A team led by Dr. Hannah Long at the University of Edinburgh has uncovered a fascinating link between Neanderthal DNA and the development of our facial features, specifically the jaw. While humans and Neanderthals share 99.7% of their genetic code, subtle variations in those remaining fractions can have surprisingly significant impacts on appearance.
This research zeroes in on a particular region within the genome associated with Pierre Robin sequence, a condition characterized by an unusually small lower jaw. Dr. Long and her colleagues theorized that even minor differences in this DNA segment between humans and Neanderthals could contribute to noticeable variations in facial structure.
Indeed, they found just three single-letter variations within a 3,000-letter stretch of DNA where the Neanderthal version stood out. Though not directly coding for proteins, this region acts as a control switch, regulating the activity of a crucial gene called SOX9, which plays a central role in facial development.
To confirm that these Neanderthal-specific variations mattered in practice, the researchers turned to zebrafish embryos. They inserted both the human and Neanderthal versions of this DNA segment into the zebrafish’s genome and observed how they functioned during embryonic development. The result was striking: the Neanderthal version proved more potent at activating SOX9 within cells responsible for forming the lower jaw compared to its human counterpart.
Further experiments using extra SOX9 in zebrafish embryos demonstrated that increased activity of this gene indeed led to an expanded area occupied by cells contributing to jaw formation, hinting at how subtle genetic differences could translate into larger jaws like those seen in Neanderthals.
This research highlights the power of studying extinct species to shed light on our own biology and evolution. By comparing genomes, scientists can pinpoint precise regions responsible for shaping unique human traits and gain insights into the complex interplay between genes and development. Dr. Long’s team plans to further explore how additional DNA sequence variations influence facial development in the lab, potentially informing diagnoses of facial conditions in humans.
