Fossil teeth discovery may explain why humans have such long childhoods

Humans stand apart from many other primates by taking more time to mature, relying on a supportive network of parents, grandparents, and community members during a long period of childhood.

This extended period of growth has long been considered crucial for acquiring the abilities required to thrive in a socially complex environment.

For a while, scientists have connected this slow development to the considerable energy demands of a growing brain. Experts remain intrigued by these social patterns.

Yet, a near-adult fossil of early Homo from the Dmanisi site in Georgia suggests there could be another explanation.

The remains, dated to about 1.77 million years ago, shed light on the interplay between cultural learning and childhood length, raising the idea that the traditional “big brain – long childhood” concept may not be the full story.

Christoph Zollikofer from the University of Zurich played a central part in investigating the unexpected details that have come to light. This site reshaped views on early ancestry.

Tracing human childhood in ancient fossils

Researchers applied synchrotron imaging to examine dental microstructures.

“Childhood and cognition do not fossilize, so we have to rely on indirect information. Teeth are ideal because they fossilize well and produce daily rings, in the same way that trees produce annual rings, which record their development,” explains Zollikofer.

This approach allowed the team to chart growth phases with remarkable precision. Such approaches boost accuracy in fossil studies.

“Dental development is strongly correlated with the development of the rest of the body, including brain development,” another specialist, Paul Tafforeau from the ESRF, remarks.

“Access to the details of a fossil hominid’s dental growth therefore provides a great deal of information about its general growth.”

The group’s effort began in 2005 and spanned about 18 years, benefiting from technological advances in synchrotron tomography.

The first scans took place in 2006, followed by initial results in 2007. High-resolution scans now guide innovative anthropological work.

Reconstructing growth from dental clues

The team discovered something that defied the usual categories.

“We expected to find either dental development typical of early hominids, close to that of the great apes, or dental development close to that of modern humans,” explains Tafforeau.

“When we obtained the first results, we couldn’t believe what we saw, because it was something different that implied faster molar crown growth than in any other fossil hominin or living great ape. It’s been a slow maturation, both technically and intellectually, to finally arrive at the hypothesis we are publishing today.”

In addition, the high-quality scans allowed the scientists to track growth from birth to death without damaging the specimen. Incremental examination helped reveal unexpected growth patterns.

Alongside that surprise, the analysis revealed a specific timeline for this individual’s life.

“The results showed that this individual died between 11 and 12 years of age, when his wisdom teeth had already erupted, as is the case in great apes at this age,” explains Vincent Beyrand, co-author of the study.

The front teeth initially progressed more quickly, while the back teeth took longer to complete. Every tooth layer illuminated unique ancient development.

Slower development in human childhood

Additional evidence highlights that youth in this early Homo likely depended on adults for an extended stretch.

“This suggests that milk teeth were used for longer than in the great apes and that the children of this early Homo species were dependent on adult support for longer than those of the great apes,” explains Marcia Ponce de León from the University of Zurich and co-author of the study.

“This could be the first evolutionary experiment of prolonged childhood.”

One skeleton found at Dmanisi belonged to a much older individual who had lost all teeth but survived with help from others. Communal responsibilities likely shaped new social conventions.

According to David Lordkipadnize of the National Museum of Georgia, “The fact that such an old individual was able to survive without any teeth for several years indicates that the rest of the group took good care of him.”

The presence of multiple generations within the same community could have enabled knowledge to flow more freely.

That knowledge might have included food processing strategies, tool use, or group coordination. Older guardians offered knowledge to younger members.

What does all of this mean?

Scientists propose that lengthening childhood in early humans might have come first, driving cultural transmission and social learning.

Over time, this dynamic may have supported brain expansion, rather than the brain growing first and pushing for extended development.

It appears that maturing slowly allowed young individuals to absorb a growing body of information from older members of the group.

It also permitted older members to share their hard-earned expertise for a lengthier period. Continued support helped cultivate lasting cultural capacities.

Then, as the amount of information to be transmitted increased, evolution would have favored an increase in brain size and a delay in adulthood, allowing us both to learn more in childhood and to have the time to grow a larger brain despite limited food resources.

By focusing on how children rely on social networks early in life, this fossil from Dmanisi emphasizes the possibility that extended childhood and intergenerational support played a decisive role in shaping the path toward modern Homo sapiens.

Researchers are now poised to reexamine the conventional views on what sparked the long adolescence so familiar to us today. Ongoing research keeps clarifying childhood’s formative contribution to humanity.

The full study was published in the journal Nature.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–