Science

Ancient Molar Hints At Interbreeding In Homo Sapiens

Ancient Molar
Image Credit: Christine Lee

A group of scientists analyzed a 160,000-year-old ancient molar fossil belonging to an archaic human which was discovered in China. The ancient molar offers insight into how Homo sapiens and archaic humans lived together, as well as the evidence of interbreeding between these two species. This marks the first morphological evidence of interbreeding between archaic humans and modern humans.

The new findings were published in the journal Proceedings of the National Academy of Sciences, and it focuses on a three-rooted lower molar, which is a rare trait found in modern Asians. Scientists had previously believed that the three-rooted molars were evolved only after the Homo sapiens species moved away from Africa. However, the new study shows the evolution of the teeth in a different light.

“The trait’s presence in the fossil suggests both that it is older than previously understood and that some modern Asian groups obtained the trait through interbreeding with a sister group of Neanderthals, the Densiovans,” Shara Bailey, a professor of anthropology at New York University and the paper’s lead author said in a statement.

In an earlier study published in the journal Nature, Bailey and her team found that the Denisovan species had lived in the Tibetan Plateau for a longer time before the Homo sapiens occupied that region. Another study from last year, found that the modern humans also interbred with Denisovans. Denisovans are at times called the “subspecies” of Homo sapiens. In last year’s study, scientists concluded that there is evidence of Denisovan and Homo sapiens genes mixing more than two times. That said, it’s no secret that Homo sapiens preferred mixing with other earlier human species.

The work published in Nature along with the new PNAS-published research focused on a hominin lower mandible that was found on the Tibetan Plateau in Baishiya Karst Cave in Xiahe China back in 1980.

However, the study published in PNAS, focused on the ancient molar that hints at interbreeding. The new research also included NYU anthropologist Susan Antón and Jean-Jacques Hublin, director of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology.

The new study should give a better understanding of the relationship modern humans had with archaic humans that lived in the caves in Asia more than 160,000 years ago, as well as the relationship with modern Asians.

“In Asia, there have long been claims for continuity between archaic and modern humans because of some shared traits,” said Bailey. “But many of those traits are primitive or are not unique to Asians. However, the three-rooted lower molar trait is unique to Asian groups. Its presence in a 160,000-year-old archaic human in Asia strongly suggests the trait was transferred to H. sapiens in the region through interbreeding with archaic humans in Asia.”