for National Geographic News
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.
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