Experts on the evolution of human nutrition

Want to eat a diet that mimics that of our Paleolithic ancestors? It might be a little more complicated than what the popular books say.

The fact is, there was never one Paleo Diet; it's more likely there were hundreds of them and that they were continually changing and broadening over evolutionary time.

That was the overarching message of an impressive lineup of experts on ancient human diets at a symposium entitled "The Evolution of Human Nutrition" organized by the Center of Academic Research and Training in Anthropogeny (CARTA) at UC San Diego on December 7, 2012.

Now, I'm happy to report, the videos of a few of the talks have been made available (embedded in this post below). You can also read what other folks on Twitter had to say about the event using the #CARTAsymp hashtag in my Storify story.

Why you can all stop saying meat eating fueled evolution of larger brains right now

Hadza returning from hunt in Tanzania. Credit Andy Lederer.

In William Shakespeare's comedy Twelfth Night, Sir Andrew, who was worried that a joke may have been made at his expense, reasons out loud that maybe his diet had something to do with his lack of intelligence, saying, "But I am a great eater of beef, and I believe that does harm to my wit" (Act I, Scene III). Dialogue like that was how Shakespeare famously poked fun at what he considered "foolery" in his time; it was a common belief of the Elizabethan Age that eating too much meat made you a meat-head. Now, it appears the tables have turned. Vegetarians are getting a taste of similar medicine from comedians of our time.

On November 15th's episode of The Colbert Report, Stephen Colbert interviewed one of the world's foremost paleoanthropologists, Chris Stringer of the Natural History Museum, about his newly published book. During their conversation, Stringer sums up nicely why meat eating may have been the primary force that drove evolution of a brain-gut tradeoff, where a shrinking gut allowed for more energy input into the brain. Here is Stringer's explanation at about minute 18:30 in the episode:

Chris Stringer: "There's a thing called 'expensive tissue hypothesis'. And this says we evolved our large brains by changing our diets. Our ancestors had great big guts because they were vegetarian. They never had enough spare energy because their guts were using 20 percent of their energy; they never had enough spare energy to evolve a large brain. When we started eating meat, a much more concentrated sort of food, it freed up energy and we could start to run a bigger brain."

Stephen Colbert: "That's why vegetarianism seems so stupid to me."

Human vs. chimps: What the "regulome" tells us about meat eating & bigger brains

Source: Greg Wray

The story about how humans evolved bigger brains begins some seven million years ago in central Africa. There, in a dense rainforest, there lived the last ancestor that we share with our closest living relatives. Our evolutionary paths diverged when the global climate changed and a new habitat took shape. While ancestors of chimpanzees retreated deeper into the rainforest to subsist on a diet mainly of fruits, our ancestors found themselves in on strange, new, dry grassland.

The savanna would mean a new way of life for our ancestors. They'd learn to use tools, communicate with each other using language, and work together to hunt animals for food. Based on fossil evidence and stable isotope data, our hominin ancestors shifted to a diet where meat was a principal energy source about two million years ago. It would be a major shift in diet that coincided with an increase in cranial capacity.

Now, scientists like Greg Wray, a professor of biology at Duke University, are beginning to better understand the genetic basis for the adaptation to eating meat and how it guided the development of our larger brains. During his plenary talk at the Council for the Advancement of Science Writing's (CASW) "New Horizons in Science 2012" annual conference in Durham, North Carolina, Wray said that the Encyclopedia of DNA Elements (ENCODE) project gave scientists like himself a "detailed street map" for seeking out the genetic changes that took place since the divergence of humans and chimpanzees over evolutionary time.