Promote a cruelty-free lifestyle long enough, and you’ll eventually bump into the expensive tissue hypothesis. No, it’s not a pet theory about the rising cost of toilet paper, but the claim (usually foisted upon you by paleodieters or some carnist who took an anthropology class once) that meat-eating made humans into the big-brained rocket scientists we are today. How ungrateful and unnatural you are to reject millions of years of evolution. Surely, your brain has shrunk from lack of essential fatty acids, to even entertain such a notion as eating vegan.
To be fair, that last bit isn’t actually the expensive tissue hypothesis (ETH). It’s just the pop culture meme that grew out of an influential idea first put forward by Leslie C. Aiello and Peter Wheeler in 1995. While “meat made us smart” is not, as you’ll see in a moment, actually what Aiello & Wheeler said, it is the message that carnist mainstream society took from the paper and ran with. It’s been the urban caveman’s naturalistic fallacy of choice ever since.
But as with many things in modern science, things look a lot different in the field today than they did 18 years ago. The idea that meat-eating was essential to the evolution of human intelligence isn’t holding up as well as your average broscientist thinks it is. What follows is a slightly edited re-post from my usual blog that explains all the details.
“Energetics and the evolution of human brain size,” published in the November 2011 edition of Nature, tests and refutes the expensive tissue hypothesis. It’s impressive work, and pretty devastating to the hypothesis that has provided a rhetorical foundation to the paleo diet mythology for over a decade now.
Their conclusion: when adiposity, phylogenetic relationships, sample bias and sex differences are controlled for, Aiello’s & Wheeler’s original data don’t support their hypothesis any better than the newer data does! In short, the ETH is wrong at the foundation, not just at the margins.