A recent study reveals that a genetic variant inherited from the Denisovans may have played a vital role in the survival of modern humans, or Homo sapiens, as they populated the Americas. Researchers, led by evolutionary biologist Emilia Huerta-Sánchez from Brown University, discovered that this variant, found in the MUC19 region of the human genome, has a significant connection to Indigenous American populations.
The MUC19 gene codes for a mucin protein, crucial for producing mucus, a substance essential for various bodily functions. Analysis indicates that individuals with Indigenous American ancestry are more likely to carry a specific variant of this gene that traces back to the Denisovans, a now-extinct group of ancient humans. Huerta-Sánchez and her team noted that genetic variation typically arises slowly over time. However, interbreeding events with Denisovans introduced a sudden influx of new genetic material.
Tracing the Genetic Pathway
The research elucidates a complex history of genetic exchange that impacted Indigenous American populations. The team found that the Denisovan gene did not transfer directly to modern humans. Instead, it underwent a winding path through multiple introgression events, first from Denisovans to Neanderthals and then from Neanderthals to our ancestors.
This genetic legacy is evident in the genomes of 23 ancient Indigenous American individuals unearthed at archaeological sites across Alaska, California, and Mexico. These remains predate European and African contact with the continent. Using data from the 1,000 Genomes Project, the researchers observed that contemporary Latino Indigenous Americans also possess this Denisovan gene at high frequencies.
As Homo sapiens migrated into North America, the study found a significant expansion of repeated sequences in the MUC19 gene. This expansion effectively doubles the gene’s functional domain, indicating its adaptive role in response to environmental pressures unique to the Americas.
Implications for Survival and Adaptation
The researchers suggest that the changes in the MUC19 gene allowed for the development of a stickier form of the mucin glycoprotein, which likely offered an advantage in new environments. While the specific benefits of this change are still under investigation, the authors point out that mucin genes, such as MUC7, are known to have variations that enhance microbe-binding properties, crucial for maintaining a healthy relationship with gut bacteria and other microbes.
Huerta-Sánchez emphasizes the significance of this genetic variant, stating, “Something about this gene was clearly useful for these populations – and maybe still is or will be in the future.” The study invites further research to explore the gene’s current functions and its potential benefits for human health.
This groundbreaking research is published in the journal Science, contributing to our understanding of human evolution and the complex interactions between ancient populations.
