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Oldest East Asian hominin fossil displays modern human dental development

In the remains of the Xujiayao juvenile fossil (above), researchers have found evidence of dental growth and development very similar to that of people today. (Photograph: Ohio State University)

Fri. 25. January 2019

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COLUMBUS, Ohio, U.S.: One of the more accurate ways to understand the evolution of human history is by examining fossilized teeth. In a new archeological finding, researchers have discovered a relative of modern humans that lived at least 104,000 years ago in northern China and found that it displays evidence of dental growth and development very similar to that of people today.

The hominin fossil is that of a 6.5-year-old who lived between 104,000 and 248,000 years ago and was found at the Xujiayao site in northern China. The team of researchers from the Chinese Academy of Sciences in Beijing and Ohio State University were the first to perform a systematic assessment of dental growth and development in an East Asian archaic hominin fossil.

Speaking about the findings, co-author of the study Dr. Debbie Guatelli-Steinberg, Professor of Anthropology at the Ohio State University, said they were surprised to find that, in most ways, the child’s dental development was very similar to what you would see in children today. “The Xujiayao juvenile is the oldest fossil found in East Asia that has dental development comparable to modern humans,” she explained.

Among other techniques, the researchers used synchrotron X-ray imaging to view the internal structure of the teeth, including growth lines that reveal the rate of tooth development. This ability to see so far back into the past is what Guatelli-Steinberg believes provides some of the best data anthropologists have regarding the growth and development of modern humans’ ancient ancestors. In addition to other findings, the team learned that the juvenile’s first molar had erupted a few months before death and had started to wear, with the root about three-quarters complete.

According to the researchers, the study’s finding of modern dental development is all the more interesting in light of the many nonmodern elements of the fossil features, such as the shape and thickness of the skull, the large size of the teeth and the quick rate at which the roots grew. “We don’t know exactly where this enigmatic East Asian hominin fits in human evolution,” said lead author Dr. Song Xing of the Chinese Academy of Sciences.

Despite the interesting similarities, Guatelli-Steinberg cautioned against making too many predictions, noting “It would be interesting to see if dental development in later childhood, such as the growth and development of third molars, was also similar to modern humans.”

The study, titled “First systematic assessment of dental growth and development in an archaic hominin (genus, Homo) from East Asia,” was published in the January 2019 issue of Science Advances.

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