{"version":1,"type":"rich","provider_name":"Libsyn","provider_url":"https:\/\/www.libsyn.com","height":90,"width":600,"title":"From the archive: Why did our brains shrink 3000 years ago?","description":" Hi friends, we will be on hiatus for the fall. To tide you over, we\u2019re 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! \u2014\u2014\u2014  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\u2014a kind of unexpected epilogue. You see, after our brains grew, they shrank. But when this shrinkage happened and\u2014of course, why\u2014have remained mysterious.  My guest today is Jeremy DeSilva, a paleoanthropologist at Dartmouth College. He\u2019s 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\u2019s team was able to establish that this shrinkage event happened much more recently than previously thought\u2014a 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\u2019s 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\u2019s about origins of upright walking in humans\u2014which it turns out, is bound up with all kinds of other important aspects of being human. So definitely check that out! Thanks folks\u2014on 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 \u00ad\u2013 A podcast episode from the Leakey Foundation about the so-called \u201cobstetrical dilemma.\u201d 5:40 \u2013 A refresher for those who have trouble keeping their \u2018cenes\u2019 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 \u2013 An article discussing the issue of unethical collections of human remains. 10:30 \u2013 The key figure form Dr. DeSilva\u2019s paper\u2014showing the changing \u201cslopes\u201d of brain size over time\u2014is available here. 19:30 \u2013 The original article by Leslie Aiello and Peter Wheeler on the \u201cexpensive tissue hypothesis.\u201d A more recent popular article on the hypothesis. 20:45 \u2013 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 \u2013 A recent paper by Jeff Stibel and an older preprint by John Hawks evaluating the \u201cbody size\u201d explanation of recent brain shrinkage.   24:00 \u2013 See our earlier episode on human self-domestication with Brian Hare.   29:00 \u2013 One of Dr. DeSilva\u2019s collaborators on this research is Dr. James Traniello, who specializes in ants. 34:45 \u2013 An overview of the earliest history of writing. 37:20 \u2013 Dr. DeSilva\u2019s book, First Steps, came out in 2021. 39:00 \u2013 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\/). You can subscribe to Many Minds on Apple, Stitcher, Spotify, Pocket Casts, Google Play, or wherever you like to listen to podcasts. **You can now subscribe to the Many Minds newsletter here!** We welcome your comments, questions, and suggestions. Feel free to email us at: manymindspodcast@gmail.com. For updates about the show, visit our website (https:\/\/disi.org\/manyminds\/), or follow us on Twitter: @ManyMindsPod. ","author_name":"Many Minds","author_url":"https:\/\/disi.org\/manyminds\/","html":"