Familial resemblance.
The oldest human fossil ever found in China suggests Homo sapiens may have mated with other human species.

Hong Shang et al., PNAS Early Edition

Interspecies Tryst While out of Africa?

The earliest modern human skeleton ever found in China provides evidence that early Homo sapiens spreading out of Africa may have mated with other human species, its excavators say. But others aren't convinced our ancestors got that chummy with their evolutionary cousins.

When H. sapiens first arose in Africa about 150,000 years ago, there were at least two other human species walking the Earth, including Homo erectus in East Asia and the Neandertals in Asia and Europe. Erik Trinkaus, an anthropologist at Washington University in St. Louis, Missouri, has generated considerable controversy with claims that some early modern skeletons show signs of interbreeding with so-called "archaic" humans, including Neandertals. One reason the matter isn't settled is that tracing the migrations of modern humans from Africa, which began at least 40,000 years ago, has been difficult because until recently, few well-preserved remains of these first colonizers had been found.

In 2003, a team led by Trinkaus and Hong Shang of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing excavated the new, partial skeleton, which had been found by workers 2 years earlier in Tianyuan Cave, 56 kilometers southwest of Beijing. The team recovered 34 pieces of bone, including the lower jaw, the shoulder blades, and arm, leg, and finger bones, although the skull was missing. Radiocarbon dating of one of the leg bones gave a calibrated date of about 40,000 years, the team reports online this week in the Proceedings of the National Academy of Sciences. Although most of the skeleton resembled other early modern humans, the researchers argue that some of its features--including the relative sizes of its front and back teeth and some features of its hand and leg bones--more closely resembled those of Neandertals. From this mixture of features, the team concludes that the Tianyuan skeleton is an example of modern humans who mated with archaic hominids on the way from Africa to East Asia.

The new skeleton "is an important find," says Chris Stringer, a paleoanthropologist at the Natural History Museum in London. However, Stringer says he is "not so convinced" that its unusual features suggest interbreeding. Katerina Harvati, an anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, seconds that appraisal. The team compared the Tianyuan skeleton with early moderns from the Near East rather than from fossil-poor Africa, she notes. Without more fossils from Africa for comparison, she says, it's impossible to know whether archaic features in the Tianyuan skeleton came from mating with other species.