Facing untold pressures to survive, Neanderthal kids grew up much faster than modern human tots, whose lengthy childhoods may be a relatively new phenomenon that has helped boost longevity.

That’s according to a study by led researchers at Harvard University, the latest to highlight small but crucial differences in early development between humans and our closest cousins who became extinct about 28,000 years ago.

Researchers made the discovery after using a new “supermicroscrope” with an advanced X-ray technique to examine the teeth of previously discovered fossils of eight Neanderthal children.

“The Neanderthal children seemed to show a lot of stress,” said lead study author Tanya Smith, assistant professor of human evolutionary biology at Harvard, noting that teeth can offer plenty of clues about overall development.

“Inside and outside, the Neanderthal teeth show a lot of these developmental defects in high frequencies. It seems like childhood was tough for Neanderthals.”

The study, which appeared in the Proceedings of the National Academy of Sciences, said that young Neanderthals’ teeth growth “was significantly faster than in our own species”.

Even when compared to some of the earliest human teeth, taken from remains of humans who left Africa 90,000 to 100,00 years ago, the differences were clear. Human teeth grew more slowly, pointing to more leisurely periods of youth.

“This indicates that the elongation of childhood has been a relatively recent development,” the study said.

During the five-year study, scientists at Harvard, the Max Planck Institute for Evolutionary Biology and the European Synchrotron Radiation Facility examined and compared the remains of Neanderthal and human children.

Using a highly developed “supermicroscope” that helped peer deeper into the dental fossils without damaging them, researchers found that the first hominin fossil ever discovered, that of a young Neanderthal girl found in Belgium, was actually about three years old when she died, not four to five as previously thought. Scientists were even able to detect a “tiny ‘birth certificate’” inside molars that offered a precise way to calculate how old a juvenile was at death, Ms Smith said.

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