A 1.9-Million-Year-Old Secret in the Jordan Valley Could Rewrite the Story of Human Migration

3 min readIn a sun-baked stretch of the Jordan Valley, not far from the Sea of Galilee, the ‘Ubeidiya archaeological site has yielded hominin fossils long thought to belong to migrating populations that crossed what is now Israel between 1.2 and 1.6 million years ago. Their remains and tools were intermingled with the bones of other animals, many of which have long since gone extinct. Although the site was already ancient, it gave up one more secret when its geological age was re-analyzed using its rock layers. ‘Ubeidiya has now been found to be 1.9 million years old.Long before it dried up, this primeval Levantine paradise was a freshwater lake. A stream that flowed into it left behind sediment deposits containing hominin and animal fossils. Also found at ‘Ubeidiya were tools made by hominins who lived on the lake’s shores, crafted from flint, basalt, and limestone from the surrounding area. The sediment originally settled in even, horizontal layers, but these were tilted when the center of the Jordan rift subsided. A kibbutz member accidentally discovered the site in 1959 while plowing, and excavations began the following year, with heavy machinery needed to expose its rock strata. Not until 2021, however, did archaeologists Omry Barzilai and Miriam Belmaker begin to suspect that hominin populations might have occupied the site earlier than previously thought.Their re-analysis showed that the sediments had a more complicated history than once assumed. “The exposure-burial history that emerges from the model implies recycling of sediments previously deposited and buried in the rift valley…subsequently exhumed, eroded, transported and then redeposited along the ‘Ubeidiya paleo lake shoreline,” they said in a study recently published in Quaternary Science Reviews.Together with archaeologist Ari Matmon of the Hebrew University of Jerusalem, Barzilai, who teaches at the University of Haifa, and Belmaker, of the University of Tulsa, led a team of researchers in dating sediment samples. They used three advanced methods that proved effective on material that’s long been difficult to date. First, cosmogenic isotope burial dating established how long the rocks had been buried. This method measures the decay of rare isotopes produced when cosmic rays interact with rocks at the surface. Second, fossilized shells from freshwater snails of the genus Melanopsis were found in the same layer as the hominin-made stone tools. Uranium-lead dating, which measures the decay of uranium into lead, gave a minimum age for those tools.The third line of evidence came from ancient records of Earth’s magnetic field orientation, which were captured in lake sediments that later turned to rock. The researchers compared these records with the documented changes in the magnetic field’s polarity over time, known as geomagnetic reversals. The comparison showed that the lake’s sediment deposits had formed during the Matuyama Chron. Chrons are intervals of time defined by their magnetic polarity, and the Matuyama, a period of reversed polarity, began at the dawn of the Quaternary. Together, the three methods pushed back the date of hominin habitation to 1.9 million years ago. This is about the same age as the Dmanisi site in Georgia, where Homo erectus settled before spreading through Eurasia. Dmanisi had long been regarded as one of the oldest known settlements outside Africa.Matmon, Belmaker, and Barzilai have suggested that this age means ‘Ubeidiya may once have been home to both Oldowan and Acheulean cultures. The oldest stone tools made by hominin hands come from Oldowan sites in Africa that are up to 2.5 million years old. (Some more debated sites in Ethiopia and Kenya go back 3.4 million years). By the time hominins reached ‘Ubeidiya, the flaking and fracturing involved in stone toolmaking had advanced. Acheulean hominins refined it further and also standardized the process. Their tools were strong enough to be used as weapons or for butchering animals for meat. The researchers think Oldowan and Acheulean hominins may have coexisted in the region. They also think Acheulean technological advances in the Levant occurred earlier than assumed.“The revised age has significant implications for understanding the routes and timing of early human dispersal,” they said. “[This prompts] a reassessment of early Homo biogeography, dispersal pathways, and the possibility of multiple or overlapping migration events out of Africa.”Elizabeth Rayne is a creature who writes. Her work has appeared in Popular Mechanics, Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.