Stone tools from an ancient lake site in Saudi Arabia have characteristics more closely associated with Neanderthal toolmaking than with Homo sapiens, suggesting that Neanderthals reached northern Arabia between about 60,000 and 50,000 years ago. The finding comes from a site where no Neanderthal fossils have been found, making the stone tools an important source of evidence about who lived there.
The site, known as Jebel Katefeh-1, or JKF-1, lies near an ancient lake in Saudi Arabia’s Nefud Desert. Stone tools had already revealed unusual differences between archaeological sites across Arabia, but it was difficult to determine what caused those differences.
Climate, geography, the type of stone available, how a site was used and the history of different human populations could all influence the tools left behind. With fossils scarce in Arabia, researchers turned to the tools themselves for clues about the people who made them.
The age of JKF-1 had also been difficult to pin down. Earlier estimates placed the occupation somewhere between 90,000 and 50,000 years ago, a span that overlaps with evidence for both Homo sapiens and Neanderthals in Southwest Asia.
Previous archaeological evidence indicates that Neanderthals expanded southward into the Levant and Zagros region roughly 75,000 to 50,000 years ago. Homo sapiens populations were also present in the broader region during this period.
That overlap made the age of the Arabian site especially important. A narrower date could help determine which population history best fit the unusual stone tools found there.
Testing what caused the tool differences
The researchers analyzed 704 complete prepared stone flakes from Africa, Arabia and the Levant, covering the period from 100,000 to 50,000 years ago.
Rather than treating differences in the tools as evidence of population history alone, the team built statistical tests to examine several possible explanations. The analysis considered the age of an assemblage, its landscape setting, environmental conditions, size and composition, the raw material used to make the tools, the type of site and population history.
The reference dataset also contained tool samples associated with Homo sapiens and Neanderthals. The two populations could be differentiated with more than 93% agreement in that dataset.
The model identified population history as the strongest explanation for differences in the shape of the prepared stone flakes.
When the researchers applied the analysis to JKF-1, the tools were more similar to assemblages associated with Neanderthals than to those associated with Homo sapiens. For the key stone-tool shape pattern, the model produced a median Neanderthal likelihood of 78%.
Only four artifacts had a higher probability of being attributed to Homo sapiens populations than to Neanderthals.
The statistical result does not provide a Neanderthal skeleton from the site. Instead, it links the technological characteristics of the stone tools to tool assemblages associated with Neanderthals elsewhere in the researchers’ dataset.
Dating the occupation more precisely
The researchers also carried out additional dating of sediments at JKF-1. They used luminescence dating, a method that estimates when sediment grains were last exposed to sunlight.
The results placed the site at around 60,000 to 50,000 years ago. That narrowed the earlier estimate of 90,000 to 50,000 years and places the occupation within the period when both Neanderthals and Homo sapiens were present in Southwest Asia.
Taken together, the tool analysis and revised dating point to Neanderthals having reached northern Arabia during this period.
Arabia as a region of human movement
The finding extends the evidence for Neanderthal presence beyond the Levant and into northern Arabia, challenging the idea that Neanderthals were confined to colder European landscapes.
The study also points to Arabia as a region where different human populations may have crossed paths. During the Ice Age, the region was positioned between Africa, Europe and Asia, and the researchers describe it as both a meeting ground for different populations and a route out of Africa.
The authors also suggest that interactions between Homo sapiens and Neanderthals, including admixture between the two groups, could have occurred across a much broader and poorly defined geographic area that included Arabia.
Because fossils and DNA are poorly preserved at low latitudes, the researchers argue that quantitative analysis of stone-tool assemblages can provide another way to investigate past hominin behavior and population history.
The study was published in Quaternary Science Reviews.
