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September 2011, Cover Stories, Daily News

Finds in Oman Push Back Date of Modern Human Exodus Out of Africa

Wed, Nov 30, 2011

Stone tool finds challenge long-held theories about early human migration out of Africa.

Finds in Oman Push Back Date of Modern Human Exodus Out of Africa

New discoveries by an international team of archaeologists and geologists in the Dhofar Mountains of southern Oman are shedding new light on when and how archaic modern humans first migrated out of their African homeland to occupy Eurasia. 

Led by Dr. Jeffrey Rose of the University of Birmingham, the team found over 100 new sites that featured "Nubian Middle Stone Age (MSA)" tools, an ancient industry known to have existed in the Nile Valley of Egypt, but never outside of Africa. According to these researchers, this provides further evidence that early humans migrated across the Red Sea region on their journey out of Africa. Says Rose, "After a decade of searching in southern Arabia for some clue that might help us understand early human expansion, at long last we've found the smoking gun of their exit from Africa. What makes this so exciting is that the answer is a scenario almost never considered."

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Nubian Type 1 core from Oman, the first time this particular stone tool technology has been found outside of Africa. Credit: Yamandu Hilbert  Rose JI, Usik VI, Marks AE, Hilbert YH, Galletti CS, et al. (2011) The Nubian Complex of Dhofar, Oman: An African Middle Stone Age Industry in Southern Arabia. PLoS ONE 6(11): e28239. doi:10.1371/journal.pone.0028239

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The findings challenge long-held theories about human migration and dispersal out of Africa. By using Optically Stimulated Luminescence (OSL) techniques, they were able to date one of the sites to 106,000 years ago, a time that significantly predates the 70,000 to 40,000 BP time range when geneticists have estimated that early modern humans made their exodus. 

Moreover, the sites were located inland, far from the coast, inconsistent with currently accepted theories that suggest that early humans made their exit by hugging the coast of southern Arabia. Says team member and co-author Professor Emeritus Anthony Marks of Southern Methodist University, "Here we have an example of the disconnect between theoretical models versus real evidence on the ground. The coastal expansion hypothesis looks reasonable on paper, but there is simply no archaeological evidence to back it up. Genetics predict an expansion out of Africa after 70,000 thousand years ago, yet we've seen three separate discoveries published this year with evidence for humans in Arabia thousands, if not tens of thousands of years prior to this date."

Why would these human groups move inland to occupy the unforgiving desert landscape of present-day Oman?  According to scientists, the answer lies in fluctuating cycles of climatic history. These lands, 106,000 years ago, were expansive grasslands - not the dry desolation we see today. Says Rose, "For a while, South Arabia became a verdant paradise rich in resources – large game, plentiful freshwater, and high-quality flint with which to make stone tools." These early modern humans may have been primarily hunters, following game and freshwater through river networks as opposed to being fishers who progressed along the coastal areas.

How long they occupied these areas through the cycles of changing climate remains to be determined through future research.  

The detailed research article is published as The Nubian Complex of Dhofar, Oman: An African Middle Stone Age Industry in Southern Arabia by Rose JI, Usik VI, Marks AE, Hilbert YH, Galletti CS, et al. (2011) in the open-access journal PLoS ONE.

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