Research in the Rift Valley in southern Jordan provides insights into early human migrations.
Homo sapiens, as evidenced by human fossils and archaeological sites discovered in various places, moved out of Africa several times between 130,000 and 70,000 years ago, eventually reaching the Levant and Arabia.
However, little is known about the routes taken by these early human migrations. A new study just published in the journal Science Advances has discovered that the now uninhabitable and extremely arid region of the Rift Valley in southern Jordan used to be regularly lush and well watered. According to research, this region featured a zone of wetland and rivers that would have made it easy for hunter-gatherers to travel from Africa to the Levant and Arabia.
Straying outside of Africa
People leaving Africa may have used platforms in the eastern Sahara, the Nile River Valley, or the western Red Sea shoreline.
Following migratory animals and hunting a variety of them for food, these small groups of hunter-gatherers would have passed into the Sinai, a land bridge that connects Africa with the rest of Asia, from there.
The southern Jordan Rift Valley would have been the next destination for many of these hunter-gatherers. With the Dead Sea to the north and the Gulf of Aqaba to the south, this valley is located in a vital area.
Three places served as the primary focus of fieldwork. The first two were located in the valley itself: Wadi Gharandal and a region close to Gregra village. Wadi Hasa, the third location, is situated in the higher reaches of the Jordan plateau. The Arabic word “Wadi” refers to a transient riverbed that only receives water during torrential downpours.
By precisely dating different layers of silt, the ecosystem of Arabia when it was a fertile land was reconstructed. A method called luminescence dating was used to determine how long the sediment grains were protected from sunlight. This allowed them to determine how old the sediment grains were.
Results from sedimentary sections ranging from 5 to 12 meters thick revealed changes in ecosystems over geological time, including cycles of dry and wet environments. Evidence of swamps and rivers was also discovered.
The sedimentary settings formed between 125,000 and 43,000 years ago, according to luminescence dating, indicating that there had been several wet periods.
Team found three stone tools at Wadi Gharandal that belonged in a wetland. Two of them were produced via the Levallois method, a distinctive production method that was used by both Neanderthals and Homo sapiens. The implements were dated to 84,000 years ago.
Collectively, the results of fieldwork in the Jordan Rift Valley show that the region previously served as a 360 kilometer long freshwater corridor that helped move people into Western Asia to the north and the Arabian Peninsula to the south.
The well known Israeli cave sites of Skhul and Qafzeh provide additional proof of a northward extension. Here, Levallois stone tools and fossils of Homo sapiens have been discovered.
Fieldwork in northern Saudi Arabia has also shown that the area originally had a network of rivers and lakes, which has implications for the south. This made it possible for humanity to enter the Nefud Desert, which was covered with verdant savannahs and grassland.
The lakeside Al Wusta site, located in the Nefud, is where a human fossil and 85,000 year old Levallois stone tools were discovered. The 84,000 year old Levallois stone tools discovered in Wadi Gharandal are consistent with these dates.
Migrations into South-West Asia
Research in the Jordan Rift Valley suggests that there were numerous early human migrations from Africa and into Asia when the conditions were favorable. This contradicts the assumption that people left Africa 60,000 years ago in a single, swift wave.
Along with the Levantine and Arabian evidence, findings imply that hunter-gatherers traversed South-West Asia using inland river and marsh systems. This defies a prevalent theory that claims they mostly used coastal roads as super highways.
Despite ancient DNA evidence suggesting that Homo sapiens interbred with Neanderthals and Denisovans multiple times when they moved into Asia, there hasn’t been much physical proof of these interactions. This findings add to the evidence that these encounters took place in this region.
But there are still a lot of unsolved questions. Few fossils of our ancestors have been discovered to support claims about how early humans actually distributed, and vast areas of South-West Asia have not yet been examined or dated.
To fully depict how humankind’s journey out of Africa transpired, we’ll need to thoroughly explore more long-ignored regions like the Jordan Rift Valley.