Did Missing Prehistoric Genes Hold the Key to the Survival of America’s First Inhabitants?

Science on August 21, 2025, their study shows that this old gene, integrated into the human genome through crossings between species, could have played a crucial role in the adaptation of the first peoples of America to their new environment. This result claims not only our understanding of human migration, but also the way in which extinguished genes can still model our biology today.

Muc19: an old gene, a surprising modern presence

The gene Muc19long, discreet in research in genetics, is today a key marker of human history in America. Present in all mammal species, Muc19 Code for proteins called mucines. They contribute to the production of mucus – a biological barrier against pathogens. This protection role makes it an essential actor in immune defense. But what intrigues researchers is not so much its function as the origin of one of its variants. The latter is found massively in the indigenous populations of the American continent.

Fernando Villanea (Cu Boulder) and David Peede (Brown University), co-authors have identified a version of this gene inherited from the Denisovians, a line of missing hominines. By analyzing the genetic data of modern populations from Mexico, Peru, Puerto Rico and Colombia, the researchers discovered that almost 33 % of Mexican ancestry individuals carried this variant in their genome. In comparison, it is almost absent from African populations, and less than 1 % among central Europeans.

This geographic imbalance suggests a very localized adaptive selection, promoting this sequence in specific environments. It seems to be linked to segments of the genome of Native American origin, reinforcing the hypothesis of an advantage conferred on the first peoples of America. The study thus highlights the still active influence of an old -tens of thousands of years old, transmitted from species today extinguished to some of the oldest human populations on the American continent.

A unique genetic trajectory between missing human species

The presence of the gene Muc19 Denisovian in the human genome does not result from a simple linear heritage. It is the fruit of a complex series of mixing events between human species today extinguished. The research team has identified an unprecedented configuration. This fragment of DNA DNA is supervised on both sides by Neanderthal DNA. This forms what the researcher describes as a ” Oreo Genetics In a university press release. It is the first time that a genetic transfer has been observed between denialis, Neanderthals, then Homo sapiens.

This scenario presupposes a first hybridization between Denisovians and Neanderthals, who cohabited Eurasia for thousands of years. Then the Neanderthals would have transmitted this DNA fragment to modern humans via new unions. This mechanism, called an archaic introgression, remains rare and difficult to demonstrate. Indeed, it requires crossing large volumes of genetic data and modeling old sequences over 50,000 years.

The analysis also reveals that this transmission is not uniform on a planetary scale. The populations of Oceania, like those of Papua Nouvelle-Guinée, have up to 5 % of denial DNA, resulting from a more direct contact. Conversely, indigenous Americans seem to have inherited the Muc19 Denisovian only via Neanderthals. An indirect, but decisive genetic route.

This discovery confirms that ancient DNA is not only a passive vestige of our biological history. He actively shaped contemporary genetic diversity. It also illustrates the porosity of the borders between human species, which met and mixed much more often than we thought until recently.

Survive in America: a biological challenge over 20,000 years

The entry of the first humans on the American continent, via the Bering Strait, was a radical upheaval for the species. These populations had to face unknown, often hostile environments: new fauna, pathogens absent from the old world, extreme climates ranging from the Arctic to the tropics. In this context, researchers believe that certain genetic variations have been positively selected, giving survival advantages.

The gene Muc19 of Denisovian origin could be one of these evolving assets. Its immune function, although misunderstood, could have made it possible to resist diseases specific to the Americas. This is not the first time that Denisovian DNA has been associated with a local adaptation: another of its variants is known for having allowed Tibetan populations to live at high altitude thanks to better oxygenation of blood.

Villanea stresses that human evolution on the American continent is not limited to cultural innovation. “” The bodies also have adapted, slowly, but powerfully “Reports Live science. This biological adaptation accompanied technical inventions – agriculture, specific tools, social practices – which have enabled these populations to prosper despite extreme constraints.

Ancient genetic evidence for an always active heritage

To assess whether the gene selection Muc19 occurred before or after the arrival of Europeans in America, the Villanea team compared contemporary genomes to those of 23 pre -Columbian individuals from different regions. The result is unambiguously revealed. The frequency of the gene was already raised before the 15th century, long before the massive introduction of diseases from Europe. This observation relends the hypothesis of a selection linked to post-colonial epidemics.

Researchers have also produced evolutionary models. They tested whether the frequency observed could simply result from a founding effect. In other words, be present from the first migratory waves. These simulations show that the increase in Muc19 Denisovian in the Amerindian populations is too marked to be the result of chance. On the contrary, it reflects an old and continuous selective pressure.

Another notable element: the almost total absence of this gene in African genomes, then excluding a universal origin. Its specific concentration in genomes with a strong indigenous component underlines that it is a localized genetic signal, carrying an evolving history specific to the Americas.

Today, researchers are wondering about the current consequences of this gene. Villanea plans to study its potential effects on modern human health: allergies, respiratory infections, even inflammatory diseases. Understand how Muc19 Works could lead to biomedical innovations, by reproducing the protective effects of this old variant. This case illustrates the contemporary scope of genetic anthropology. It allows us to clarify not only the past of humanity, but also its present challenges, in public health as in biology of evolution.

Source: Fernando A. Villanea et al., “The muc19 gene: an evolutionary history of recurrent intrrogation and natural selection”. Science (2025).