A set of 47 human teeth found in China is giving scientists food for thought.
The teeth have been dated as at least 80,000 years old - perhaps even older. The problem is that most researchers believe humans only left Africa for the first time around 60,000 years ago. And even then, they were thought to trek to Europe first, not Asia.
The teeth, described in a paper published on Thursday in Nature, were found in a cave in China's Hunan province, and bear a close resemblance to those seen in modern humans. The researchers believe they're undoubtedly those of Homo sapiens.
"This is stunning, it's major league," Michael Petraglia, an archaeologist at the University of Oxford who was not involved in the research, told Nature. "It's one of the most important finds coming out of Asia in the last decade."
The researchers believe this may be a sign that humans were ready to leave the nest long before they trekked into Europe. It's possible that Neanderthals, who were in Europe at the time the owners of these teeth were in China, were in the way of a westward migration.
"The coincidence between the arrival of H. sapiens to Europe and the Neanderthal extinction has often been interpreted as evidence of the superiority of modern humans," co-author Maria Martinon-Torres of the National Centre on Human Evolution in Spain told Discovery News.
"However, we now wonder that if modern humans were already present in southern China more than 80,000 years ago, why were they not capable of entering Europe until 45,000 ago? Maybe because Neanderthals were there, it was not easy to take over 'their' land."
Indeed, recent research on Neanderthals has suggested they were much more formidable than we once gave them credit for.
Evidence indicates they were intelligent enough to make art and jewellery, and may have culturally been quite similar to humans living at the same time. There probably wouldn't have been room for both of us.
In a commentary article for Nature, the University of Exeter's Robin Dennell, who wasn't involved in the study, suggests the warmer climate of Asia might have made it a more attractive destination for early settlers.
To better understand how these humans arrived and what they were doing there, the researchers will have to confirm their dating, which other researchers have suggested is compelling but not definitive. And we'll have to find more remains.
While these teeth are a great start, they were found without any other signs of human life. There are no tools to indicate a settlement had been made in the cave. In all likelihood, the researchers say, these remains were simply dragged into the cave by predators that lived there.
In any case, it's unlikely that the teeth came from ancestors of modern Asians, as DNA testing suggests that those groups stem from humans who came to Asia by way of Europe, picking up some Neanderthal DNA along the way. What happened to these early travellers? We can only hope that future fossil finds will reveal the answer.