There’s much evidence out there to suggest that ancient hominins—a group that also includes the ancestors of us Homo sapiens—started out in Africa millions of years ago. Findings from DNA studies show this very story; genetic variations in populations from within and outside the African continent reveal as much. One of the topics that require much discussion within this realm, however, is how exactly our ancestors and their relatives got out of Africa to begin with. Nowadays, the African continental mainland is separated from the Eurasian mainland by arid lands, like the Sahara desert and the Arabian peninsula. At first glance, it seems counterintuitive for ancient hominins to leave the comforts of the savannah to head out into an arid desert, yet nowadays there are humans in all corners of the Earth.
A team of researchers may have found a key to unlocking this peculiar mystery in ancient hominin migrations: our ancestors and our relatives may have crossed a relatively “greener” Arabian peninsula, resting near water spots like lakes and rivers. This seems to be the case implied by new findings obtained from ancient lake beds in a site called Khall Amayshan 4 (KAM 4), in northern Saudi Arabia.
The lake beds contained stone tools—clear evidence of hominin presence in the area at some point in time. Sediments obtained from the ancient beds reveal a history of wetter periods, or when the areas received considerably larger amounts of rain compared to other time periods; these rains created lakes and rain-fed rivers, perhaps attracting the hominins who were journeying out of Africa at the time. These areas also contained fossils of ancient hippos and wild cattle, meaning humans weren’t the only animals taking advantage of the wet spells in the area.
This comes after analysis of the items of interest in KAM 4 revealed what were possibly five separate periods of occupancy for the area, spread across 400,000 years. According to archaeologist Huw Groucutt, from the Max Planck Institute for the Science of Human History in Jena, Germany, these five groups were doing “roughly the same things” in the area: the ancient inhabitants camped by the lakeside, forming stone tools for hunting, food preparation, and woodworking.
The oldest occupancy period, dated to about 400,000 years ago, left behind hand axes formed from stone. The research team notes that this occupancy period cannot be composed of H. sapiens, as earlier evidence points to H. sapiens appearing in Africa about 100,000 years later. According to the team, this points to another Homo population becoming the first group to occupy the KAM 4 area. This also makes the 400,000-year-old stone axes in Kam 4 the oldest evidence of hominin presence in the Arabian peninsula by far.
Another period of occupancy, dated to about 300,000 years ago, included more finely-crafted hand axes. Given that other researchers believed H. sapiens may have appeared in Africa at roughly the same time, the research team believes it may be unlikely for our ancestors to have made it this far into the Arabian peninsula in such a short time. They then suspect that a separate, as-of-now unknown Homo species, possibly originating from north Africa or southwest Asia, were the second occupants of the KAM 4 area.
Three other occupancy periods were recorded, at about 200,000 years ago, 100,000 years ago, and 55,000 years ago. Artifacts dated to the third occupancy period were similar to artifacts obtained from northeast Africa that were made by H. sapiens, so Groucutt and the team suspect that our ancestors passed through this area before reaching southwest Asia around that time. The later two periods, represented by artifacts from the youngest two KAM 4 dig sites, may be represented by either H. sapiens or Homo neanderthalensis, or the Neanderthals, according to Groucutt. As Neanderthals reached the Middle East by 70,000 years ago according to earlier studies, they could have reached this area of the Arabian peninsula by about 55,000 years ago, and could have interbred with the H. sapiens already living in the area. According to Groucutt, this is a new possibility never proposed before that may demand further expeditions and research. Also, the five occupancy periods were represented by distinct archaeological “signatures,” much like how cultures nowadays differ by their own cultural artifacts.
The artifacts obtained from the area do resemble previously-obtained artifacts from inland Africa more than those obtained from the Arabian peninsula but at later dates, corresponding to the theory that hominins may have passed through sites like KAM 4 as they trekked their way to other parts of Eurasia. The findings from KAM 4 also reveal the close link between human migrations out of the African mainland and climate change patterns, seemingly only exiting the continent for other lands once weather conditions became favorable. Questions remain about the true identities of the KAM 4 settlers across these five occupancy periods, however, as well their fates once they exited out of the Arabian subcontinent. It seems that to get closer to the answers to questions like these, we must venture out and explore—much like our ancestors did, hundreds of thousands of years before.
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- Bower, B. (2021, September 1). Stone Age humans or their relatives occasionally trekked through a green Arabia. Science News. Retrieved September 16, 2021, from https://www.sciencenews.org/article/arabia-stone-age-tools-humans-migration-green-lakes-desert
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