Humans indistinguishable from those living today had evolved by 92,000 years ago -- about 50,000 years earlier than has been generally accepted -- and lived in the Middle East, a team of French and Israeli scientists reported yesterday in the British journal Nature.
If the date is confirmed, the finding would indicate that anatomically modern people evolved before the earliest generally accepted appearance of the Neandertal people, who are considered anatomically more primitive. Some experts had held that Neandertals (the spelling anthropologists prefer) were the ancestors of modern humans.
Anthropologists differ in their interpretation of the French-Israeli findings. To some the findings suggest that modern human beings evolved in Africa more than 100,000 years ago, but did not migrate much beyond the Middle East before Neandertals arose in Europe around 75,000 years ago.
This view is also based on evidence put forth a few years ago that fully modern people were living in southern Africa as far back as 110,000 years ago. The accuracy of this date, however, has been questioned.
It was not until about 35,000 years ago that modern peoples entered Europe and the Neandertals became extinct -- either wiped out by the modern people or interbred until they disappeared as a distinct race. Until now the skeletons of those modern invaders, which included the Cro-Magnon people, were the earliest known remains of modern humans.
The Nature report was published by Bernard Vandermeersch of the University of Bordeaux, Helene Valladas of the French research agency CNRS in Gif sur Yvette and four other researchers from France and Israel. Their report concludes that a close evolutionary relationship between modern humans and Neandertals is now "untenable."
The new findings are based on a new method of determining the antiquity of skeletons discovered many years ago in an Israeli cave called Qafzeh, near Nazareth. It had been estimated that the bones, which are anatomically like those
of living humans, were between 35,000 and 40,000 years old.
The new dating method, called thermoluminescence or TL, was applied not to the bones but to flint flakes found with the bones. TL makes use of the fact that certain products of radioactive decay in stony materials become trapped until the materials are heated. Then the products escape as tiny flashes of light. The amount of light emitted is related to the length of time the decay products have been accumulating in the stone. Once the material cools, a new accumulation starts.
The Qafzeh flints were heated in what was probably an ancient campfire, thus resetting the TL clock. When the flints were again heated inside a TL detector, the amount of light emitted revealed that the campfire burned about 92,000 years ago.
"The paleoanthropological implications of such an age are enormous," Chris Stringer, a human evolution specialist at the British Museum (Natural History), wrote in a commentary in Nature. "Evolutionary models centered on a direct ancestor-descendent relationship between Neandertals and modern Homo sapiens must surely now be discarded."
The older date also raises a new mystery, Stringer said. What kept the Qafzeh people for more than 50,000 years from spreading into Neandertal Europe or eastern Asia? "Were environments to the north so unsuitable or Neandertals so well established that they prevented early modern human radiation until much later?" Stringer asked. "Or are relatives of the Qafzeh people waiting to be discovered elsewhere in Eurasia?"
One clue to the mystery may lie in the stone tool technologies of the two kinds of human being. At first the Qafzeh people and the Neandertals had essentially the same kinds of stone tools. The Neandertal people did not disappear until after the modern people invented a variety of new and better weapons and other tools.
Accepting the truth of the new Qafzeh date and putting aside some relatively minor problems, several anthropologists said the following scenario probably represents a consensus view of how modern humans arose:More than 3 million years ago in Africa, a small apelike species called Australopithecus began walking erect. The original species gave rise to several other forms of Australopithecus. By 2 million years ago one of the forms had changed, again in Africa, into a somewhat larger-brained species called Homo habilis, the earliest definite maker of stone tools. At around 1.5 million years ago, Homo habilis gave rise to Homo erectus, which had a still larger brain and was the first human ancestor to migrate out of Africa and to control fire. Homo erectus spread through much of Eurasia. By about 300,000 or 400,000 years ago, at least one population of Homo erectus evolved still larger brains and became what anthropologists call the archaic form of Homo sapiens. It is unclear where this happened but it was likely so gradual that interbreeding among clans spread the more advanced genetic traits over much of Eurasia and Africa. At some time before the Qafzeh people lived, a population of archaic Homo sapiens evolved into fully modern humans, probably in Africa. These people spread to southern Africa and into the Middle
East. Some time later, the archaic Homo sapiens living in western Europe evolved into the Neandertals, who slowly spread eastward. Fifty thousand years later, when the fully modern people invented more effective technologies -- whether for hunting or for war is an open question -- they took over all of Eurasia, sailed to Australia and entered the New World.