Unlike other mammals, humans experience prolonged childhood. Human children continue to grow and depend on their parents for much longer than other species. Although different theories explain the reason for this long life stage, one of the most popular suggests that it is due to the development of larger brains. Now, clues to the origins of our long childhood have been discovered in 1.77 million year old teeth.

In a new study published in Nature On Wednesday, researchers analyzed the tooth growth of a prehistoric youth who lived in what is now Dmanisi, Georgia. They discovered that the fossil teeth of the 11-year-old individual, belonging to our genus, Homoexperienced developmental delay like that of modern human children during the first years of life. Then they took on a larger, monkey-like growth.

If we compared the length of human childhood to that of other primates, “a great ape would probably barely have time to go to kindergarten, and by then it would already be an adult,” explains the lead author. Christoph Zollikoferpaleoanthropologist at the University of Zurich, Popular scienceThis is Laura Baisas. Humans, on the other hand, spend an enormous amount of time “growing up in a very complex social environment.”

A key question in paleoanthropology is determining when this pattern of slow development first appeared in our genus, Alessia Navabioarchaeologist at Sapienza University of Rome who was not involved in the study, says ScienceThis is Ann Gibbons.

“Now we have an important clue,” she adds.

To explore this mystery, the researchers measured the growth lines of the molars of the prehistoric youth. These growth lines on the teeth look like the rings of a tree. Just as a tree adds a layer of material to its trunk each year, teeth accumulate layers of dentin which provide insight into development of the individual.

“You can cut the tooth, see the growth rings and see how it has grown. It can be like a movie about how the tooth developed from birth to death,” says Zollikofer. Popular science.

Previous research has focused on fossil teeth from individuals younger than 4 years old, says a paleoanthropologist. Kevin Kuykendall at the University of Sheffield in England who did not participate in the study, for Scientific news“Bruce Bower. This is the first “fairly complete” reconstruction of dental development in an ancient hominid, he told the outlet.

The newly examined teeth were found in 2001 and were well preserved enough that the team was able to take X-ray images of their growth lines. Using this imaging, researchers studied how different teeth formed and developed over the course of the young person’s life.

They compared tooth growth to that of modern humans and other great apes, such as chimpanzees. The results fell somewhere in between: The youngster’s teeth followed a slow, human-like growth pattern until around age 4, according to the paper, then caught up with that of a chimpanzee around the age of 8. The youngster would have reached dental maturity around the age of 8. 12 to 13.5 years old.

Dmanisi Dental Development

For Debbie Guatelli-Steinbergpaleoanthropist at Ohio State University, “the bottom line is that we’re starting to see this slowdown before a major increase in brain size,” she explains. Science. “Very exciting” results suggest Homo species may have evolved long childhoods to spend more time learning social behavior, before brain development escalates.

However, Kuykendall emphasizes Scientific news that it is difficult to draw definitive conclusions. Rather than being linked to social learning or brain size, slowing early dental development Homo individuals could have been shaped by available foods or by age at weaning.

Although the new study provides clues about the evolution of the prolonged period of growth in humans, “many puzzles remain,” Guatelli-Steinberg writes in Nature news and views. Studying the chemical signatures of fossil tooth enamel, for example, could shed more light on the origins of man’s prolonged childhood.