New Teeth Analysis Reveals Humans and Neanderthals Split 800,000 Years Ago, Yet We Have a Mysterious Common Ancestor
New details regarding human evolution continue to come up in front of researchers. In 2019, a revelation regarding the evolution trajectory challenged many of the previous assertions held by experts regarding this subject, stated Live Science. Findings about these developments have been published in the journal Science Advances.
The study claimed that humans and Neanderthals split around 800,000 years ago. This implies that the common ancestor, which is present in the lineage of both modern humans and Neanderthals, existed back then. This challenges the past findings, which claimed that the split happened somewhere between 500,000 and 300,000 years ago. The findings were made based on the examination of several teeth belonging to humans and their relatives.
In total, 931 teeth were taken for analysis. These teeth were from around 122 individuals associated with eight different groups. One hundred and sixty-four (164) specimens came from the early Neanderthals living in the Sima de los Huesos ("Pit of the Bones") site in Spain. These Neanderthals existed 430,000 years ago, during the middle Pleistocene epoch. Several features of these teeth were recorded, especially the tooth shape. The differences in these features helped experts in estimating the evolutionary rates for dental shape change amongst these subjects. This further allowed researchers to determine when humans and Neanderthals split from the last common ancestor.
The study assumes that the evolution of tooth shape happens steadily and in a predictable fashion. Many researchers have expressed doubts about this assumption, but there have been no insights that have been garnered to date that indicate the tooth development does not take a predictable route. "At the moment, there is the idea of a steady evolutionary rate change in the shape of cheek-teeth," said Fernando Ramirez Rozzi, director of research specializing in human evolution at France's National Center for Scientific Research in Toulouse, who was not involved in the study, stated Live Science.
If humans and Neanderthals did split 800,000 years ago then Homo heidelbergensis is not the common ancestor, as it is widely believed. "H. heidelbergensis cannot occupy that evolutionary position because it postdates the divergence between Neanderthals and modern humans," Aida Gómez-Robles, a paleoanthropologist at University College London, explained. "That means that we need to look at older species when looking for this common ancestral species." The assertion, if true, has the potential to alter present perceptions regarding the fossil record and the relationship between different human relatives.
Ramirez Rozzi claims that the pushing back of the split implies that humans and Neanderthals were separated for much longer than previously believed. He wants experts to reexamine the interbreeding that happened between these two groups 60,000 years ago. Researchers associated with the study were surprised that this interbreeding could happen even on the back of a long evolutionary trajectory. "In other words, almost 1 million years of evolution was not enough to establish barriers (genetic, endocrinological, behavioral, etc.) to separate definitively these two species?" Ramirez Rozzi asked. Bruno Maureille, director of research at the National Center for Scientific Research (CNRS), was impressed by the finding but cautioned experts that they should examine more Neanderthal specimens before validating the discovery.