Fermentation, fire, and our big brains
Many Minds
The Evolution of the Brain
Brain size expansion started around 6 million years ago at the divergence of the ancestor that led to humans and chimpanzees/nAustralopithecines had chimp-sized brains and bodies initially but brain size slowly increased over time/nSelective pressure allowed for brain expansion in Australopithecines/nCrucial time window for the lineage that led to humans started around 2 million years ago/nApproximately a tripling of brain size happened over the last 2 million years/nThe expensive tissue hypothesis suggests that brain tissue is metabolically expensive
Brains are not cheap. It takes a lot of calories to run a brain, and the bigger your brain, the more calories it takes. So how is it that, over the last couple million years, the human brain tripled in size. How could we possibly have afforded that? Where did the extra calories come from? There's no shortage of suggestions out there. Some say it was meat; others say it was tubers; many say it was by mastering fire and learning to cook. But now there's a newer proposal on the table and—spoiler—it's a bit funky.
My guests today are Katherine Bryant, Postdoctoral Fellow at Aix-Marseille University, and Erin Hecht, Assistant Professor in the Department of Human Evolutionary Biology at Harvard. Katherine, Erin, and another colleague are the authors of a new paper titled 'Fermentation technology as a driver of human brain expansion.' In it, they argue that fermented foods could have provided the caloric boost that allowed our brains to expand.
Here, we talk about how the human body differs from the bodies of other great apes, not just in terms of our brains but also in terms of our bowels. We discuss the different mechanisms by which fermented foods provide nutritional benefits over unfermented foods. We consider how fermentation—which basically happens whether you want it to or not—would have been cognitively easier to harness than fire. Along the way, we touch on kiviaq, chicha, makgeolli, hákarl, natto, Limburger cheese, salt-rising bread, and other arguably delectable products of fermentation.
This is a fun one friends. But before we get to it: a friendly reminder about this summer's Diverse Intelligences Summer Institute. This a yearly event in St Andrews, Scotland; it features a rich program of lectures and events devoted to the study of cognition, mind, and intelligence in all its forms. If you have a taste for cross-disciplinary ferment and bubbly conversation, DISI may be for you. The application window is now open but is closing soon. You can find more info at DISI.org. That's D-I-S-I.org.
Alright, friends, on to my conversation with Erin Hecht and Katherine Bryant. Enjoy!
A transcript of this episode is available here.
Notes and links
3:00 – A popular science article about the "infectiously delicious confection" that is salt-rising bread. A recipe for the bread.
6:00 – An article about makgeolli, a Korean rice wine. An article about chicha, the traditional corn-based fermented beverage that has been banned in some places.
11:30 – An article about the role of the arcuate fasciculus in language processing. A recent paper by Dr. Bryant and colleagues comparing the arcuate in humans and chimpanzees.
12:30 – A recent article by Dr. Hecht and colleagues on the evolutionary neuroscience of domestication.
13:00 – For discussions of the encephalization quotient (aka EQ) and of human brain evolution, see our previous episodes here and here.
15:00 – The classic paper on the "expensive tissue hypothesis."
22:00 – An article about the role of meat in human evolution; an article about the role of tubers. The cooking hypothesis is most strongly associated with Richard Wrangham and his book, Catching Fire.
26:00 – A recent article on evidence for the widespread control of fire in human groups by around 400,000 years ago.
31:30 – A paper on how fermenting cassava reduces its toxicity.
38:30 – There have been various claims in the ethnographic literature that the control of fire has been lost among small groups, such as in Tasmania. See footnote 2 in this article.
44:30 – A popular article about kiviaq.
45:00 – The article from the New Yorker, by Rebecca Mead, about the foodways of the Faroe Islands.
53:00 – For more discussion of the so-called drunken monkey hypothesis, see our previous episode about intoxication.
1:00:30 – A popular article about hákarl, which is fermented Greenland shark.
Recommendations
The Botany of Desire, by Michael Pollan
The Art of Fermentation, by Sandor Katz
Wild Fermentation, by Sandor Katz
"How humans evolved large brains," by Karin Isler & Carel van Schaik
Many Minds is a project of the Diverse Intelligences Summer Institute, 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. Our transcripts are created by Sarah Dopierala.
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