domingo, 21 de septiembre de 2014

Chinese Homo sapiens fossil shifts perceptions of dispersal

The discovery of two teeth in Lunadong, a cave site located in Guangxi (southern China), lends weight to the possibility that the exodus of modern humans from Africa may have been earlier than 60,000 years ago, as traditionally thought.
Christopher Bae, a palaeoanthropologist at UH Mānoa, and Wei Wang of the Guangxi Museum of Nationalities in Nanning, China, have been leading a team of researchers at the Lunadong cave site.

A small clue

Found in stratified deposits dating between 70,000 and 126,000 years ago, a period when eastern Asia was traditionally thought to have been only occupied by more archaic human species, at least one of the teeth can be comfortably assigned to modern Homo sapiens.
Dating results of the Lunadong teeth, which include a right upper second molar and a left lower second molar, indicate that they may be as old as 126,000 years.
“The Lunadong modern Homo sapien’s teeth contribute to growing evidence that modern and/or transitional humans were likely in eastern Asia … [during] a period that some researchers have suggested no hominins were present in the region,” the palaeoanthropologists write in the journal Quaternary International.
“The primary point of our paper is that the human evolutionary record, particularly when accounting for increasing finds in eastern Asia, is a lot more complicated than generally believed,” Associate Professor Bae says. “There were probably multiple dispersals of modern humans out of Africa and into Eurasia, with some degree of interbreeding occurring.”

Rethinking the model

“The findings from the Lunadong study clearly indicate that certain aspects of the Out of Africa model need to be rethought. That is, that there was at least one other earlier Out of Africa migration event that pre-dated 60,000 years ago. This palaeoanthropological find, in addition to other recent studies from western and southern Asia, suggest that modern humans may have dispersed out of Africa in multiple waves rather than as one major single migration event 60,000 years ago as commonly thought,” said Bae.
The Out of Africa theory presently suggests that modern humans migrated from Africa approximately 60,000 years ago following a southern route along the Arabian Peninsula to Southeast Asia.  Recent fossil finds in eastern Asia, including the Lunadong teeth, support the theory of a more complicated dispersal model with migrations not only occurring earlier than originally believed, but also involving later dispersal patterns from Northwest Asia to Europe, and finally into Siberia then the Americas.
Bae has spent the past two decades developing a deeper understanding of the eastern Asian human evolutionary record. He has published extensively on a wide range of topics related to eastern Asian palaeoanthropology, with many publications appearing in top tier scientific journals. He has also co-edited Asian Paleoanthropology: From Africa to China and Beyond (2010; Springer) and three special issues of the journal Quaternary International (2010, 2012, 2014).

Other research

Earlier work, published in the journal Science, describes findings from an eight-year archaeological excavation at Jebel Faya (2011) in the United Arab Emirates led by Professor Hans-Peter Uerpmann of Eberhard Karls University in Tübingen, Germany.
The researchers analysed the Palaeolithic stone tools found and the site in Sharjah Emirate and concluded they were technologically similar to artefacts produced by early modern humans in east Africa. But they were notably different from tools created to the north, in the Levant and the mountains of Iran.
In light of their excavation, an international team of researchers suggested that humans could have arrived on the Arabian Peninsula as early as 125,000 years ago — directly from Africa rather than via the Nile Valley or the Near East, as suggested in the past. This is 65,000 years earlier than the generally accepted date for the first substantial human migrations beyond Africa, excepting the recent potential find in Israel, which still has to be confirmed, see ( New work casts doubt on Out of Africa theory - 28th Dec 2010).
Professor Adrian Parker of Oxford Brookes University, studied sea levels and climate change for the region and concluded that the direct migration route was possible between 140,000 and 130,000 years ago, as the Red Sea was about 100 metres lower than today due to vast quantities of water stored as ice during an earlier Ice Age.
The earlier routes of dispersal seem to be gaining acceptance, however, Chris Stringer of the Natural History Museum in London cautions that this is still a minority view, but agrees that evidence has left him “open to the possibility“.
For further critique of the evidence, read Human exodus may have reached China 100,000 years ago  08 August 2014 by Catherine Brahic in the New Scientist.

Source: Past Horizons:

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