and wanting to live as long as possible, they're not really talking about life expectancy, they're thinking more like maximum lifespan or like amongst the people who can make it to age 70, how can we maximize the chance that we make it to age 100 or 110? Whereas I think if we're really interested in the, in the, the greatest good for the greatest number, then life expectancy is a good measure, right? Because it does reflect, you know, if 1/3 of the population is not making it to their 5th birthday, Then, yeah, that's great for the people who are making it into 70s and 80s and 90s. But what about, you know, all those lines that were cut tragically short. So if we really want to maximize the lived years in a population, Then the lowest hanging fruit is actually all of those deaths in the 1st 7 decades, if not even the 1st 2 decades. And especially, you know, it's not just in high-income countries, but all over the world, uh, we could do a lot better for improving survival within those 1st 7 decades, uh, and that would improve life expectancy, probably more and definitely more per dollar spent. Then trying to focus on making it from age 80 to age 110.

18:09 Ricardo Lopes: Right. Uh TELL us also about uh dependency ratio. I mean, what is that and why is it important?

18:18 Michael Gurven: Oh, Trying to remember the context in which I talked about it. Probably when we think about, so we've talked about aging of individual bodies, uh, but when we think about population aging, then it's this idea, well, as, as the population is getting older and older. And so currently, for example, in the United States, like 1 in 6 people is over age 65 and we're frantic because, you know, just within a couple of decades we're gonna, that's gonna be like 1 in 5, if not even leaning towards 1 in 4. And so as the, the shape of the, the, like the population pyramid where the bottom is like the youngest, and then the oldest is at the top, you know, for the longest time, it kind of looked like this. And then over time, as we get older and older, and we have fewer and fewer kids, the pyramid starts to look like this. And, and so it is a, it actually highlights two things. One, The fact that we're getting older, living longer, meaning there's more old people in the population. But it's also, it's important that we're having fewer kids. Because if it was just that we're living longer, the population could still stay like this. Uh, IF we're still, you know, having lots of kids, but when both those things are going on at once, the, the population pyramid starts to, you know, look very cylindrical and sometimes even the reverse, it becomes top-heavy. We have more, you know, uh, I forget the year, but pretty soon we're approaching where we're gonna have more people over age 65 than we might have, you know, under, under age 5, for example, and so. Uh, WHAT that means in terms of dependency ratio is that it's usually defined as something like how many dependents are there in a population, individuals that need or require care, and typically you would think, well, those are children, but it could also be, you know, older adults. Uh, NOW this is where it starts to matter if you're, if you just use age 65 plus. But we're actually healthier than we used to be, then maybe those people aged 65 to 75, are they really dependent, or are they not? So, you know, I talked about this a little bit in the book that uh It's not the best way of, of kind of measuring it, uh, but it's the way it's often done. Um, AND so if the dependency ratio is high. Then that just suggests, OK, we have more and more people to take care of. And so there's the, the individuals that need care, and then the individuals who are giving the care, the caregivers, the producers. So we think about GDP and, and productivity, and so it's uh, you know, how do you make a society run, given that we all come in all flavors of age and sex. And so, with the basic idea that if too many of us are in the dependent category, are things sustainable? Who's gonna do all the caregiving? As it is, if you have few people who are of, you know, working ages, If those folks have to take time off work to be caregivers, then that's even, that's reducing the effective number of people out there in the workforce even more. So this is where dependency ratio becomes this sort of critical uh turning point for thinking about like these societal issues about aging.

21:57 Ricardo Lopes: Mhm. Uh, IN the book you also use this term health span. Uh, WHAT does that mean?

22:05 Michael Gurven: Yeah, so. I mean, in some ways, health span is just the sexier way of thinking about lifespan that, you know, lifespan is just literally referring to the number of years, whereas, you know, even now, I think it's hard to find someone that is just so committed to extending that number uh without regard to the quality of those years, right? And so the idea of health span would be like sort of your lifespan of healthy years. So in the best possible world, your health span equals your lifespan. In other words, you're, you're healthy all your life, and then as soon as things turn bad, you die, right? Whereas in the other extreme, health span is relatively short compared to lifespan. So it might be great that you're living a long life, but if you're spending a good number of those years sort of unhealthy, then one, you yourself might not be very happy. Uh, YOU might be suffering, but also the toll it might take on the healthcare system, the need for caregivers, you know, and all, all the things that go along with that. So yeah, this is why people talk about, you know, they don't, they're not maximizing lifespan. They want to maximize health span and reduce that lifespan, health span gap.

23:23 Ricardo Lopes: Uh, IN traditional societies, is health span, uh, longer. I mean, how much time do people spend in older age, uh, dependent? I mean, how, how much time do, do they depend on others before they die?

23:43 Michael Gurven: You know, it's a great question and it's actually never really been addressed and, and. You know, I've been playing around with my next grant that I, I'd like to write, uh. Just, you know, moving beyond years and thinking about, you know, yes, different ways of thinking about the quality of those years, uh, health, physical health being one aspect of it, but mental health, uh, certainly another, um, you know, what does that look like at all ages, so that you can, can you apply some of the, the, the common metrics that are used to calculate, um, health span like in high-income countries, can we also do that in some of these traditional populations? And it's never been done, you know, I think people's guess about things is that, uh, the, the gap between health span and lifespan is relatively short. What I kind of suspect though is that it's not that, you know, we tend to think of it like health, the gap between health span and lifespan is at the end of, at the end of that health span. So that, you know, wow, you, you, you live the 1st 65 years really healthy, but then if life expectant, if life span is like 75. Then from 65 to 75, those are the unhealthy years. But I think in a lot of traditional societies, those unhealthy years are really distributed across the life course, right? That certainly when infection is a major source of morbidity and mortality, that's occurring at all ages. So it's not all concentrated to the end, the end of life. But in general, the idea that the, the, the, the number of years spent with like elder care, you know, would be relatively short in traditional societies. And you know, that was one of the first questions about You know, when we discovered that there wasn't much heart disease, you know, the, the sort of skeptic, internal skeptic was like, well, maybe there is heart disease, but people just don't live long with it, right? Again, that like life gets cut short when morbidity presents itself. And so, so yeah, that we need to study more to understand really what does health span look like over that, over that life course and And certainly as lifespan starts extending, right? Cause even in a lot of traditional populations, you know, things are changing in ways that are, there's positive and negative. The positive is that lifespans are longer, but what is that actually doing to health span? Is health span moving in concert with lifespan, or is it moving more slowly? And if it's moving more slowly, that means we're adding more unhealthy years than we are adding healthy years.

26:21 Ricardo Lopes: Um, WHAT can we learn from studying longevity record breakers like super centenarians, and I mean, I know that, of course, super centenarians, people who, who live beyond. 100 years. Uh, I mean, it's a very small number of people, and I also know that perhaps there are some variables there that are very hard to control like their habits, and I also know that some of them, uh, appear to be just Uh, lucky in terms of their genetics because there have been cases of people who were super centenarians and smoked and they have not really healthy diets and and uh things like that. So, uh, what can we, uh, learn from studying them, if anything?

27:13 Michael Gurven: Yeah, so the, the. The pessimistic skeptic answer is, uh, nothing. Right, because, you know, I think you captured some elements there. Um, IT'S a very small subset of the population, uh, and it's folks who, you know, You know, lifespan, you know, certainly has genetic, uh, underpinnings, uh, for the most part. Um, AND as you get to those older, older ages, uh, the genetic underpinnings are much stronger. So, you know, making it beyond 100, you know, you have, uh, you know, a, a healthy set of genes that, you know, are affecting from DNA repair to, you know, nutrient sensing in your cells to, you know, cancer surveillance, you know, that you managed to evade all the, the major killers. And, you know, I do think it's instructive and interesting because they are exceptions, right? Just, just like, you know, super exceptional athletes, you know, certainly exceptional athletes have put in their 10,000 hours, but, you know, uh, uh, an excellent soccer goalie is not gonna be 5'4, right? Uh, uh, AND so Prince was an amazing musician but was never gonna be an amazing Uh, basketball player, that's why the, the Dave Chappelle skit of Prince playing basketball is a, is a classic. Um, SO yeah, I think, uh, they're entertaining stories, um, but you're right. Uh, THERE are a couple of studies. Um, ONE was a study with Ashkenazi, uh, Jews who lived beyond age 95, and comparing them to, you know, Americans that didn't make it that late, and You know, there's not any difference really in their cigarette smoking, their alcohol consumption, their diet, their physical activity. So they're not really doing a whole lot different, but they're reacting very differently to their, their environments, you know, and, but there is another study that did show Uh, you know, the chance of making it to as, as a centenarian, you probably did have, you know, sustained healthier habits. Um, BUT again, when I say we can still learn something from that, but it's not something that we don't kind of already know from many other epidemiological studies, you know, that there's just, you know, a handful of habits, you know, prevention, that if, you know, if you are not a major, you know, consumer of alcohol, you have a relatively, you know, healthy diet, you're moving your body in a physically active way, uh, you know, and To the volume of, if you don't smoke, yeah, you don't smoke, uh, stay away from, you know, heavy, you know, opioids, uh, try to manage stress, just those like 6 things alone will, you know, basically, you know, really increase your chances of making it to age 70, if not 80, 90, or 100. And, and so we kind of know that without even going to the people living beyond 100. Uh, CERTAINLY I think it's just really amazing to talk to those people just because think about the lives that they've lived, you know, the experiences over such a long haul of history, the things that they've seen. Uh, I do think they're like our super elders and, and so the same way that there's a lot to learn from older people, I think there's a lot we can learn from them, but not necessarily, which I think is what you're asking. Can we learn how to live to 100 from talking to those people? Probably, absolutely not.

31:02 Ricardo Lopes: Yeah, I mean, because if you listen to some of them, that French lady who still holds the record for the longest lifespan, I mean, it was 122 years, and I don't know how many days, but uh I mean, if you follow her advice, the only thing she mentioned was that she ate chocolate every day, she used a lot of olive oil, and uh she never married. Yeah, yeah, I mean, I'm not, I'm not sure if those are the three secrets to reach 120 years of age.

31:38 Michael Gurven: I mean, it's the same thing, you know, you wanna be, you look to, you know, people in Hollywood or celebrities to, you know, what to wear as if like that's gonna make us, you know, turn us into celebrities and You know, you can pick and choose the habits that you like. I mean, Jean Carmon had a, had a great sense of humor, right? I, I remember my favorite quote from her, you know, I only have one wrinkle and I'm sitting on it, you know, so cer certainly, you know, that probably helped her get through things. Um, uh, IT doesn't mean it's gonna work for the rest of us. You know, comedians are hilarious, uh, but I would guess that the average comedian lifespan is significantly lower than the average lifespan in the population, but

32:27 Ricardo Lopes: Yeah, it's, it's probably also not a good idea to try to be a comedian out of a comedy context, because, yeah, I mean, you might get punched in the face.

32:38 Michael Gurven: Exactly, exactly, yeah.

32:41 Ricardo Lopes: Oh, OK, so, uh, you've already partly answered this question before, but what can we learn from approaching aging and lifespan from an evolutionary perspective?

32:54 Michael Gurven: Yeah, uh, I think that's a, that's a great question and that we're. There's so many elements to it, right, from just like the simple idea that, you know, while our body is sort of a well put together machine, you know, that it, it, it's, it's not a machine, right? It's not designed, you know, with blueprints, uh, from the outset. And so, you know, the way it's sort of built upon, you know, past forms. Uh, IT means there's lots of imperfections, and there's lots of design features that, you know, wouldn't be ideal if our goal was to make it, you know, as long as possible in, in a healthy way. Uh, JUST for example, you know, lower back pain, uh, not only is that one of the most common forms of morbidity around the world, you know, in the small-scale societies I've worked in, it's also one of the number one complaints, lower back pain. Um, AND so, You know, an evolutionary perspective, you know, sort of aligns the fact that, yeah, we'd like to live a long healthy life, but that's a means to an end, right? And if the end is sort of, you know, reproductive success, then once we start thinking about, uh, You know, What are the impacts of different body systems on the combined goals of survival and reproductive success, you know, it changes a little bit how we, how we think about design and how we think about health. So the other aspect too, like successful aging or healthy aging are these popular concepts out there. That, you know, I think are, are, are great for, you know, clinical approach, like we wanna live long and we want that to be healthy years. But again, we can't just look to hunter-gatherers and say, well, what they did must get us there because, you know, evolution and all that stuff, like, no, uh, there's so much misguided ideas about, you know, paleo this and paleo that, um, That, you know, the very fact that OK, groups like the Tsimane don't have heart disease, don't have Alzheimer's, but they also You know, rarely live into their 90s and beyond, right? And they're more likely to die at every age of life compared to your average European or American. And so yeah, they're not getting heart disease, but they're more likely to suffer from a common cold or pneumonia than, than we are. And so, you know, an evolutionary approach, I think, helps us think about all the trade-offs involved and helps us think about sort of the force of selection. So, it's kind of zooming out, you know, the, the classic evolutionary approach just takes it, you know, Are you, are you producing babies? Right? And the force of selection, you know, once you start reproducing, the force of selection is declining to the point where if you're no longer producing babies, then the force of selection, you know, kind of goes to zero. And so that means any gene that has harmful effects on your health, but those harmful effects, you know, only expressed in what's called the selection shadow, like after menopause, then those genes over evolutionary time can accumulate. And so you can get something like aging, and that could be favored by natural selection because genes that basically have those effects, a good number of them probably also have beneficial effects on surviving earlier in life and on fertility older, older in life. And because surviving without fertility is an evolutionary dead end. Evolution is always gonna favor genes that basically lead to some fitness enhancing effect throughout life, even if it comes at the cost of making you more likely to die in the selection shadow. So, just even that basic elements, I think have been really instructive for thinking about Uh, aging and lifespan, uh, across the tree of life, uh, certainly evolutionary approaches. You know, we, if you just think about humans, that's kind of limited. But just to know out there, you know, each species is like a different natural experiment and that, you know, Greenland sharks can live several 100 years, you know, that's amazing, right? Uh, THERE'S, you know, other species that, you know, effectively can live thousands of years, like certain trees. And so, certainly, you know, there might be lessons to be learned, um, Uh, you know, to date, just, you can't just take simple tree genes and then, you know, plant them in humans and have us live a long life. Uh, BUT, I think we're getting more insight into the forces that shape. Um, A typical lifespan and that shaped the likelihood of being around for a long, uh, long life. So, you know, we have a species typical lifespan, and that, and that's kind of where, you know, seven decades speaks a little bit closer to what would have been more typical. Uh, LIFESPAN, so a potential lifespan, not an average life lived or anything like that, but how long you could live under reasonably good conditions over most of our evolutionary history. Uh, AND, and the one thing I'll say then before I shut up, the good news there, right, cause your listeners who are in their 70s or 80s, they were like, what the hell am I? Uh, IS that I think we've done better, and that that typical lifespan now, uh, you know, in 2025 is definitely closer to 8 or 9 decades. And so, you know, making it well into adulthood, yeah, there's a really good chance that you can make it into your 80s, uh, and even into your 90s.

39:08 Ricardo Lopes: You, you know, you mentioned,

39:10 Michael Gurven: but not 150 is what I was gonna say that we still, it's a variation on the theme, but you're not doubling our lifespan.

39:19 Ricardo Lopes: Right. No, I was just going to say before I ask you about another topic that at a certain point you mentioned uh paleo approaches to health there, and I mean, those kinds of things I have to say really irritate me because whenever I talk with anthropologists, what I learned is that They never, what people say uh about that never makes sense when it comes to diet, for example, I mean, I've talked with several anthropologists on the show study diet across different uh traditional societies and basically the conclusion is that people eat whatever they have. So in their environment, so, I mean, and if you, if you are to look across all traditional human traditional societies, I mean, you don't have one single diet that everyone eats, right? I mean, so it doesn't make sense to talk about a paleo diet. Yeah,

40:21 Michael Gurven: that, that's exactly right, um, um, but, but even if there was a single kind of diet. Just because hunter-gatherers were eating that diet, again, hunter-gatherers though weren't living as long as we would hope to live. And so it might still be the case that there's foods out there or combinations of nutrients that if our goal was only to live longer, could be, could do better, right? And that's not even the case, right, because yes, hunter-gatherer diets are fairly diverse, and yeah, people ate, you know, locally, cause that's all there was. Um, YEAH, so, right, it's, it's, it's quite ridiculous. Now there are some commonalities though, certainly, you know, processed foods with lots of kind of crazy unknown ingredients that doesn't exist in any hunter-gatherer diet, uh, but it also doesn't exist in, you know, most diets of just any kind of traditional subsistence populations, herders, farmers, uh, and even our own population, you know, a couple 100 years ago. So, so that would be kind of a something right. But that, that's not usually what, when people think about paleo, they're thinking about how much meat, what kinds of meat, you know, should I go full keto and uh eliminate carbs, I shouldn't eat this, or seed oils and obsess over all these things. Um, AND that part is a bit ridiculous, yeah.

41:47 Ricardo Lopes: Yeah, also, because many of those people who propose paleo diets exclude even for populations who have had the past of being agricultural societies, they exclude things like cereals and vegetables and milk, and I mean. At this point, we know that at least societies who have evolved um with agriculture that had uh milk available and cereals and vegetables and all of that. I mean, we have evolved adaptations, uh gastrointestinal adaptations to process those types of foods as well.

42:30 Michael Gurven: That's right, yeah. In fact, you know, the pace of genetic evolution, you know, accelerated with the growth of populations in the last, you know, 10, 12,000 years, and a lot of those, you know, local adaptations are, you know, related to diet, you know, pathogens and diet, right, the two things that vary a lot locally. So, you know, even if there was a single diet that was the best, the healthiest, like say a Mediterranean diet. Doesn't necessarily mean that it's gonna be the healthiest for every possible body around the globe. Uh, CERTAINLY it might be better than one just filled with ultra-processed foods and sugary sodas and things like that. Um, BUT yeah, I still think there's, there's a, there's kind of a lot to learn, and, and, you know, the, well, I would say the biggest thing with diets is just we generally eat too much. Right? So regardless of the food, it's just the sheer quantity of calories that we consume, you know, more than anything else is probably res more responsible for our obesity epidemic than, you know, the relative contributions of carbs and protein and fats.

43:43 Ricardo Lopes: Mhm. So let me ask you, because when it comes to waging, there are those people who say that we should or argue that we should approach aging as a disease itself because they then start talking about how aging is associated with all kinds of damage to the body. From genetic damage to cellular damage to extracellular damage to other kinds of damage that is cumulative and then that's what's also associated with uh chronic diseases of different kinds. Uh, BUT I mean, do you think that we should approach aging aging itself as a disease?

44:29 Michael Gurven: Yeah, uh, also another good, yeah, good questions, um,

44:35 Ricardo Lopes: I mean, I interviewed, I interviewed Aubrey de Grey a few months ago, so that's why I, that came to my mind.

44:42 Michael Gurven: Interesting. OK, yeah, so. I mean, certainly, we're used to fighting diseases, right? And so I think, you know, if you wanna fight something, you call it a disease, you know, it's, it's kind of one approach, I think. You know, there, there's also a, a legal aspect, at least in the United States, where if you wanna sell drugs, then it has to be, you know, in order to get FDA approval, it has to be because it's uh helping prevent or treat disease. And so otherwise then it just becomes like a supplement and then kind of gets grouped with all the new agey stuff that you know maybe people won't take it seriously and so there's that practical aspect to it um. The thing that then gets wonky in thinking about a disease is none of us are escaping aging, right? That means we're all gonna get the disease. Right? So is it really a disease if it's something that everyone gets? I mean, in the past, you know, Pregnancy was labeled a disease. Masturbation is a disease. I mean, all these things that like Yeah. Is it a disease of, OK, so, yeah, um. So I don't think that it's super helpful to think of aging uh as a disease, uh, other than sort of as a rallying cry. Uh, um, YOU know, certainly the, the whole kind of field of geoscience is, you know, oriented around, well, rather than dealing with sort of these symptoms of the larger issue. Like, OK, if you, if you whack, like playing whack a mole, right? You, you, you can treat some of the heart disease, you can treat some of the diabetes, but then something else is gonna rear its ugly head, uh, if you survive those things. And so this idea that let's deal with the real disease, let's deal with aging, and if you could slow aging, Then yeah, it probably is the case that all the other diseases of aging would probably, you know, become less common or delayed as well. So I do think, but I think we need to not put all of our eggs in one basket or the other that it's still, it's still the case that many of us get, do get these diseases and for those people, we do wanna treat colon cancer, right, especially as that's something that's appearing younger and younger. Uh, RIGHT now, in a lot of countries. Uh, SO, yeah, that's real. We don't wanna wait for the miracle of, you know, slowing aging generally and hoping it's gonna affect those things. So I do think we need, we need to still kind of keep the one disease at a time approach, uh, while, you know, there's other work going on that's also funding for thinking about Uh, you know, aging processes, the hallmarks of aging that, you know, you know, in the hierarchy of things are connected to those downstream diseases, but are somewhat distinct from it. But because aging is something that affects like the entire body, uh, yeah, it just It's so much more difficult to think about and treat. I mean, we have a hard enough time even just thinking about Like, like cancer, right? We actually understand cancer, what it is and what's going on in the body. But that knowledge doesn't allow you to treat it effectively, right? In fact, most of the advances with cancer are really about, uh, early detection, uh, right? So like, um, Pap smears for cervical cancer, um, has gone done more to reduce cervical cancer than any kind of treatment, uh, of cervical cancer per se, uh, and then of course like HPV vaccines again further prevention. You know, that's gone a long way, um, but just the fact that, you know, your cells go rogue, uh, and we know these mutations occur and there's a whole set of cascading processes, but that doesn't allow us the ability to actually act on that and make a change in our underlying biology in ways that eliminate cancer. So if we can't do that with one disease, how can we do that with aging that affects all of our cells in our body. And, you know, just quite practically, the, the, the successes that we've seen in Drosophila, uh, and even in rodents, you know, just so far don't really apply to humans.

49:21 Ricardo Lopes: Uh, SO, uh, these 70 years of, uh, lifespan, um, I mean, these 70 years on average that we live, I mean, if, of course, we exclude the A high child mortality rate, at least in more traditional societies. How have we evolved to live around 70 years? I mean, why is it that we don't have a shorter, a shorter lifespan or a longer lifespan?

49:52 Michael Gurven: Oh yeah, another good question. Why, why not 80? Why not? Or why not 40?

49:57 Ricardo Lopes: Uh, WHY

49:57 Michael Gurven: not

49:57 Ricardo Lopes: 100?

49:58 Michael Gurven: Yeah, why not 100 and So they're definitely, you know, one hypothesis, right, is, is. That You know, the, the niche that humans inhabit. Uh, SO the easiest comparison we can make sometimes is, is. You know, to chimpanzees. So, chimpanzees are sort of our best guess of what our common ancestor would have been like, you know, in different aspects of the, of their ecology, but also in terms of their life history. Uh, AND so, you know, in chimpanzees, you know, their life expectancy is a lot lower, but their adult life expectancy is a lot lower in particular. In fact, early in life, there's a bit of overlap. Um, BUT, you know, no chimpanzee is living really well into 7 decades. Uh, IN the wild or under captivity, very, very, very few. And so, uh, you know, 11 hypothesis is that, you know, when we kind of shifted our lifestyle towards a more hunting and gathering dependent one, that, that this was something that kind of extended development because it wasn't very easy. You weren't just picking fruits off a tree. That were ripe, you know, this was like learning a whole set of skills, uh, you know, and it's not just like hunting, but even like gathering roots, you can't even see them, they're underground. So you need to know where to look, what rocks to turn over, you know, how to dig. Uh, AND so, you know, that, that kind of learning. You know, we, we find in, in studies that kind of measure at what ages are, are people able to be effective hunter-gatherers on their own, you know, that, that takes, well, you know, up to about, you know, almost 2 decades, kind of like the equivalent of graduating hunter-gatherer high school before people can start, you know, making a living, you know, relatively on their own. And certainly, but by that point, they've been so heavily subsidized by others that they haven't really paid it forward yet. And so this idea that, OK, so we, we shifted a lifestyle of hunting and gathering, where you basically created, you know, going back again to dependence, right? The first, you know, almost two decades of dependency. It would only really make sense if you had a, a lengthy period in adulthood where you were sort of net positive, where you're basically reaping in these, these surpluses. And so that's what we see in hunting and gathering societies, that uh adults can be really, um, you know, bringing in these bonanzas of, of food. And you see that peak uh of production. Just calories brought in per day, you know, well into the 30s, if not even sometimes into the 40s, especially once you add uh some farming, groups like the Chianes, you know, that peak is more in the 40s than, than in the 30s. So that, that alone sort of like the whole life course, like in order to kind of balance your, your accounting sheets. That we would have delayed, uh, aging and, you know, reduced mortality in ways that, uh, In ways that um a hunting and gathering lifestyle became, became more viable. In fact, the hunting and gathering lifestyle was only really viable because we were able to increase survival well into adulthood. And so, you now you have multi-generational provisioning and cooperation, and that that Uh, that's why I argue in the book that that in many ways. You know, our longevity is not sort of a consequence of our success as a species, but it's one of the reasons that we've been a successful species because of that ability to kind of learn, uh, you know, the necessary skills in your environment, um, and then to become really effective, uh, producer in your environment. And then to be kind of involved in multi-generational cooperation in ways that not 1, not 2, even 3 generations. Uh, ACTIVELY cooperating with divisions of labor, uh, allowed us to really succeed. So Now I can't even remember what the original question was. Was it about uh

54:51 Ricardo Lopes: Uh, I, I mean it, it was, it was about basically how, uh, and how we evolved to,

54:57 Michael Gurven: uh, 7 decades, yeah, yeah, yeah, yeah, yeah, yeah, and so 7 decades. When you look at that production that I was mentioning, uh, It doesn't last forever, right? So you become good, but, you know, as your physical prowess starts to decline, uh, and even some of our cognitive, uh, uh, Maintenance is, is compromised, you know, you start to see this sort of coordination in the life course that at the time when production is starting to decline. The, the type of transfers that individuals are making. So the flow of resources and services is also starting to decline, and it's at a time when, you know, survival is starting to decline, our health is becoming more compromised, and all of that seems to be occurring around 7 decades. So that was sort of the coordination there. Uh, NOW you, you could argue, well, all right, that makes sense as a coordinated system, but why is that, why is that coordinated system happening at 7 decades and not at 80? Why aren't there 70-year-old hunters that are really effective and still producing? You know, that, that's a kind of a more difficult question, right? Because then it, it, it really You know, why aren't our muscles, why isn't our VO2 max preserved to peak at age 45 instead of age 25? There's so many kind of coordinated systems and what I do in the book is try to outline a framework for thinking about these things, like, what would be the marginal benefit on fitness if you could shift VO2 max a little bit, so that now it peaks at age 30 instead of age 25. You know, maybe it is a benefit, but at what cost does it come? And is that the best allocation of limited resources in our body to make it all happen. And so, even though we might want that peak to be 8 decades instead of 7, it just doesn't seem to be that that's what was worked out evolutionarily, uh, over time in, in our particular species. So I will say that there was a little bit of, it, there was no back of the envelope calculation saying, look, 7 decades, it was starting off actually looking at lifespans and hunter-gatherer populations uh that are around today, but also even into the past and looking and saying, huh, it seems to be the case that there's this big kind of mountain of lifespans in adulthood with the peak of that mountain at around 7 decades. How can we understand that in relation to what everything we know about the human body. So a little, a little bit working backwards. So, but it does seem that there's a lot of coordination. And even though we've done really well with ourselves now, as I mentioned, 9 decades, uh, 8 or 9 decades, it's still the case though in that period of 67 decades where, you know, heart disease, you know, cancers, they're all increasing rapidly. Uh, SO even our, although our ability to kind of withstand those assaults is improved now compared to the past, uh, there's still some inevitabilities that are kind of built into our biology that haven't gone away. Uh, THOSE things aren't being well delayed too much into the future.

58:24 Ricardo Lopes: So in the more traditional societies, uh, we've already talked about infant mortality, but how are lives cut short? I mean, apart from infant mortality and particularly in the, in the case of adults, uh, what do they die from usually?

58:43 Michael Gurven: Yeah, uh, good question. And so, uh, uh, a lot, pretty much almost everything except for, you know, the major killers that we tend to see like in, in the industrialized world, right? So not the heart disease, uh, and not just because people aren't living long enough to see that. I mean, some of the studies we did on heart disease is focused on people in the age ranges that would have gotten heart disease, uh, in our populations. Um, SO just like accidents, for example, are a lot, are fairly common. So even in the absence of cars, there's certainly a lots of accidental deaths, drownings, you know, falls, fatal falls, you know, you're, you wield a machete every day, and sometimes, you know, you, you lop right into your, cut right into your foot, um, and then your foot gets infected and then we can die of secondary infections. Uh, CERTAINLY kind of warfare-related deaths, especially on men, were more common in the past than they are now. And then for women, that kind of gets balanced out in women with, uh, deaths related to childbirth. So maternal mortality rates are way higher in subsistence-oriented populations in the absence of healthcare, uh, partly they have so many more children. Right, so the, the average Thumane woman over her reproductive life has 9 births. So that's 9 chances, right, where, uh, there's the possibility of, you know, potentially dying from childbirth-related illness,

1:00:17 Ricardo Lopes: but there's a low probability that all 9 of those children will reach adulthood, right?

1:00:24 Michael Gurven: Oh yeah, yeah, I mean, if all 9 kids made it to adulthood, we would all be sane by now, right? The, the, the, the growth rate. Uh, WOULD be astronomical. Now, it is the case though, the growth rate of groups of a lot of indigenous groups living traditional lives, uh, is quite high. So the Tsimane, it's, it's over 3.5% growth rate, which is like a doubling time, you know, under 20 years. Uh, WHEN I first started working with the Tsimane, uh, you know, estimates were like 7, 8000. Chiane, and now the estimates are closer to 18,000. So, uh, certainly the growth rate of the population is higher now than it would have been in the past. So, so even, you know, when groups like the Tsimane live a much more traditional lifestyle compared to how we live, but their lives have changed a lot, right? I mean, 3% growth would not have been sustainable, let alone the fact that, you know, there'd be many more sane around today than there are if, if that kind of growth rate was going on for a long, long period of time. Um, SO yeah, those are the kinds of things, but, but largely, you know, what we find is that about half the deaths at almost all ages are due to one type of infection or another. And, and this, you know, we kind of know, right, in the big epidemiological transition that hit uh high-income countries, you know, that we made that shift, you know, we cleaned up the water supply, we cleaned up trash off the street, you know, we didn't have open sewers. Uh, AND then after that, you know, antibiotics and medicine, you know, we really were able to largely eliminate lots of infection. Vaccines, you know, back when we actually thought those were good things, you know, eliminated so many infections, so much so that we kind of forgot how harmful and deadly those infections are until now, of course, they're starting to come back. Uh, EVEN where I am in California, we're seeing more measles and whooping cough, uh, cases than we've ever seen before. Um, BUT yeah, largely eliminating lots of infections was, you know, a huge boost to life expectancy and years lived in, in around the world. Uh, AND that doesn't exist in, in a lot of small-scale traditional populations.

1:02:57 Ricardo Lopes: Uh, WHEN it comes to maternal mortality rate, I mean that affects, uh, women a lot in traditional societies, does it have to do primarily with the fact that, um. I mean, our, uh, our brains, our craniums, uh, it became, uh, very large in our evolutionary history and the, uh, birth canals, uh, didn't, uh, catch up, uh, fast enough. I mean, does it have anything to do with that or not?

1:03:34 Michael Gurven: I mean, it could, it could, um. You know, it's, it's, I mean, there's You know, from, you know, disrupted placentas to, you know. Uh, HIGH, you know, gestational diabetes, um, You know, there's a lot of different reasons why women sometimes die in and around childbirth or, you know, months after childbirth. Uh. Some of those could be related to, you know, the big head that they're squeezing through their body. Um, BUT even now, right? That, that Where there's so many mothers that have C-sections, uh, in so many ways that sort of prevented what might have been, uh, fatal in childbirth, uh, for baby and or and or mother, uh, but now that also requires additional preventive measures, right, because you've just done major surgery. And so that, that's ripe for infection and, and, and there is a small percentage, right, of women that, that suffer from sepsis after a C-section surgery. And so, um, Yeah, I think, uh, it's probably contributes to that, but it's not really the, the, the sole reason for that. An infection is still kind of a big kind of relevant part there for, for maternal mortality.

1:05:07 Ricardo Lopes: And so why is it that we live past our reproductive years? I mean, because it could just be the case that, uh, once we can no longer reproduce, we would just die. So why is it that we have post reproductive lifespan?

1:05:28 Michael Gurven: Yeah, well, for most species, that is the case, right? That, that, you know, the aging of your muscular skeletal system, you know, tracks along with the aging of your reproductive system. And that's kind of what makes most sense from kind of a natural selection perspective that as your ability to put genes in the next generation starts declining, then everything in your body starts declining. Uh, AND yeah, humans are kind of one of those rare species that where they seem to be separate. Uh, WE'RE not the only species that where that occurs, but certainly one of the, one of the fewest. And, you know, and there's two things that could be going on. One, you know, there's, you could have a long life, but just extend. The age of menopause, right, like, so they can still track, or if menopause is sort of constrained, then your only thing you can move is lifespan, and so you get this post-reproductive lifespan. And so it does seem to be that, you know, menopause is a bit and reproductive senescence is more constrained than our ability to just live. And so you see that bigger gap, um, and that's where, that's another reason why the seven decades is kind of an important. Discovery because, you know, one idea was just that, well, we only live well beyond 50. Let's say 50 at the age of menopause, we only live well beyond 50 more in more recent human history, and so it's not really an evolutionary puzzle why there's post-reproductive lifespan if post-50 lifespan is recent. But no, the idea is that even in hunter-gatherers, even in our past, uh, women would have spent, you know, if they made it into adulthood, a good chunk of their adult life in a post-reproductive state, that this is something that has existed long enough and it's costly to achieve that. Natural selection should have something to say about this. And that's where, you know, I guess I would say, you know, the biggest contender for thinking about the why of all of that is that it must be the case that the force of selection is not zero. So you're not. Directly putting genes in the next generation by having babies, but you're, you must be indirectly doing it by, uh, improving your fitness in other ways, right? Helping your children survive, helping your children find mates, helping your children with their own children, so your grandchildren, and so all the different things that, that. Adults do, that could be impacting the fitness of their relatives, uh, and of themselves, but in ways that just don't involve directly having babies themselves. And so that's sort of the big kind of contender for, for thinking about post-reproductive lifespan. Um, AND why, you know, the seven decades is we kind of gets us back to your earlier question that grandmas are great. Right, but a grandmother at age 60. Might not be contributing to fitness in the same way as a grandmother at age 85. Right. And so there's a point at which those benefits of having grandmother alive become a bit saturated, uh, relative to the cost of keeping her alive. So, you know, that in that balancing act, that's where I think 7 decades sort of comes out, uh, uh, a bit. That, you know, well beyond 7 decades, uh, frailty settles in, and even the ability to indirectly reproduce through all the different things that older adults do, like, You know, helping Ken when they're, when they're fighting and not getting along, you know, helping kids, you know, instructing them in all the, the ways of the local culture, uh, you know, those benefits, you know, become small or even impossible to confer relative to the, just the fact that you're a physical body that still needs to eat every day. And if you're mobile, that's even worse because you need to be physically moved as the group is moving, and that those costs become, you know, heavy relative to the benefits, and somewhere in that ballpark, I think 7 decades comes out.

1:10:00 Ricardo Lopes: Yeah, uh, I mean, there's the grandmother hypothesis, but what about men? I mean, why is it that we also have grandfathers, because it could just be the case that grandmothers would do the bulk of the work and who we wouldn't even need grandfathers,

1:10:19 Michael Gurven: yeah, right. Yeah, well, and that's where. You know, the, the, the. I mean, we're, we're mammals and we share a lot of our biology, uh, you know, the developmental plan works out in certain ways, you know, men have nipples, right, even though we're not breastfeeding, and so, you know, one idea is that, you know, let's just say that all the fitness benefits accrue to one sex, but then the other sex gets dragged along, right? So, you know, one view of the world, it's all about grandmothers, grandfathers are irrelevant. Granted, if they're, if they're surviving longer because of shared biology with grandmothers, then maybe, hey, they're gonna kick in and help out a little bit too. Uh, YOU know, another idea is, well, the benefits really are accruing to men because they don't have menopause, so they could continue reproducing until well past age 50. Uh, YOU know, it actually turns out that, yeah, on average, you know, men tend to be a few years older than the women. That they're married to. So if people's, if men's wives' fertility is declining, their fertility is declining too, just offset by, by a few years. And so even though men don't have physical menopause though, they kind of have an effective menopause, just delayed a little bit. Um, BUT there's been some modeling done showing that, you know, the excess fertility benefits men might get might be enough to offset that declining force of selection, and in that case, women will be dragged along. But I think, you know, I just, kind of like there's no single paleo diet. I feel like there's no single ecology where uh it's all women or it's all men. It's one of those things where uh to varying degrees and in different currencies, men and women are gonna be contributing uh to their fitness. And yeah, in different places, it might vary a little bit and maybe like in more gerontocratic. Hurting societies where men have multiple wives, you know, maybe they are some few men. Are reproducing well into their 70s, uh, but even in those cases, you know, the majority of men are not. Um, BUT on average, there could be a net effect and maybe, and, but then those men might not be doing a lot of caregiving, but then the older women might be doing a lot more caregiving. You know, we just haven't really done the studies, you know, the very few studies that have been done have been mostly like food provisioning, because food is easy to, it comes in every day when people come back from, from hunting and gathering, uh, or from their fields, and so it's easy to measure things, but Uh, older adults are making contributions in so many different ways. And so, just the same way where we used to think like, oh, where men were bringing in the bacon all the time, but we were discounting all the ways that women were contributing to production. And once you consider all those ways, then it, it boosts women's productivity relative to men's. Uh, AND I think it's a similar kind of thing that, that men and women are both making fitness contributions. Uh, I don't think they have to be equal just because. You know, the moral dictates of gender equality say it has to be that way, uh, but I do, so I think it will vary across, uh, populations and context, um, but I don't think we should necessarily be thinking it's all just grandmothers or all just grandfathers, and that's an important point because The grandmothering hypothesis, I, you know, I think it was a very influential and helpful, but there's so many studies that have only looked at the effects of grandmothers, and so we, we can't even know in those societies what grandfathers were even doing because it was assumed they're irrelevant, so they weren't even studied. And so, yeah. Uh, I guess my more gender neutral approach is that we just need to see what older adults are doing and all those, all those manifold ways that they're indirectly contributing to their fitness if we really want to understand something about kind of aging and that balance between those fitness benefits of being alive at later ages and the costs uh of being alive.

1:14:45 Ricardo Lopes: Yeah, and I mean when it comes to fathers and grandfathers, of course I'm, I don't want to make too broad a statement here that might be incorrect, uh, but uh at least in human societies we have uh some degree of paternal and I guess grand paternal. INVESTMENT, right? Of course I, I, I'm sure it varies depending on uh the ecology to what extent uh men, the fathers also invest in their offspring and so on, but there's always at least some degree of paternal investment, right.

1:15:27 Michael Gurven: Yeah, yeah, exactly, and, and, you know, and certainly. And you've probably talked to other people. Well, if you've had 1200 interviews, you know, I'm sure someone was talking about paternity certainty, uh, and how that kind of plays into, you know, paternal investment. And, and again, that's just another part of the ecology that, you know, if paternity certainty is lower, then maybe men are making fewer investments and, and, you know, investing more in mating effort. Uh, BUT on the whole, you know, you do see plenty of male investment in children, uh, and grandchildren around the world.

1:16:11 Ricardo Lopes: Mhm. So, uh, OK, this is going to be a, a darker question, I guess, but when, uh, people, older people become too much of a burden, a burden in, uh, traditional societies, how are they dealt with? Because at a certain point in the book you also talk about, for example, Geronticide. So, I mean, what happens there?

1:16:39 Michael Gurven: Yeah. Yeah, you know, I was at a. A mini workshop a few months ago on caregiving and, and most people were there talking about caregiving of infants and children and I gave a talk about elder care and then, you know, geronticide as a form of caregiving, so which probably was not what what the organizers were expecting, uh. But there's a little bit of truth to this idea, right? So, Uh, certainly, throughout his our, our history, um, there's a range of behaviors that, for lack of a better term, have been called death hastening behaviors were based, you know, on the extreme and could be like murder, right? You kill an old person, um, you know, and, on a more mild and it could be like mild neglect, right? Maybe when, you know, it's dinner time. Uh, THEY get the last plate, you know, and they eat if there's a lot, but if there's not a lot, maybe they, they eat a little bit less. Uh, AND so. And you can imagine that. When circumstances are harsher, so in more nomadic hunting and gathering groups where you have to move camp every couple of days, uh, It's all else equal, a lot more difficult to care for someone who's in a frail state. And so, you know, almost always these, these cases of death hastening. You know, are applied to what's what's called like the old old or like the, you know, very frail, uh, elders. Um, And And it seems to be more common under those harsher conditions. As soon as you have farming, and now you have somewhat semi-permanent settlements and you're not moving camp every other day, all of a sudden it becomes a lot easier, uh, so, uh, even if you go out to your field for the day, you could leave Grandma at the house, and there's a good chance she'll still be there. You can leave a pot of food even for her. Uh, AND, you know, assuming they're not being raided by anyone, that, uh, you know, she would be, she would be OK. Um, So it makes a big difference, those kinds of things, uh, but I think in many ways, you know, geronticide sounds kind of exotic and harsh and terrible, but you know, we're, you know, we're faced with the same kinds of decisions now about euthanasia and people willfully wanting to end their lives, you know, and there's certain legal ramifications like is it a terminal illness, uh. And it's a weird thing too, where certain uh ramific uh stipulations that, you know, should be terminal, you also can't be depressed, cause like that's, that's Which is, uh, you know, if you have a terminal illness that might depress you, but if you're so depressed that you can't make a rational judgment, then, then, you know, that goes into play. But it's a similar kind of idea, these, these trade-offs, right? It's not someone like cruelly murdering an old person because they get joy out of it. It's, it's in some ways it's, it's, well, it's ending potential suffering because that older person just might be miserable. Uh, THAT older person might also recognize that they, you know, they feel like they're a burden, that they can't make the same contributions they were making before, and that doesn't make them happy. No one wants to feel like they're a drain on their, on their kin, and especially in the context, you know, in the, in high fertility societies, you can quite literally see that. You know, calories that are going to feed you are calories that are being taken away for growing children in a context again, where a lot of children don't make it uh throughout childhood and so every calorie helps. So in those contexts, uh, The cases where there was sort of like outright ran aside, these were sort of like joint decisions that were made, you know, by an elder and a close family member, and oftentimes it's, it's the close family member that, you know, deals the final blow. And so yeah it's, it's, it's a different, it's not what people think when they think about Toronto side uh what was that that movie like once once you turn a certain age, you know, you're pushed off a cliff. Uh, BECAUSE that, again, that's not how it is, right? There's no magic age. It's really about going to your first question, what's old age, right? When you're really frail and can no longer, especially what I see in Bolivia, when it comes to the point where you can't, you can't go to the bathroom yourself, you can't dress yourself, you have a hard time walking and getting around, uh, and there's not maybe available caretakers, you know, this is when you really see. Uh, KIND of neglect, uh, and sort of an accelerated death, uh, still not really outright Toronto side, but sometimes people even try to end their own lives, uh, when circumstances become that bad.

1:22:19 Ricardo Lopes: Yeah, no, I also read a while ago that, for example, among the Inuit, uh, there, the elder people, I mean, some of them at least at a certain point when they notice that they can no longer, uh, follow the group, they just, uh, stay behind and let themselves die in the cold or something like that, so they, they make the decision, the decision themselves.

1:22:48 Michael Gurven: Yeah, yeah, I think that's, that's, that's true, that it's, it's sort of an active con they're active contributors to that, to that decision. Um, YEAH, I mean, I'm sure there's been some exceptions to that, but it, it's always, I think, been in the context of these, these sort of harsh but practical kind of trade-offs, um, where, you know, it's really hard to care for everyone at the same time. I mean, sometimes, you know, the, the kind of caretaking needs come in direct conflict. With trying to make a living, right, especially when making a living means leaving home and going out and about, uh, for foraging. So, yeah, that's exactly right.

1:23:38 Ricardo Lopes: So when it comes to the sort of age-related changes that we tend to see in modern industrialized and post-industrial societies like changes in muscular strength and endurance, changes in the immune system, uh, cognitive functions like decision making, memory, and so on. Uh, IS that, uh, something that we also tend to see in traditional societies? Are those, are those same types of changes occurring there?

1:24:13 Michael Gurven: Yes, yeah, they are, uh, you know, the ages, you know, might vary a little bit, um, but the, the, the shape of the relationships tend to look fairly similar, um, so even though, you know, groups like the Chiane and the Hadza are so physically active every day. That doesn't mean that their VO2 max or their muscular strength is staying high and preserved well preserved all throughout life. You're seeing sarcopenia or muscle wasting in those populations just like you see, uh, in, in our population, uh, and. You know, different aspects of heart health even. Um, SO even though like Tsimane have healthy hearts, you know, we've looked at their like ejection fraction and uh other components of like VO2 max, and you see declines in efficiency with age. Now, they're still sort of in a very fairly healthy range, but you're still seeing that decline with age. Um, And so yeah, there's no, there's no real kind of getting around all of those things, uh, you know, osteoporosis, and so weakening of, you know, loss of bone mineral, uh, all of that, we, you know, we see in traditional populations. Um, So yeah, those aspects are all, are all the same, you know, and the same thing with the brain that, you know, relative to other You know, like, whereas your heart VO2 max might peak in your twenties, early thirties, you know, certain cognitive functions show kind of peaks in young adulthood and then decline thereafter, like different things related to like your executive function, but other aspects that reflect your cumulative knowledge show increases throughout the life course. And you know that one possibility, you know, I hypothesize in the book is because we're, we inhabit such a brain-based ecology, right, where there's so much knowledge and, you know, decision-making involved with hunting and gathering lifestyle that it really prioritizes, it puts the premium on brain-based capital, right, that, you know, quite literally our babies and children. ARE like have fat heads and tiny little bodies, and all development is making that the body is getting bigger relative to the head and then it's like filling the head, but it, it, everything's been going designed towards like prioritizing the brain and its development. And, and so when we have it like such a skills-intensive Kind of feeding, you know, ecology, uh, there's a premium to sort of keep that brain online and to keep it reasonably intact, uh, for as long as possible. So that even when our body, this is like getting into that framework of like, OK, if we could, if we lost 10% of muscle mass, Uh, relative to say 10% of brain mass, uh, and cognitive function, which one would have a bigger impact on survival? Which one would have a bigger impact? Maybe on food production or something like that, you know, and, and because, you know, the importance of our cognition is so great, you know, I suspect that we could sacrifice some of our physical capacity and still get by pretty well as long as our brains are relatively intact. And so it is, it does seem to be the case that the brain aging aspect. IS slower compared to other aspects of our physical aging, and that seems true for, for all humans.

1:28:27 Ricardo Lopes: Yeah, and I mean, I, I was going to say in terms of our orthopedic health, I mean the, the, the health of our muscles, bones, etc. um, I guess that uh In our more modern, um, industrialized societies, we tend to have the issue of people underusing their bodies. They don't move around enough, but in the case of more traditional societies, perhaps, and maybe in our own societies, we also see that with athletes or at least professional athletes, some of them. Uh, PERHAPS in more traditional societies, they, uh, perhaps in some cases at least they would have the, the opposite issue. Perhaps they overuse their bodies or misuse them in some ways, right?

1:29:15 Michael Gurven: Yeah, yeah, so for example, we've done studies of bone mineral density and, and Uh, it's true that, that men in particular have higher bone mineral density, you know, in traditional subsistence populations, you know, compared to, say, the West where we're more sedentary, uh, but it's not terribly different for women. So even though women in subsistence societies are a lot more physically active, uh, they also, if it's a natural fertility population, Uh, or context, they're having a lot of children and especially if those children are more kind of closely spaced together, and that's sort of having an impact on your bone mineral density that kind of counterbalances the fact that they're more physically active. So the net effect is actually that, uh, an American woman aged, you know, 35, her bone mineral density doesn't look terribly different than a Timane woman age, age 35. Um, SO yeah, I mean, that's, that's exactly right that, uh, There's, even though we're, in some ways, we're healthier, but there's a lot of ways for things to kind of go wrong. And, and again, goes back to just basic physical activity and sedentary activity too. You know, right now, I'm sitting on a chair and I'm not sitting in a way that like I'm not using any core muscles right now to maintain my balance, you know, and, you know, if I do that enough, yeah, I do think I'll, I'll be more prone to injury and um My bone mineral density is probably gonna, you know, winnow away. Um, Yeah,

1:31:03 Ricardo Lopes: So, uh, earlier you were saying, for example, that er when it comes to, uh, I think you mentioned heart disease that we see uh lower rates of heart disease in older people in traditional societies, but are chronic diseases that are common in industrialized societies like heart disease, diabetes, cancer, dementia, inevitable?

1:31:31 Michael Gurven: Yeah, well, that's, I, I think some of the, the hopeful message of some of my work and my colleagues' work, uh, that work with like more subsistence-oriented populations is they don't seem to be inevitable, uh, right, because the very fact that, um, Not just one or two, you know, extraordinary athletic, health-conscious people avoided heart disease, right? We have those people in our society, uh, but kind of writ large, the vast majority of the population, uh, didn't get heart disease, uh, and they're much more likely to die of something else. You know, that, that shows that prevention really, you know, can be very critical, uh, and that it's not inevitable. So, certain, and that's, that's sort of been one of the things that we've learned from a lot of this, of this work, you know, it's not inevitable that your blood pressure has to always increase with age. It's not inevitable that testosterone declines rapidly with age. It's not inevitable that, you know, your prostate is gonna get larger with age. These are all things that we've kind of found from different, from different studies. Uh, IT'S not inevitable that, you know, you'll get diabetes or Alzheimer's, um. And so That it does suggest that there are possible things we could do, uh, and maybe that gets us to that, that last question about, you know, what can we do, what can we learn, and obviously, we're not gonna, we, we're not all gonna become hunt hunter-gatherers, right? Not only is it not feasible, uh, it probably isn't something that most of us would want, right? A hunting and gathering life is very difficult life. And so there's a reason why. You know, hunter-gatherers don't exercise, right? Why would they, you know, they don't, they move their body when they have to. They move their body because if they don't move their body, they're not gonna eat that day. And so it makes sense that we sort of evolved to conserve energy and that if you could drive to the supermarket, you're gonna do so, uh, rather than like just go out of your way to walk and carry like 20 pounds of food. Uh, YOU know, no one really does that unless it's something they consciously put themselves towards, but it's almost like fighting evolution because, you know, we've evolved in ways to sort of conserve energy, to consume energy when it's available, uh, to consume dense packets of energy when it's available, you know, and to enjoy the flavor of fatty, sugary foods and all that. That would have been in limited supply. And so, so much of what we have to do to stay healthy in a land of abundance. I avoid things and avoid things that sort of come somewhat naturally to us. We have to fight our instincts, uh. And that's what becomes really, really hard. And you know, I think there's no easy solution to that other than, you know, well, there's no easy solution, you know, the, I think the solution has to be, we have to shift the incentives, we have to shift the structure of how our societies are organized so that the easiest options are healthier options, right? If, if, if you build housing in relation to a livable situation. So everyone can kind of walk to a market. That already makes a huge difference, that, that everyone can walk and do their food shopping as opposed to kind of needing cars all the time. Um, YOU know, if you make it such that You know, at, at eye level, you know, the healthy foods in the market compared to the unhealthy foods, you know, little things like that, that can go a long way towards, you know, nudging us towards healthier lifestyles, I think, you know, can make, can make a big difference.

1:35:53 Ricardo Lopes: Yeah, I imagine that if uh hunter-gatherers came to our industrialized societies and saw people at the gym running on the treadmill and lifting weights, they would be like, what the heck? What are you doing with that?

1:36:09 Michael Gurven: Yeah, well, yeah, the very fact like what are these torture machines? Uh, WHY do these exist? And why are people doing this? Like, it's just, I remember just for the longest time, like, at the very least, why aren't these exercise machines like hooked into the grid, at least generate the electricity that's powering uh the gym. Uh, AND apparently, you know, some gyms have started doing that. And uh you can reduce your monthly fee because you're contribute, you're helping keep the lights on. Uh, THAT at least it makes sense. You can feel like you're being productive in a way that you're actually helping, uh, doing something rather than just like mindlessly doing this. But, you know, uh, that's OK. Fine, we, we need this because our lifestyle is such that, you know, we tend to be more sedentary. But I still think even like with the gym, you know, so many people buy their gym memberships on December 31st, right? And then by January 2nd, you know, they, they already like aren't really going and, and apparently just buying the membership doesn't make you healthy. You actually do have to go. Uh, BUT I think even something as simple as like buying memberships like in, in pairs, having a buddy to go to the gym with makes a huge difference. Now you've made it a social activity. And you're more likely to go, you're more likely to have someone make you go, uh, and you vice versa, and, you know, maybe the hanging out and conversation becomes primary and the working out is just secondary, you know, again, another way of sort of nudging ourselves to, to being healthier, even in the sort of artificial way of relying on, on gyms. Mhm.

1:37:53 Ricardo Lopes: OK, so let me ask you this question. So, do you think it's possible to say at least on average, whether, uh, let's say a 65 year old, because that's usually the age that uh medical institutions, the WHO. Joe and so on used to define uh old age. Um, DO we know if a 65 year old person living in a traditional society, a contemporary traditional society or a traditional society from the past, uh, would be healthier than a 65 year old living in, in a contemporary industrialized society or vice versa? Is it possible to say that?

1:38:37 Michael Gurven: Yeah, that's sort of like the, the $10 million dollar question, uh, and that also kind of motivated a lot of my work early on, like, really basic question, and, you know, 20-some years later, you know, I, I, I do have a better answer maybe than before, but it's not, it's certainly not an easy answer because on, on certain aspects, Like the ability to walk 8 miles and do work, I do think we're probably maybe a little bit less healthy than we would have been, um. Uh, THAT being said, I do think our ability to sort of withstand a variety of onslaughts, assaults in our environment is better. And so our ability to survive infection is better, a 65 year old in our society now compared to say what probably would have been the case in, in the past. And so I think our, our reserve in, in a way is, is better now than in the past. And, and we, you know, The shorthand for that is just that. The, the, so life expectancy, you know, when, when you ask me that question, You know, I don't know. It feels like 3 hours ago or 20 minutes ago, um. What I told you is life expectancy at birth, but you can calculate a life expectancy at any age. So the life expectancy is 65, you know, it could be, it's how many years do you expect to live if you've made it to 65, and just based on that alone. Uh, THAT number is larger now than it ever was before, right? So it might be like 15 years or 20 years, but in the past, that might have been like 5 years or 8 years. So, Now, it's not just that you're more likely to get struck by lightning in the past compared to now, that it is probably something about your health and well-being and your ability to withstand different assaults and recover from infection and all that stuff that is contributing to, you know, a doubling of the life expectancy at age 65. And so I, you know, I would argue that, yeah, I think we are. Healthier on average from what we, what we even take into account, you know, our, you know, that we're more likely to be obese, we're more likely to have diabetes, we're more likely to have a variety of these chronic diseases, but as a whole, I think for the things that kind of matter in the most practical way, we're doing, we're better off now than we were in the past at age 65.

1:41:30 Ricardo Lopes: Do you think that in our contemporary industrialized societies we are, we perhaps are exposed to some evolutionary mismatches in the sense that for example we have easy access to high caloric food, we have easy access to sugary food, uh, salty food, we have, uh, the way we tend to move around, I mean, is not usually by food but using motor vehicles. Uh, AND the, uh, the kinds of jobs that we have, we tend to be sitting, uh, most of the time. So do you think that some of those things, uh, if we're, uh, approaching aging and, uh, health from an evolutionary perspective are evolutionary mismatches?

1:42:22 Michael Gurven: Yeah, I mean, I think that's kind of the, the common framework for thinking about a lot of the chronic diseases of aging, right? That, uh, and for some of these like newer types of diseases and morbidities, uh, that, you know, our genome didn't evolve in the particular context in which we, we live now. Um. But I think it's, it's uh, it's usually not so straightforward, um, because, you know, certainly if you're, if you're 75, And you have arthritis and you have a hard time getting around. Well, having a car that you can still drive to get yourself to where you need to go is still a benefit, right? And you know, of course, over-reliance on cars to the point where your, your body is never moving. I mean, that's where certain things can be taken to, to an extreme. So it's really how we kind of use some of those technologies, uh. Rather than like the whole environment is kind of thrown out of whack. Cause certainly plenty of people still manage to move their bodies, um, and get lots of physical activity, uh, and not just because they kind of go to the gym. In fact, in many ways, I think, you know, city living. Uh, IS effective for lots of reasons, but, you know, if nothing else, people are moving around and walking, you know, it's not as, you know, you can't find parking and it's expensive. So, you know, you're using public transportation and you're walking a lot. And so you're getting more steps per day, uh, and, you know, the higher physical activity that, you know, groups like, you know, the Tsimane and Hadza get. You know, it's not because they're running vigorous, you know, half marathons every day, you know, it's a lot of light and moderate activity that they're engaged in, which is a hopeful message to us, right? Because that, I think we can all handle light and moderate activity. We all wouldn't want to run marathons. And so that's, that's sort of attainable, you know, light and moderate activity. And, you know, the, the epidemiological studies sort of show this, that at any activity level, if you're fairly sedentary. Improving and just walking a little bit more, uh, makes a big difference. Um, IN fact, it makes more of a difference if you're inactive than if you're already really physically active and you add a couple of 1000 steps. So, yeah, I think those, those are hopeful messages for, for us moving forward.

1:45:00 Ricardo Lopes: Uh, LET me ask you, uh, because this is something that in psychology, I guess social psychology specifically, people talk a lot about, uh, people, uh, talk a lot about how in older age, there's, there's that sort of late age. Contentment that older people uh tend to be more content, tend to suffer less from depression, for example, than the younger people is late age contentment a human universal? I mean, do we also see that in traditional societies?

1:45:38 Michael Gurven: Yeah, another good question that I think, uh. You know, this, this is one of those cases where I think In some ways, the mismatch works to our advantage, not to our disadvantage. Most of the time we hear about mismatch where something, it's cause it's quite literally defined that way. Our health is poor because our genome doesn't match the conditions under which that genome evolved. Uh, BUT in this particular case, you know, So studying late age, kind of contentment, life satisfaction, happiness, well-being, you know, put all this under the umbrella of well-being, and yeah, I know the psychologists, they care about which terms are used, you know, contentment is a little bit different than your momentary happiness, uh, but still thinking about well-being overall. Um On average, yeah, older people in many places around the world, uh, tend to, you know, coming off of a midlife kind of slump that they become more content with age, right? And you, you know, in some ways this might make sense, right? Uh, YOU learn, maybe you become a little bit less competitive, a little bit less ambitious. Uh, YOU learn not to sweat the small things. Um, MAYBE

1:47:06 Ricardo Lopes: you perhaps you don't care too much about people's opinions anymore.

1:47:11 Michael Gurven: Oh, right, the fact that you don't care so much, you know, your reputation is established already. You're not jockeying for status. Um, YOU can focus on the positive, a little bit less on the negative. You gain perspective, you know, if you wanna call it wisdom, you know, all these things are things I think matter that. Can improve our outlook and improve our well-being, uh, and what's remarkable about that is that that's a if that's improving with age, uh, that's happening at the same time that our physical health is actually declining, yet healthy body, healthy mind, uh, all else equal, being healthier makes you happier. So in spite of, uh, suffering from more physical ailments, we actually seem to get more content with age. And even more so. If you also consider what's happening with age, you know, kids are fledging the nest, uh, you know, if you live long enough, you know, you're gonna start seeing everyone around you die. Uh, AND so again, these social losses, you know, combined with your physical health decline, yet in spite of all that, you've got improved well-being. You know, so I think that's pretty remarkable, and. Now, but it is a little bit variable even in the West, sometimes well-being increases throughout life. Sometimes you do see it sort of flatten out in the 70s. And so I do think there, there is a sort of trade-off. Shit is happening that is not good in your life, and to what extent is it offset by other things? And this is the case where if you live under a context where You have labor-saving technologies, you have a car, you have, you, you know, you have uh life insu or health insurance, you have disability checks coming in. So, you know, there's a sort of institutional buffering that allows you to still have an income and still get by, uh. Then, you know, maybe it's a net positive, and you can be content. But in traditional context, even in the, this is where it was, you know, to many, I think surprising, cause we tend to think, well, in small-scale societies, everyone's surrounded by family and it takes a village and people are cooperative.

1:49:47 Ricardo Lopes: Yeah, the, the social aspect of our lives, we tend to think that it's more taken care of in traditional societies than in, uh, contemporary, uh, industrialized societies. Yeah,

1:49:59 Michael Gurven: but you know, it might be a double-edged sword is because you're, you are embedded in these networks, you know, when I talked about, uh, You know, the 85 year old grandmother compared to the sixty-five-year-old grandmother. And if you feel like you're a burden, now all of a sudden, you're a burden to all these people in your network, uh, and that doesn't feel good. And, and so I think, you know, in what we found, uh, is just a whole lot more variability in well-being at later ages. Uh, SOMETIMES you see those improvements like you see in the West. But more often than not, you either see no relationship with age, or you see the opposite, like things are getting worse with age. Uh, AND I just think that that's maybe more typical in a context where your physical health is sort of Primary for making a living, for, for being useful to others. Um, AND where there's no cars to drive you around and no Ubers to, to move your body from here to there. And so that aspect of physicality becomes really critical, uh, and that ability of being useful to others becomes really critical. I mean, it's true in our society, no one wants to think of themselves as a burden. No one wants to feel that they're not useful to other people. But maybe it becomes a little bit less necessary here because you still can have a viable livelihood. Uh, EVEN if you kind of live alone. Um, SO yeah, I think, you know, that aspect is a little bit more surprising, both that one, in small-scale societies, everyone's not happy at late ages, and if anything, those people might be the most miserable at the latest ages.

1:51:59 Ricardo Lopes: Yeah, maybe we will find out that in industrialized societies, at least, uh, people get more content in older age because they actually do not fear death, but they were living for so long. They're like, oh my God, finally this is coming over. Finally, I'm in the last 100 m of the marathon.

1:52:23 Michael Gurven: Yeah, yeah, yeah, I think so. I think so. Well, we, we certainly have a, a big culture that kind of focuses on these things and Uh, yeah. Um, No, it's, it's a, it's a good question, and I, and I do think it's sort of what we need to understand better. Cause ultimately, uh, we do wanna improve our survival and live longer, but we wanna, we want a happy life. We want a healthy life, we wanna be content. Uh, AND if that's ultimately what matters most, well, we should be studying that a lot more systematically than we are just whether you're alive or dead at a given age. So.

1:53:06 Ricardo Lopes: OK, so I have just uh two more questions I want to ask you. Uh, LET'S talk a little bit about retirement because of course we have retirement in, um, contemporary industrialized societies, but what about traditional societies? Is there such a thing as retirement there and what are the effects of retirement in for old people?

1:53:35 Michael Gurven: Yeah. So Short answer, no. There is no retirement. Like no, no formal retirement like the way we think of it. Like you reach a target age, and then you no longer work. Um, THAT doesn't exist. And so, so that's also, you know, a bit of a mismatch. Um, AND even more so a mismatch cause when, you know, 65, you know, was placed as a, as an arbitrary age, at least in the US. Uh, YOU know, that was occurring at a time where that was already older than our life expectancy. Right? And now that's well below our life expectancy. And so, The, the question about, you know, should we have formal retirement and then secondarily, if, if so, at what age? You know, these are kind of, these are gonna be questions that are gonna be part of the national conversation. If we are younger at 65 than we used to be, then should we be retiring at all at age 65? Maybe that should be 70, 75. And so, so those questions are gonna come out, but I, and I, and especially I think. Um, You know, in small scale traditional societies, even though I said you're not formally retiring, it doesn't mean that people are still doing the same things until they die. Uh, THERE is a shift in what people are doing, and so people will, will still try to be useful and participate in a lot of different activities, but they might not be doing some of the really physically intensive ones. So Timani men, for example, they're not really using axes and chopping down really thick trees, you know, when they're in their 70s. Uh, THEY still might chop down little trees, and with a machete they might still do a lot of clearing in their field, but they're not doing sort of the heavy physical labor, uh, and And they're not, and they're not hunting as well, right? And not just their physical strength declining, but if your ability to see and particularly your ability to hear become compromised, then your ability to be an effective hunter just kind of goes out the window. So, so yeah, those things are changing, but there's a lot of other ways of being useful. That uh people find. Uh To keep active and still be included, still participate, uh, not just in the economy, but into the politics, uh, and the social scene in small-scale society. So, in other words, they're still relevant, whereas in our society, because work is life, uh, oftentimes, once you're retired, people actually get really depressed sometimes. Uh, THERE'S a little spike in mortality. Uh, AFTER retirement because people don't know what to do with themselves, um, granted, that's not always the case, right? Some people are thrilled once they retire, uh, and they can do all the things that they held back, but this idea that you retire and, and then all of a sudden your life becomes one. Focused on leisure that that didn't exist throughout, you know, our, our history and, um, you know, and I think that's part, you know, the last couple of chapters in my book kind of focus on that aspect that, you know, rethinking that because, you know, the burden of population aging, you know, maybe that could be flipped on its head to, you know, as more of a An untapped potential, uh. But not if everyone is just focused on their leisure. But instead, they're kind of focused on, you know, how can I still contribute? What are all the different ways I can contribute, um, you know, That dependency ratio and all those other aspects that are seen as problems in an aging society, maybe those things wouldn't be, it wouldn't exist in the same way.

1:57:43 Ricardo Lopes: Yeah, and I guess that at the same time maybe we can also put things in perspective here, right, because it's not, uh, we tend to think as having an occupation or doing something useful in our societies uh as being the same as having a salaried job, but there are many people that even if Even if they are retired, they're still doing useful things and practical things. They're taking care of their grandchildren, they're doing housework, and so on and so forth. It's not just because you don't have a salaried job that you can't be useful in society.

1:58:24 Michael Gurven: Yeah, that's exactly right. Yeah, it's, it's all the, you know, certainly in hunter-gatherer societies, you know. The same way that we focus on income, you could focus on calories, and those are just one. Aspect of contribution and what really matters, right, or if it's impacts on, you know, fitness and well-being, you know, we, for our purposes, uh, yeah, money is just one way of one way of being productive and, and even better, right, if you, if you can get Social Security, you could still have some income coming in. With the ability to then either generate more income from doing other services, uh, and of course, just. All the other things that, that older people could do as well that make contributions, you know, one, you know, one difference though, what you could say is, you know, making these vague, these contributions to society or society is sort of like this vague thing, you know, maybe community is easier to think about, family is easier to think about, uh, but we also have smaller families than we ever had before, uh, and some of those families that when we do have them, they tend to live far away. Which makes it more difficult, uh, but it doesn't mean that that urge to sort of be seen as valuable, uh, and useful, uh, it's still there. And, and yeah, money doesn't have to be, you know, the language in which one judges your utility. Uh, AND so even, you know, people make contributions to their church, you know, they, they volunteer in schools, um. There's so many different ways to kind of feel useful and feel like you're making a difference and, and in a way that Not only does an older person feel more accomplished and better about themselves and their own well-being, and it motivates them to be healthier when they feel their life has purpose, uh, but it's usually improving someone else's life, right? If you're helping at a school, you're building literacy, you're reducing, you know, teenage delinquency and all that stuff. So this is why it's been argued where if we can improve the contributions and the ability for elders to really contribute to the extent that they want to, that it's a win-win for society. Uh, BUT our society isn't really structured that way quite yet, right? If you can no longer drive, uh, then you can't get to where those schools are. If you live in a rural area where there's no public transportation. Then you don't have an ability to get from where you live to where that need might be. And so, again, this is the sort of rethinking about how can we, uh Build upon the untapped strengths of our elder population, uh, to help contribute to, to society.

2:01:29 Ricardo Lopes: OK, so one last question then, and I guess that over the course of our conversation, we've already addressed this question in different ways, at least indirectly, but Um, I mean, do you think that even with our evolutionary mismatches, some of them negative, some of them positive, as we talked about here, uh, that, um, we as people who live in industrialized societies can learn something from how, uh, people age in more traditional societies that could, uh, that we could apply ourselves.

2:02:07 Michael Gurven: Um, YEAH, I mean, I, I think. You know, we touched upon this a little bit, right? We can't become hunter-gatherers, uh, but then one of the lessons is, you know, nor do we, I think we even want to, uh, but There are certain lessons, right, you know. From little to large, like. Like on the physical activity front, right? That, that's the one commonality to all small-scale subsistence populations. Uh, PEOPLE are fairly physically active. We know that physical activity in some ways is the best non-drug drug that we can, that we have. Um, AND it's free. Everyone can afford it. And it doesn't have to involve gyms. It can be involved just, you know, walking around, you know, your neighborhood. Um, AND so, Being more physically active and in ways that don't necessarily require athletic equipment, you know, I think, uh, Is one big lesson and just. Trying to incorporate it into your life as a lifestyle rather than as an exercise activity. No one wants to, a lot, well, I speak, maybe for myself, no one likes, like, I'm gonna go exercise now. It's like a chore, you know, versus, you know, I have to go pick up my prescription or I have to go uh to Trader Joe's and get, get some food, so I'm gonna, I'm just gonna walk there. And so I think that mentality is, is important. Uh, I think there's other things about It's easy to get caught on various, you know, competitive treadmills and focused on minutia in ways that just increase our stress. They increase our stress and they also erode our sleep. So we don't really sleep as well as we could, you know, we're staring into screens, you know, and, and disrupted sleep, you know, messes up your circadian rhythms, it messes up your immune system, it messes up almost everything, your vascular system, uh, whereas, you know, a lot of hunter-gatherers, they're tired, they go to sleep, you know, and, and so, I think again, there's kind of very practical kind of lessons of just. Uh, Trying to extract the positives of our technology in our current environment while minimizing. Uh, THOSE harms. You know, I, I do think one lesson about the diverse types of diets that hunter-gatherers have had, uh, maybe means don't, don't overstress about what you're eating if you're, you know, at the level of like, you know, there's a couple of rules of thumb, more fiber, good. Zero fiber, bad, right? Uh, SO like empty carbs, you know, Processed sugar, added sugar as an ingredient and things, bad, you know, less of that, you know, good. You know, as opposed to like, does everything have to have a paleo label of approval? Uh, AM I eating, you know, the right this, that, and the other thing, you know, to the extent that, you know, like Michael Pollan's You know, advice if, if your grandmother wouldn't recognize, you know, the ingredients, then, then maybe don't go for that. Uh, BUT again, if nothing else, also just eating less, uh, than you otherwise. Uh, MIGHT, and, you know, one way I think of maybe it helps doing that is, um, To the extent that if we eat socially. And not while we're like watching TV and mindlessly just kind of shoveling food in, uh, you're probably less likely to overeat. So, you know, that kind of, you know, people wanna call that mindfulness, mindful eating, you know, that can make a difference. But, you know, all those are sort of like little lessons about how we can sort of capture some of the healthy aspects of hunter-gatherer lifestyles without being hunter-gatherers. You know, I do think there's probably another set of lessons that are a little bit harder to Incorporate, but. You know, on the infectious side of things, you know, most infections are bad, but certainly hunter-gatherer microbiome, gut microbiome is a lot more diverse than our more industrialized microbiome. Um, Hunter-gatherers have a richer, more diverse set of pathogens that they've been exposed to. Uh, AND one hypothesis is that their immune systems are better regulated than ours, and so they're less prone to autoimmune disease, uh, but also might be less prone to other ways that our immune systems can go awry. I mean, heart disease, in effect, is. You know, partly due to the way our immune systems, you know, attack our own, you know, little tears in our arteries, right? The way that Uh, inflammation is actively involved in part of that whole atherosclerotic process. And, you know, maybe hunter-gatherer, uh, immune systems aren't working in the same kind of way that affects those systems, uh, in a harmful way. And so, since our immune systems were designed to sort of attack pathogens, uh, if our immune systems are a bit awry, well, that suggests we really need to work hard to Make sure that our immune systems are better regulated. And one way that can maybe occur is maybe not obsessing so much with, you know, hygienic, super clean environments. Um. You know, you know, the 5-second rule of food has been on the floor for 5 seconds, you know, I tend to have like a 5-minute rule personally. Oh my God. Uh, HEY, but I'm healthy so far, as far as I know. Um. Yeah, so there's the little things. I mean, obviously, it's a, it's a, it's a nice balance, right? You don't wanna, you know, In fact, you know, expose an infant, you know, needlessly to harm, but, you know, at the same time, you don't want to be so sheltered and protected that you don't build those defenses. Uh, YOUR armies, uh, can go awry if they're not well trained. And so even like. Having your kids in daycare, uh, exposes them to lots of childhood, other infections in ways that if they're like kept at home and exclusively, you know, that they might increase the, the likelihood of, of having weird allergies or, you know, I mean food allergies. I mean, who had, who had nasty, deathly, you know, nut allergies, you know, 50 years ago. I mean, Those are things that are much newer uh now than, than the past, and we know it has to do something with our immune systems. And so that, that's still a work in progress because you wanna be able to add, you know, resilience, but you don't want to increase danger, right? So, people shouldn't be out infecting themselves left and right in the hopes that, you know, cause we just don't know enough and immune systems are so individualized that There's not a single magic bullet that that works equally well for everybody. But I do think we can be a little bit practical there, like, you know, don't bombard your system with antibiotics unless you really have to. Uh, YOU know, and there's good rules of thumb about, you know, those kinds of things. You treat an infection, uh, fever. Well, if it's 104, you probably should treat that fever. If it's 99 °F, you know, uh, wait and see, you know, that's, that's almost nothing. So I think there's a lot of those kinds of lessons, uh, you know, hunter-gatherers are also intensely social. I think, again, you know, some of these health fitness circles, you know, a lot of dialogue is, is on like what to do with our individual bodies as, you know, individual agents making decisions, but, you know, hunter-gatherers are so intensely social, you know, that to the extent that, you know, our social lives, a healthy social life, I think feel like. It, it, it, it leads itself to lends itself to just being motivated to eat healthy and to move your body and to do all these things. And, and yet that's not something you can easily prescribe, like, you know, take two pills and, and add two friends at the end of the day, like, and, and so, We don't know how to do that as well as, as all the other things, and yet it's such a key aspect of well-being that I think we do need to put a lot more attention to, to our social lives. And so, and that's something that hunter-gatherers do all the time. Um, SO yeah, uh, I don't know. That's a, a, a kind of laundry list of, of things, the easy things, uh, I think that we can implement in our lives to sort of capture some of the healthier aspects of hunter-gatherer lives.

2:11:54 Ricardo Lopes: OK, so Doctor Gervin, one of the things that I certainly implement is when I start to get tired, I go to sleep and it's already 77 p.m. here in Portugal, and I'm a morning person, so in a few minutes, my brain will start to shut down slowly, so let's. Perhaps wrap up our conversation here and the book is again Seven Decades, How We Evolved to Live Longer. I'm leaving a link to it in the description of the interview and Doctor Gerven, apart from the book, where can people find you and your work on the internet?

2:12:29 Michael Gurven: Oh, Well, there aren't very many Gurvens out there in the world. So even if you just put Gurven, G U R V E N, you know, you'll probably find my website. I post, you know, all of our publications on there and gives you a little bit more information about Me and the work in my lab. Um, I think there's some YouTube videos out there, probably some talks, uh, Yeah, I think it's the easiest way. My email address is on there if people want to get in contact. Um, YEAH, the book can be found pretty much. I hope anywhere you, you enjoy, uh, buying books, um, should be available. So, yeah, thank you, Ricardo. This was, this was a lot of fun. In fact, I'm seeing now over 2 hours, so it flew by, so that means it was good, great questions. Uh, GREAT conversation and thank you.

2:13:30 Ricardo Lopes: No, thank you so much for doing this. It was an immense pleasure. Hi guys, thank you for watching this interview until the end. If you liked it, please share it, leave a like and hit the subscription button. The show is brought to you by Enlights Learning and Development done differently. Check their website at enlights.com and also please consider supporting the show on Patreon or PayPal. I would also like to give a huge thank you to my main patrons and PayPal supporters, Perergo Larsson, Jerry Muller, Frederick Sundo, Bernard Seyaz Olaf, Alex, Adam Cassel, Matthew Whittingbird, Arnaud Wolff, Tim Hollis, Eric Elena, John Connors, Philip Forst Connolly. Then Dmitri Robert Windegerru Inai Zu Mark Nevs, Colin Holbrookfield, Governor, Michel Stormir, Samuel Andrea, Francis Forti Agnun, Svergoo, and Hal Herzognun, Machael Jonathan Labran, John Yardston, and Samuel Curric Hines, Mark Smith, John Ware, Tom Hammel, Sardusran, David Sloan Wilson, Yasilla Dezaraujo Romain Roach, Diego Londono Correa. Yannik Punteran Ruzmani, Charlotte Blis Nico Barbaro, Adam Hunt, Pavlostazevski, Alekbaka Madison, Gary G. Alman, Semov, Zal Adrian Yei Poltontin, John Barboza, Julian Price, Edward Hall, Edin Bronner, Douglas Fry, Franco Bartolotti, Gabriel Pancortez or Suliliski, Scott Zachary Fish, Tim Duffy, Sony Smith, and Wisman. Daniel Friedman, William Buckner, Paul Georg Jarno, Luke Lovai, Georgios Theophannus, Chris Williamson, Peter Wolozin, David Williams, Dio Costa, Anton Ericsson, Charles Murray, Alex Shaw, Marie Martinez, Coralli Chevalier, Bangalore atheists, Larry D. Lee Jr. Old Eringbon. Esterri, Michael Bailey, then Spurber, Robert Grassy, Zigoren, Jeff McMahon, Jake Zul, Barnabas Raddix, Mark Kempel, Thomas Dovner, Luke Neeson, Chris Story, Kimberly Johnson, Benjamin Galbert, Jessica Nowicki, Linda Brendan, Nicholas Carlson, Ismael Bensleyman. George Ekoriati, Valentine Steinmann, Per Crawley, Kate Van Goler, Alexander Obert, Liam Dunaway, BR, Massoud Ali Mohammadi, Perpendicular, Jannes Hetner, Ursula Guinov, Gregory Hastings, David Pinsov, Sean Nelson, Mike Levin, and Jos Necht. A special thanks to my producers Iar Webb, Jim Frank Lucas Stink, Tom Vanneden, Bernardine Curtis Dixon, Benedict Mueller, Thomas Trumbull, Catherine and Patrick Tobin, John Carlomon Negro, Al Nick Cortiz, and Nick Golden, and to my executive producers, Matthew Lavender, Sergio Quadrian, Bogdan Kanis, and Rosie. Thank you for all.