Genetics & Genealogy

New Evidence on the Origin of the Human Species

Norman Hammond, Archaeology Correspondent
The Times, August 2000

Neanderthal man was one of our ancestors after all, a Portuguese archaeologist claims. DNA studies which claimed that Neanderthals were too genetically different to have been part of our family tree failed to take account of primate variability, and although there was a long period of separate development, the two human types came back together in Western Europe some 25,000 years ago.

A child's skeleton found in Portugal shows features of both Neanderthal and modern man, and is the result of interbreeding between the two sub-species Dr João Zilhão reports in Archaeology. This proves, he says, that "Neanderthals had not simply disappeared without descendants - they had been absorbed into the modern human groups that started to take over Iberia 30,000 years ago". The child was found at the back of a shallow cave at Lagar Velho, 85 miles north of Lisbon, at the end of 1998, and studies of the skeleton by the Neanderthal expert Dr Erik Trinkaus have been in progress ever since. Dr Trinkaus concluded that the child presented a mosaic of Neanderthal and modern features, with the former's short, robust limbs and compact body form and the latter's pointed chin and dentition.

"Body proportions are particularly important because they are genetically inherited and the basic patterns of body shape are already established at the foetal stage of development" Dr Zilhão says. "This makes it possible to compare the Lagar Velho child with not only children but adult skeletons from the same period".

Of the two possible ancestral populations, Neanderthals had compact, heat-saving arctic body proportions, while early modern human beings had tropical proportions, with long heat-dispersing limbs, betraying their relatively recent African evolutionary origin. Although modern humans had moved out of Africa more than 100,000 years ago, and probably much earlier than that, the Neanderthals' ancestors had been in the cold northern climes for much longer, and their body form had adapted.

Radiocarbon dating of the child showed that it was only 25,000 years old, a date which fitted in with the rituals carried out at burial, including the deposition of joints of meat and the presence of jewellery made from shells and teeth. Both are found commonly with anatomically-modern humans in the Upper Palaeolithic 40,000 years ago.

The late date, some 3,000 years after Neanderthals themselves had apparently become extinct in Western Europe "made it clear that the mosaic of anatomical features in the Lagar Velho child could not have been the result of a rare chance encounter of a Neanderthal mother and modern father, or vice versa: it had to represent a mixture of populations." Dr Zilhão says "Neanderthals had contributed to the gene pool of subsequent Upper Palaeolithic populations, and had to be continued among our ancestors: they were family."

These findings directly contradict the "African Eve" hypothesis currently accepted by many scientists, that all living humans descend only from people who moved out of Africa less than 100,000 years ago. This view was strongly supported by analysis of DNA from the original Neanderthal skeleton from Germany, which was so different from that of modern humans as to suggest two different species (The Times, July 11, 1997). A new study of African ape DNA counters this argument, Dr Zilhão says:

"Living and interbreeding chimpanzee populations are genetically more diverse than modern humans and Neanderthals put together. Modern humans are thus abnormally homogeneous, which is consistent with a recent "Out of Africa" origin but does not prove that Neanderthals were a separate species. Instead, it confirms what the bones tell us: Neanderthals were a geographically separated branch of humanity, who although they are now extinct, nevertheless contributed to our own gene pool. Although the word is now more often used as an insult, or to describe the appearance of a fearsome front-row forward, it reflects reality.

The interbreeding suggested by the Lagar Velho child shows that our early modern human ancestors "saw Neanderthals as fellow human beings" Dr Zilhão says. "If they were just people - perhaps a little funny looking, but people nonetheless - why should we persist in trying to put them into an entirely different category ?"

Discovery suggests humans are a bit Neanderthal

John Noble Wilford, New York Times, 27 April 1999

Neanderthals and modern humans not only coexisted for thousands of years long ago, as anthropologists have established, but now their little secret is out: they also cohabited. At least that is the interpretation being made by paleontologists who have examined the 24,500-year-old skeleton of a young boy discovered recently in a shallow grave in Portugal. Bred in the boy's bones seemed to be a genetic heritage part Neanderthal, part early modern Homo sapiens. He was a hybrid, they concluded, and the first strong physical evidence of interbreeding between the groups in Europe.

"This skeleton demonstrates that early modern humans and Neanderthals are not all that different," said Dr. Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis. "They intermixed, interbred and produced offspring." Although some scientists disputed the interpretation, other scientists who study human origins said in interviews last week that the findings were intriguing, probably correct and certain to provoke debate and challenges to conventional thinking about the place of Neanderthals in human evolution.

Neanderthals and modern humans presumably were more alike than different, not a separate species or even subspecies, but two groups who viewed each other as appropriate mates. Recent DNA research had appeared to show that the two people were unrelated and had not interbred. Neanderthals lived in Europe and western Asia from 300,000 years ago until the last of them disappeared on the Iberian peninsula about 28,000 years ago. In the prevailing theory today, modern humans arose in Africa less than 200,000 years ago and appeared in great numbers in Europe, starting about 40,000 years ago.

The new discovery could, at long last, resolve the question of what happened to the Neanderthals, the stereotypical stocky, heavy-browed "cave men." They may have merged with modern humans, called Cro-Magnons, who appear to have arrived in Europe with a superior tool culture. In that case, some Neanderthal genes survive in most Europeans and people of European descent. The skeleton of the boy, buried with strings of marine shells and painted with red ocher, was uncovered in December by Portuguese archeologists led by Dr. João Zilhao, director of the Institute of Archeology in Lisbon. The discovery was made in the Lapedo Valley near Leiria, 90 miles north of Lisbon. Realizing the potential significance, Dr. Zilhao called in Dr. Trinkaus, an authority on Neanderthal paleontology, who went to Lisbon and examined the bones in January.

The boy, who was about 4 years old at death, had the prominent chin and other facial characteristics of a fully modern human. But his stocky body and short legs were those of a Neanderthal. Dr. Trinkaus compared the limb proportions with Neanderthal skeletons, including some children. He said he was then sure of the skeleton's implications. "It's a complex mosaic, which is what you get when you have a hybrid," Dr. Trinkaus said. "This is the first definite evidence of admixture between Neanderthals and European early modern humans."

The age of the skeleton, determined by radiocarbon dating, showed that full Neanderthals had apparently been extinct for at least 4,000 years before the boy was born. "This is no love child," Dr. Trinkaus said, meaning that this was not evidence of a rare mating but a descendant of generations of Neanderthal-Cro-Magnon hybrids.

Dr. Trinkaus and Dr. Zilhao have completed a more detailed scientific report to be published soon in the Proceedings of the National Academy of Sciences. DNA tests on the skeleton have not yet been done. Other Neanderthal specialists reacted favorably to the discovery. Dr. Fred H. Smith of Northern Illinois University in De Kalb called it "very convincing and absolutely right." Dr. Smith noted that he had come upon other skeletal material in central Europe that raised the possibility of interbreeding between the groups. Though most scholars in the field will probably accept the possibility of interbreeding, he said, a significant number will probably not.

The more ardent exponents of the out-of-Africa hypothesis of modern human origins may be holdouts. They have argued that early modern humans all emerged from Africa and wiped out the Neanderthal population in Europe. Whether the relationship was fraternal or genocidal has been much debated. But many have argued that the two groups were distinct, with humans displacing and probably slaughtering their rivals.

Dr. Chris Stringer, an expert on Neanderthals at the Museum of Natural History in London, who is a leader of the out-of-Africa forces, said that he was willing to consider the Portuguese findings with an open mind. He told The Associated Press that the current evidence was not sufficient to convince him of Dr. Trinkhaus's hybrid interpretation.

An alternative theory, known as regional continuity, holds that the earliest human ancestors arose in Africa and spread around the world more than a million years ago. Modern humans then emerged in different regions through separate evolution and interbreeding. A leading advocate of this theory is Dr. Milford Wolpoff, a paleontologist at the University of Michigan in Ann Arbor.

"This find should be devastating to the out-of-Africa people," Dr. Wolpoff said. "It shows their theory doesn't work, at least in Europe. And it shows that fundamentally, Neanderthals are the same species we are and they contributed their genes to European ancestry."

By now, scientists said, only a small fraction of Neanderthal genes have survived, the European gene pool having been further mixed through migrations during the spread of agriculture and invasions from the east. But Dr. Wolpoff cautioned that it would take more than one skeleton to tell the effects of interbreeding apart from ordinary evolutionary changes, the result of genes modifying in response to environmental stresses.

Dr. Alan Mann, a specialist in human evolution at the University of Pennsylvania, called the Portuguese hybrid skeleton "some of the most important data we ever got about Neanderthals in human evolution," but said he was not sure that interbreeding had been established.

Dr. Trinkaus said the discovery "refutes strict replacement models of modern human origins" and also seemed to undermine interpretations of recent DNA research. Two years ago, Dr. Svante Paabo of the University of Munich in Germany, reported that a study of the genetic material DNA from Neanderthal remains and living humans indicated that Neanderthals did not interbreed with the modern humans. At the time, scientists said the DNA results reinforced the idea that Neanderthals were a separate species from modern humans. If the new findings are correct, though, the two groups were probably more like different races of the same species.

"The problem with the DNA research was the interpretation," Dr. Trinkaus said. "It's demonstrably wrong. All that they showed is that Neanderthal biology is outside the range of living humans, not modern Homo sapiens back then."

Dr. Alan Templeton, an evolutionary geneticist at Washington University, said that some hybridization occurs without the effects showing up, for example, in mitochondrial DNA, which is passed only through the mother. "But if you look deep enough in evolutionary time, you find a lot of interbreeding," Dr. Templeton said. "That is what humanity is all about: we interbreed a lot."