Study finds 55 ancient lakes in Rub' al Khali desert but no evidence of ancient humans
Researchers found evidence of ancient lakes at 55 of the 125 locations they investigated in the Rub' al Khali desert, but found no traces of ancient humans, according to a study published in Nature.
The Rub' al Khali, also called the Empty Quarter, stretches for 1,000 kilometers (620 miles) of endless sand across the Arabian Peninsula and is the world's largest continuous sand desert. During wetter phases of the Pleistocene, temporary green corridors emerged in the Empty Quarter, supported by ancient pop-up lakes that have since disappeared.
Previous research dated lake deposits in the region to approximately 122,000–67,000 years ago. For decades, researchers have hypothesized that these ancient, temporary lakes and neighboring grasslands would have attracted human settlement as groups migrated from Africa, across Arabia, and into Asia.
A team of researchers trekked across approximately 1,500 kilometers of the Empty Quarter, looking for clues of these ancient lake deposits and signs of hominin settlement. "We stood on the shore of one ancient lake after another, yet found nothing made by human hands," says geoarchaeologist Rudolf Dellmour from the University of Vienna in Austria.
The researchers found only 10 sites featuring geological deposits of knappable stone that would have enabled ancient humans to develop stone tools, and all were located on the outer margins of the desert. The surface geology of the desert's central basin is composed of carbonate and evaporite formations, which were not suitable for stone tool manufacture.
Prehistoric archaeologist Emanuele Cancellieri from the University of Algarve in Portugal, who was not involved with the study but authored a commentary on it in Nature, said: "That humans need more than just a water supply is hardly a new archaeological insight." He added: "The importance of this research lies instead in subjecting that idea to an ambitious study."
Alongside their fieldwork, the researchers developed a model to refine predictions of ancient settlement sites in the region, incorporating both water availability and geological considerations. According to their calculations, 57 percent of the terrain that would have been accessible to water in prehistoric Arabia lacked suitable stone for tool-making.
The researchers note that the availability of knappable stone has previously been linked to human occupation in several historical and geographical scenarios, including Libya, Tibet, Egypt, South Africa, and North America. They write that these convergent patterns provide analogical support for a "tethering" effect whereby stone-tool-dependent populations become tied to raw-material sources.
The researchers explain that the Arabian Peninsula seems to have comprised a patchwork of discrete zones where water and lithic raw materials co-occurred. They state that dispersal models that omit lithic raw-material distributions may systematically overestimate the area habitable by stone-tool-dependent populations.
