Early humans migrated out of Africa through the Middle East with the help of a favorable climatic window, using today’s Israel and the surrounding region as a steppingstone on their way to Europe and the rest of Asia, according to a new study.
The Jordan Rift Valley likely provided a green corridor for early humans to migrate north during a regional “humid interval” when people were first establishing a permanent foothold outside Africa.
Homo sapiens set up long-term settlements in the region over some 8,000 years, including on the shores of a large freshwater lake around the modern Dead Sea, the researchers from several German universities wrote. Their findings were based on archaeological remains in Jordan, which were correlated with ecological data from the Dead Sea to ascertain the local environment at the time.
The study suggests that early human migration out of Africa was not a continuous expansion, but a long process facilitated by complex interactions between early humans and their environment. The opening of the corridor was likely a necessary precondition for the migration to Eurasia, with the early humans slowly expanding through the north-south passageway, rather than in all directions.
“Human presence consolidated in the region under favorable climate conditions,” said the study’s lead author, Dr. Jürgen Richter of the University of Cologne. “Humans did not come by steady expansion out of Africa through the Levant and farther to Europe and Asia. Rather, they first settled in a coastal strip along the Mediterranean Sea.”
Scientists believe permanent, established settlement of the area only began around 43,000 years ago, however.
The team studied artifacts around a prehistoric campsite called Al-Ansab 1 near the ancient city of Petra, in Jordan, and examined pollen sediments around the Dead Sea, seeking to understand the climate at the time of early human expansion out of Africa. The research lasted over 10 years.
The Early Ahmarian period in question was a “major expansion and consolidation phase” of migration in the Levant that lasted from 45,000 years ago until 37,000 years ago, the researchers wrote.
Described as a “techno-cultural unit,” the Early Ahmarian people have been studied at over 50 paleolithic sites, and are the earliest Middle East cultural group that is clearly tied anatomically to modern humans, and not Neanderthals.
The favorable climate at the time is illustrated by Lake Lisan, the prehistoric body of fresh water located in the Jordan Rift Valley. At its largest, it stretched from the modern Sea of Galilee to beyond the southern shore of the Dead Sea.
Most of the water in Lake Lisan evaporated around the end of the last ice age, around 11,700 years ago, leaving behind the hypersaline Dead Sea.
The German researchers found evidence of the early inhabitants at Wadi Sabra, where Al-Ansab 1 is located. Today, the wadi, or channel, is subject to seasonal flash floods, but at the time of early human settlement, it was continuously wet, allowing people to thrive.
Archaeologists have identified numerous paleolithic sites at Wadi Sabra, which is located 15 kilometers south of Petra, and the German research group uncovered one Early Ahmarian site embedded in sand in the area. There are flint deposits in the area, which early humans used for tools, and a nearby spring, making the site attractive to the arrivals.
The researchers found stone artifacts, including small pointed blades and scrapers, alongside bones, charcoal and other remains at Wadi Sabra. The tools were used for both hunting and other activities at the site. The only bones that could be identified were from gazelles, which were likely the inhabitants’ main prey. Charcoal at the site was dated to around 38,000 years ago using radiocarbon dating.
They found two marine shells, one stained with ochre, which were likely used for ornamentation and transported at least 90 kilometers from the Red Sea or the Mediterranean Sea, indicating connections to those areas.
The researchers did not find relevant remains of vegetation at Wadi Sabra, but were able to extract pollen drilled in the area of the Dead Sea to inform them of the climate in the region during the same period.
At the Dead Sea site the team analyzed terrestrial pollen remains, but not aquatic flora.
The region had a stable climate suitable to steppe, woodland and desert vegetation, mostly grasslands and shrubs, offering a range of habitats for animals and people.
The researchers, studying pollen deposits, found that the area formed a long-lasting green corridor, which stretched from Egypt’s Sinai peninsula, through the Negev Desert and eastern Jordan, into southern Lebanon and Syria. A handful of caves belonging to the cultural group have been found in Turkey, marking its northernmost known location.
The Early Ahmarian cultural group is mainly identified by stone blades the people produced for hunting weapons, which were invented or introduced to the corridor around 45,000 years ago, especially bladelets called El-Wad points, named for a site in Israel. The name of the group comes from an archaeological site in the Judean Desert.
The early humans inhabiting the area were likely small, highly mobile hunter-gatherer groups that moved around according to the seasons. During the wet season, the groups probably positioned their campsites near animal paths for hunting, and during the dry season, near reliable water. The Wadi Ansab site, with a water source, was likely a dry season encampment, the researchers said.
The sites in today’s Jordan may have been marginal outposts of a territory centered farther west, the researchers wrote. The hunter-gatherers likely vacillated annually within the region between the Mediterranean coast, the Negev and the Jordan Rift Valley.
In the Negev desert in today’s Israel, and in Egypt’s Sinai peninsula, the group was likely better established than in the Jordan Rift valley farther east.
In addition to gazelle, the western Ahmarian groups hunted ibex, horses, deer and rhino.
The study by researchers at Germany’s Cologne, Bonn, and Aachen universities was published earlier this month in the peer-reviewed online science journal PLOS One.