Did early humans and Neanderthals know they were different species? Perhaps, here's how

Regardless of how far apart we sit on branches of the evolutionary tree, human faces are very different from those of our ancestors. Modern humans can be recognized by their smaller facial structure when compared with Neanderthals and other hominin ancestors.

Anthropologists have long wondered why this difference exists and what kind of developmental changes in our facial bones led our species toward this slimmer appearance.

This difference is particularly noticeable when modern humans are lined up alongside the fossils of bigger-boned ancestors from distant eras.

Researchers recently compared the evidence of facial bone growth in humans, Neanderthal remains, and chimpanzee skeletons.

One of the lead investigators, Alexandra Schuh from the Max Planck Institute for Evolutionary Anthropology, found that variations in the pace of bone growth may offer a core explanation for how our faces became more refined.

Human vs. Neanderthal faces

Studying different groups side by side helps scientists pinpoint which growth patterns set each group apart.

By measuring bone sizes at various life stages, experts see how the developing face changes over time.

This reveals important clues about broader evolutionary shifts that shaped our modern appearance and separated us from our extinct predecessors.

This comparative approach also pulls in data from surviving primate relatives like chimpanzees, which share many features but do not have the same facial proportions as seen in humans.

By including such living primates, scientists build a clearer timeline of how certain traits might have deep roots that stretch back millions of years.

Growth pattern of human faces

One key discovery is that our faces stop expanding earlier than those of other large-faced primates and extinct hominin groups.

A shorter growth window makes a difference in the final adult profile, since less time for bone growth means a smaller overall structure.

This sets modern humans apart from their hefty-boned relatives that are seen in archaeological finds.

Scientists observed that Neanderthal faces, for instance, keep growing for longer, allowing for a robust jaw and broader midface to develop.

This pattern contrasts with ours, where growth slows around adolescence and locks in a leaner form, perhaps hinting at an evolutionary tweak that conserves energy while still supporting vital functions like chewing.

“Our findings reveal that a change in development – particularly during late growth stages – led to smaller faces. Compared to Neanderthals and chimpanzees who continue growing longer, human facial growth stops earlier, around adolescence, resulting in a smaller adult face,” said Schuh.

Inside the face structure

Shifts in bone activities, including when cells deposit new layers or break down older layers, appear to guide this reduced growth.

If the process winds down sooner, the upper jaw – called the maxilla – does not project forward as much, leading to a face that is more compact and less imposing than that of a Neanderthal.

In larger-faced species, these bone activities remain more intense for a longer period, boosting the formation of thicker and more protruding features.

This ongoing bone growth helps explain why some ancient skulls are strikingly big, and it shows that timing has a powerful role in setting each group’s appearance.

Faces grow less as we age

Even though certain facial traits appear early in life, a major distinction between species emerges in those final developmental years before adulthood.

“Identifying key developmental changes allows us to understand how species-specific traits emerged throughout human evolution,” said Schuh.

Researchers note that humans have a relatively extended childhood, yet our facial structures do not keep scaling up throughout that entire stage.

Environmental or genetic influences

Some experts argue that better food processing and cooking might reduce strain on our jaw, but this alone seems insufficient to explain every detail.

Others point to social or behavioral factors, suggesting that selective pressures may subtly shape how the face grows over time.

Biological data indicate that genetic mechanisms controlling bone growth may strongly steer the pace at which the face expands.

Hormonal changes during adolescence could further speed up or slow down these processes, but researchers caution that the full story likely involves an interplay of genes, environment, and daily habits.

Connecting human and Neanderthal faces

Building on these findings, scientists plan to examine more fossils from different time periods to see if other ancient human groups followed a similar pattern.

They hope to trace shifts in facial growth rates across regions, comparing how different populations balanced the demands of survival with changes in jaw development.

By mapping these variations, experts hope to gain insight into which traits are universal and which might be unique offshoots of specific environments.

This sort of detective work across the fossil record pulls together biology, culture, and history, giving us a broader grasp of what shaped our defining look.

Clues also emerge about social evolution, given that facial expression and recognition might factor into how communities function.

A smaller face could offer advantages in communication or other areas, though pinning down a direct link calls for deeper investigation into prehistoric behavior and ecological pressures.

What did we learn?

Scientists agree that the timeline of facial growth stands out as a key to understanding why we appear different from ancestral humans.

Once that window shuts, the face remains smaller and less projected, a shift that may have opened doors to new adaptations while still meeting our species’ unique developmental needs.

These insights show that it is not only the shape of our face that changed, but also the time it took to get there.

As research continues, discoveries about early growth may help us see that each subtle change in our bones has powerful consequences for our evolutionary course.

The study is published in the Journal of Human Evolution.

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