What Ancient Teeth Teach Us About Human Development

Tracing the evolution of human growth and development through dental clues

If you like nature documentaries as much as I do, you have probably considered this, especially if you have children!

How come most mammals are giving birth to their own young within 1 to 5 years from birth while humans still need to put all their efforts into making sure their ten-year-old stays alive? Aren’t we “the smart species” in the room?

However, there’s something we sometimes fail to contemplate or even consider: these animals’ lives are a lot less complex and they may need to master fewer less skills to survive within their societies. 

They don’t have multiple types of languages to master (e.g., verbal, nonverbal, written, etc.), complex social hierarchies, or sophisticated crafts to choose from to find a place in society. Things are simpler for these species. 

Indeed, understanding this phenomenon has puzzled archeologists and anthropologists for centuries, and while we don’t yet have all the answers, a new study on the internal structure of an ancient teenager’s teeth may provide some clues to this enigma.

In what is now Georgia, a discovery from nearly two million years ago has been shaking up how we think about human evolution. The fossilized teeth of an almost 2 million years old early Homo individual, found at the Dmanisi site, are giving scientists a rare insight into the lives of our ancient relatives.

However, these teeth don’t just tell us about what this individual ate or how they lived — they may hold the key to understanding how long childhood emerged as a critical phase in human development.

What do we mean by that?

Well, modern humans are unique among primates for many reasons, but one standout trait is our extended childhood. Have you seen any other species that takes 18 years to reach some resemblance of adulthood?

For humans, it’s during this time that children absorb the complexities of their social environment, developing the skills needed to thrive in a group. Traditionally, this long developmental period has been thought to coincide with the growth of our large, energy-demanding brains. However, new findings suggest this relationship might not be as straightforward as once believed. Let’s look at this research a bit further, should we?

The researchers, an international team led by Dr. Christoph Zollikofer from the University of Zurich, turned to teeth for clues. “Childhood and cognition do not fossilize, so we have to rely on indirect information,” Dr. Zollikofer explains. 

But why are teeth so good for this? Well, they are an excellent proxy because they grow in daily layers, much like tree rings, recording detailed information about their development.

So, what did the authors do to get all this information? 

Using synchrotron imaging, a cutting-edge method that creates highly detailed virtual slices of the teeth, the team tracked this individual’s dental development from birth to death. Impressive, right?

This technique allowed them to reconstruct the growth patterns of the teeth with unprecedented precision, even noting stress markers that appeared as lines in the enamel. Remember: it’s science, not magic.

And what did they find besides very cool images?

The Dmanisi individual died at around 11 or 12 years old, just before reaching full dental maturity. In a way, this timing is similar to that of great apes. Yet, the teeth told a more nuanced story. 

The back molars (your chewing teeth) developed later than the front teeth, a pattern seen in modern humans but not in great apes. This delay suggests the individual relied on their “milk teeth” for a longer period, possibly because they remained nutritionally dependent on adults.

“This could be the first evolutionary experiment of prolonged childhood,” says Dr. Marcia Ponce de León, a co-author of the study. The findings indicate that early Homo may have spent more time as juveniles under adult care, much like modern human children.

Perhaps the most striking implication of the research is its challenge to the long-standing assumption that an extended childhood evolved hand-in-hand with increasing brain size. But why?

The brains of early Homo individuals, including those at Dmanisi, were only slightly larger than those of great apes. Yet, they exhibited traits associated with prolonged development. This suggests other factors, such as social and cultural dynamics, played a bigger role in extended childhood than previously thought.

One of the fossils at Dmanisi adds weight to this argument: the skull of an elderly individual who had lived for years without teeth. “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,” says Dr. David Lordkipanidze of the Georgian National Museum. 

This kind of intergenerational support could have been a critical driver in the evolution of longer childhoods. If they were taking care of their elderly, they provably were also caring for their young. 

But what’s the bigger picture here?

These findings push us to think beyond biology and consider the importance of social factors in shaping human evolution. A prolonged childhood likely allowed for better cultural knowledge transmission, such as making tools, finding food, and navigating social relationships.

Over time, this extended period of learning might have driven the need for larger brains to store and process the growing pool of shared knowledge.

While this study focuses on a single fossil, it’s part of a broader effort to piece together the complex puzzle of human origins. By studying the teeth of ancient individuals, scientists are uncovering the roots of what makes us human: the ability to learn, share, and cooperate.

The Dmanisi teeth remind us that evolution isn’t always about physical traits alone. Sometimes, it’s the social and cultural innovations — taking care of the young, supporting the old, and passing on knowledge — that shape the trajectory of a species. 

It’s a story written in the fine lines of fossilized teeth, connecting us to a distant past and reminding us of the deep roots of our humanity.

Published in Fossils et al. Follow to learn more about Paleontology and Evolution.