Evolutionary psychology sits on a Stone Age foundation.

Recent evidence suggests strong directional selection on complex human traits.

Natural selection accelerated with the Neolithic Revolution.

“The evolved structure of the human mind is adapted to the way of life of Pleistocene hunter-gatherers.” —Leda Cosmides, John Tooby, and Jerome Barkow, 1992

“Evolution is happening constantly, and it’s rapidly responding to the cultural, economic, and environmental changes we’ve imposed on ourselves over the last 10,000 years.” —David Reich 2026

A generation ago, in the summer of 1992, the Canadian anthropologist Jerry Barkow and his Harvard-educated collaborators, John Tooby and Leda Cosmides, published their landmark volume, The Adapted Mind. It set evolutionary psychology on a Stone Age foundation. “Our ancestors spent the last two million years as Pleistocene hunter-gatherers, and, of course, several hundred million years before that as one kind of forager or another. Homo sapiens is adapted to Pleistocene conditions,” they wrote in their introduction. A year later, Cosmides and Tooby doubled down. “Our ancestors spent well over 99 percent of our species’ evolutionary history living in hunter-gatherer societies. That means our forebears lived in small, nomadic bands of a few dozen individuals who got all of their food each day by gathering plants and by hunting animals.” We might not be foragers anymore, but we’re all living with Stone Age brains.

Last April, a paper in Nature pushed back. Ali Akbari and his coauthors, many from David Reich’s lab at Harvard, analyzed ancient DNA samples from almost 16,000 West Eurasians, and found that hundreds of alleles have been affected by strong directional selection—over just the past 10,000 years. Genes involved in immunity were most likely to show evidence of selective pressure: viruses evolve fast, and hosts evolve........

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