A study published in Science identified a Denisovan-derived version of a specific gene that appeared at unusually high frequencies among peoples with Indigenous American ancestry.
Researchers compared Denisovan DNA with genomes from contemporary Latin Americans with Indigenous heritage, and 23 pre-Columbian individuals unearthed in Alaska, California, and Mexico. They’ve concluded that the MUC19 variant was already widespread before Europeans and Africans reached the continent.
MUC19 belongs to a family of 22 genes that encode mucins, the proteins that form the mucus lining the digestive tract and lungs. While everyone carries MUC19, the Denisovan-like version was far more common in the Americas: about one in three people of Mexican ancestry carried at least one copy, and high frequencies also appeared in Peru, Puerto Rico, and Colombia. By comparison, it occurred in roughly 1 percent of people with Central European ancestry and was almost absent in Africans.
The fragment sat on an unusually long stretch of archaic DNA flanked by Neanderthal sequence. “It’s like an Oreo, with a Denisovan center and Neanderthal cookies,” said Villanea. Genetic analysis indicated that the piece moved from Denisovans to Neanderthals and later to Homo sapiens, the first documented instance of DNA following that route.
Selection appeared to boost its prevalence. Statistical tests showed a large expansion of repeated sequences inside the MUC19 region as humans entered North America, effectively doubling a functional domain of the mucin and implying an adaptive advantage.
Because mucins help regulate immune responses, the team suspects the variant aided early Americans in resisting unfamiliar pathogens or interacting with beneficial microbes. “It seems like MUC19 has a lot of functional consequences for health, but we’re only starting to understand these genes,” said Villanea. “Something about this gene was clearly useful for these populations—and maybe still is or will be in the future,” said Huerta-Sánchez, according to Scientias.
The discovery added to evidence that extinct relatives still shape modern genomes. Denisovans, who lived in parts of Asia between roughly 300,000 and 30,000 years ago, left behind only fragmentary fossils, yet their DNA persists in people around the world. Most living humans carry some Neanderthal DNA; up to 5 percent Denisovan ancestry occurs in populations from Papua New Guinea; and an immune-related Denisovan segment now appears at high frequency in the Americas.
“From a biological standpoint, we identify a gene that appears to be adaptive, but whose function hasn’t yet been characterized. We hope that leads to additional study of what this gene is actually doing,” said Huerta-Sánchez, according to Discover Magazine. Villanea said he plans follow-up work on how different MUC19 variants influence disease risk today, adding that the earliest Americans crossed “every single type of biome in the world,” a success that reflected both cultural ingenuity and biological resilience.
The preparation of this article relied on a news-analysis system.