DNA from giant tooth fossil linked to strange human cousin

Scientists have discovered a link to a newly found species of ancient hominids within the DNA in a fossilized tooth from Siberia. According to a report from National Geographic, the finding suggests that Homo sapiens likely shared the Earth with other primate species including Neanderthals and the owner of the tooth fossil, Denisovans.

The study was published in the Proceedings of the National Academy of Sciences, and used high-tech nuclear and mitochondrial DNA sequencing techniques to establish the link between Denisovans and early humans.

The tooth, along with a finger bone, were discovered in the Denisova cave in the Altai Mountains of Siberia. Svante Pääbo explained that it was the only place in the world where three distinct species of hominids coexisted.

The DNA found in the tooth and finger bone revealed that Denisovians contributed up to five percent of the genome in certain groups of modern humans, including the Melanesians of Papua New Guinea and the Pacific.

After the initial discovery of these fossils, archaeologists returned to the Denisova cave and dug up another wisdom tooth. Anthropologist Bence Viola of the University of Toronto initially thought it belonged to a bear due to its size and the shape of its roots. The shape of the tooth suggested that Denisovans likely had large mandibles.

The head of the DNA analysis team, Susana Sawyer from the Max Planck Institute for Evolutionary Anthropology, worked with Pääbo to control for contamination from present day humans and microbes, as well as that of ancient scavengers that likely roamed the cave.

The DNA analysis allowed the researchers to determine where on the human family tree Denisovans diverged from a common ancestor. Since the second tooth discovered in the cave had relatively fewer genetic mutations than the other two samples, it must have been an older individual.

Despite the exciting new clues, scientists still know little about Denisovans. The study can be found here.

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