Jordan Valley Site 'Ubeidiya Pushed Back to 1.9 Million Years, Matching Georgia's Dmanisi

Beside the Dead Sea rift in the Jordan Valley, the 'Ubeidiya Formation has held a puzzle for decades: stone tools shaped on both sides, including hand axes, sitting in the same layers as the fossil bones of animals. Scientists knew the site mattered. What they could not say with confidence was how old it was. A new study now answers that, and the answer is older than anyone had firmly shown: at least 1.9 million years.

The work was led by Prof. Ari Matmon of the Hebrew University of Jerusalem, Prof. Omry Barzilai of the University of Haifa, and Prof. Miriam Belmaker of the University of Tulsa. Their team combined three advanced dating methods to build a more reliable timeline for the site. The result places 'Ubeidiya at roughly the same age as Dmanisi in Georgia, putting both among the earliest known human settlements outside Africa.

'Ubeidiya has drawn attention for its early evidence of the Acheulean tradition, known for large tools worked on both faces, such as hand axes. The site also holds a rich assemblage of animal fossils, including species originally associated with Africa and with Asia, several now extinct. Earlier estimates generally put the site between 1.2 and 1.6 million years old, but those figures leaned on comparisons with other archaeological and geological evidence rather than direct measurement.

To fix that, the researchers collected new samples and ran three independent techniques. The first, cosmogenic isotope burial dating, relies on rare isotopes created when cosmic rays strike rock exposed at the surface. Once the rock is buried, the isotopes decay at known rates, so what remains indicates how long it has been underground. The second looked at the ancient magnetic field recorded in sediments laid down at the bottom of a lake. Matching that record against known magnetic reversals showed the deposits formed during the Matuyama Chron, which began more than two million years ago. The third used fossilized shells of Melanopsis, a genus of freshwater snail found in the sediment. Uranium-lead dating of the shells gave a minimum age for the layers containing the stone tools.

All three pointed to an age well beyond the earlier estimates. One complication needed explaining. The first cosmogenic measurements suggested some rocks were about three million years old, far older than the magnetic, fossil, geological and archaeological evidence allowed. The team traced the conflict to the sediments' history. Material had been deposited, buried, exposed and moved repeatedly within the Dead Sea rift and surrounding landscape, and some had been buried long before it was redeposited near the ancient lake at 'Ubeidiya. In the researchers' words, the model implies recycling of sediments previously deposited and buried in the rift valley, then redeposited along the paleo lake shoreline. The rocks therefore recorded a history longer than that of the archaeological layers themselves. Accounting for this reconciled the readings and strengthened the revised age.

The match with Dmanisi suggests human populations were expanding into different regions at about the same time. The two sites also hint at something about technology. Dmanisi is associated with the Oldowan tradition of relatively simple stone tools, while 'Ubeidiya carries the more sophisticated Acheulean. Rather than one tool tradition following another out of Africa, the two may have left at roughly the same time, carried by separate groups of early humans entering new environments.

Whether that reading holds is the next question. Testing the idea of multiple populations with different toolmaking traditions will fall to future research.