[LINK] "Ancient Tools May Mark Earlier Path Out of Africa"

[rfmcdonald]

The ancient human diaspora from our species' east African homeland may have begun at a much earlier time, Brian Switek writes at Wired Science. Tools have been found.

Uncovered at a Jebel Faya rock shelter, just west of the Straits of Hormuz at the mouth of the Persian Gulf, the tools are 125,000 years old. Previous estimates placed the dispersal of modern humans from North Africa around 70,000 years ago. If correct, this new study indicates that humans in eastern Africa left earlier, and traveled to Arabia.

The tools include small hand axes, scrapers and notched tools called denticulates. They’re described Jan. 27 in Science. According to researchers led by University of London paleogeographer Simon Armitage, the tools resemble those made in the same era by humans in eastern Africa, rather than tools found at later sites along the Mediterranean’s eastern border.

On the basis of these tools, Armitage and co-authors propose that humans crossed from eastern Africa to Arabia around 130,000 years ago. Lower sea levels may have opened a path, and increased rainfall would have made the Jebel Faya area less arid than it is today.

From southeast Arabia, humans “would have reached South Asia much earlier than assumed and would have had more time to adapt to all kinds of environments encountered in the whole of Eurasia,” wrote study co-author and University of Tübingen archaeologist Hans-Peter Uerpmann.

The findings support a scenario suggested by University of Birmingham archaeologist Jeffrey Rose in December 2010 in Current Anthropology. He described how a “Gulf Oasis” could have sheltered humans 100,000 years ago, and even earlier.

io9 has an extended question-and-answer post. One of the people asked, Adrian Parker, explained why that was a plausible timeline for settlement.

We need to go back to where modern humans emerged in east Africa. This occurred approximately 200,000 years ago. The period between 200,000 years ago until 130,000 years ago corresponds to time when there was a global ice age. During ice ages global sea levels fall as water becomes locked up in the vast ice sheets in the northern and southern hemispheres. When ice ages occur, the world's major desert belts also expand and thus modern humans would have been restricted to east Africa as the deserts of the Sahara and Arabia posed major geographical barriers that prevented movement out of the region.

By 130,000 years ago global climatic conditions changed and we moved into an interglacial, a period of warmer, global temperatures. At this time, the Indian Ocean monsoon system was forced northwards, bringing rainfall into Arabia. The previously arid interior of Arabia would have been transformed into a landscape covered largely in savannah grasses with extensive lakes and river systems. At the onset of the inter glacial, sea levels in the southern Red Sea were over 100 meters lower than today. this led to a brief window of time when sea levels were still low and Arabia experienced a wetter climate, thus humans would have been able to cross a much narrower Red Sea, perhaps as little as four kilometers wide before sea levels rose sufficiently to make the crossing more difficult."