Friday, September 28, 2007

Almost 8 million year old Fossils from republic of Georgia

The discovery of four fossil skeletons of early human ancestors in the republic of Georgia has given scientists a revealing glimpse of a species in transition, primitive in its skull and upper body but with more advanced spines and lower limbs for greater mobility.

The findings are considered a significant step toward understanding who were some of the first ancestors to migrate out of Africa some 1.8 million years ago. They may also yield insights into the nature of the first members of the human genus, Homo. Until now, scientists had found only the skulls of small-brain individuals at the Georgian site of Dmanisi. They said the new evidence apparently showed the anatomical capability of this extinct population for long-distance migrations.

“We still don’t know exactly what we have got here,” David Lordkipanidze, leader of the excavations, said in an interview on a visit to New York. “We’re only beginning to describe the nature of the early Dmanisi population.”

Other paleoanthropologists said the discovery could lead to breakthroughs in the critical evolutionary period in which some members of Australopithecus, the genus made famous by the Lucy skeleton, made the transition to Homo. The step may have been taken sometime before two million years ago, a period with only fragmentary fossil remains of the human past.

The international team headed by Dr. Lordkipanidze, director of the Georgian National Museum in Tbilisi, found several skulls and stone tools at Dmanisi in the 1990s. They were dated to 1.77 million years ago and resembled the species Homo erectus, the immediate predecessor of Homo sapiens. The fossils were tentatively assigned to the erectus species.
But erectus had been thought of as a species with more affinities to modern humans, with large bodies and long faces, teeth smaller and brains bigger than its predecessors. A young erectus man in Africa, dating to 1.5 million years ago, had a modern body and stood almost 6 feet tall.

The Dmanisi specimens were quite different. Their skull sizes indicated that they had brains not much larger than those of a chimpanzee. Their size was closer to the brains of Homo habilis, a poorly understood earlier ancestral species. In the last few years, however, the researchers collected more extensive, well-preserved skeletal remains of an adolescent and three adult individuals. Some of the fossils resembled those of later erectus specimens in Africa. The lower limbs and arched feet, for example, reflected traits “for improved terrestrial locomotor performance,” the discovery team reported.

Over all, though, the fossils were “a surprising mosaic” of primitive and evolved features. The small body size and small craniums, the upper limbs, elbows and shoulders were more like the earliest habilis specimens. “Thus, the earliest known hominids to have lived outside of Africa in the temperate zones of Eurasia did not yet display the full set” of evolved skeletal features, the scientists concluded.


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