Every person has a unique face, shaped by countless tiny details in our DNA. But scientists still don’t fully understand how our genes decide the shape of our noses, jaws, and brows.
To find answers, researchers have turned to our ancient cousins—the Neanderthals. These early humans had faces that looked quite different from ours, with large noses, heavy brows, and strong lower jaws.
A new study from scientists at the University of Edinburgh in the UK has discovered one reason why Neanderthals had such distinctive faces.
The research, published in the journal Development, found that a small region of Neanderthal DNA activates a gene linked to jaw formation more strongly than the same region in modern humans. This could help explain why Neanderthals had larger, more powerful jaws.
The research team, led by Dr. Hannah Long from the MRC Human Genetics Unit, compared the Neanderthal and human genomes. Scientists have already sequenced the full Neanderthal genome using DNA from ancient bones. It turns out that our DNA is 99.7% identical to theirs, meaning the small differences may be responsible for how our species looks today.
Each human and Neanderthal genome contains around three billion DNA letters, which makes it extremely difficult to identify which small sections influence physical traits such as facial features. Fortunately, Long’s team had a clue where to look. They focused on a region of DNA known to affect a rare genetic condition called Pierre Robin sequence.
This condition causes babies to be born with unusually small lower jaws. Some people with this condition have large deletions or rearrangements in this part of their DNA, which disturb normal face development. The scientists suspected that smaller differences in the same region might subtly affect jaw size in different species.
When they compared the Neanderthal and human versions of this DNA region—about 3,000 letters long—they found only three single-letter differences. The section doesn’t contain any genes itself, but it acts like a switch that controls another gene called SOX9. This gene plays a key role in shaping the face during early development.
To test how these small DNA changes worked, the researchers turned to an unexpected helper: zebrafish. These tiny fish are often used in genetic research because their transparent embryos allow scientists to watch cells develop in real time.
The team inserted both the human and Neanderthal versions of the DNA sequence into zebrafish and tagged each version with a different fluorescent color.
As the zebrafish embryos grew, both versions of the DNA were active in cells that help form the lower jaw—but the Neanderthal version was noticeably more active. This meant that the Neanderthal DNA turned on the SOX9 gene more strongly, which could lead to a larger jaw structure.
‘It was very exciting when we first saw this activity near the developing jaw,’ said Dr. Long. ‘Seeing that the Neanderthal DNA worked more powerfully really made us think about how this might have changed face shape in the past.’
To explore further, the scientists increased SOX9 activity in the zebrafish embryos. They found that cells involved in building the jaw spread over a larger area, supporting the idea that more SOX9 activity could produce a bigger or stronger jaw.
Dr. Long says the next step is to study other small DNA differences between Neanderthals and humans to see how they might affect facial features. Her lab is also developing new ways to mimic facial development using human cells in the lab, which could help doctors understand genetic conditions that affect the face and jaw.
This research highlights how studying extinct species can teach us about our own biology. By comparing ancient and modern DNA, scientists can see how small changes shaped the faces of our ancestors—and, ultimately, our own.
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