Study Reveals DNA Difference Behind Neanderthal Jaw Size
Recent research has uncovered a significant genetic difference that explains why Neanderthals had larger lower jaws compared to modern humans. A study published in the journal Development identifies a specific section of the Neanderthal genome that influences jaw development. This finding sheds light on the distinct facial features of Neanderthals, despite their genomes being approximately 99.7 percent identical to those of humans.
The study focuses on a tiny segment of Neanderthal DNA that plays a crucial role in jaw growth. Scientists have long been fascinated by Neanderthal physical characteristics, such as their prominent brow ridges and large noses. Understanding the genetic underpinnings of these traits can provide deeper insights into human evolution.
Unlocking the Neanderthal Genome
In 2010, researchers successfully sequenced the first draft of the Neanderthal genome using ancient bones discovered in Vindija Cave in Croatia. This groundbreaking work allowed scientists to explore the genetic similarities and differences between Neanderthals and modern humans, confirming interbreeding events that occurred between the two groups approximately 50,500 to 43,500 years ago.
The Neanderthal and human genomes consist of around 3 billion DNA letters, which determine the structure and function of proteins within the body. The recent study aimed to pinpoint the specific genetic elements responsible for Neanderthal jaw size, a task likened to finding a needle in a haystack due to the vast amount of genetic data involved.
Identifying Key Genetic Differences
To tackle this challenge, researchers focused on a specific region of the genome linked to the Pierre Robin sequence, a rare condition that results in an undersized lower jaw. Dr. Hannah Long, a geneticist at the University of Edinburgh, explained that while some individuals with this condition have significant alterations in their DNA, they hypothesized that smaller differences might also affect facial features.
Their investigation revealed that the Neanderthal and human versions of this specific genome region, comprising only around 3,000 letters, differ by just three single-letter changes. Although this region does not contain any genes, it regulates the activation of the SOX9 gene, which is essential for proper facial development.
To observe the effects of these genetic variations, researchers inserted both Neanderthal and human versions of the DNA segment into the embryos of zebrafish, which are transparent and allow for easy observation. This innovative approach enabled them to track the activity of each version in cells responsible for jaw formation. Notably, the Neanderthal DNA exhibited increased activity compared to its human counterpart.
Dr. Long expressed her excitement about the findings, stating, “It was very exciting when we first observed activity in the developing zebrafish face in a specific cell population close to the developing jaw, and even more so when we observed that the Neanderthal-specific differences could change its activity in development.”
By further manipulating the embryos to include additional copies of the SOX9 gene, researchers discovered that the Neanderthal genetic region influenced the size and shape of the jaw, resulting in a broader developmental area for jaw-related cells.
Now that they have identified the genetic factors contributing to Neanderthal jaw size, researchers are turning their attention to how different parts of the genome may relate to other facial features. This ongoing investigation could provide additional insights into the physical distinctions that set Neanderthals apart from modern humans and deepen our understanding of human evolution.
As science continues to unravel the complexities of our ancient relatives, studies like this one highlight the intricate relationship between genetics and physical traits, revealing the remarkable stories hidden within our shared ancestry.
