Neanderthals and humans interbred in Europe for 5,400 years

A 55,000-year-old incomplete skull found in Israel may belong to a human group that interbred with Neanderthals. Discovered deep in a cave by amateur speleologists, the partial cranium also fills a major gap in the fossil record of Homo sapiens’ journey from Africa to Europe. “Here we actually hold a skull of a human being that was living next to the Neanderthals,” says Israel Hershkovitz, the leader of a study published today in Nature (I. Hershkovitz et al. Nature dx.doi.org/10.1038/nature14134; 2015). “Potentially he is the one that could interbreed with the Neanderthals,” says Hershkovitz, who is a physical anthropologist at Tel Aviv University in Israel.



Genome studies of Neanderthals (Homo neanderthalensis) and of both ancient and contemporary H. sapiens suggest that the two species interbred somewhere in the Middle East between 50,000 and 60,000 years ago (Q. Fu et al. Nature 514, 445–449; 2014). But the problem with this idea is that no remains of anatomically modern humans have been discovered in the Middle East from this crucial period, after H. sapiens left Africa and before it colonized Europe and Asia. In 2008, a bulldozer clearing land for a development near the Sea of Galilee in northern Israel revealed an opening to a limestone cave that had been sealed for more than 15,000 years. Amateur speleologists were the first to explore the cave, and they spotted the battered bone — the top portion of a skull — resting on a ledge. The Israel Antiquities Authority soon launched a complete survey of Manot Cave, finding buried stone tools at several spots that are still being excavated.



The skull was unquestionably from H. sapiens, says Hershkovitz: it was similar in shape to those of earlier African and later European humans. A patina of calcite coated the fragment, and the researchers used radioactive uranium in the mineral to date the bone to about 55,000 years old. That means that “the Manot people are probably the forefathers of the early Palaeolithic populations of Europe”, Hershkovitz says. The Manot people are also a leading candidate for the humans that bred with Neanderthals — exploits that have given all of today’s non-African humans a sliver of Neanderthal heritage. The Manot Cave is not far from two other sites that held Neanderthal remains of a similar age. “The southern Levant is the only place where anatomically modern humans and Neanderthals were living side by side for thousands and thousands of years,” Hershkovitz says. The ultimate proof would be to look for the presence of Neanderthal ancestry in DNA from the skull, but the region’s balmy temperatures mean that ancient DNA is unlikely to have been preserved.


This undated photo provided by the Israel Antiquities Authority on Tuesday, Jan. 27, 2015 shows a partial human skull excavated from a cave in Israel's western Galilee region. Israel Hershkovitz of Tel Aviv University says the bone dates from around 55,000 years ago, about the time scientists believe the migration from Africa reached that area. "This is the first evidence we have of the humans who made this journey," apart from some ancient tools, said Eric Delson of Lehman College and the American Museum of Natural History in New York. ISRAEL ANTIQUITIES AUTHORITY, CLARA AMIT AP PHOTO

Jean-Jacques Hublin, a palaeoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, agrees that the chances of recovering DNA from the skull fragment are slim. But he hopes that further excavations will find human remains that have stayed cool enough to still contain DNA. These digs might also connect the skull to stone tools and other relics of daily life, which could strengthen the Manot skull’s link to early Europeans. The artefacts uncovered so far are thought to be much younger than the skull. “We have a skull, and we have a site where there is some archaeology, but there is no link between the skull and the archaeology. It’s a bit annoying,” Hublin says. “This specimen is really important and exciting, as — assuming the dating is correct — it shows for the first time that modern humans existed in the Near East at the same time as Neanderthals,” says Katerina Harvati, a palaeoanthropologist at the University of Tübingen in Germany. “Until now we had no evidence that the two even coexisted in this region during this time period. So this is a crucial piece of the puzzle.”

Nature 517, 541 (29 January 2015) doi:10.1038/517541a

They are largely thought to have roamed the freezing landscapes of Europe during the last ice age, but it seems Neanderthals may have spread far further east and lived alongside modern humans there for longer than was previously thought. Two new pieces of research have suggested that the ancestors of modern East Asians may have interbred with the now extinct Neanderthals far more than they did in Europe. Analysis of the traces of Neanderthal DNA found in the genomes of modern humans has shown that people in East Asia carry between 15 to 30 per cent more of their DNA than Europeans.



Scientists now say there appears to be two distinct occasions when Neanderthal mixed with modern humans in East Asia compared to just one occasion in Europe. This suggests that Neanderthals were able to spread further towards East Asia than was previously thought. Almost all of the remains of Neanderthals have been found in southern Europe and western Asia. They were not thought to have gone much further east than the Altai Mountains in central Asia, on the borders of what are now Russia, Mongolia and Kazakhstan. But the new findings have raised the prospect that Neanderthals lived in the east of the continent and may have clung on there for longer than their European relatives, who died out around 30,000 years ago - we have just yet to find the archaeological evidence.



Professor Joshua Akey, a geneticist at the University of Washington who led one of two new studies, said: 'The history of admixture between modern humans and Neanderthals is most likely more complex than previously thought.' The research was conducted by two separate teams working at the University of Washington and the University of California, Los Angeles. Professor Akey and his colleague Benjamin Vernot analysed distinctive patterns in the DNA of 379 modern Europeans and 286 modern East Asians from China and Japan. Using computer models they attempted to simulate how the mixtures of Neanderthal DNA seen in the European and East Asian genomes could have occurred. They concluded that one theory - that modern Europeans interbred more with populations from Africa to water down the Neanderthal DNA they carried - was unlikely.



Instead they found it was more likely that ancestors of the East Asian populations had bred with Neanderthals more than once. Mr Vernot said: 'One thing that complicates these analyses is the fact that humans have been constantly migrating throughout their history - this makes it hard to say exactly where interactions with Neanderthals occurred. 'It's possible, for example, that all of the interbreeding with Neanderthals occurred in the Middle East, before the ancestors of modern non-Africans spread out across Eurasia. 'In the model from the paper, the ancestors of all non-Africans interbred with Neanderthals, and then split up into multiple groups that would later become Europeans, East Asians.



'Shortly after they split up, the ancestors of East Asians interbred with Neanderthals just a little bit more. The important thing is that we show that we didn't just meet Neanderthals once in our history - it looks like we met them multiple times. But as we are able to look at individuals from more and more populations, we'll hopefully get a better idea of where our ancestors have been, and where they may have interacted with Neanderthals.' Previous research has led to theories that modern humans first interbred with Neanderthals as they migrated through the Middle East 55,000 years ago before they then moved further into Europe and Asia. The evidence that a second mixing between the two species took place among East Asian populations implies that this occurred sometime later and further East than the first interbreeding event.