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Feb 10, 2022

Why did our brains shrink 3000 years ago? With Jeremy DeSilva (podcast)

After ballooning for millions of years, the human brain changed course and began to shrink. A paleoanthropologist at Dartmouth shares why in this episode of Many Minds.

By Templeton Staff

This episode of Many Minds podcast — a project by the Templeton World Charity Foundation-supported Diverse Intelligences Summer Institute — features Jeremy DeSilva, a paleoanthropologist at Dartmouth College.

Host cognitive scientist, podcaster, and writer Kensy Cooperrider introduces the episode:

“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!”

Play the full episode with the above player.

Learn more about Templeton World Charity Foundation's Diverse Intelligences initiative.

Templeton World Charity Foundation's Diverse Intelligences is a multiyear, global effort to understand a world alive with brilliance in many forms. Its mission is to promote open-minded, forward-looking inquiry in animal, human, and machine intelligences. We collaborate with leading experts and emerging scholars from around the globe, developing high-caliber projects that advance our comprehension of the constellation of intelligences.

Many Minds is a project of the Diverse Intelligences Summer Institute (DISI), made possible through a grant from TWCF to the University of California, Los Angeles (UCLA). The Many Minds podcast is hosted and produced by Kensy Cooperrider, with help from assistant producer Cecilia Padilla. Creative support is provided by DISI Directors Erica Cartmill and Jacob Foster. Artwork is by Ben Oldroyd.