Neandertal genes point to interbreeding, inbreeding

A high-quality chunk of DNA extracted from a Neandertal woman’s roughly 50,000-year-old toe bone has sharpened scientists’ view of genetic ties among Stone Age humans and their nearest, now-extinct relatives. The Neandertal fossil comes from a Siberian cave that also yielded a DNA-bearing finger bone from the Denisovans, close genetic relatives of Neandertals.

Neandertals contributed around 2 percent of the DNA carried by non-African people today, a team led by paleogeneticist Kay Prüfer of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reports December 18 in Nature.

Comparisons of the Neandertal DNA with human and Denisovan DNA indicate that Denisovans inherited at least 0.5 percent of their DNA from Neandertals and a small percentage of genes from another, unknown hominid species that first appeared at least 1 million years ago.

Signs of low genetic diversity in the Neandertal woman’s DNA indicate that her parents were closely related, possibly half siblings. Small population sizes encouraged inbreeding among Neandertals, the researchers suggest.

Prüfer’s group located a set of genetic segments in people today that don’t occur in Neandertals, Denisovans or living apes. Those segments may contain clues to the evolutionary success of Homo sapiens.