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2008-10-11 – Nuove tracce in Cina: I primi umani lasciarono l’Africa 1,8 milioni di anni fa (China, early humans)

Early humans left Africa 1.8 million years ago, suggests ancient fossil trail

October 10th, 2008 – 4:40 pm ICT by ANI

Washington, Oct 10 (ANI): Using advanced dating techniques, scientists have determined that a trail of stone tools and fossil bones found in China, suggests that early humans left Africa 1.8 million years ago.
Over a million years ago, a band of early humans left their stone tools and two front teeth near a stream in southwest China.
For decades, the precise age of the fossils has remained a mystery, leaving open a central question in paleontology that how quickly did our human ancestors reach China after leaving Africa?
Now, thanks to advanced dating techniques, scientists may finally have the answer.
Chinese paleontologists discovered the two incisors in 1965 and the relatively simple stone tools in 1973 in the Yuanmou Basin.
The teeth came from a hominin, the group that includes humans and our exclusive ancestors, and might be from the species Homo erectus, a direct ancestor of humans that may have been the first human to spread beyond Africa about 1.8 million years ago.
Lacking solid dates, researchers thought until a decade ago that the earliest humans didn”t reach Asia until 1 million years ago.
But a series of dates for fossils from one site in Java, Indonesia, in particular, have recently shown that Homo erectus was there 1.66 million years ago and possibly earlier.
This changed the old textbook view that human ancestors spread around the globe only after they had big brains and more advanced stone hand axes, which appear in Africa about 1.6 million years ago.
Now, a team of Chinese and American researchers has redated the Yuanmou Basin site using a paleomagnetic technique that relies on rock samples to determine the direction of Earth’’s magnetic field when the rocks were formed.
Although the original hillside where the fossils were found has been excavated, the discoverers recorded the layer of sediment where they uncovered the teeth and tools.
The new team traced that sediment layer – or time horizon – throughout the basin, collecting 318 rock samples from it.
The researchers reported that the fossils came from a layer of rock just above a magnetic landmark known as the Olduvai-Matuyama reversal boundary, which is at least 1.77 million years old.
This makes the fossil site slightly younger, about 1.7 million years old.
This age estimate represents “the oldest definite fossil and archaeological evidence of early hominins in China and mainland East Asia,” according to co-author Rick Potts, a paleoanthropologist at the Smithsonian Institution in Washington, D.C.
Taken together, these dates from at least three fossil sites are convincing many researchers that early humans were moving rapidly across Asia 1.77 million to 1.66 million years ago. (ANI)



ottobre 11, 2008 - Posted by | 1 Olocene b, Asia, P - Paleoantropologia, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , , , , ,

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