Recently listening to the Radiolab episode on “Guts,” I was reminded of Richard Wrangham’s great book, Catching Fire: How Cooking Made Us Human. (Both discuss William Beaumont’s research into human digestion with his patient Alexis St. Martin in the early 19th century.)
As described by Dwight Garner in his review of the book for The New York Times, Wrangham’s thesis is simple, novel, and compelling:
Apes began to morph into humans, and the species Homo erectus emerged some two million years ago, Mr. Wrangham argues, for one fundamental reason: We learned to tame fire and heat our food…. The energy that we formerly spent on digestion (and digestion requires far more energy than you might imagine) was freed up, enabling our brains, which also consume enormous amounts of energy, to grow larger. The warmth provided by fire enabled us to shed our body hair, so we could run farther and hunt more without overheating. Because we stopped eating on the spot as we foraged and instead gathered around a fire, we had to learn to socialize, and our temperaments grew calmer.
The book isn’t without it’s flaws, but it’s well worth a read. If you want to get a flavor of it, check out Garner’s review, Christine Kenneally’s review at Slate, and especially Wrangham’s appearance on NPR’s Talk of the Nation Science Friday.