New research puts the divergence of Neanderthals and modern humans to at least 800,000 years ago, which is around 300,000 years earlier than scientists previously believed.
While there are debates regarding the divergence of Neanderthals and modern humans, DNA analyses have generally placed it around 300,000 to 500,000 years ago. However, new dental analyses reveal that the two species must have diverged long before this time.
Looking At Ancient Teeth To Track Evolution
For the new study published in the journal Science Advances, researchers from the University College London did not examine the DNA, but the teeth of extinct human species. The team analyzed dental evolutionary rates of a variety of hominins, including bones from Sima de los Huesos in Spain that are ancestors of Neanderthals.
Previous dating efforts have indicated that the Sima fossils are 430,000 years old, which indicates that the last common ancestor of the Neanderthals and modern humans must have been before this time.
To figure out how far back this common ancestor may have lived, researchers led by Aida Gómez-Robles of University College London turned to hominin teeth. Dental shape has evolved at extremely consistent rates across all hominins, so experts can trace the changes over time and estimate the time of divergence of the different species.
An Earlier Divergence
By using dental evolutionary rates, scientists were able to calculate the time at which Neanderthals and modern humans should have diverged to make the evolutionary rate of the Sima de los Huesos Neanderthals consistent with the rate of other hominins: at least 800,000 years ago.
It's significantly earlier than expected, but Gómez-Robles explained that any divergence time set later than 800,000 would have meant the early Neanderthals from Sima de los Huersos had an unusually rapid dental evolution.
"Sima de los Huesos hominins are characterised by very small posterior teeth (premolars and molars) that show multiple similarities with classic Neanderthals," she said in a news release. "It is likely that the small and Neanderthal-looking teeth of these hominins evolved from the larger and more primitive teeth present in the last common ancestor of Neanderthals and modern humans."
Since the Sima hominin's teeth feature very stark differences from what's expected from the Neanderthal's last common ancestor with modern humans, it's likely that they evolved separately over a long span of time.
These findings produce significant implications in the hunt for modern humans' last common ancestors with Neanderthals, since it rules out all hominins that came after 800,000 years ago. This includes one of the strong contenders, the Homo heidelbergensis, who lived 700,000 to 300,000 years ago.
