Sit down with an anthropologist to talk about the nature of humans, and you are likely to hear this chestnut: “Well, you have to remember that 99 percent of human history was spent on the open savanna in small hunter-gatherer bands.” It's a classic cliché of science, and it's true. Indeed, those millions of ancestral years produced many of our hallmark traits—upright walking and big brains, for instance. Of course, those wildly useful evolutionary innovations came at a price: achy backs from our bipedal stance; existential despair from our large, self-contemplative cerebral cortex. As is so often the case with evolution, there is no free lunch.
Compounding the challenges of those trade-offs, the world we have invented—and quite recently in the grand scheme of things—is dramatically different from the one to which our bodies and minds are adapted. Have your dinner come to you (thanks to the pizza delivery guy) instead of chasing it down on foot; log in to Facebook to interact with your nearest and dearest instead of spending the better part of every day with them for your whole life. But this is where the utility of the anthropologist's cliché for explaining the human condition ends.