By John Noble Wilford January 27, 2004 |
Ever since their discovery in the 19th century, Neanderthals have been like the uncomfortably odd relatives who show up at a family reunion. Should they be seated with the closest kin, sent to the back of the room with the distant cousins or tossed out as rank interlopers, despite a family resemblance? In short, were the now-extinct Neanderthals of Europe full members of the modern human species, a subspecies or an entirely different species? The answer has implications for the ancestry of modern Europeans: whether some Neanderthal blood could flow in their veins. Although many scientists think Neanderthals were a subspecies, which could have interbred with Homo sapiens, new research appears to confirm the more widely held view that Neanderthals and modern humans were significantly different, enough to qualify as separate species. The findings were based on detailed measurements of variations in the skulls of modern humans and Neanderthals as well as 12 existing species of nonhuman primates. The research team, led by Dr. Katerina Harvati, a paleoanthropologist at New York University, reported its results yesterday in The Proceedings of the National Academy of Sciences. "What we are really saying is that Neanderthals did not co ntribute to the a ncestry of modern Europeans," Dr. Harvati said in an interview. The research lends strong support for the single-origin theory of modern human evolution, one of two models that have split anthropology into warring camps. This theory holds that modern Homo sapiens is a new species that arose relatively recently in Africa - more than 100,000 years ago - and spread out to replace indigenous archaic populations around the world. Neanderthals were one such group, a separate species that did not breed with the newcomers before it vanished. The opposing regional-continuity theory holds that the new migrants from Africa bred at least to some extent with the archaic populations they encountered, perhaps accounting for some superficial differences among people today in different regions. In this view, Neanderthals were a subspecies and at least partly ancestral to modern Europeans. Dr. Eric Delson, a paleontologist at the American Museum of Natural History and Lehman College, both in New York City, said the new research was a mathematically rigorous approach to the question of Neanderthal-human relationships. "It's a very convincing piece of work," Dr. Delson said. But not convincing enough, it seems, to put the controversy to rest. "This research will not change many minds," said Dr. Erik Trinkaus, a specialist in Neanderthal studies at Washington University in St. Louis. His research has suggested that there was some interbreeding. "We have known for a long time what these fossils look like," Dr. Trinkaus continued. "We know that Neanderthals are distinctive, but this research doesn't address their underlying biology." In the new research, Dr. Harvati and her colleagues, Dr. Stephen R. Frost of the New York Institute of Technology in Old Westbury and Dr. Kieran P. McNulty of Baylor University in Waco, Tex., used a technique known as geometric morphometrics to measure the degree of variation between and among living primate species, including chimpanzees, gorillas, baboons, monkeys and humans. The researchers focused their analysis on the same 15 "landmarks" on the cranium and face of each specimen. They were examined in 3-D to determine even the finest variations in shapes. The purpose, Dr. Harvati said, "was to devise a quantitative method to determine what degree of difference justified classifying specimens as different species." The differences measured between modern humans and Neanderthals were found to be significantly greater than those found between subspecies or populations of the other species studied. The two living species of chimpanzees, for example, appear to be more closely related to each other than Neanderthals are to humans, the scientists concluded. In a statement about the findings, Dr. Harvati said the research provided "the most concrete evidence to date that Neanderthals are indeed a separate species within the genus Homo." |
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Skull Details Suggest Neanderthals Were Not Humans
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