Some of the earliest humans in the Americas didn’t just bring tools and skills; they also carried a powerful genetic variant known as MUC19. This gene, inherited from an ancient relative called the Denisovan, seems to have helped these early settlers adapt to new diseases, foods, and environments.
A team of scientists from the University of Colorado Boulder and Brown University studied this Denisovan version of MUC19. Their research found that this gene is notably common among people with Indigenous American ancestry. “This shows a remarkable adaptation and resilience,” said Fernando Villanea, an anthropology professor and lead author of the study.
The story of MUC19 links a deep past to the future. Long before humans crossed into the Americas, Denisovans and Neanderthals interbred. Later, Neanderthals shared their genetics with early humans. This Denisovan gene variant eventually became helpful in the Americas through natural selection.
Denisovans were closely related to humans and Neanderthals, spreading from Siberia to Oceania and beyond. Their fossils are rare—scientists first recognized them through DNA analysis just 15 years ago. While we can only guess about their appearance, their genetic legacy is clear. Villanea noted, “We know more about their genomes than we do about what they looked like.”
MUC19 is part of a family of genes that produce mucus, offering a vital barrier against pathogens. Villanea highlighted, “We’re just starting to understand the functional consequences of these genes.” Just 5% of modern humans have Denisovan genes, while most carry Neanderthal DNA.
The team explored genomes from Indigenous groups in Mexico, Peru, Puerto Rico, and Colombia. Their findings showed that about one in three people of Mexican descent carry the Denisovan variant of MUC19. In contrast, only about 1% of Central Europeans have it. This points to how vital this gene became for adaptation to the new American environment.
Furthermore, they discovered that the Denisovan genetic fragments sit within a larger section of Neanderthal DNA. Villanea described it as “an Oreo,” with MUC19 in the center. This suggests a complex pathway where Denisovans passed MUC19 to Neanderthals, who then passed it on to humans.
Once humans arrived in the Americas, they faced a radically different environment, filled with new challenges. Villanea remarked, “People had to find new ways to adapt and survive.” The MUC19 gene may have given early Americans an advantage, improving their health against new pathogens and diets.
Human migration from the Bering Strait into the Americas was a remarkable journey through diverse terrains. As Villanea stated, Indigenous Americans adapted biologically and culturally to their new homes, which include everything from rainforests to deserts.
Looking ahead, scientists are eager to see how different versions of MUC19 impact health today. Does the Denisovan variant affect mucus properties? Could it influence infection risk? These questions connect the past to our current health landscape.
In a world where human history is intertwined like a braided river, MUC19 is a testament to how ancient genes helped shape lives. The first settlers adapted with culture and innovation, and, as this study shows, with a little aid from their ancient DNA.
For further insights, the findings were published in the journal Science.
