Modern humans may have left Africa for Arabia up to 65,000 years earlier than previously thought and their exodus was enabled by environmental factors rather than technology, scientists said on Thursday.
Their findings suggest the migrants followed a direct route to the Arabian Peninsula from Africa, and did not travel via the Nile Valley or the Near East as suggested in previous studies.
An international team of researchers studied an ancient tool kit containing hand axes, perforators and scrapers which was unearthed at the Jebel Faya archaeological site in the United Arab Emirates.
"Our findings should stimulate a re-evaluation of the means by which we modern humans became a global species," said Simon Armitage, of the University of London, who worked on the study.
Using luminescence dating -a technique used to determine when mineral grains were last exposed to sunlight -- they found that the stone tools were between 100,000 and 125,000 years old.
Sea levels more important than tools
Hans-Peter Uerpmann of Eberhard Karls University in Tuebingen, who led the research, said the craftsmanship ruled out the possibility the tools were made in the Middle East.
He said the tools resembled those made by early humans in east Africa instead, suggesting that "no particular cultural achievements were necessary for people to leave Africa."
The research, published in the journal Science, suggests environmental factors such as sea levels were more important than technological innovations in making the migration possible.
The researchers analyzed sea-level and climate-change records preserved in the landscape from the last interglacial period - around 130,000 years ago - to determine when humans would have been able to cross Arabia.
They found that the Bab al-Mandab strait between Arabia and the Horn of Africa would have become narrower at this time as sea levels were lower, providing a safe route out of Africa both prior to and at the beginning of the last interglacial period.
Uerpmann said the straits may have been passable at low tide, making it likely that the modern humans walked across or travelled on either rafts or boats.
It was previously thought that the deserts of the Arabian Peninsula would have hindered an exodus from Africa but the new study suggests Arabia became wetter during the last interglacial period, with more lakes, rivers and vegetation, making it easier for humans to survive the passage.
Although the timing of modern humans moving out of Africa has been the subject of much debate, previous evidence suggested the exodus took place along the Mediterranean Sea or Arabian coast around 60,000 years ago.
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