Jessica Thompson, a paleoanthropologist at Yale University who was not involved in the study, said that the results of the study supported the view that the periodic greening of this typical hot desert played a key role in the process of human leaving Africa, and provided the strongest evidence so far for different human groups to leave the African continent through the Sinai Peninsula.
Today, the sparsely populated Nefd desert is full of sand dunes and slender drought-tolerant shrubs. However, previous excavation and paleoclimate model research show that in the past 500,000 years, the short humid and warm climate has brought seasonal rainfall to this area, turning low-lying basins into lakes, ditches into rivers, and deserts into lush grasslands temporarily, but when dry weather comes, it becomes sand again.
In 20 13, scientists locked several ancient lake beds in the west of Nefud desert, which showed unusual colors in satellite images. Michael Petraglia, an archaeologist at Max Planck Institute for Human History Science (SHH), suspects that his marble deposition zone reflects several drainage and refilling periods.
Petraglia and her colleagues went to a place called Khall Amayshan 4, which is located between huge sand dunes. "There are stone tools everywhere." Shh, archaeologist Hugh Grukat said.
The researchers used excavators to dig on the lake bed, dated these strata, and recorded the stone tools related to each stratum. The results show that four ancient lakes in Halamai Mountain formed and dried up six times. Researchers recently reported that stone tools are related to five of these long-lost lakes, and the history of the latter can be traced back to 400,000 years ago, 300,000 years ago, 200,000 years ago, 654.38 million years ago and 55,000 years ago. In another ancient lake in Jiuba Oasis, about150km east of the site, they found stone tools dating from 200,000 to 75,000 years ago.
In addition to tools, researchers also found animal bones in many dry lakes, which shows that African animals such as hippos, elephants and ostriches left Africa along this "green route"-at least during the rainy season. No human fossils were found in the new excavation.
Grukat said that it is not clear what kind of ancient humans left tools, but relatively rough pointed hand axes are usually thought to come from close relatives of humans, such as Homo erectus. The researchers pointed out that the tools found in rock formations 200,000 years ago, 654.38+10,000 years ago and 75,000 years ago were smaller and finer, similar to those made by human beings.
The latest tools 55,000 years ago are very similar to Neanderthals. Scientists found the remains of Neanderthals on the northwest edge of Arabian Peninsula. If these new findings are established, it shows that Neanderthals also migrated to the periodic "grassland paradise" in the Arabian Peninsula. Wenlele