A new analysis of 400,000-year-old teeth has provided a rare glimpse into the interactions between early human relatives, suggesting that Homo erectus may have interbred with other ancient hominins. The findings add to a growing body of evidence about the complex origins of modern humans.
Homo erectus emerged in Africa around two million years ago and spread to parts of Asia and possibly Europe. Remains have been found in Indonesia, Spain, China and Georgia. However, the fragile nature of ancient genes and proteins has made studying their biology difficult.
In the new study, researchers extracted ancient enamel proteins from the teeth of five men and one woman recovered from sites in China. The teeth carried two key mutations in a protein found in tooth enamel. One mutation has not been observed before and may be a unique marker for East Asian members of the species. The other is also present in a small proportion of modern humans and in Denisovans, an extinct human relative.
This suggests H. erectus may have mated with Denisovans and passed on genetic material, which later reached modern humans when our ancestors interbred with Denisovans. "This traces who we are now back to our ancestors in a really cool and exciting way, using new methods," said Ryan McRae, a paleoanthropologist at the Smithsonian National Museum of Natural History, who was not involved in the research.
The exact relationships between these groups remain unclear. McRae noted that H. erectus could simply be an ancestor of the Denisovans, who inherited those genes over time. "We really need to get more DNA and bits of H. erectus to figure out how this predecessor is exactly related to other humans," said study author Qiaomei Fu of the Institute of Vertebrate Paleontology and Paleoanthropology in China.
