#499 Humans Aren’t Supposed to Live This Long (Grandmothers Might Explain Why) - Dr Kristen Hawkes

Kristen Hawkes (0:00)

And the thing about mammal males is they keep producing sperms throughout adulthood. So where females get all of the cells that can become oocytes, you know, early in life, and then they lose them, that's because of our longevity. We have this big fraction of our adulthood that is like my postmenopausal, right? Well, that's not true of our closest living relatives. There's the other great apes, chimpanzees and bonobos and gorillas and orangutans. That for them, adult mortality is higher, and they usually don't outlive their fertility. It all had to do with adult mortality. If it's high, then you can't really spend a lot of time growing up, because chances are you'll get nailed and you won't leave any descendants. And if it's lower, well, then you can take a longer time and grow bigger before you stop growing and start putting it into reproduction.

Siim Land (1:04)

Dr. Kristen, welcome to the show.

Kristen Hawkes (1:07)

Thank you.

Siim Land (1:09)

I'm excited to have you on the podcast, and you're one of the first anthropologists as well on the show to discuss about something that's very interesting, and many people haven't, I guess it's not like the most mainstream theory of or part of human longevity. So yeah, today we're going to talk about one of the or the main theories that you proposed, which is the grandmother hypothesis. So it sounds very interesting, at least for me. So maybe we can start with, how did you come up with the idea behind it and what it is as well?

Kristen Hawkes (1:50)

Well, I'm very terrible at short answers, so you'll have to interrupt me. But when my first, I started out as a sort of garden variety cultural anthropologist. My dissertation fieldwork was in Highland, New Guinea with people who are gardeners and pig keepers. And when I then again, and it's a long story, how I came under the influence of a theoretical biologist, Eric Charnov, when I was at the University of Utah and began to realize there were all of these amazing tools in evolutionary biology for explaining this ape. And so, good heavens, my first ethnographic work was with people who actually know how to live on wild foods in Eastern Paraguay. And the question we were directed toward then was specifically, how do people choose which resources to take? And I thought, as did my collaborators, they were my students at the time, but it wouldn't have happened without them. We all thought that we knew that the hunting hypothesis was the story of us, that what happened with climate change was hunting became a better way to make a living if you were in those savanna environments. And so, that meant that males, ancestral males, were spending time going after vertebrate animals, big animals. Actually, there's a story about that, because we learned pretty quickly that there are other apes that hunt vertebrates. Chimpanzees are also hunters. But anyway, that what happened with our ancestors was males started going after big animals and bringing home the bacon to their mates and offspring. And that meant that moms could have piled up the babies. And that was essentially what was going on. And what we found, because we were collecting quantitative data, people were wonderful. They let us follow them around and wait what they took and time how long it. And then because of special things about this ethnographic context, because these foragers, they move almost all the time. And that meant, and they were in the forest, and it meant that they didn't clear an enormous space. And so everybody was very close together. And so we could not only record what food resources people took, but also what stomachs it went into. And there were the data showing that it was not the case that what men were doing was acquiring things that went especially to their wives and kids. No. In fact, if that's what they were aiming to do, they wouldn't be doing what they're doing. So that meant this question of what the heck is going on. So my, I came out of that project with this what in the heck are, well, not that I wasn't always wondering about male strategies, living a human life. But anyway, what is it that is the underlying payoff fitness related for what these guys are doing? And then, so lucky to be invited to join this project that Nick Blurton Jones, who was at UCLA, was starting with podza foragers in northern Tanzania. And he invited me and my colleague at Utah at the time, an archaeologist, Jim O'Connell, he invited us to join him in this project. And O'Connell, an archaeologist, who had, he started out as working in North America and realized that if he wanted to figure out what was going on with all the archaeology, if he could actually watch people doing stuff that resulted in that distribution of stuff, that he'd be in much better shape to figure it out. So, that was his question. And mine is still what's going on with males, but because the kind of observation we were doing once again was quantitative. You know, again, the Hadza folks were so welcoming and let us, you know, hang out, follow them around, time, everything.