Humans differ from many other primates by taking longer to mature and relying on a support network of parents, grandparents, and community members for a long period of their childhood.
This extended period of growth has long been considered crucial for acquiring the skills needed to thrive in a socially complex environment.
For a time, scientists associated this slow development with the enormous energy demands of a growing brain. Experts remain intrigued by these social models.
Yet a near-adult fossil of early Homo from the Dmanisi site in Georgia suggests there may be another explanation.
The remains, dated to around 1.77 million years ago, shed light on the interplay between cultural learning and the length of childhood, raising the idea that the traditional concept of “big brain – long childhood” may not be the whole story.
Christoph Zollikofer, from the University of Zurich, played a central role in investigating the unexpected details revealed. This site has reshaped views of early ancestors.
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 that record their development,” says Zollikofer.
This approach allowed the team to chart growth phases with remarkable precision. Such approaches improve the accuracy of fossil studies.
“Dental development is strongly correlated with the development of the rest of the body, including brain development,” notes another specialist, Paul Tafforeau of the European Synchrotron Radiation Facility (ESRF).
“Access to the details of a fossil hominid’s tooth growth therefore provides a lot of information about its general growth.”
The group’s efforts began in 2005 and lasted about 18 years, benefiting from technological advances in synchrotron tomography.
The first scans took place in 2006, followed by the first 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 great apes, or dental development close to that of modern humans,” explains Tafforeau.
“When we got the first results, we couldn’t believe what we were seeing, because it was something different that involved molar crown growth faster than in any other fossil hominin or living great ape. It took slow maturation, both technically and intellectually, to finally arrive at the hypothesis we are publishing today.”
Additionally, the high-quality analyzes allowed scientists to track growth from birth to death without damaging the specimen. Incremental examination revealed unexpected growth patterns.
Along with this surprise, the analysis revealed a specific timeline of this individual’s life.
“The results showed that this individual died between 11 and 12 years old, while his wisdom teeth had already emerged, as is the case in great apes at this age,” explains Vincent Beyrand, co-author of the study.
The front teeth first progressed more quickly, while the back teeth took longer to complete. Each dental layer illuminated a unique ancient development.
Slower development in human childhood
Additional evidence highlights that the young of these early Homo likely depended on adults for a prolonged period.
“This suggests that baby teeth were used longer than in great apes and that children of this early Homo species depended on adult support for longer than those of great apes,” explains Marcia Ponce de León from the University of Zurich and co-author of the study.
“This could be the first evolutionary experience of prolonged childhood.”
A skeleton found in Dmanisi belonged to a much older individual who had lost all his teeth but survived with the help of others. Community responsibilities probably 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 teeth for several years indicates that the rest of the group took good care of him.”
The presence of several generations within the same community could have allowed knowledge to circulate more freely.
This knowledge could have included food processing strategies, tool use, or group coordination. Older tutors offered their knowledge to younger members.
What does all this mean?
Scientists propose that longer childhoods among early humans may have been the priority, promoting cultural transmission and social learning.
Over time, this dynamic may have favored brain expansion, rather than the brain expanding first and favoring prolonged development.
It appears that slow maturation allowed young individuals to absorb an increasing amount of information from older members of the group.
This also allowed older members to share their hard-earned expertise for a longer period of time. Ongoing support helped develop 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 to both learn more in childhood and have time to grow larger brains despite limited food resources.
By focusing on how children rely on social networks from an early age, this Dmanisi fossil highlights the possibility that extended childhood and intergenerational support played a decisive role in shaping the path to modern Homo sapiens.
Researchers are now ready to reexamine conventional views about what triggered the long adolescence that is so familiar to us today. Ongoing research continues to clarify childhood’s formative contribution to humanity.
The full study was published in the journal Nature.
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