What is memory for?
Many Minds
Everyone loves a good evolutionary puzzle. Why do we have appendices? Why do we dream? Why do we blush? At first glance, memory would not seem to be in this category. It's clearly useful to remember stuff, after all—to know where to find food, to remember your mistakes so you don't repeat them, to recall who’s friendly and who’s fierce. In fact, though, certain aspects of memory—when you hold them up to the light—turn out to be quite puzzling indeed. My guests today are and . Ali is a philosopher at the London School of Economics (LSE); Johannes is a philosopher at York University,...
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Of breeds and brains
Many Minds
It's hard to say exactly when, but some tens of thousands of years ago, our best friends were born. I'm referring, of course, to dogs. This didn't happen overnight—it was a long process. And it not only changed how those canids behaved and what they looked like, it also changed their brains. As wolves gave way to proto-dogs, and proto-dogs gave way to dingoes and dalmatians and Dobermanns and all the rest, their brains have continued to change. What can we learn from this singular saga? What does it tell us about dogs, about domestication, and about brains? My guest today is . Erin is...
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Monsters and their makers
Many Minds
It seems we've always had monsters among us. We've long been enthralled by dragons and giants, by the likes of Frankenstein and Godzilla and Dracula, by witches and werewolves and countless others. They roam our maps and creation myths; they crop up in our dreams, in our children's books, in our political rhetoric. Where do these beings spring from? What do they do for us? How have they changed over time? And, ultimately, what do our monsters say about their makers? My guests today are and . Both are historians of science and authors of recent books on monsters: Natalie's book is . Surekha's...
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The age of social AI
Many Minds
AI therapists and caregivers. Digital tutors and advisors and friends. Artificial lovers. Griefbots trained to imitate dead loved ones. Welcome, to the bustling world of AI-powered chatbots. This was once the stuff of science fiction, but it's becoming just the stuff of everyday life. What will these systems do to our society, to our relationships, to our social skills and motivations? Are these bots destined to leave us hollowed out, socially stunted, screen-addicted, and wary of good-old-fashioned, in-the-flesh human interaction? Or could they actually be harnessed for good? My guest today...
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Brains of a feather
Many Minds
Birds do the darnedest things. They fly, of course. They sing. They hunt in pitch darkness. They hide their food and remember where they put it. They use tools and migrate over astonishingly vast distances—sometimes even sleeping while in flight. How do they do all this? What's going on in their brains that makes these and other remarkable behaviors possible? How did their evolutionary path mold them into the incredible creatures they are today? My guests today are and . Andrew is a comparative neuroscientist and Associate Professor at the University of Lethbridge in Canada. Georg is a...
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How nature restores the mind
Many Minds
One afternoon you decide to snub your responsibilities and go for a hike. You spend a few hours in the woods or the mountains. You study the bark of trees, you bathe in birdsong, you let your eyes roam along a distant ridgeline. And you come back feeling better, restored somehow—like you have more energy, more patience, more bandwidth. We've all, I'm guessing, had experiences like this. But what's behind these effects? Why would nature restore us? What's the evidence that it really does? And what is even being restored, actually? My guest today is . Marc is an Associate Professor in the...
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From the archive: Revisiting the dawn of human cognition
Many Minds
Hi friends! We're taking a much-needed summer pause—we'll have new episodes for you later in September. In the meanwhile, enjoy this pick from our archives! ------- [originally aired June 1, 2023] There's a common story about the human past that goes something like this. For a few hundred thousand years during the Stone Age we were kind of limping along as a species, in a bit of a cognitive rut, let’s say. But then, quite suddenly, around 30 or 40 thousand years ago in Europe, we really started to come into our own. All of a sudden we became masters of art and ornament, of symbolism and...
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From the archive: Of molecules and memories
Many Minds
Hi friends! We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives! _____ [originally aired February 8, 2024] Where do memories live in the brain? If you've ever taken a neuroscience class, you probably learned that they're stored in our synapses, in the connections between our neurons. The basic idea is that, whenever we have an experience, the neurons involved fire together in time, and the synaptic connections between them get stronger. In this way, our memories for those experiences become minutely etched...
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From the archive: Consider the spider
Many Minds
Hi friends! We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives! _____ [originally aired May 30, 2024] Maybe your idea of spiders is a bit like mine was. You probably know that they have eight legs, that some are hairy. Perhaps you imagine them spending most of their time sitting in their webs—those classic-looking ones, of course—waiting for snacks to arrive. Maybe you consider them vaguely menacing, or even dangerous. Now this is not all completely inaccurate—spiders do have eight legs, after...
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The shaman with a thousand faces
Many Minds
When you hear the word "shaman," I'm guessing a web of associations starts to form in your mind. Perhaps you imagine strange ceremonies and strong substances; maybe you think of an earlier time when magic and superstition reigned. But shamanism is not just some relic of the past, or a curio from exotic lands. It's part of our present, and it will almost certainly be part of our future. This is because the roots of shamanism lie within us all. My guest today is . Manvir is an Assistant Professor of Anthropology at the University of California, Davis and to The New Yorker. He's also the author...
info_outlineHi friends, we will be on hiatus for the fall. To tide you over, we’re putting up some favorite episodes from our archives. You may not be surprised to hear that the paper featured in this archive pick attracted a lot of attention. In the time since we first aired this episode, it prompted at least one direct critique, which then occasioned a reply by the authors.
Enjoy!
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You have a big brain. I have a big brain. We, as a species, have pretty big brains. But this wasn't always the case. Way back when, our brains were much smaller; then they went through a bit of growth spurt, one that lasted for a couple million years. This steady ballooning of brain size is one of the key themes of the human story. But then there's a late-breaking twist in that story—a kind of unexpected epilogue. You see, after our brains grew, they shrank. But when this shrinkage happened and—of course, why—have remained mysterious. My guest today is Jeremy DeSilva, a paleoanthropologist at Dartmouth College. He’s an expert on the evolution of the foot and ankle. But, it turns out the body is all connected, so he also thinks about brains and heads. In a recent paper, Jerry and his colleagues took up the mystery of human brain shrinkage. They first set out to establish more precisely when in our past this occurred. Using a large database of crania, spanning few million years, Jerry’s team was able to establish that this shrinkage event happened much more recently than previously thought—a mere 3000 years ago. Naturally, the next question was why? What happened around that time that could have possibly caused our brains to deflate? To answer this, Jerry and his collaborators turned to an unexpected source of insight: Ants. That’s right, ants. They argue that these ultrasocial critters may offer clues to why we might have suddenly dispensed with a chunk of brain about the size of a lemon. This is a really juicy paper and a super fun conversation, so we should just get to it. But I did want to mention: Jerry has a recent book from 2021 called First Steps that I whole-heartedly recommend. It’s about origins of upright walking in humans—which it turns out, is bound up with all kinds of other important aspects of being human. So definitely check that out!
Thanks folks—on to my chat with Dr. Jerry DeSilva. Enjoy!
The paper we discuss is available here. A transcript of this episode is available here.
Notes and links
3:00 – A podcast episode from the Leakey Foundation about the so-called “obstetrical dilemma.”
5:40 – A refresher for those who have trouble keeping their ‘cenes’ straight: the Pleistocene refers to the period from 2.58 million years ago to 11,700 years ago; immediately after that came the Holocene, which we are still in today.
7:00 – An article discussing the issue of unethical collections of human remains.
10:30 – The key figure form Dr. DeSilva’s paper—showing the changing “slopes” of brain size over time—is available here.
19:30 – The original article by Leslie Aiello and Peter Wheeler on the “expensive tissue hypothesis.” A more recent popular article on the hypothesis.
20:45 – An article by a major proponent of the social intelligence hypothesis, Dr. Robin Dunbar. A more critical review of the social intelligence hypothesis.
23:00 – A recent paper by Jeff Stibel and an older preprint by John Hawks evaluating the “body size” explanation of recent brain shrinkage.
24:00 – See our earlier episode on human self-domestication with Brian Hare.
29:00 – One of Dr. DeSilva’s collaborators on this research is Dr. James Traniello, who specializes in ants.
34:45 – An overview of the earliest history of writing.
37:20 – Dr. DeSilva’s book, First Steps, came out in 2021.
39:00 – A recent paper discussing the evolution of rotational birth in humans.
Dr. DeSilva recommends:
Kindred, by Rebecca Wragg Sykes (featured in an earlier episode!)
Origin, by Jennifer Raff
You can find Dr. DeSilva on Twitter.
Many Minds is a project of the Diverse Intelligences Summer Institute (DISI) (https://disi.org), which is made possible by a generous grant from the Templeton World Charity Foundation to UCLA. It is hosted and produced by Kensy Cooperrider, with help from Assistant Producer Urte Laukaityte and with creative support from DISI Directors Erica Cartmill and Jacob Foster. Our artwork is by Ben Oldroyd (https://www.mayhilldesigns.co.uk/). Our transcripts are created by Sarah Dopierala (https://sarahdopierala.wordpress.com/).
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