Telltale Face Betrays Neandertals as Non-Human
for National Geographic News
|August 2, 2001|
Tens of thousands of years ago, Neandertalsa race of people that somewhat resembled modern humanscrisscrossed the landscapes of Europe and western Asia and lived over a wide range for many millennia.
At times, they lived near or alongside the biological ancestors of modern humans, who had left Africa and were spreading gradually throughout the same regions.
Then, some 20,000 years ago, Neandertals disappeared from Earth.
Anthropologists still aren't certain they know what happened to them, but there are two popular theories.
For decades, scientists have been studying bones, genes, and ancient tools in an effort to determine which of the theories is accurate. Now, two scientists in Switzerland are weighing in with the results of a novel analysis.
One of the two competing theories holds that Neandertalsstrong, intelligent, and with the knowledge and dexterity to make simple but effective toolswere barely different from other ancient peoples. Those other groups, the thinking goes, biologically assimilated Neandertals in the process of outcompeting them or perhaps killing them off.
If it's true that Neandertals were absorbed into other groups, their distinctive DNA is likely to have been introduced into the gene pool of the survivors in small amounts and passed down through the generations. In this telling of prehistory, some of us may be descendants of the Neandertalsor at least have a few of them high in the branches of the family tree.
But a popular alternative version maintains that the ancient race left no living legacy. It suggests that Neandertals were a biologically different species that was incapable of matingand therefore biologically mixingwith the modern humans they may have encountered.
This week in the journal Nature, Marcia S. Ponce de León and Christoph P.E. Zollikofer at the University of Zurich describe their analysis using a computer-modeling technique to reconstruct and compare facial growth patterns in humans and Neandertals. Their study showed that members of the two groups developed in distinct ways and looked quite different from each other from a very young age.
"The developmental evidence is quite strong that we have two species," said Zollikofer.
The findings support the notion that Neandertals were a different species, and that there was little, if any, interbreeding between them and the ancestors of modern peoples.
No Generation Gap
Ponce de León and Zollikofer had assumed that infants of the two groups looked relatively similar. They expected to find that differences in the shape of the face and the head and in the growth pattern of teeth arose only as individuals grew older.
"But what we found," said Zollikofer, a paleoanthropologist, "was [that children] had the same differences as adults" of their respective populations.
In juveniles, environmental factors such as physical activity by the individuals couldn't explain the occurrence of such differences. Therefore, he concluded, "the differences were deeply genetic."
The two Swiss researchers studied 16 Neandertal fossils from across the ancient group's geographical range. One specimen came from Gibraltar, off the coast of Spain, and others from as far east as Uzbekistan, in central Asia. Several more came from Israel, but political difficulties left one well-preserved specimen in Iraq off limits.
The scientists spent eight years traveling to study the fossils, which also required packing them carefully in plaster casts and shipping them back to Switzerland for additional examination.
They used a computer-modeling technique to compare these Neandertal fossils with those of modern humans. The latter group of fossils represented people of many ethnicities and included some ancient individuals who could have passed unnoticed among people today.
Eleven of the Neandertal specimens examined were "immature," meaning that not all of the individuals' adult teeth had grown in. That enabled Ponce de León and Zollikofer to reconstruct how different parts of the faces of Neandertals and modern humans changed as both groups grew older.
New Look at Juveniles
About half of the fossils of Neandertals and ancient humans that anthropologists have found are of juveniles. "It's a demographic fact that 50 percent of [those ancient] populations died before reaching maturity," said Zollikofer.
In past scientific studies, the remains of children were usually excluded from the sample because they were assumed not to reflect the developmental patterns that could reveal differences between the adults of two species. Ponce de León and Zollikofer, however, have found that even young members of a species exhibit full-blown growth patterns parallel to those of adults in the groups.
The new research contradicts the claims made by discoverers of a hotly debated fossil find in Portugal's Lapedo Valley two years ago. The so-called Lagar Velho fossil, of a young child who died 24,500 years ago, appears to be Neandertal, but has distinct characteristics of a modern human.
Its discoverers, who included João Zilhão, director-general of the Portuguese Institute of Archaeology, saw it as evidence that humans and Neandertals interbred and produced hybrid offspring. In a paper he wrote about the fossil last year, Zilhão observed: "Neandertals were just peopleperhaps a little funny-looking, but people nonetheless."
But most anthropologists still disagree with that conclusion, and Zollikofer's evidence bolsters the argument that humans and Neandertals did not interbreed, and probably were not biologically capable of doing so.
Nevertheless, the Lagar Velho specimen is "amazingly interesting," said Zollikofer. He and Ponce de León have joined a large effortled by Zilhão, another Portuguese anthropologist, and Erik Trinkhaus of Washington Universityto publish a book describing the Lagar Velho find and exploring its implications for our understanding of human evolution.
Zollikofer plans to study the Lagar Velho fossil using the same computer-aided technique he applied to the Neandertal specimens. Determining whether the head and facial growth patterns of the child are more characteristic of Neandertals or of modern humans may help answer uncertainties about its alleged mixed parentage.
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