The article is “Restless Genes” from National Geographic. An excerpt:
There is another self-reinforcing dynamic operating in exploration—an ongoing conversation between culture and genes, wherein genes shape what sort of culture we create and the culture in turn shapes our genomes.
This is culture in a broad sense—shareable knowledge, practices, or technology that people use to adapt to an environment. These things exist only because our genetic traits evolved to the point where we could create them, and we reshape them constantly. But this changing culture can likewise shape our genetic evolution, sometimes in stunningly quick and direct ways.
The classic culture-gene example is the rapid rise of a gene for digesting lactose. If you lack this gene, you’ll have trouble digesting milk after infancy. If you have it, you’ll easily digest milk all your life. Almost no one carried this gene 15,000 years ago, because it gave no advantage. It was just a mutation floating around. But when early farmers in Europe started raising dairy cattle about 10,000 years ago—a culture utterly novel then, an entirely different way of living—this gene suddenly gave people access to a reliable year-round food source. They could survive food shortages that starved other people. This advantage rapidly spread the gene throughout Europe, even as it remained rare most other places. Culture and genes started selecting for each other: A new culture made a gene more valuable, and as the gene spread through the population, it made dairy-farming culture more important.