At a Glance
- A gene variant from extinct Denisovans is found at high frequencies in modern and ancient Indigenous American populations, suggesting it provided an evolutionary advantage during their migration and settlement.
- The gene, MUC19, is involved in the immune system and is associated with an increased number of protein-coding repeats in individuals who carry the archaic version.
- This Denisovan DNA did not pass directly to humans but was first inherited by Neanderthals, who then passed the combined genetic segment on to the ancestors of modern humans.
- This complex transfer of genetic material from Denisovans to Neanderthals and then to humans represents a newly identified and intricate pattern of ancient interbreeding among hominin groups.
- The positive selection of this archaic gene underscores how introgression from extinct relatives was a crucial mechanism for human adaptation to novel environments encountered worldwide.
A new study reveals that many people with Indigenous American ancestry carry a unique segment of DNA inherited from an ancient, extinct group of humans known as the Denisovans. This genetic material, centered on an immune-related gene known as MUC19, appears to have been favored by natural selection as the first peoples migrated into and populated the Americas thousands of years ago. Published in the journal Science, the research suggests this ancient DNA may have been crucial for adapting to the novel environments and diseases of a new world.
The research, led by scientists at the University of Colorado Boulder, explores the intricate history of interbreeding between different human species. Denisovans are ancient relatives of modern humans who lived across Asia and whose existence was only confirmed about 15 years ago from a bone fragment found in Siberia. They, along with Neanderthals, interbred with early modern humans, leaving traces of their DNA in our genomes today. The gene MUC19 is involved in producing mucins, the key proteins in mucus that protect the body’s tissues from pathogens.
In a surprising twist, the team discovered that the Denisovan gene variant did not pass directly to modern humans. Instead, the evidence suggests a multi-step journey where Denisovans first passed the MUC19 gene variant to Neanderthals. Later, these Neanderthals interbred with modern humans, who then carried this genetic package with them. Researchers describe the unique DNA structure as an “Oreo,” with a Denisovan gene variant sandwiched between sections of Neanderthal DNA. This is the first time scientists have identified such a clear case of DNA jumping from Denisovans to Neanderthals and then to humans.
The study found that while this “Oreo” haplotype is rare in most global populations, it is present at high frequencies in individuals with Indigenous American ancestry. This pattern strongly indicates that the MUC19 variant conferred a survival advantage, a process known as adaptive introgression. While the exact benefit is still under investigation, researchers believe it may have enhanced immune responses to new pathogens or facilitated the digestion of new foods, highlighting the remarkable biological resilience of the first Americans as they adapted to a new continent.
References
- University of Colorado at Boulder. (2025, August 21). DNA from extinct hominin may have helped ancient peoples survive in the Americas. Phys.Org; University of Colorado at Boulder. https://phys.org/news/2025-08-dna-extinct-hominin-ancient-peoples.html
- Villanea, F. A., Peede, D., Kaufman, E. J., Añorve-Garibay, V., Chevy, E. T., Villa-Islas, V., Witt, K. E., Zeloni, R., Marnetto, D., Moorjani, P., Jay, F., Valdmanis, P. N., Ávila-Arcos, M. C., & Huerta-Sánchez, E. (2025). The MUC19 gene: An evolutionary history of recurrent introgression and natural selection. Science, 389(6762), eadl0882. https://doi.org/10.1126/science.adl0882
