The analysis of genetic data from more than 6,000 volunteers across Latin America was designed to find genes that determine the shape of a person's facial profile but also learned that one of the genes appears to have been inherited from the Denisovans, an extinct group of ancient humans who lived tens of thousands of years ago.
The team found that the gene, TBX15, which contributes to lip shape, was linked with genetic data found in the Denisovan people, providing a clue to the gene's origin. The Denisovans lived in central Asia, and other studies suggest they interbred with modern humans, as some of their DNA lives on in Pacific Islanders and Indigenous people of the Americas.
Diagram showing measurements of facial features, such as nose roundedness, nose protrusion, and lip thickness (Bonfante et al, 2021).
Researchers have only been able to analyze complex genetic data from thousands of people at once over the last two decades, since the mapping of the human genome enabled the use of genome-wide association studies to find correlations between traits and genes. This study compared genetic information from the study participants with characteristics of their face shape, quantified with 59 measurements (distances, angles and ratios between set points) from photos of the participants' faces in profile.
The findings of this research could help understand the developmental processes that determine facial features, which will help researchers studying genetic disorders that lead to facial abnormalities. The results also contribute to the understanding of the evolution of facial appearance in human and other species. One of the newly discovered genes found in this study is VPS13B, which influenced nose pointiness; the researchers also found that this gene affects nose structure in mice, indicating a broadly shared genetic basis among distantly related mammal species.
Co-corresponding author Dr Kaustubh Adhikari University College London said, "The face shape genes we found may have been the product of evolution as ancient humans evolved to adapt to their environments. Possibly, the version of the gene determining lip shape that was present in the Denisovans could have helped in body fat distribution to make them better suited to the cold climates of Central Asia, and was passed on to modern humans when the two groups met and interbred."
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