Ancient teeth hint at canoodling between early human relatives
NEW YORK– An analysis of ancient teeth is giving scientists a rare glimpse into interactions between related humans hundreds of thousands of years ago that left a lasting imprint on our species.
A new study reveals genetic clues to a human ancestor called Homo erectus. H. erectus appeared in Africa about 2 million years ago and spread to other parts of the globe, including Asia and perhaps Europe.
Scientists have discovered the remains of these early humans in countries including Indonesia, Spain, China and Georgia. But genes and proteins don’t preserve well, so information about the internal makeup of early humans has proven elusive.
In new work, researchers siphoned ancient proteins from the tooth enamel of H. erectus belonging to five men and one woman that were recovered from several locations in China to discover how these early humans may have mixed.
The 400,000-year-old teeth all had two key mutations in a protein found in tooth enamel. A mutation has never been observed before and could be a unique calling card belonging to the East Asian members of H. erectus.
The second, however, was more complex. Scientists have identified a variant that is also present in a small fraction of modern humans – as well as one of our extinct cousins called Denisovans.
This indicated to scientists that H. erectus might have mated with the Denisovans and passed on their genes in the past. But how did it happen to us? Scientists believe this may have happened later, when our ancestors mixed with the Denisovans.
“It traces who we are now back to our ancestors in a really cool and exciting way, using new methods,” said paleoanthropologist Ryan McRae of the Smithsonian National Museum of Natural History, who was not involved in the new research.
The exact relationships between all of these first human relatives are still a little murky. It could be that H. erectus is actually just an ancestor of the Denisovans, who inherited these genes over time, McRae said.
This is a difficult puzzle to solve with extremely limited data. Finding more fossils and testing the limited evidence for DNA remains can help solidify the story of human evolution.
“We really need more DNA” and pieces of H. erectus to understand how exactly this predecessor “is related to other humans,” said study author Qiaomei Fu of the Institute of Vertebrate Paleontology and Paleoanthropology in China.
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