(CN) — The Nefud desert in Saudi Arabia is one of the world’s most arid and inhospitable regions. But in a new study, archaeologists say their discovery of thousands of stone tools has revealed early humans periodically lived there when rainfall transformed it into lush, lake-filled grasslands.
Scientists have long posited that Southwest Asia, as the land connecting Africa and Eurasia, is where Neanderthals interbred with Homo sapiens, given that a small amount of Neanderthal DNA is in the genomes of modern-day people of European and Asian ancestry.
Neanderthals, an extinct subspecies of ancient humans, evolved in Europe and Asia while the modern human Homo sapien species was evolving in Africa. Yet evidence of the species’ mixing in Southwest Asia was scant.
A team of led by researchers from Max Planck Institute for the Science of Human History in Jena, Germany and the Heritage Commission of the Saudi Ministry of Culture has started to fill in that gap in human evolution.
In a study published Wednesday in the journal Nature, the scientists describe how they excavated a hollow between 300-foot dunes in the Nefud desert and found thousands of stone tools with different types associated with phases of lake formation that occurred 400, 300, 200, 100 and 55 thousand years ago.
They located the ancient lakes using satellite mapping analyses developed by team members Paul Breeze and professor Nick Drake of King’s College London.
They used a method called luminescence dating, which shows when tiny grains of sediment were exposed to sunlight, to link each occupation to a time when rainfall is known to have increased in the area.
Their discovery of hippopotamus fossils gave them more evidence the region was periodically transformed by rainfall, as hippos need permanent bodies of water several feet deep to survive because their skin is very sensitive to direct sunlight.
“The findings therefore show that, within a dominant pattern of aridity, occasional short phases of increased rainfall led to the formation of thousands of lakes, wetlands, and rivers that crossed most of Arabia, forming key migration routes for humans and animals such as hippos,” the researchers said in a press release.
Due to their further discovery of the fossils of cape buffalo and antelopes, which are both native to Africa, in the region, alongside fossils of animals endemic to northern Eurasia, the scientists say this indicates it was a “a key biogeographical nexus between Africa and the rest of Eurasia” and “may have also comprised an important interaction zone” for Neanderthals and Homo sapiens.
The scientists also found 75,000 to 200,000-year-old stone tools 31 miles to the east of the lake site. And they have much more to explore in Saudi Arabia.
“Across Arabia we have identified thousands of sites where lakes formed in the past,” Breeze said, “and have visited many over the last decade.”
Buoyed by their success, they are now applying their methods to deserts in Asia to see if they can find more puzzle pieces of the story of human evolution.
“Arabia has long been seen as empty place throughout the past,” said the study’s lead author Dr. Huw Groucutt, an archeologist at the Max Planck Institute in Germany. “Our work shows that we still know so little about human evolution in vast areas of the world and highlights the fact that many surprises are still out there.”
Scientists from universities and organizations in Australia, Pakistan and Spain were also involved in the study.Follow @cam_langford
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