The Postmenopausal Longevity Paradox and the Evolutionary Advantage of Our Grandmothering Life History [transcript]

Written by Christopher Kelly

April 2, 2020

[0:00:00]

Christopher:    Well, Kristen, thank you so much for joining me this morning. I very much appreciate you.

Kristen:    Looks like a beautiful day there. 

Christopher:    Absolutely, yeah, it quite often is at this time of the year in Santa Cruz. I'm very lucky to be recording outdoors right now in the mountains of Santa Cruz. It's fantastic. Perhaps we should start with some disclosures. Are you a grandmother?

Kristen:    No. I mean, this is so tricky. What do we mean by grandmother? If you mean -- we use it in so many senses. I am definitely a post-menopausal woman. The way I think about the riddle of our life history and the fact that there are so many people like me running around, so many, apparently healthy, productive, post-menopausal women, which is we are the only primate where it's like that. Our longevity is remarkable, and this post-menopausal stage is really distinctive. It has interested evolutionary biologists really making major contributions. They've noted it and then they've just gone onto talk about something else because it's easier to simplify it away, but it is a distinctive clue to what happened in our evolution. So, in that sense, yes, I am a healthy, productive, post-menopausal human.

Christopher:    Excellent. Well, tell me about how you became interested in grandmothering in the first place. Where were you? Who were you with?

Kristen:    I don't think there was a single eureka moment. There's actually a long history of my -- I didn't start out as an evolutionary biologist. I started out really as a kind of garden variety cultural anthropologist. I did my dissertation fieldwork in Highland, New Guinea. I was a little quantitative but not that quantitative. I had collected data systematically on who gardens with whom and things like that. 

    I was here at the University of Utah, on the Faculty, and I was analyzing, still analyzing some of the data from my dissertation. There was a guy in the Math Department. I can tell you this story is such a long story if I start at the beginning. There was a guy in the Math Department I often went to for statistical advice. I told him what I was trying to do, and he said, "Well, we have a visiting professor this term who is interested in these things. You ought to meet him." I did, and he was amazing. 

    Oh, what is his first name? Watson, there are many Watsons actually. This is not one of the many. He was a biostatistician. He was a student of RA Fisher's, an actual student of Fisher's. He said to me, he said, "There's a guy on the faculty here who works on this stuff that you ought to meet."

    He set up a lunch with Eric Charnov in the Biology Department here, the theoretical biologist, and Charnov was amazing because here I was, thinking I knew all kinds of stuff. Boy, I had had some biology in my background, but I just did not know very much about evolutionary biology, and Charnov was so patient with me on my failure to know really fundamental things.

    He got me into reading the literature and just being astonished at, oh, my God, we could actually figure this out, sexes, aging. Wow, this is astonishing! So I had come to be really interested in trying to use some of the tools that people who study other animals are using that try to explain stuff about them.

    Charnov had been working on foraging strategies and building some pretty simple models but aiming to take into account the important pieces of the economics of foraging and using those tools to try to explain the variation in foraging theory, in foraging patterns in all kinds of animals. 

    At the same time, this guy joined the faculty here, Jim O'Connell, who's a paleolithic archeologist and who also thought there were some things from evolutionary biology, especially theoretical ecology that might be relevant. He joined the faculty here, having just completed a long post-doc in Australia.

    He spent a lot of the time in Central Australia with people who used to be full-time foragers, Aranda folks, trying to -- because he knew, as a, actually Western North American archeologist, to begin with, if I could just watch people who are trying to solve these problems of how you actually make a living, I would begin to have some clues about what I'm looking at in the archeology. 

[0:05:05]

    So, he came to Utah with MacArthur's Geographical Ecology in his pocket and with the notion that there are these big questions in what happened in human evolution that I had not really thought very much about and turned me onto those.

    Then Kim Hill came to Utah, having spent time in the Peace Corp in Eastern Paraguay. He had asked for a Peace Corp assignment with an indigenous population and so he had spent time with these Ache foragers in Eastern Paraguay. 

    So, Kim Hill showed up in a class of mine. I was talking about these things. He got really excited about it. So we decided we would take some of these models that Charnov was developing and actually go see whether we could measure the right things if we spent time with the Ache in the forest.

    We actually collected data on the time people spent searching and the profitability of the different resources, and we did all that. Could we explain the things that they were choosing to acquire? We did, and it was amazing. It turned out that absolutely, it was -- the simple models are really useful.

    It was also true that this was very unusual ethnographic situation where these guys, they move around all the time in the forest, which is actually the Brazilian highlands in Eastern Paraguay. They don't establish a really large domestic space because you're only going to be there one night most of the time and moving, so everybody is very close together.

    In the southern winter, it actually can get down to zero, in the winter, can be really cold and people not wearing very much, but just around the fire, lying on each other to stay warm. People are so close together that you can actually watch whose stomach all the food goes into. So we had all these data on the foods that were acquired and then where it ended up getting consumed. 

    Oh, there's another part of the story here where Hilly Kaplan joined our research team in this Ache project, and Hilly's dissertation was actually looking at that part of the data, who acquired something and then whose stomach it went into. Because of the close quarters, we had these enormous data sets, and it was possible to see that the things that a man acquired, did not go deferentially to his own wife, his own mate and his own kids.

    I had come to this project just assuming that the hunting hypothesis is the story of human evolution because that's in all the textbooks, and there are all kinds of reasons why everybody thinks that's the story. Here were these data saying this is the case in which that is not what's happening.

    Then Nick Blurton-Jones who was at UCLA, invited me and Jim O'Connell to join him. He had just been working in Southern Africa with Kung-speaking foragers around Dobe. He had developed a way of thinking about the way food was acquired that could account for the really long birth spacing that Nancy Howell had described for this population that was consistent with his background because he was actually a student of Niko Tinbergen's.

    He had started out as a bird guy and then he got interested in using a lot of the tools from evolutionary biology to look at this primate. What's going on with this one? So, he had been invited by Mel Konner because they had a mutual interest in kids, to go to Dobe. He built this model. It looked like, wow, this is so useful. He wanted to take it to someplace that was slightly different, ecologically. So, he started this project in Northern Tanzania with the Hadza, and he invited me and Jim O'Connell to join him. 

    So, here are the three of us, and each one of us had slightly different questions in mind. O'Connell, as an archeologist, wanted that one of the issues that was very hot in the early '80s in paleolithic archeology was what to make of these archaeological assemblages. There was a lot of dispute about it.

[0:10:09]

    Here was an opportunity in a place where it's modern people, of course, because that's all we've got on the planet anymore is us, moderns, and modern people who are using these powerful bows and arrows. So, they would go back that far in the archaeological record, but they are bipedal tool-users. 

    In this environment, also, there are all these carnivores that are going after a lot of the same animals. Many of the issues in the archeology had to do with how much of this is the hominids, and how much of this is the other carnivores and so on.

    So, O'Connell was focused on what actually happens to these big animals? How do people deal with a big, dead animal? We paid attention to every single one, every single big animal. These guys are very effective, aggressive scavengers. If a lion or a hyena had killed a big animal, well, you hear about it. There are all the circling vultures. There's no way you can hide this giant amount of meat, and everybody comes to the carcass.

    O'Connell was paying attention to the location of these sites, what kind of site it is, what was happening as the animal was butchered, and then what happened to -- how it was eaten, all kinds of focus on this. We were, as behavioral ecologists, we were doing systematic observations on everybody interested in both sexes, all ages, how they spent their time, when they were acquiring food, what they got for the time they spent, what it was worth. We were doing all that.

    So, here I was, spending a lot of time watching these old ladies in the sun. We were right on the equator. It's high, so it isn't really that bad all the time, but digging these deeply buried tubers which is the most energetically expensive way of acquiring clan food. At one of the first papers we published on this research was about how effective these old ladies were. The return rates they were getting was the same as the rates that the younger women were getting, but they were spending more time on those particularly energetically expensive ones.

    Grandmothers, they had not even thought of that as an issue. I still had in my head, what the heck are these men doing, because of the riddle that came out of the Ache work. 

    At the same time, Charnov, as I said -- you shouldn't ask me questions like this because I'm going to tell such a long story. Charnov was working on life history evolution, so theoretical biologist interested in explaining his focus, especially on vertebrates, and trying to account for how selection could shape this wide variation in life histories. Actually, it varies in interesting ways between birds and mammals and snakes and lizards but focusing especially on the mammals.

    The question was, what can account for the fact that we've got this mouse to elephant curve? Here are some mammals that take a long time to grow up and then they live a long time as adults. They produce babies at a very slow rate. At the other end, those little rodents, and they quickly grow up. They have lots of babies and die. He was building models to explain that.

    Of course I was spending a lot of time talking to him, still trying to get my mind around what a powerful tool selection thinking can be to try to explain variation. I was thinking about men and hunting as though that's the crucial thinking, and here is Charnov, his models were just about the females. 

    If you looked across the mammals, it didn't matter what the males were doing. The variables that he had put into his pretty simple optimization accounted for this striking regularity and the allometries in all of these features of life history and thinking, wow, wasted life, what could be going? 

[0:14:57]

    Then we were looking at something and not seeing it until you know to look for it. Because our data sets showing the time that women spent at different foraging tasks and what they got for it, so we had this variation across the ages, and we had this variation across little kids. 

    There was the evidence that the little kids, at the things that are the year-round staple, are things that little kids are trying when they're little. They're trying to dig these tubers. There are some kinds of tubers of underground storage organs that they're pretty good at, but those are the ones that are close to the surface. The deeply buried ones, they're just not big enough or strong enough to be able to do it, so they have to depend on their moms. 

    We were waiting, people, I wish we'd wait more often than we did, but we were, regularly enough, that then, out of the data, came this evidence that the way the kids were growing, the way they were gaining weight depended on their mother's foraging until she had a new baby. Then there was no link, and the correlation was with grandmother.

    So, right there with these modern people, using this suite of resources, we saw that moms could move on and have that next baby because the kid who could still not feed itself was being subsidized by the productivity of grandmothers. These are things that I don't think I've talked about enough, but in the last little while, it has been clear to me that it's just so important to underline the economics of these resources because it's really different from what goes on with other mammals, with other primates, with other apes certainly.

    If we talk about other apes, now we've got this great data from chimpanzees that shows that chimpanzee babies are already, even while they're still nursing and their mom is carrying them along as she's foraging and feeding herself and they're drinking mother's milk, but they start to acquire the same things she's acquiring before they're even weaned. Then when they're weaned, they feed themselves.

    Now we've got really good data. Julia Badescu and collaborators at Ngogo have shown this in the isotopes. Melissa Emery Smith and collaborators at Kanyawara have shown this in the behavior, how the chimpanzee kids, as soon as they're weaned, they're fully competent foragers on their own, not even close for this primate, right?

    The kind of foods that these Hadza guys are depending on in this savanna environment -- so, the other apes are in the forest, and we know that those forests were retreating with ancient climate change. The savannas were spreading. If you are going to be in those savanna places then the things that are payoffs, year-round, for adults are not directly accessible to little kids. So, mom is going to have to subsidize them longer which would make her birth spacing even longer, but she's not the one that has to do it.

    The way you actually are an efficient forager on these things is not the kind of one-at-a-time feeding that characterizes what the other apes do. You do it in these piles. There is this pile of tubers and if we add cooking, which is another issue, there's all this processing. Here is a thing that is an opportunity for all those little appropriators to be in there, taking shares.

    If that's the kind of foraging you're doing, it's going to be the case that the women who are still fertile can have the next baby sooner, without losing the older one because her whole trade-off surface has changed. Now it's the case that those little kids are taking advantage of the foraging of the older females. 

    So, out of all this, came, recognizing that, wait a minute, if we go back to Charnov's model, one of the regularities that he saw across the mammals was this relationship between age of first birth and adult mortality or average adult life span. He had actually published a figure just for primates to show that this holds across the primates, and it included this primate. 

[0:20:06]

    The book was published in '93, and that was the time when we separated the apes, the Pongids and the hominids as two separate taxon. Now we know that actually, we belong to the same family. We're all hominids. Chimpanzees are actually closer to us than to gorillas. Anyway, they were separated there. Yet the human point fit on regression, and it should have been. How is that possible? I should have recognized that in '93, didn't.

    Coming back to it, oh, look at that. The way in which that would make sense, given Charnov's model, is if that post-fertile period was actually subsidizing the fertility at the younger ages. If that were true then there is another feature of his model that, within the model, should stand out like a sore thumb, and that is that it should mean that the birth intervals are way shorter than would be expected for a mammal with our age of first birth. Voila, there it was.

    The first papers write back to back. The one where we really focused on that theory were going back, looking more closely at what the best data were at the time for the other apes, what the best data are for this ape but in foraging circumstances, so, among hunter-gatherers. We showed how well the human case fit the model if we included the contribution, the future generations, the future gene pools that came from the subsidies of the older females.

    This is dangerous, Christopher, because I can go on, and then -- 

Christopher:    It's fantastic. You're interviewing yourself. I don't even need to be here. This is brilliant.

Kristen:    No, it's a terrible way to do it. It's so boring. I'm telling it as a history. Then we were so lucky to have this mathematical biologist, Peter Kim, get interested in the problem because you could say, "Oh, yeah, well it fits the model but, come on, how do we know that happened?" Of course, how do we? 

    You can build models. The thing about Charnov's model is it was just about the females. So, Peter took this grandmother hypothesis, assumed the regularities, the specific allometries that are in Charnov's model, and made it a two-sex model. It had both males and females and then built an agent-based model to see whether if you started out with a great ape life history, especially paying attention to chimpanzees because we have the best data for them.

    If you start out with that and then you allow those very few females that are out living their fertility because boys are rare among chimpanzees, but you now allow them to subsidize the still dependent juveniles, and there you can see in the figures in the papers where all it takes is that.

    Then what happens in these agent-based models is life history goes from something that looks very chimpanzee-like to something that looks very much like what you see in humans in those foraging circumstances, with about a third of the adult females past the fertile ages. So, very exciting stuff. See, now, I can -- it just goes on and on. 

    When we were talking earlier, I said, I just keep being surprised there's another thing. We can talk about implications for because now we've got two sexes, but everybody is living longer. The thing is fertility is ending in the females, not in the males because you continue to make sperm all the time. 

    Mammals, generally, spermatogenesis continues throughout adulthood. In female mammals, generally, there's also some similarity with birds. Females start out with all the oocytes they're ever going to have. In us, that's when you're still a five-month old fetus and then you just start losing them. So, reproductive physiology is really different in the two sexes.

    Now, with a life history like ours, you've got these fertile ages for females and now, all these old guys who are still fertile. Well, the only way that they are going to get genes into future generations is by mating with the still fertile females. We get a bunch of stuff about mate guarding.

    A thing that I will definitely want to talk about is the brain side of the story and the social cognition side of the story for us, as a primate, but why it is the challenges to infants coming into a life history like ours that set up the sorts of things that really rang our bell, cognitively, and shape us to be doing this. Here I am. Do you see what I'm trying to paint here as a story?

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    This is a thing that we -- it is for us. It's what we always want to do all the time. There is a story here about how that is a thing that came with the peculiar life history that marks us out. So let me pause, stop ranting, which of course, there we have the danger, I am likely to do that, and take a breath and say, did that make sense?

Christopher:    It absolutely made sense. What you're saying is that humans are perhaps unique in their ability to reproduce more rapidly. The space between babies is much shorter, and the reason we can do that is because we have other people, especially grandmothers, that can invest in that initial generation while mom goes onto have more babies. 

    My question is, is it unique to human? Why is it that -- I sometimes heard people refer to humans as the third chimpanzee. You've got chimpanzees, bonobos and then humans. If this strategy is optimal and comes with this increased life expectancy, why is it that just humans do this and not chimpanzees and bonobos?

Kristen:    Because -- so going back to the thing that set this off -- if you are a chimpanzee or a bonobo, then what's happening is as mom is eating the soft fruits and so on, and the THV if you're a bonobo, or leaves and so on, in the forest; mom is carrying you along. You've got her attention. You don't have to do anything to get it. 

    She's holding you, and she is feeding herself. You begin to do that as an infant before you're weaned. Then you can do it independently when, increasingly, less and less of what you require comes from mother's milk. Now you're feeding yourself, and now she has another one. Your social relationship with her may be important, but now you are feeding yourself.

    Well, a very different setup comes from colonizing those savanna habitats and taking advantage of resources that are not this hand-to-mouth thing, that are not things that little, nursing infants can possibly begin to feed themselves directly on. It is the case that as you are foraging for these things that give you a high rate as an adult, it requires the strength of an adult to do this.

    If you're going to exploit those, you don't do it one at time. You don't do, oh, that's part of a tuber, let me stop and eat that. No, because now, you've opened the whole getting the rest of that one and the one next to it and so on. In fact, having somebody doing that near you means you're, neutralistically, getting higher returns. 

    Then if you cook them together, what you have is a whole different foraging economics and the opportunities then for both adults and children, but especially for those little kids, means that mom doesn't have to be the one that's continuing to feed that kid.

    The whole thing about slower maturation that goes with the increased longevity that all of this is favoring because of the productivity of the older females which is making all of this possible, so, all those pieces go together, that mean that if those are the kinds of resources that you're exploiting, a bunch of things follows in the ways in which there is interdependent resource acquisition, which we do not see in any other primate. 

    I mean, within chimpanzees, chimpanzees hunt. This is kind of, well, maybe a red herring but always has been of interest. I paid a lot of attention to chimpanzee hunting when I still thought, oh, the human evolution is all about hunting. What's the difference between what chimpanzees do and what humans do?

    One of the things about chimpanzee hunting is the ones who end up eating most of the monkeys that they hunt are the males. It's a whole different story that seems really more to do with politics among the males. The patterns of food acquisition, the fundamental issue of getting the nutrients you need to carry on and do what you do, is so different if it's these savanna resources that you're exploiting.

[0:30:15]

Christopher:    I see, I see.

Kristen:    So, if you're a gorilla kid, mom is eating these leaves, and you're starting to eat them too, while you're still a nursing infant and then you're independent as soon as you're weaned. Think about your two-year-old, think about your two-year-old, what if he had to get his own lunch? That would -- yeah.

Christopher:    Yeah.

Kristen:    Right.

Christopher:    Yeah, not happening.

Kristen:    Not happening, not happening, and the allometries are also part of the story, by which I mean these life histories feature scale. It is the case that there are primates that have shorter adult life spans, mature earlier, have shorter intervals, so it's not that we have the shortest. It's that they're so short for an ape. 

    Again, because we have this later age of maturity, so there are all kinds of reasons why later maturity goes with slower maturation, goes with increased longevity. Those pieces were in Charnov's model already. These two things are happening in our evolution that the duration of development is slower and weaning is earlier.

    If we start to throw brains into the story, which I completely ignored for a long time. I thought, we've got all these other tools that are so useful. Everybody thinks it's all about this big brain we have, and that's the story of our evolution. Now I happen to run across Barbara Finlay who is a cognitive neuroscientist, have taken on board what she and her lab have been doing for more than the last few decades about what actually runs the variation in brains across the mammals and its duration of development, and that depends on longevity. It's duration of development that accounts for why our neocortex is so big because what -- and Finlay and her group have explained all this. 

    This big brain goes with this life history, and the thing that really sets up all these interesting features of the cognitive ecology that human infants confront comes from the fact that brains are, they're going to get bigger. They're developing more slowly, and weaning is earlier. Wow, so you've got those things. If you take on board the allometries and you look at our weaning age compared to what would be expected, we are just really outliers. That should have been the focus of attention. 

    Now that I see these two things, this extremely early weaning compared to these aspects of maturation and the post-menopausal survival, that these are linked, in a way, that sets up the cognitive ecology for human infants that then makes whatever because your mom, likely, has another kid now. She's stacking up these dependents, yet you're completely dependent on attention, support, tolerance, all kinds of things, from other conspecifics. You want them to like you. You want them to support you. You want to -- and a whole array of things that then explain why we are so socially precocious. 

    Human infants, even though they're just babies, remember when your two-year-old was -- I mean, now, a toddler sounds like it's rattling off stories and so on by two, but remember when that baby was just a baby, unable to do anything, motorically, and yet so prepared to be engaged and smile at you. You just melt. Oh, you just want to get a giggle out of that kid, and a whole array of things going on there that are --

    This is where Sarah Hrdy's insights about the cognitive ecology of babies in our species, given that they don't have the full engagement of their mother as a chimpanzee mother is fully engaged with his kid because she has only got this one at a time and only when it's independent that she’ll have the next. That's not what we do, and that sets up these challenges for human infants with a whole array of consequences that, I think, developmental psychologists have been paying attention to. Most of them not focused so much on the evolution story, just trying to imagine this. Here is a baby coming into the world. How does it figure it out?

[0:35:11]

    So, there's a long history of developmental psychology of trying to both describe and explain that, and now I see the links between what they've been talking about and this peculiar life history that begins with the move into these savanna resources and the productivity of older females and so on.

Christopher:    If you would allow me to raise --

Kristen:    Please.

Christopher:    -- a common objection, isn't it true that living past child-bearing years is the direct result of modern medicine?

Kristen:    Oh, I'm so glad you raised it. My longtime collaborator, Nick Blurton Jones, if he were here, he would be cheering that because he's the guy who has done all the heavy lifting, demographically, in our Hadza project. Because lots of skepticism about the kind of longevity that you see in living populations, how far that goes back in time, is in the literature.

    When Nancy Howell, who was the demographer for the Harvard Kalahari project, when she reported that, oh, look, these are all of these -- this substantial fraction of the population that is over 60, there was a lot of skepticism about that. She took a lot of heat from people who should have known better. There was a lot of argument that, oh, she used these models. Because she was trained as a sociological demographer and used these models to try to figure out how to do demography on a population where you can't say to people, "What's your birth date? Let me see your driver's license."

    Imagine trying to do this with non-human animals where the chances of figuring out how old everybody is, are so difficult. It's no wonder that it took so long to begin to have data on that, but there are a lot of human populations in which figuring out how old everybody is, is really tricky and to estimate what's the likelihood of dying at a particular age and then you would have, you'd know what the survival curve looks like. Boy, is it difficult to do that.

    The idea that, gee, now we've got all these old people floating around, and we're worried about them. We're worried about us now because in the current scare about the coronavirus, but the notion that there weren't any old people in the past comes partly -- and I actually hear this from people who are really smart and they know about stuff that I don't know and I want to know what they know. 

    One of the things that's really misleading is to use the parameter life expectancy because life expectancy is an average. If you use that to characterize a population, life expectancy at birth, and if there's high fertility and there are a lot of dying babies, dying children, then you have a lot of really short life spans that go into that average. 

    For example, in the three best demographic studies of foraging populations; one is the Ache, and that's Kim Hill and Magdalena Hurtado; one is the Kung, that's Nancy Howell's work; and then the third is Hadza, this will be Nick's work; the Hadza, life expectancy is less than 40 in every case, but that's because of all the dying babies and children. If you actually make it to adulthood and you're female, your chances of living past your fertility are way better than not. I don't have those numbers in front of me. It's like 70% of more, if you make it to adulthood.

    So, what has misled us is looking at -- a wonderful paper at the beginning of the 2000s, Oeppen and Vaupel -- I find myself disagreeing with Jim Vaupel about a lot of things, but this paper was so important. What they did was they pulled together life table data, demographic data from all over the world and pulled out the nation -- so now we're talking about societies that have nation states and where there is census data. They pulled out the winning nation for each year, beginning, I think they started in 1850 and then showed what happened each year, picking the winning nation.

[0:40:07]

    They showed this march an increase in life expectancy that was just extremely regular, all the way up to wherever they ended, which was not very long before they wrote the paper, see this increase. The thing that is fueling that is the decline in fertility and infant and child mortality. So, if you take Sweden, which was the winning case in 1850 -- this is an example I've often used in talks. I should remember the data better. I think life expectancy in Sweden was 45.

    In Oeppen and Vaupel's data set, you don't get life expectancy past 50 until the beginning of the 20th century. So, there's a good census for Sweden. You can look at that at the life table, and there you see the same things that you see in these foraging cases. A third of the females are past the end of their fertility, and the thing that is making that average low is not that there aren't any old people, it's that there are a lot of short lives that go into the average.

Christopher:    Yeah, it makes sense. I wonder why anyone uses that term, life expectancy, so incredibly misleading. Same thing, how much damage has been done to people's understanding of humanity by that term?

Kristen:    I can think of so many examples of things where using an average is so misleading. Yet, if you can only know one thing, sometimes statisticians will say, "If you can only know one thing, the expectation is especially valuable." So, there you go. I could then talk about these issues around hunting. If you take the average that is contributing to the diet from these occasional bonanzas, then you think, oh, it's all about meat, and that continues to be the thing that's in the literature. It's the same kind of error.

    Those bonanzas are big deal. Everybody pays attention, woohoo, this party, party, but when it comes to eating every day, when it comes to the kind of thing that's required for selection to actually favor the kinds of shifts that we're talking about, it has got to be this reliable daily thing, and those bonanzas are anything but. But if you look at the average, so, yeah.

Christopher:    Talk about estrogen. Something else I've heard for menopause is that maybe nature is done with you and that hormone replacement therapy is a good idea because your estrogen is going to go away. You probably don't want what nature wants for you and so perhaps you should think about replacing those hormones. I'm not sure that's necessarily true. What do you think?

Kristen:    Yeah, well, I think the data that have followed from concerns about the heavy emphasis on hormone replacement, showing how dangerous it can be, and a lot of studies that then got stopped as a consequence of recognizing that, yes. So, let's take it in the form of a riddle because it is. 

    You need estrogen for all kinds of things, for all kinds of things that go on. You need it as well as I need it. My brain needs it. So many of my tissues need -- there are so many parts in my physiology that require it. Yet, here I am, post-menopausal. I am getting no estrogen from my ovaries. What the heck, where is that coming from?

    Well, the thing about these steroid hormones is, with the right accessory proteins, the peripheral tissues convert other steroids into the estrogen they need. You get the estrogen in your peripheral tissues from the conversion of testosterone. I get that estrogen in my peripheral tissues from the conversion of adrenal androgens, probably DHEA, DHEAS.

    There was, maybe still is, a Canadian endocrinologist. I have not ever met this guy. I think he's retired. Maybe he's not around anymore, and has said, for instance, some strange things about evolution, but he was very interested in trying to understand, as an endocrinologist, what is going on with all these hormones. One of the things that he concluded -- humans were his animal of interest -- one of the things that he concluded was that even during the cycling years, women get 75% of their estrogen from the conversion of DHEA, DHEAS.

    So, the notion that it requires ovarian estrogen to run all these things -- well, once again, your brain needs estrogen. You don't have any ovaries probably. So, we've got the recognition that these steroids play important roles but, boy, this amazing physiology that nature has given us does really incredible things in conversion of one steroid into another.

[0:45:22]

    In a lot of ways, the connection between hormones and fertility -- there was all kinds of weird stuff about how you'll slow aging if you inject it with monkey gonads and -- I mean, there's a lot of crazy stuff that went on when people made the connection between hormones and other things. A lot of it, when you look back on it, it's like bleeding people when they had various kinds of pathological conditions. Good heavens, it's amazing that people live through it.

    So, physicians who have a practice with women who are experiencing uncomfortable symptoms associated with perimenopause and really want to know what to do about that, I don't have patients like that. It does seem to be the case from the literature I read that we have this very interesting feature -- and you may actually know more about this than I do, Christopher, because it may be something you follow more closely.

    There is this very interesting thing about testosterone which, once again, men are making testosterone throughout adulthood, starting well before that, but if you look at circulating levels of testosterone in different populations, it is Western men -- there are probably more data now. I know this from a while ago when it was a Boston sample, compared to a few other cases. One of them was the Ache.

    Remember we started out with the Ache, these guys in Eastern Paraguay. Those guys are, they're extremely buff, and they do this very energetically expensive thing, running through the closed forest when they're hunting. If you compare circulating T in Ache men with age -- this is Richard Bribiescas' thesis -- you compare that to the levels with Boston men, what you see is that this young age, high T is missing among the Ache. 

    I think the data sets are more complicated, but I think we have a similar thing with women that levels of estrogen can be high in populations like ours that are under-exercised and overfed and under-diseased and all those things. We can afford to have these high levels compared to populations that are experiencing an ecology that's a lot more like most of our history in which there's more exercise, less food, more disease and so on.

    To segue back to the question of perimenopausal symptoms, is that it could well be that if associated with other metabolic characteristics of our population, that that makes perimenopause -- associates it with discomfort in ways that are not typical. There are anthropologists, I think of Lynnette Sievert who has looked at menopausal symptoms in lots of different populations using various kinds of devices like putting monitors on women that are measuring their body temperature and also giving them something to record when they think they're having a hot flash, and finding disconnect between what's happening, physiologically, and what women are reporting. Her work is -- 

Christopher:    Oh, interesting.

Kristen:    -- continues to be interesting. All those things are the variation among populations, depending on probably not only the current experience, but also so much about earlier parts of life and development that continue to affect us through adulthood.

Christopher:    Yeah, and it's relevant here. I think what's interesting to think about for men is how the social structure has changed, and the facultive role of parenting in men. If there's no grandmother, there's no alloparent to take up the slack, then perhaps the man will step in. I've learned from Sarah Hrdy that there may be some physiological changes, including an increase of prolactin, decrease in testosterone. That is indeed what you see on the beach of Hawaii, is the man bottle feeding a baby, dripping in prolactin, with moobs. That's what I just saw while I was on holiday recently. It did make me think about that, the facultive role of the father figure. 

[0:50:00]

Kristen:    You think about these ethnographic cases in which the way things are arranged, this is in some traditional societies, is to keep young men away from children and babies. Don't let any of that happen because we need them to go off and be fierce and compete with each other. I've heard Sarah Hrdy talk about imagining that you have a bunch of, I don't know, military guys all sitting around and throw some babies on the table and see if you can change the mood, yeah.

Christopher:    So you're not seeing that. You might think then that some of these symptoms surrounding perimenopause might be mismatched diseases, as perhaps Daniel Lieberman would say.

Kristen:    No.

Christopher:    You're not seeing hot flashes in the Ache or the Kung or the Hadza, for example.

Kristen:    Well, I would have to say that it isn't something I ever looked for or looked at. I've learned so often that I can be staring right at something, taking notes about it and not see what I'm looking at, but, no, I was completely unaware of that being an issue. The burden of evidence looks so much like -- 

    There is actually a historian who has written a book about the history of menopause. Although I think she isn't bought into the grandmother hypothesis, but I think that she is onto something that it surfaces as an issue in our contemporary socioecology, in ways that wouldn't even come up in, for example, in --

    One of the questions that Hadza women would ask is, why does she have more kids than I do? So, there would be questions like that. Some women are more successful at keeping babies alive. Let's say, grandmothers really doing their job in those cases, and those things do vary. Nick has shown that having a grandmother has this huge effect on the chances that a kid will survive in the Hadza case. So, I think recognizing this feature of our lifetimes that we even have such a thing is almost a construct of our culture that we make it a big deal because of our focus on youth and health. 

    One of the things that makes me worry sometimes, young women, so let's say college students, who don't know about our life history and don't know about this evolutionary story, I think it's so easy for them not to take on board that this is a feature of being human, and especially what's happening with our socioecology where you don't want to have a kid yet until you're established. You think, I want to make sure that I have a good job because I want to be able to -- therefore the age of first birth keeps getting later and later. 

    Women think, well, as long as I'm healthy then I'll just keep putting it off until, without realizing that menopause is part of our evolution. Although every once in a while, it does get into the magazines, the biological clock issue. I think it is that women do not realize that you can be very healthy and yet the readiness with which you conceive begins to decline, at least according to the IVF data sets. Maybe there are some problems with those. But it actually begins to decline in your late 20s.

    One of the things that -- so, with Ken Smith who is a demographer and who runs the Utah Population Database, he and I looking at -- so the Utah Population Database is this incredible resource because it records all these births and deaths for the colonists who came to Utah. It actually starts in the 18th century and so you have these long family histories.    We were using that data set for something. 

    One of the things that, it was so striking as we were looking at these was seeing in Nick's data that there are a large fraction of Hadza women who will not have another birth after 35, and it was essentially the same in this very pronatalist population we were looking at in these Utah colonies, that it's about the same fraction. 

    Once again, there's all kinds of individual variation. It's like, what is the age of menopause, and why is that hard to measure? The WHO says, you measure it when one year has passed since your last period. Well, what woman knows that? The data that are available show there's a lot of variation. It can range from 40 to 60 actually.

[0:55:10]

    People who have studied menopause find that the age at last birth and the age at menopause, they can be ten years apart, at least. So, wherever we started with whatever is going on with both parenting and family structure in our current socioecology, the extent to which knowing something about our love life history allows people to make better choices, I don't know whether that does follow or not.

    I remember having a conversation with a student last term. We were talking about some feature of our biology, and she was saying, "It's not fair." I was saying, "Yeah, I've always thought that it isn't fair that I can't fly, damn." Although there was a time when you could get on a plane, I guess.

Christopher:    That's true. So, talk about the implications for cognition. You hinted at that earlier. If the woman's role is changing and you're better off investing in your grandchildren than you are, having your own kids; what does that mean for your cognition?

Kristen:    Well, the hook to cognition that, for me, is the one to emphasize is the one that Sarah Hrdy saw. As I said, it amazes me that I didn't see this, and I didn't see it until she -- because I think she wrote way earlier than the 2009 book. It's just that in the 2009 book, which people keep citing as 2011, maybe it was reissued then. Anyway, this is "Mothers and Others." 

    This is where she makes the connection to what Michael Tomasello has been talking about with this shared intentionality thing, that we have this appetite to try to be on the same page with others and find ways to do that. We have those concerns. She links that to the challenges to infants, given the moms moving on, having the next kid before this one is independent, mom having -- 

    She talks about ambivalent mothering, and she has pulled together really relevant data on this question. It is, following her on this, it is, in our order of primates, for the most part, the danger of infanticide to infants comes from males. This is another place where her work was so groundbreaking on understanding male infanticide and then counter-strategies to that.

    We are an unusual primate in that it is the case that it's moms who sometimes kill their own kid. Her label for this ambivalent mothering connects it to this feature of our life history so that this baby that I'm just about to have, I've got these other kids who are still dependent, so this issue of how I decide to allocate my limited resources among these things is going to make me very sensitive to discriminative solicitude, making choices about where to put my attention and effort. 

    That, as she argues, sets up these amazing challenges for infants. Here is this newborn, and it does not have, as a birthright, full maternal engagement which, if you're another kind of primate, when you have that baby, you don't have any other dependents, so that's where your attention is. Well, that's not true for us, and that sets up these challenges -- this is her way of framing this -- sets up these challenges for infants that then means tendencies and capacities that are effective at soliciting engagement, come to be so important for likely survival through infancy.

    Then, linking back to the arguments that I've been making about this interdependent foraging, those things continued in ancestral populations because you are still dependent on others even after you're weaned. Therefore, this appetite for social engagement, for shared attention, for this thing that Tomasello calls shared intentionality, is enormous. 

[1:00:03]

    Tomasello's experiments, Esther Hermann was the first author on this paper, but it's the one that's so frequently cited, where they did experiments with orangutans, chimpanzees and then little kids. The little kids were, on average, about two and a half, just like your son and the twins. 

    They were all given similar problems to solve. When it came to the physical problems -- I forget what they were, object permanence and things like that, I should remember -- it was pretty similar. They were equally good, but when it came to a social cue, identifying, contributing to the problem and the solution, well then the kids are really different.

    What's underlying there is, that now takes me back to what developmental psychologists have been saying for decades, that there are these core domains of knowledge. There's baby physics, which is about stuff like gravity and object permanence; baby biology, which is about how animals and plants are living things and that's different; and then this third thing, baby psychology, which is about, what's the intention of that individual?

    That third thing -- the first two are baby anythings, have to do that. They have to figure out gravity and object permanence. This other thing with the preferences, the intentions of other people, of your conspecifics are absolutely crucial to your survival. 

    So, that whole domain of getting your brain wired to attend to that, to make predictions about that, to adjust around that, your brain is wired to prioritize that. Back to the things I was saying about brains before, that this brain is developing really slowly to be bigger. This wiring is going on so early, getting wired to that as just taking priority over so many things, and that kind of prioritizing reputation is that -- 

    Do you know those experiments from the Yale Baby Lab when these are just tiny infants? I forget how old they are, less than a year, way less than a year, but where they showed them shapes, they showed them cartoons and shape going up the hill and then the bad shape pushing it down and then the good shape helping it.

Christopher:    Oh, this is something familiar.

Kristen:    Yeah, I'm sure you've come across that. What they find is this really big effect that the babies prefer the helpful ones, so, paying attention to reputation already, and there are all kinds of reasons why that would be so important for survival. So, tendencies to do that, get wired really early and then they continue because, again, in ancestral circumstances, you're still dependent. You are -- all these other individuals where the foraging is so interdependent, that's different from what we see with other primates and with other apes.

    So, the whole cognitive thing that fluoresces in us, it was Hrdy's insight to link that to this feature of our life history, then that continues through life. Grandmothers were babies once. This is another line from Gopnik, the developmental psychologist, work, talking about -- I told you "The Scientist in the Crib" is the title of one of the books, and she and another collaborator say, "We're not saying that scientists are babies -- I'm going to screw up the quote, so maybe I won't give it, but that scientists are grownup babies. I would say we're all grownup babies. This is stuff that got wired into us early on, and it continues through life. We care about reputations and a whole array of other things.

Christopher:    I thought you were going to tell me about implications for grandma. If the whole reason why you're still here, age 60 and above, where all the old chimpanzee women are gone, is to invest in your grandchildren, what does that mean for your cognition? Is there something you should be thinking about if you don't have access to grandchildren?

Kristen:    Well, you know the famous bumper sticker which maybe has proliferated now, the retired couple with the bumper sticker, we're spending our grandchildren's inheritance. Right? Yeah, you mean, does having this life history suggest that, for the good of future gene pools, we should be doing X? I'm too much of an evolutionary biologist to be very comfortable with anything that has this good of the group, good of the species, good of the population flavor.

[1:05:20]

    I think the shared intentionality thing is just as big a deal through all the ages, and I think that neuroscientists would talk about how the plasticity of brains, I underline this, being wired early for these particular things in us, but there's a lot of plasticity that continues through life that is adjusting to current circumstances, but what we've been experiencing matters. 

    This reminds me of a story that a colleague at a conference, she's Japanese, lives in Japan, and for reasons that I don't quite recall, we were talking about -- and I think her mother is in an old folks home. We were talking about the use of robots. There's a name for these little things that squeak that seem so cute. There's the baby Yoda story of course where everybody is just so excited about baby Yoda. Isn't he cute?

    She was telling me that her mother had one of the robot-like things that was regularly doing something, delivering to her, maybe squeaking at her, I don't know. The, the place where she was, they got a new generation of robots that were much more human-like. They had things that were more like faces. Her mother experienced the new robot, and she was so sad because she was so used to the other robot. She wanted it back. She had become so attached to that robot, and this thing --

Christopher:    That's so sad.

Kristen:    -- that is, it's part of this. Relationships matter so much to us. We're so invested in them. In fact, I told you that when I was first reading Sarah Hrdy's "Mothers and Others," it was right before it came out. I had a free publication copy. I was reading it on an airplane, and the first thing I thought about was that helps explain the grief that we feel when we lose a partner, that this thing with a long-time, close friend or spouse or somebody that we have shared a lot of things with, when we lose them, we lost so much of who we are. The sense of grief that goes with that is part of this shared intentionality thing and the grandparent connection to grandchildren, just like the parent connection to children and just --

    Of course I have lots of ideas about what, in ancestral populations, what hunting was about, what is going on with the evolution of our parent habits and what is going on with male-male competition, which I think is such a huge thing. I don't think any of it is at all contradictory with these really strong relationships that men can have with either their own kids or somebody else's kids. It's part of this social cognition that we all have and that we can become so attached to particular individuals that we then have done things with, engaged with, know, and it becomes a part of our stories about ourselves.

Christopher:    Can you talk about -- have you any thoughts about the implications for how we organize society today? You spend however many years investigating the importance of grandmothering and then when I look around me today, I see those people quite often isolated from the very people they should be investing in. I wonder what that means for us, as a society today, and if you have any thoughts on it.

Kristen:    Well, yeah, I register the same thing. One of the things that people who live in more communitarian context and then they visit the United States, it seems so cold and cruel, and the whole nursing home thing that seems so, really, have we come to that? There is a thing that is associated with the shared intentionality thing. I wonder if I can say something coherent here. I'm not sure that I can but that because we are so attached, we don't want to lose the people that we're close to. Of course that fuels our enormous medical establishments to try to slow aging, to try to save people who would otherwise die, to do everything we can to keep them with us.

[1:10:21]

    Again, I'm enough of an evolutionary biologist to think that a result of natural selection is senescence. That is, again, part of our evolutionary legacy of a history of natural selection, but the attempts to try to keep people alive as long as possible is so easy to understand. To some extent, it's successful. 

    One of the things that I've spent a little of time on is looking across what goes on with the demographic profile of different populations, and one of the things that characterizes all populations, not just human ones, but there's all this heterogeneity, individuals who are a lot different in all kinds of ways.

    In context, where there is high mortality early on, the more vulnerable are more likely to die earlier. As you keep moving through the ages, you get a more and more select subset of individuals who have had a lower probability of dying all along, and they're the ones who are left. 

    There is a famous feature of survival curves that's called the Strehler and Mildvan correlation that shows that the higher the, what's called the initial mortality, which is supposed to be an estimate of just how dangerous things are, the way it relates to then the rate of increase through adulthood in mortality; that the higher the overall mortality is, the shallower the slope. In other words, it makes it look like higher overall mortality means slower aging. That sounds crazy. That doesn't happen. How can that be?

    One interpretation of that is one I already suggested, that if the mortality is very high then you have this increasingly select subset in populations like ours where very low fertility, and even though we worry about the high infant mortality that we have, it is astonishingly low actually in our population. 

Christopher:    Right.

Kristen:    Because we do everything we can to not let people die, it means that as we move through those ages, the heterogeneity is still there. That means it's not just the most robust that are still left. It's all of us. Those of us that would have died of something else, we're still there. That helps explain why it looks like then the mean increases faster.

    All of this is connected back to this idea that we don't want the people we're close to, to die. We spend all kinds of things trying to prevent that. People write now movingly about the terrible deaths that people end up having in hospitals, with all kinds of money spent and strapped up to all kinds of stuff which seems so awful, and other ways in which we do not handle death well in this society. We're always trying to prevent it. 

    We have this contradiction that we don't want people to die, and so they end up, often, dying in ways that are undesirable, that they would not desire. This is maybe old data, maybe outdated, but I remember a few years ago, reading that the people who are the ones who work in medical facilities where they have to do this, who are asked to check boxes about Do Not Resuscitate, they all say, "Do not resuscitate," because --

Christopher:    Yeah, I've heard about that data. That it's one morphine, nothing else.

Kristen:    Yeah, because they know with what the odds are, it will just be this huge, enormous expense and a not pleasant death.

Christopher:    I've just finished reading "Natural Causes" by Barbara Ehrenreich which is a fantastic book. She wrote about this, that you're not extending life. You're extending death.

Kristen:    Yeah, absolutely, right. Well, I haven't read it, but she's amazing, so I should put it on my list to read. 

Christopher:    She's a woman scorned, but she's very, very good.

Kristen:    Oh, scorned for that?

Christopher:    Well, no, just in general because she's quite cynical, you might say, but she writes so well. I really enjoy her.

Kristen:    Right, well, isn't she Nickel and Dimed? Or is that somebody else?

[1:15:00]

Christopher:    That's exactly right, and I forget, oh, Bright-Sided, Bright-Sided is the other one. It's super good.

Kristen:    Oh, I haven't read that one, yeah. So, I'm…

Christopher:    Yeah, it's a book about positive psychology, very good.

Kristen:    … Behind. I have to catch up.

Christopher:    So, tell me about your future directions. What are the things that you would like to know?

Kristen:    The thing that I'm trying to figure out how to make distance on now, because of this -- well, a combination of things, the learning of stuff about brains from Finlay and her colleagues and what they've been doing. I don't know whether I -- I don't think I did lay this out, but what they've shown is that across the mammals --- well, it's a little different in marsupials.

    Across the Eutherian mammals, the thing that predicts brain size is the duration of development which is predicted by longevity. It's not only the final brain size but the size of several of the key components like the neocortex that we think is such a big deal.

    There is an allometry. I've mentioned allometries before. One of the reasons it was so easy for me to hear what she was talking about was because I worked on that, trying to understand Charnov's models, but the neocortex increases, allometrically, with size. So, as brains get bigger, with longer duration of development, the relative size of the neocortex gets bigger. All of this is going on, says me, as a consequence of our grandmothering life history. That's why we have that.

    So, the early wiring of this brain for this extreme sociality, sets us up where the social context is so important. One of the things that sometimes there are evolutionary psychologists have been working on is across contemporary populations in the state societies like ours -- I don't quite know what to use as a label for this, but you know the acronym, WEIRD societies. That comes from white, industrial, educated, democratic and -- that so many of the experiments and the reports have features that are essentially human come from subjects that are part of WEIRD societies.

    It's not just that. It's the middle classes. Actually, within societies like ours, the range of variation is -- this is another example where averages can be misleading -- people who haven't found their place in our society and, unfortunately, increasing numbers of people who find themselves like that, what it is then that babies growing up in those circumstances, how exactly they deal with those things.

    I have an incoming student who brings special insights about this, and I'm looking forward to seeing where this goes. There's another story to tell about this. I mentioned the Yale Baby Lab and those things with animations showing the good shapes and the bad shapes, and babies with a really strong effect. Well -- can I say parentheses -- there is an argument that has gotten attention in the last little while about our evolution that features the claim that we're cooperative because of self-domestication. Have you come across this?

Christopher:    Hmm.

Kristen:    Richard Wrangham recently has a book about this, and he and Brian Hare -- some of the initial papers, Brian Hare was involved in and --

Christopher:    I was going to mention him earlier when you were talking about Survival of the Friendliest and Dognition. I got this book on dogs.

Kristen:    Oh, yeah, he does, that's right. He's really interested in dogs and so on, but he also has been interested in aspects of human evolution. He and Wrangham, together, were working on this self-domestication argument which I do not buy. It's very inconsistent with most things I know, so I would have more to say about that. Well, maybe I have to say more about it right now. The thing that I think Sarah Hrdy was right about, that it's this life history feature that underlies why our social cognition seems to have characteristics that we don't see in any other apes.

    With this self-domestication idea, it didn't start with Hare and Wrangham, but they got intrigued by trying to understand the bonobo-chimpanzee difference which is a fascinating one. These are our --

[1:20:00]

Christopher:    Oh, yeah. 

Kristen:    -- closest living relatives, right? 

Christopher:    Right.

Kristen:    Yet they seem to be so different from each other, and the argument that they elaborated was that bonobos were nicer and more cooperative and with all these other interesting social aptitudes because of self-domestication. What had happened in bonobos was that females were just not having aggressive males. They were out, and the consequence was self-domestication. That hadn't happened in chimpanzees.

    The way they made the argument originally, it was that the self-domestication is associated with social neotony and being childlike, longer. So, they did these experiments with chimpanzees and bonobos, showing that bonobos seem to be delayed in various kinds of things. They seem to be childlike, longer, and so that was supposed to be consistent with the argument, but then the argument is that we are self-domesticated. 

    My challenge to that was, wait a minute, bonobos are self-domesticated, and an index of that is that they are so neotenous, socially, compared to chimpanzees. We are self-domesticated and yet we are socially so precocious compared to either one of them. So, wait a minute. Is it that self-domestication slows social development or speeds it up? Which is it? Those are inconsistent, was my argument. Well, here is the background, some of the background to my attention to what they're finding.

    Within the last couple of years, Brian Hare, with a collaborator whose name I'm sure I should mention, but not only has he been doing interesting stuff with dogs, but he also has been doing interesting stuff with bonobos. So, in one of these refugee places in Africa, they actually managed to do a version of the Yale Baby Lab experiment with bonobos. Now, that that could happen is astonishing, but of course, in the paper, just simply ignores all this.

    So, the expectation should have been that here are the bonobos with the choice between whatever it is, the bad square and the good triangle or whatever, that the bonobos would, because they're bonobos and they're so cooperative, they would favor the good. It's just the reverse. They prefer the strong, dominant. So I see this as such a challenge to the argument that they have been making about self-domestication of bonobos.

    The fact that they can make this experiment so portable means that maybe we could do some similar things to what the Baby Lab did in Yale Baby Lab, actually in places where people are trying to figure out how to deal with being unsheltered. So, maybe we can start to get some data in how humans respond in this period when I think their social sensitivities are going to be so extreme. Do they really prefer the strong dominant, or do they prefer the nice and helpful?

    The student whose name is Megan Milano, she has a strong hypothesis that under those circumstances, when everything is very dangerous and you are very unsure about anything, you definitely want some strong, dominant ally.

Christopher:    Oh, I see, so she's going to say it's context-dependent.

Kristen:    Isn't that -- 

Christopher:    Interesting.

Kristen:    -- interesting?

Christopher:    Yeah, it's fascinating.

Kristen:    The results that we get from a lot of the developmental psych is mostly these are children of faculty members in surrounding universities, yeah, so, really a point there are -- I spend a lot of time trying to characterize what I think has been the social context for most of human experience which is very different from what we -- trying to find ways to talk about that to people, so they can see how those things differ from what we experience now. 

    In some ways, the contrast within our own society may be even greater than comparisons between you and me and folks in traditional societies if we -- there are parts of what people cope with, in our society, that are unlike, in a very different way, unlike most of human experience and how they do that, may broaden our notion of what we think of "human nature." 

[1:25:20]

    Again, this comes back to Hrdy's insights about that, combined with Finlay. They have to go together, that Finlay -- so, I've written about building on Hrdy before I crossed paths with Finlay and learned the stuff I now know about brains, and I will talk about it a little differently now. Because I think the evidence from people who look at what's happening, actually happening with brains is the way that they wire is so experience-dependent.

    So, it's Sarah Hrdy's insights about the cognitive ecology from a human infant's, but that plasticity thing and the early wiring and so on comes out of Finlay's demonstration. It makes our early weaning just so strikingly different from certainly other apes, from other primates. That could be the heart of why we're doing this.

    I want you, Christopher, do you see what I'm talking about? Yeah.

Christopher:    You've given me a ton to dig into, and I'm really excited to follow up on some of these names that you've been mentioning. I have a feeling that my cognitive dissonance will just grow, the more I learn. There are these huge discrepancies that I see between what you're describing and characterizing, and what I see in society today. It just couldn't be more different --

Kristen:    Right.

Christopher:    -- in every aspect of our life, but it's fascinating nonetheless.

Kristen:    Well, thank you. Thank you for -- and, yeah, keep giving me hints about things I need to pay attention to, and places where it doesn't -- wait a minute, what about that? Wait a minute, well that doesn't seem consistent with this. Please do that.

Christopher:    Yeah, absolutely.

Kristen:    It's the role you have cut out for yourself, to do that.

Christopher:    Oh, I like that. I like that. Thank you. Where's the best place for people to come and find out more about your work and perhaps even support your work? I know that funding could be challenging. 

Kristen:    Oh, funding.

Christopher:    Perhaps you have some ideas about that.

Kristen:    Funding is so challenging, yes, and it gets worse all the time. I think everybody is going to be in a funding disaster for the next little while, everybody, whatever they do.

 Christopher:    Of course.

Kristen:    Yes, so I'm on the Faculty at the University of Utah, in Anthropology. I'm not a writer of books. Books I recommend are Sarah Hrdy's, but I have written lots of papers, continue to do that. I'd be happy, if you don't have access to them, just send me an email, and I'll be eager to send you a paper. Then you can tell me what you think and where you think I'm missing the boat because that's -- I mean, having an audience to talk back is part of a thing that maybe by continually doing that, we get closer to being closer to getting it sort of correct, maybe, maybe

Christopher:    Maybe. What about helping to support your lab?

Kristen:    Well, yeah, that would be great, so here I am. I am on the Faculty at the University of Utah, in Department of Anthropology, so if you want to send us --

Christopher:    We'll find you there.

Kristen:    -- yeah, support, we'd be so pleased.

Christopher:    Excellent. Well, Kristen, you've been very generous with your time. It's been fantastic. 

Kristen:    Oh, thank you, Christopher.

Christopher:    I'm super excited by your work, so, thank you so much working with you. 

Kristen:    Thank you, thank you.

[1:28:53]    End of Audio

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