At Nature, researcher Chris Stringer of the Natural History Museum in London asks what makes a modern human. Compared to their ancestors, modern humans have evolved certain traits that are easy to distinguish, like the shape of their skulls or skeleton constructions. After that, it gets a little harder to tell the ancestors' traits from modern humans' traits, Stringer says.
Genomics researchers today share a similar dilemma, as some populations of modern humans seem to carry more "archaic genes" than other populations, Stringer says. "These genes might be expressed in the phenotype, and may require a rethink about how and when regional variation developed in H. sapiens. Those with alternative agendas may also try to use these new data to rank modern human populations in terms of supposedly different degrees of modernity." What's important isn't that some populations have more archaic DNA than others, he says, but that the majority of modern humans' genetic makeup and behavior derives from the same place. "What unites us should take precedence over that which distinguishes us from each other," he adds. However much ancient DNA different populations carry, they all are Homo sapiens, and are modern humans by definition. "We will have learnt nothing in the past 50 years if we let small segments of distinct DNA govern the way we regard regional variation today," Stringer says.