Why can Denisovans help us understand how we became the only humans on Earth?

“Scientists expected to find a Neanderthal genome, but when they examined it, they realized it was something unique,” ​​says Fernando Villaña, professor of anthropology at the University of Colorado Boulder (USA), in an interview with BBC News Mundo, the BBC’s Spanish-language news service.

According to the geneticist specializing in prehistoric human populations, “the number of differences observed in the genome was similar to the divergence between the Neanderthal genome and the human genome, which indicates the existence of a new species of them.”

The new strain was named after the place where it was found.

But who are the Denisovans and how did they arise?

“It was a group that separated from the Homo sapiens lineage about a million years ago,” says Sylvana Condémy, a French paleoanthropologist and one of the greatest experts on the subject.

According to Kondemy, “The most likely hypothesis is that the divergence between the two branches (Neanderthals and Denisovans) occurred during the exit from Africa, which we know was done by Neanderthals.” Homo heidelbergensis“, a species that arrived in Europe and had the ability to use fire in a very long and intense period between ice ages.” The secret world of Denisova (The Secret World of the Denisovans, free translation).

“Without a doubt, climatic conditions explain the separation between Neanderthals and Denisovans, as the area was fragmented by that glaciation,” added Condimi, who is also research director at the French National Center for Scientific Research, one of the country’s main scientific institutes.

But how has this group remained under the radar for so long? The expert attributes this to the lack of fossil remains and errors in classifying already known discoveries.

The Denisovans occupied large areas of East Asia, and even reached as far as Oceania.

In July 2024, Chinese researchers discovered fragments of Denisovan DNA in a skull found in northern China. Similar results occur with jaws from Tibet and Taiwan.

According to Villania, of the University of Colorado Boulder, “These data suggest that Denisovans inhabited coastal and tropical regions, but also cold mountainous environments. The breadth of this environmental spectrum indicates a high capacity for biological adaptation, linked to some type of technology.”

As they expanded geographically, Denisovans coexisted and mingled with other human species they encountered.

“When the first Homo sapiens They left Africa, came into contact with Neanderthals and hybridized them; The same thing later happened with the Denisovans as they advanced east, Kondemy said.

Recent studies indicate that this “mixing of races” contributed to ensuring human survival The wise one.

“After years of research, many unique genes that Denisovans possessed were identified that gave them advantages in certain climates and regions… and some of these Denisovan genetic variants can still be found in modern humans,” explained Villania, from the University of Colorado Boulder.

Kondemy cites, as an example, the EPAS-1 gene, which is found in more than 80% of the current Tibetan population. “This denisovan gene improves oxygen transport, which is essential for those living at high altitudes.”

Condimi, of the French National Center for Scientific Research, points out that the TBX15 and WARS2 genes, which are located in very specific variants of chromosome 1 and whose origins can also be traced to the Denisovans, have been found in some high-altitude populations in Asia.

“These genes play a role in body growth and, in particular, in the distribution of brown adipose tissue, which is used to generate heat in cold climates,” explains Kondemy.

Another Denisovan gene that has also been found in Neanderthal and modern human fossils is MUC19, which is involved in the production of proteins that form saliva and the mucus barriers of the respiratory and digestive systems that protect tissues from pathogens.

“This gene is found in one in three people of American Indian descent,” says Villania, who participated in the research with scientists from Mexico, Denmark, Italy, France and Ireland.

But did the Denisovans reach America? “No, but because of your genes, yes,” Kundimi answers. “Asians have Neanderthal and Denisovan genes, just like Americans and Latin Americans, because part of America’s indigenous population comes from Asia.”

“If you are from South America and send your DNA to an American company that conducts studies for US$100 (about R$530), you will find out that you have Neanderthal and Denisovan DNA,” says Kondemy. “Depending on your ancestry, you could have twice as much Denisovan DNA: what came through the Bering Strait, and what later arrived with Pacific peoples.”

However, in Latin America with European origins, the Neanderthal genetic background predominates, explains Condimi.

But returning to the MUC19 gene, Villaña points out that he suspects it gave an “advantage” to the immune defense of a portion of the American population, which may have contributed to their adaptation to conditions on the continent.

For Kondemy, the discovery of the Denisovans was a turning point in understanding humanity’s origins and ways of investigating the past.

“Ancient anthropology was based on bones, but today we work with many other fields, such as genetics, biology and botany,” the researcher says.

The use of genetics has been revolutionary in these studies. “Our entire history can be read through DNA,” says Kondemy.

“It’s not just about our personal history, or our family history, or our country’s history, but our history as a species, our migrations, our encounters with diseases, how we adapt to certain foods and environments. It’s all in our genes.”

Villania follows the same line. “Although we do not have a complete skeleton, tools or other reference materials, the complete genome of the Denisovan individual has provided us with a lot of information.”

But there is still much to be discovered about these ancestors and their disappearance.

In terms of their physical appearance, Denisovans had large heads like Neanderthals, Kondemy says.

“Neanderthals had an elongated, dog-like face with completely side cheeks, but Denisovans had more pronounced cheekbones and had very large teeth, much larger than those of Neanderthals and modern humans.”

Regarding the Denisovan extinction, Villania states that evidence points to a combination of factors.

“The fossil evidence we have is quite incomplete, but we have obtained certain clues in the genome of an individual from the Altai Mountains (in Central Asia). Genetic evidence suggests that Denisovan populations had a small number of individuals at least thousands of years before their extinction.”

Furthermore, “geological information suggests that the end of the Denisovans coincided with the end of the Ice Age in Europe, revealing that they adapted to living in cold ecosystems and may have relied on hunting megafauna species that were on their way to extinction.”

But at that same moment he was Homo sapiens I followed their paths.

“The same process of climate change that wiped out the Denisovans also allowed modern humans to expand from the warm regions of Africa to the Mediterranean and the coasts of Asia, where they encountered the last Neanderthals and Denisovans, giving rise to the heritage that humans have today,” Villania concludes.