Stone Age humans or their relatives occasionally trekked through a green Arabia
Long-ago rains drew hominids in phases to what’s now dry desert
By Bruce Bower
Arabia, known today for its desert landscape, served as a “green turnstile” for migrating Stone Age members of the human genus starting around 400,000 years ago, a new study finds.
Monsoon rains periodically turned northern Arabia into a well-watered oasis, creating windows of opportunity for long-ago humans or their relatives to trek through that crossroads region from starting points in northern Africa and southwest Asia.
That’s the implication of a series of five ancient lake beds of varying ages, each accompanied by distinctive stone tools, unearthed at a northern Saudi Arabian site called Khall Amayshan 4, or KAM 4. Sediments from the lake beds, which were linked to periods when the climate was wetter than today, also yielded fossils of hippos, wild cattle and other animals. Like hominids, those creatures must have migrated into the region along rain-fed lakes, wetlands and rivers, an international team reports online September 1 in Nature.
Until now, the oldest stone tools in Arabia dated to at least 300,000 years ago (SN: 11/29/18). Previous finds only hinted that Stone Age Homo sapiens or other Homo species temporarily inhabited green, wetter parts of Arabia, a conclusion largely resting on discoveries at two other Saudi sites, each preserving stone tools from a single point in time (SN: 11/1/18).
Aside from providing the earliest known evidence of hominids in Arabia, the new finds demonstrate for the first time that ancient Homo groups traveled there when conditions turned wet, say archaeologist Huw Groucutt of the Max Planck Institute for the Science of Human History in Jena, Germany, and colleagues.
As a result, northern Arabia could have served as a key, if intermittent, passageway out of Africa for humans or close evolutionary relatives who reached South Asia by around 385,000 years ago (SN: 1/31/18), southern China between 120,000 and 80,000 years ago (SN: 10/14/15) and the Indonesian island of Sumatra between 73,000 and 63,000 years ago (SN: 8/9/17).
The number, completeness and time frames of KAM 4’s ancient lake deposits make this site “one of a kind … that will continue to produce remarkable results,” says archaeologist Donald Henry of the University of Tulsa in Oklahoma, who did not participate in the new study.