Research on fossilised teeth redefines human and Neanderthal history
LONDON, UK: Looking back in time through archaeology has revealed many insights to explain where Homo sapiens came from. By examining teeth, scientists have discovered that Neanderthals and modern humans diverged at least 800,000 years ago, substantially earlier than indicated by most DNA-based estimates. The study has major implications for the identification of the last common ancestral species of Homo sapiens and Neanderthals.
Working in the Sima de los Huesos caves, a site in the Atapuerca Mountains in Spain, archaeologists have recovered about 30 hominin fossils over a period of several decades. Previous studies date the site to the Middle Pleistocene epoch, around 430,000 years ago, making it one of the oldest and largest collections of hominin remains discovered to date.
In this new discovery, researchers analysed dental evolutionary rates across different hominin species, focusing on early Neanderthals. It showed that the teeth of hominins from Sima de los Huesos, who are ancestors of the Neanderthals, diverged from the modern human lineage earlier than previously assumed.
Study author Dr Aida Gomez-Robles from University College London said, “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.”
“There are different factors that could potentially explain these results, including strong selection to change the teeth of these hominins or their isolation from other Neanderthals found in mainland Europe. However, the simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years. This would make the evolutionary rates of the early Neanderthals from Sima de los Huesos roughly comparable to those found in other species,” explained Gomez-Robles.
In order to arrive at these conclusions, the researchers used quantitative data to measure the evolution of dental shape across hominin species, assuming different divergent times between Neanderthals and modern humans, also accounting for the uncertainty about the evolutionary relationships between different hominin species.
“The Sima people’s teeth are very different from those that we would expect to find in their last common ancestral species with modern humans, suggesting that they evolved separately over a long period of time to develop such stark differences,” said Gomez-Robles.
The study, titled “Dental evolutionary rates and its implications for the Neanderthal–modern human divergence”, was published in the May 2019 issue of Science Advances.