MARCELO CAMARGO / AGENCY BRAZIL
One in three indigenous people in South America have the MUC19 gene, inherited from the Denisovans
A new study found that a certain genetic variant inherited from the denisovans may have given modern humans an advantage in the occupation of the American continent.
Thousands of years ago, the first humans undertook a risky journey, crossing hundreds of kilometers of ice in the Bering Strait to the unknown world of the Americas.
Now, a new study conducted by the University of Colorado Boulder suggests that these nomads took something with them surprising – A Fragment of DNA inherited from a kind of hominid Already extinct, which may have helped humans adapt to the challenges of their new home.
The results of the were presented in an article published on Wednesday in the magazine Science.
“From the point of view of evolution, This is an amazing jump”, Said the anthropologist Fernando Villanearesearcher at UC Boulder and first author of the study at the University. “It shows a adaptation and resilience level within a population that is simply remarkable. ”
The study focused on a species known as. These ancient relatives of the human being lived from the territory of present-day Russia to Oceania, also extending to the west to the Tibetan Plateau. Recently, a study found that.
Denisovans will have disappeared for tens of thousands of years. Its existence, however, continues to be little understood: scientists have identified the first Denisovan for 15 years only from the DNA of a bone fragment found in the Denisova cave in Russia.
The extinct group of humans, in part for reasons that attach to archeology, and partly for a legal reasons.
Like neanderthals, the denisovans may have had protruding eyebrows and absence of chin. “We know more about your genomes and how your biochemistry works than about,” explained Villanea.
More and more investigations have shown that denisovans have crossed as much as with humans, deeply shaping the biology of today’s populations.
To explore these calls, Villanea and his colleagues – including Brown University co -author David Peede – analyzed the genomes of people from around the world. In particular, the team focused on a gene called Muc19which plays an important role in the immune system.
The group found that People with American Indigenous Ancestry are more likely than other populations of transporting a variant of this gene from two denisovanos.
This ancestral genetic inheritance may have Helped humans to survive In completely new ecosystems in North and South America, the study authors say.
A little known gene
According to Fernando Villanea, the function of the MUC19 gene in the human body is almost as mysterious as the denisovans themselves. Is part of a set of 22 genes in mammals that produce mucinas. These proteins form mucus which, among other functions, protects tissues against pathogenic agents.
“It seems that MUC19 has relevant functional consequences For health, but we are just starting to understand these genes, ”he said.
Previous studies had already shown that the denisovans had their own variant of the MUC19 gene, with a Unique sequence of mutationswho transmitted to some humans.
This type of genetic mix It was common in the ancient world: Most living people today, while Denisovane DNA represents up to 5% of the genome of some populations in Oceania.
In the study now published, Villanea and colleagues wanted to understand better how they “Genetic Time Capsules“They shaped our evolution.
The team analyzed already published data on the genomes of modern humans in Mexico, Peru, Puerto Rico and Colombia – regions with a strong presence of American indigenous descent.
Found that one in three individuals of Mexican ancestry has a Copy of Denisovana Variant of MUC19 – Especially in segments of genome associated with American indigenous heritage. In contrast, only 1% of people with ancestry from central Europe has this variant.
The investigators found Something even more surprising: In humans, the denisovana variant of the gene seems to be surrounded by Neanderthal DNA. “This DNA It’s like an Oreo cracker, with a denisovano filling In the center and two Neanderthal layers, ”said Villanea.
A New World
This is the authors of the study suspect that it happened: Before humans cross the Bering Strait, the Denisovans crossed with Neanderthals, conveying to them the MUC19. Then the Neanderthals intersected with humans, sharing part of this Denisovano.
This is the first time that scientists have identified DNA to move from Denisovans to Neanderthals and Only then to humans.
Later, when humans migrated to the Americas, the natural selection favored the spread of this inherited MUC19.
It is not yet known because the Denisovana variant has become so common in the Americas and not in other parts of the world.
Villanea points out that the first inhabitants of the American continent probably faced unique conditions in human history, including new types of food and diseases. Denisovano DNA may have given them additional tools to deal with these challenges.
“Suddenly, people had to discover new ways to huntof cultivating, and developed impressive technologies in response to these challenges, ”he said.“ But, over 20,000 yearstheir bodies were also adapting at the biological level. ”
“What the American indigenous populations did was truly extraordinary,” he concluded. “They departed from an ordinary ancestor in the Bering Strait region and managed to adaptbiologically and culturally, to a new continent that contains all types of biomes in the world. ”
