New genetic analysis of people living in Papua New Guinea shows a sharp genetic divide between 10,000 and 20,000 years ago that was likely determined by whether their ancestors lived a more nomadic life in the highlands or a more sedentary one in the lowlands.
Why it matters: The genetic divide began at about the same time people began farming in the lowlands. In other parts of the world during the Bronze and Iron Ages, migration and innovations were the prime forces that shaped human evolution. But that doesn't seem to be the case in Papua New Guinea, where the transition to cultivating crops had the opposite effect. Study author geneticist Chris Tyler-Smith told Science that "is a big surprise."