WASHINGTON — A study on teeth fossils showed that modern humans and their closest relatives Neanderthals diverged much earlier than previously estimated, providing a new clue to the search for modern humans’ last common ancestor with other species.
The study published on Wednesday in the journal Science Advances showed that the ancestors of Neanderthals and modern humans may diverge at least 800,000 years ago, based on the dental evolutionary rates of the teeth of hominins found in a cave in Spain.
Sima de los Huesos is a cave site in Atapuerca Mountains of Spain, where archaeologists have recovered fossils of almost 30 people, believed to be ancestors of the Neanderthals. Previous studies dated the site to around 430,000 years ago.
Modern humans share a common ancestor with the extinct Neanderthals, but when and how they diverged are still a matter of intense debate. Ancient DNA analyses have indicated that they diverged around 300,000 to 500,000 years ago, making it possible that those hominins in the Spanish cave is also modern human’s ancestors.
However, the anatomical features observed in the hominins from the cave told another story.
Sima de los Huesos hominins showed multiple similarities with classic Neanderthals but they are characterised by very small posterior teeth.
It is likely that the small and Neanderthal-looking teeth evolved from the larger and more primitive teeth present in the last common ancestor of Neanderthals and modern humans, according to the study.
“Any divergence time between Neanderthals and modern humans younger than 800,000 years ago would have entailed an unexpectedly fast dental evolution in the early Neanderthals from Sima de los Huesos,” said Aida Gomez-Robles, an anthropologist at University College London and one of the paper’s authors.
The simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years, according to Gomez-Robles.
The new findings ruled out any hominins postdating 800,000 year ago to be a common ancestor of modern humans and Neanderthals.