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When I discuss my concern that psychologists and behavioral economists rely on a thin and peculiar slice of humanity in order to understand HUMAN psychology, they often reply with the strong intuition that they (but perhaps not others) are studying “basic processes,” etc.
To assess how difficult it is to identify these “basic process” without both evolutionary theory and serious cross-cultural research, let’s put aside psychology and focus on physiology and anatomy. Surely, those are “basic.” #WEIRDPeopleProblem
WEIRD medical research suggests that inflammation is a risk factor for heart disease. But, when Gurven, Kaplan et al. studied the Tsimane (Amazonia), they found that the Tsimane have HIGH inflammation but virtually no heart disease. The Tsimane should have terrible heart disease. 
That's from The Lancet: tinyurl.com/yxpy3ctj @TheLancet
Why would this be? Much research needs to be done, but a leading candidate is parasitic worms (helminths). Humans coevolved with helminths, and they may do things to the body that prevent heart disease. If you study WEIRD people (only), you get the wrong (or incomplete) answer.
Maybe illness is a special case. What if you studied running form? We clearly evolved to run, so, surely, one can make broad and accurate generalizations about how humans run by studying WEIRD people?
When evolutionary anatomists Dan Lieberman and his team compared people who grew up as barefoot runners to WEIRD people (habitual shoe wearers), they got totally different patterns. Here's one @nature paper on the topic: nature.com/articles/natur…
It turns out that people who habitually wear running shoes, develop a very different running form from the ‘human standard’ that develops when people run barefoot (as we evolved to do). Here’s the culprit:
What if you are actually measuring hormones, like say testosterone? Surely, the manner in which male T levels decline as men age, after marriage and with fatherhood, are features of the species? This is "biology", after all
While more research is needed, the evidence suggests that these patterns are due to WEIRD normative monogamous marriage and male childcare. Traditionally, 85% of societies have been polygynous and many had little male childcare. The same T declines don't appear.
Heart disease, running form and T profiles are all peculiar in WEIRD populations because we live in a helminth free world, strap cushions to our feet when we run, and constrain everyone to one spouse (at a time). #WEIRDBiology.
Given that that's hard to physiology and anatomy right by studying WEIRD people, in our exotic environments, we should not be surprised that so much psychological variation is now being documented around the world.
