How Did Climate Affect Humanity’s First Steps Out of Africa?

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We often use this little corner of the intertubes to think about how globalization is physically changing the earth – be it via our addiction to air travel or jeans made on the cheap. But we’re not sticklers. Recent research published in the journal Science presents archaeological evidence that might shed new light on exactly the converse of that equation: How did environmental changes affect the very first phase of globalization?

Quite a bit, according to the authors of the study. The findings of the international team of scientists, published January 28, suggest that the first wave of modern humans might have left Africa via the Arabian Peninsula as much as 65,000 years earlier than previously thought.

Homo sapiens (that’s us) evolved in Africa around 200,000 years ago. When and how we decided to make our way to other continents, eventually spreading around the world, has generated much debate, but the prevailing consensus these days suggests it was generally about 60,000 years ago, and that we migrated out of Africa along the Mediterranean and Arabian coasts.

Something like this:

Courtesy of Wikipedia

The Science paper, however, suggests the first wave of humans might have instead left across the Bab el-Mandeb strait between the horn of Africa and the Arabian Peninsula from 100,000 to 120,000 years ago.

Their evidence, gathered during an eight year dig in Jebel Faya in the United Arab Emirates (on the far east coast of the Peninsula), is a set of Palaeolithic stone tools whose design and use were unique to modern humans in east Africa at that point in time. The researchers say that other hominin species that might have made the tools, like Neanderthals that were living in Europe and Asia at the time, were not using the combination and style of objects that were found, and that the site was out of their habitat range.

The paper further suggests that it was the particular environment of that time period that could have made this new ‘southern route’ out of Africa possible. Professor Adrian Parker, one of the paper’s authors, studied sea level changes in the region, finding that before the tools were left at Jebel Faya, the strait between the horn of Africa and the Peninsula was shallow and narrow enough that our ancestors may have been able to make the crossing on foot or by raft.

Another key environmental difference Parker noted was the climate of the Arabian Peninsula: during that period, there was heavier rainfall in the area, and more bodies of water, vegetation and game in the region, making the area habitable enough for a crossing.

The group’s theory has not been universally embraced. Archaeologist Paul Mellars of the University of Cambridge told Science that there was not “a scrap of evidence there that [the tools] were made by modern humans, nor that they came from Africa.” Others have not outright rejected the idea, but have been cautious in their endorsement. “One site does not confirm the out-of-Africa-via-Arabia hypothesis,” Mark Beech, a visiting fellow at the University of York told the journal.

We’ll let the archaeologists go to the mat over that one. But it’s pretty interesting to think about how — be it 60,000 years ago or 120,000 years ago — we are again facing an epoch when changes in the planet will be drastically affecting where and how we can live as a species. (In fact, as I write this, a film about climate change refugees is up for Best Short Documentary at the Oscars.) But there is a difference. This time around, we’ve only got ourselves to blame.