Meat made us smarter: it gave us bigger brains
The role of meat in brain expansion is genuinely contested, with cooking and starch as serious competing accounts. Either way, it describes the past.
Human brains are enormously expensive organs, and our ancestors could only afford to grow them once they began eating calorie-dense, nutrient-rich animal foods, which let a smaller gut free up energy for a larger brain. Meat-eating is therefore not an incidental habit but part of what made us human, woven into our evolutionary history and our anatomy. To turn away from it is to reject the very diet that shaped the minds now doing the rejecting.
The expensive tissue hypothesis proposed that a shift to nutrient-dense animal foods permitted a smaller gut and a larger brain. It remains influential, and subsequent work has not settled the question. Richard Wrangham's cooking hypothesis attributes the change primarily to cooking, which increases the digestible energy available from both meat and starchy tubers, and there is a substantial case for cooked starch specifically, supported by the expansion of salivary amylase gene copies in humans.
The honest summary is that this is an open area with several live explanations. And the prescriptive step fails regardless of which wins: an account of how a trait arose says nothing about what the organism should now do with it.
Moving from a description of how things are to a claim about how they ought to be, without supplying the moral premise that would connect the two. Identified by David Hume.
How it applies here: An account of how our brains developed is converted into a conclusion about how we should eat now, with no premise licensing the move.
Presenting only the evidence that supports a conclusion while leaving out evidence that tells against it.
How it applies here: Presents one contested hypothesis as settled, while competing accounts centred on cooking and on starch remain live in the literature.