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, Smith said.
“Teeth are remarkable time recorders, capturing each day of growth much like rings in trees reveal yearly progress,” she said.
Previous research has pointed to differences in how early humans and apes mature and grow.
For example, ape females have shorter pregnancies that result in offspring growing up faster and reproducing at younger ages than humans. Chimpanzees on average bear their first babies at age 13, compared to age 19 in humans.
“It doesn’t make any sense to lengthen your childhood if there is no guarantee you are going to make it to a ripe old age,” said Smith.
However, it is less clear when this evolutionary shift began to occur in the path of human development.
Smith described the change as a “costly yet advantageous shift from a primitive ‘live fast and die young’ strategy to the ‘live slow and grow old’ strategy that has helped to make us one of the most successful organisms on the planet.”
When the researchers examined tooth specimens from the earliest members of our own species, using one set of dental remains found in Morocco 160,000 years ago and one that dates back 90-100,000 years found in Israel, they found they were remarkably similar to modern humans.
“They look pretty much like us,” said Smith. “This longer period of growth and development is a condition that is unique to our own species.”
The advances in examining the age of the teeth were possible by using what the study called a “supermicroscope” that employs “extremely powerful X-ray beams” developed at the European Synchrotron Radiation Facility in Grenoble, France.
The synchotron at Grenoble is the largest in the world, and has been visited by museum curators and scientists bearing rare fossils from around the world so that they can be imaged and analyzed anew, the study said.
A study released last week showed that the brains of Neanderthals, believed to be modern humans’ closest ancestor, were similar to humans’ at birth but developed differently in the first year of life.