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Our fossil find suggests humans spread to Asia way before they got to Europe

New discovery has put some teeth into our understanding of human evolution. Credit: S. Xing and X-J. Wu

It’s hard not to feel slightly superior when you belong to the only human species on the planet. Behind us there is a long track of extinct relatives that did not make it to our days. The Neanderthals in Europe went extinct some 40,000 years ago, just as we got there – leading us to believe we forced them out by being so much more advanced.

But science often teaches us to be humble. We have discovered 47 human teeth in China that are between 80,000 and 120,000 years old, suggesting it took early humans at least twice as long to enter Europe than they did to expand throughout Asia. The result, published in the journal Nature, challenges our current understanding of how humans evolved and spread – especially how we ended up replacing the Neanderthals.

Clear evidence

Researchers believe that our species evolved in East Africa around 190,000 to 160,000 years ago. After this, human fossils from the archaeological sites of Es Skhül and Jabel Qafzen, in Israel, suggest they spread there between 80,000 and 120,000 years ago. However, these samples preserve some archaic features that place them “on verge of modernity” but not fully modern yet. They have therefore been thought of as the result of a failed dispersal out of Africa that barely managed to reach beyond the borders of the African continent. So that means that modern humans were at the gates of Europe, but it took them another 50,000 years to be able to enter the land of the Neanderthal.

Genetic studies have indicated that the earliest successful “out of Africa” migration was around 60,000 years ago. But the newly discovered teeth, first found by a team of researchers at the Institute of Vertebrate Paleontology and Paleoanthropology of Beijing in the Fuyan (Daoxian) cave in southern China, are truly modern. The team dated the sample to be more than 80,000 years old, indicating that our species was present in Asia considerably earlier than had previously been suspected. In fact, it implied that anatomically fully modern humans lived in Asia 30,000 to 70,000 years earlier than in Europe and the eastern Mediterranean.

The team’s estimation that the teeth could be as old as 120,000 years was hard to believe at first. That was a big claim to make. So when they invited us to come and visit the site, we were eager to go. In this case, the challenge was not to prove the species the teeth belonged to, but to be sure about the context and the dating of the teeth.

Seeing the fossils with our own eyes. Martinon-Torres and colleague., Author provided

When we first arrived in China we did not have any doubt about the teeth belonging to our own species, Homo sapiens. After a few weeks studying and comparing the teeth with our colleagues in Beijing we took a plane to cross the more than 2,000km distance between Beijing and the Daoxian County, followed by a long trip by car full of excitement and expectations. Was it really possible to find such a modern member of our own species so far in the east?

When we reached the small village of Daoxian and visited the cave we were speechless. The rock and sediment layers in the cave were simple and easy to understand. There were four clear horizontal layers that were easily tracked across the more than 300 square meters of excavation.

The teeth were found in a layer that was sealed by a continuous calcite floor, like an enormous gravestone that would have made it impossible for any soil or more recent fossils to accumulate below. There was a small stalagmite, an upward-growing pillar of mineral deposits from water dripping in, on top of this flowstone that experts from China and US have dated to be around 80,000 years old. As the stalagmite was formed after the calcite floor sealed the layer with the fossils, everything below had to be older than that.

Geographical location and interior views of the cave, with the dating sample (lower left), plan view of the excavation area with rock layer marked (centre), researcher finding human tooth (right). Credit: Y-J Cai, X-X Yang, and X-J Wu

The human teeth were consistently mixed with mammalian remains, including extinct hyenas, pandas and elephants that helped to infer a maximum age of 120,000 for the human fossils. The context was clear and we spent hours inside the cave concluding that there were no doubt that the evidence were consistently pointing towards the beginning of the Late Pleistocene age.

From that moment, we remember the rest of our trip in China with the dizziness of the excitement and the shock. But also the warm welcome of the local people from Fuyan who celebrated our visit with all sort of luxury food and drinks. However, it was us who should pay the honour of having visited the earliest known site in the world with fully modern humans outside Africa.

Human origins puzzle

Our flight back was filled with unforgettable buzz and brainstorming about the possible origin and fate of the first H. sapiens outside Africa. Could it be that some of the present-day populations are descendants of that very early expansion? Or are all of us descendants of a later wave?

We also thought it was time to restore the honour of the Neanderthal species, or at least to leave open a door about the advantages that one would have had over the other. We have long looked at Neanderthals as a species that became extinct because it could not cope with the invasion of a species that was allegedly culturally and biologically superior.

But why then was it so much easier for modern humans to move into Asia, where there were no Neanderthals? This species was after all able to master a land of harsh and sub-freezing winters that was too hard for a tropical species like H. sapiens to cope with, which it may be why it took us so long to get there. Maybe after hundreds of thousands of years isolated and punished by merciless winters, Neanderthals started to fade. It may be that was only then when H. sapiens saw the opportunity to take over their empire for hundreds of thousands years.

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