I’m a fairly regular reader of Geotimes, a magazine devoted to geology and Earth-related topics like climate and, sometimes, anthropology. So imagine my surprise when my eye catches the credit to the photograph shown here of the African savannah belonging to an anthropologist friend and then another photo (shown below) to yet another friend! As far as I know, Kambiz Kamrani and Jeff Rose don’t know each other, but I was happy to see them both showcased in the same article all the same.
Kambiz Kamrani, the brains and muscle behind Anthropology.net has the lead photo in the article, “Out of Africa: Following the Arabian Trail“, published in the January issue of Geotimes and written by Erin Wayman.
Jeff Rose is an archaeologist, currently teaching at Oxford Brookes University in the Department of Anthropology and Geography and his specialty is lithics of prehistoric hominids.
The meat of the article is discussing the migration of humans from Africa to the rest of the world through a southern Arabian route via the Horn of Africa. This isn’t necessarily a new idea, but recent discoveries in both archaeology and genetics have put it in a favorable light in recent years. I recall several discussions and lectures I attended with Dr. Rose (who hates to be called “doctor,” so I include this with both respect and fun) in which this very topic was discussed.
Basically, the hypothesis is that there existed a cycle of wet and dry periods in the region during prehistoric times which cause fluctuations in sea levels and periods of dry, inhabitable climates as well as lush, fertile climates on the Southern Arabian Peninsula that were flora and fauna flourished.
Of course, modern humans evolved in Africa, but Rose suggests that much of the worldâ€™s genetic diversity might have emerged from a population outside of Africa. For example, geneticists do not know for certain when the worldâ€™s three main mitochondrial lineages â€” M, N and R â€” branched from the founding African lineage, L3. But estimates of the ages of the worldâ€™s oldest M lineages, found in modern African, Indian and southwest Arabian populations, overlap in time, Rose says. This means the initial divergence of L3 might have happened in Africa, or it might have happened in India or southwest Arabia. â€œThe verdict is still out there,â€ Rose admits, but he says a lot of genetic variability seems to cluster around southwest Arabia â€” an indicator that modern human dispersals might have originated in the region.
The primary obstacle to the migration, according to the Geotimes article (and admitted by Jeff elsewhere) is the Bab al-Mandeb Strait, which is 18-30 km wide, depending upon where you stand. The article cites 30 km, but the Perim Narrows are about 18 km wide and at least 50 m deep. During the Pleistocene, this distance may have been shortened to approximately 11 km and 17 m of depth, but still a hazardous distance to cross for Pleistocene humans. But even today the shores of Arabia are visible to those that stand on the African side of the strait, and the temporary switch of current provided by the Indian Ocean Monsoon, which may have temporarily abated the strong outbound current of the Red Sea, which might have swept would be seafarers out to sea. Could such a promise of new territory have presented a temptation for Pleistocene hunter-gatherers?
There is a lot of evidence to suggest that migrations across the Red Sea were certainly possible. Papio hamadryas (the Sacred Baboon), a desert-adapted primate, is found on both sides of the Red Sea and mtDNA studies show that the branching of P. hamadryas lineages occurred between 74-37 kya, which correlates to the branching evident in the mtDNA haplogroup M of human lineages. In addition, lithic assemblages -the stone tools of early humans- show a remarkable similarity on both sides of the Red Sea for periods consistent with the hypothesized migration.
The concept is fascinating and there’s definitely more data to obtain and analyze, but for further reading, I recommend:
Rose, Jeffrey (2007). The Arabian Corridor Migration Model: archaeological evidence for hominin dispersals into Oman during the Middle and Upper Pleistocene. Proceedings of the Seminar for Arabian Studies, 37, 219-237.