This is cross-posted to MDK10 Outside.
Paleo dieters avoid post-agricultural foods. The argument is that agriculture is a product of culture and so it introduced sources of nutrition that our genes haven't caught up with, especially grains, refined sugar, and other concentrated carbs. By eating vegetables and lean meats (so the argument goes) we are more in tune with paleolithic humans and therefore should be healthier.
There are any number of problems with that argument (not least of whic is that adherents often seem disinterested in empirical testing of it), but an interesting question is: couldn't we apply similar arguments to our cognition? The way we think about the world, or possibly even, that we think about the world, started undergoing profound changes about 40,000 years ago. Of note, this time corresponds with humans leaving Africa, developing specialized tools, hunting larger game that required team planning, and the spread of the current form of the FOXP2 gene and subsequent use of language and the cognitive modernization of humans; it marks the boundary between the upper and lower paleolithic. That is to say, until about 40,000 years ago, we solved problems in a primitive, isolated way, and knowledge could be shared only at a much more basic level. Suddenly we have language, reasoning, and mountains of cultural transmission in the form of tools and worldviews so that what we achieve in working memory can be expanded across a whole lifetime, or indeed indefinite lifetimes (i.e., among other things, the idea of an alphabet, hit upon by some clever Phoenician twenty-five centuries ago, allows us to more easily share these ideas right now). This has profoundly changed our physical environment in ways that have outrun our genes' ability to respond - including agriculture.
Therefore, shouldn't a person making the paleo argument for diet also make a similar argument for post-paleo (or at least post-lower paleo) cognition? That is to say, if you're really concerned that agriculture-based food is a threat to the fluorishing of H. sapiens because of its newness and alienness, aren't things like reasoning and systematic institutional research just as bad, if not profoundly more dangerous? Shouldn't we be approaching problems with blunt emotions and a vague memory of some chance association from last time we were in this part of the world with no way to obtain or share knowledge from others? Shouldn't the males of the species be getting in fights with people that look different from us or look at our woman for a second too long, with a resulting homicide rate of 30%? (The actual number for some hunter-gatherer groups.) This is what we're adapted for - our cognitive environment for thousands of centuries. How can the alien world we've built for ourselves in cognitive modernity not be hurting us?
In extension you could even make a Nagel-like argument here that paleo defeats itself, that if you think paleo is the way to go because profoundly biologically novel activities are threatening to an animal's well-being, then you should also eschew reasoning, and therefore eschew paleo, which was arrived at with a very un-paleo process (reasoning, communicating about it with large groups of people, and institutional research).