Ancient human and Denisovan interbreeding gave Indigenous Americans a genetic advantage
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Ancient human and Denisovan interbreeding gave Indigenous Americans a genetic advantage
Genetic study suggests that interbreeding between ancient human species may have given a survival advantage to the groups which migrated to the Americas thousands of years ago. The study focused on a gene called MUC19. This gene is involved in the production of proteins which form saliva and mucus barriers in the digestive and respiratory systems. A variant of the M UC19 present in modern people with Latin American and Indigenous American ancestry didn’t come from ancient Homo sapiens – it came from the archaic human species known as Denisovans. The Denisovan gene likely came into modern human DNA through interbreeding with Neanderthals who had previously interbred with Denisovan. There is even evidence to suggest that Denisovan genetics may have helped strengthen the immune systems of these people.
A genetic study suggests that interbreeding between ancient human species may have given a survival advantage to the groups which migrated to the Americas thousands of years ago.
The study published in Science focused on a gene called MUC19. This gene is involved in the production of proteins which form saliva and mucus barriers in the digestive and respiratory systems.
A variant of the MUC19 present in modern people with Latin American and Indigenous American ancestry didn’t come from ancient Homo sapiens – it came from the archaic human species known as Denisovans.
Denisovans were first discovered in Siberia in 2010. They are most closely related to Neanderthals, having split from that species about 400,000 years ago. Modern humans and Neanderthals diverged at least 500,000 years ago. Genetic evidence shows that all 3 species interbred.
Fossils of Denisovans have been found in Siberia, Tibet, northeastern China and Taiwan.
While Denisovans went extinct about 30,000 years ago, they left their mark on modern Homo sapiens.
Denisovan DNA has been found in modern people from Papua New Guinea. There is even evidence to suggest that Denisovan genetics may have helped strengthen the immune systems of these people.
The new study shows that DNA from archaeological sites of ancient modern humans in North and South America also contained the Denisovan version of the MUC19 gene.
The rate at which the gene appears in modern human populations suggests that it was advantageous in the natural selection of Indigenous Americans’ ancestors.
Denisovan MUC19 may have provided a survival or reproductive advantage.
“From an evolutionary standpoint, this finding shows how ancient interbreeding can have effects that we still see today,” says author Emilia Huerta-Sánchez, a professor at Brown University in the US. “From a biological standpoint, we identify a gene that appears to be adaptive, but whose function hasn’t yet been characterised. We hope that leads to additional study of what this gene is actually doing.”
Huerta- Sánchez and colleagues compared Denisovan DNA with modern genomes through the 1,000 Genomes Project – a global study of human genetic variation.
Denisovan-derived MUC19 is found in high frequencies in populations with Indigenous American ancestry. It is also abundant in the DNA of 23 individuals uncovered at archaeological sites in Alaska, California, Mexico and elsewhere in the Americas.
Statistical analysis showed that the gene was found in unusually high frequencies in ancient Indigenous American populations. It was also in a very long stretch of archaic DNA. Both of these factors signify a gene which is subject to positive natural selection.
“Something about this gene was clearly useful for these populations – and maybe still is or will be in the future,” Huerta-Sánchez comments.
The genetic analysis revealed another surprise. The Denisovan MUC19 gene likely came into modern human DNA through interbreeding with Neanderthals who had previously interbred with Denisovans, rather than direct interbreeding between Denisovans and ancient modern humans.
“Typically, genetic novelty is generated through a very slow process,” Huerta- Sánchez adds. “But these interbreeding events were a sudden way to introduce a lot of new variation.”
How this sudden new genetic variation helped ancient modern humans who migrated to the Americas will be the subject of future research.
Study Reveals Genetic Advantages from Ancient Human Interbreeding
A recent study highlights the critical role of ancient interbreeding with archaic human species in shaping the genetic makeup of modern humans. This research, published in the journal Science, zeroes in on the MUC19 gene, which is instrumental in producing proteins that create saliva and mucosal barriers in the respiratory and digestive systems. A variant of this gene, stemming from the Denisovans, has been identified in contemporary Latin Americans of Indigenous American descent. DNA samples from archaeological sites across North and South America also exhibit this Denisovan-derived genetic variant. The prevalence of the gene indicates that it underwent significant natural selection, suggesting it conferred a survival or reproductive advantage, potentially aiding in immunity against pathogens encountered during the migration to the Americas.
The study reveals that a variant of the MUC19 gene, stemming from the Denisovans—an archaic human species—has been identified in contemporary Latin Americans of Indigenous American descent. Furthermore, DNA samples from archaeological sites across North and South America also exhibit this Denisovan-derived genetic variant. The prevalence of this gene in modern populations indicates that it underwent significant natural selection, suggesting it conferred a survival or reproductive advantage, potentially aiding in immunity against pathogens encountered during the migration to the Americas thousands of years ago.
Emilia Huerta-Sánchez, a professor of ecology, evolution, and organismal biology at Brown University and a lead author of the study, remarked on the evolutionary significance of this finding, noting that it illustrates how ancient interbreeding continues to impact modern humans. She emphasized the urgency of further research to elucidate the specific functions of this seemingly adaptive gene.
The Denisovans, who inhabited parts of Asia between approximately 300,000 to 30,000 years ago, are poorly understood, with only a few fossil remains available, including those recovered from Denisova Cave in Siberia and other sites. Previously, Huerta-Sánchez explored the implications of a gene variant derived from Denisovans, which may have enabled Sherpas and Tibetans to thrive in high-altitude environments.
In this recent study, researchers compared DNA samples from Denisovans with contemporary genomes sourced from the 1,000 Genomes Project, a large-scale assessment of global genetic diversity. Results indicated high frequencies of the Denisovan MUC19 variant in Latino populations with Indigenous American ancestry, along with evidence of this gene in the DNA of ancient individuals excavated from sites in Alaska, California, and Mexico.
To reinforce their findings, the research team conducted various statistical tests demonstrating that the Denisovan variant of the MUC19 gene rose to unusually high frequencies in ancient Indigenous American populations, as well as in present-day individuals of Indigenous descent. Furthermore, the persistence of this gene on a notably prolonged stretch of archaic DNA suggests that natural selection played a vital role in increasing its prevalence. The analysis indicates that this gene was likely transmitted through interbreeding between Denisovans and Neanderthals before making its way to modern humans.
Huerta-Sánchez articulated the valuable genetic variation brought about by these interbreeding events, underscoring that such genetic novelty typically arises through slow evolutionary processes. However, interbreeding provided a rapid influx of beneficial genetic traits.
The MUC19 gene appears to have been advantageous for populations migrating into the Americas, potentially enhancing their immune responses. Huerta-Sánchez expressed optimism that acknowledgment of this gene’s significance will catalyze further investigation into its biological functions, particularly due to its role in altering protein sequences.
Co-authors of the study include Fernando Villanea, now at the University of Colorado, alongside students and a global team of collaborators. Funding for this research was provided by various institutions, including the Leakey Foundation and the National Institutes of Health.
Source: https://cosmosmagazine.com/history/archaeology/ancient-human-interbreeding-americas/