The people of this island nation have an extraordinarily high percentage of DNA from another human species, preserved by 50,000 years of genetic isolation.
Genes from the extinct Denisovans give Papua New Guineans an advantage in fighting certain diseases and thriving in environments that would leave most of us gasping for air, according to a study published today in Nature Communications.
Papua New Guinea is an island nation in Oceania, located on an island just north of Australia and east of Indonesia.
Genetic Legacy from the Denisovans
The people of Papua New Guinea have inherited several immune and altitude-adaptation advantages from the Denisovans, an extinct species of humans.
"Papua New Guineans are very unique because they have been isolated since they settled there more than 50,000 years ago," study co-author François-Xavier Ricaut, a biological anthropologist at the French National Centre for Scientific Research (CNRS), told Live Science.
Ricaut and his colleagues analyzed the genomes of 54 highlanders from Mount Wilhelm, who live between 7,500 and 9,000 feet (2,300 and 2,700 meters) above sea level, and 74 islanders from Daru Island, who live below 330 feet (100 m) above sea level.
They found that mutations likely inherited from Denisovans boost the number of immune cells in the blood of the lowlanders.
For instance, Denisovan gene variants may enhance the function of a protein called GBP2, which helps the body fight pathogens common in the lowlands such as malaria parasites. These genes may have been favored by natural selection, the researchers said.
This would have been especially valuable on this isolated island nation, where infectious diseases cause up to 40% of deaths in the community.
Meanwhile, the highlanders have evolved mutations that increase the number of red blood cells, which helps alleviate the oxygen deprivation that people from lower altitudes typically feel at high altitudes.
A High Percentage of Denisovan DNA
People in many other parts of the world, including people of Asian descent, also carry DNA from Denisovans.
However, the percentage of Denisovan DNA in Papua New Guineans is extraordinarily high, at about 5%. Most other people outside of Papua New Guinea have only about 2% or less Neanderthal or Denisovan DNA.
Previous research suggests that Homo sapiens — our species — arrived on the island about 50,000 years ago. They may have encountered and interbred with Denisovans who were already there, and then preserved that genetic legacy due to their limited contact with other populations around the world.
The Denisovans, like the Neanderthals, were a species of humans closely related to Homo sapiens. As a result, the species were able to interbreed, and they did so in several places around the world.
Both of these archaic human species went extinct more than 30,000 years ago.
Summary
The people of Papua New Guinea carry an unusually high percentage of DNA from the extinct Denisovans. This DNA gives them advantages in fighting certain diseases and thriving in high-altitude environments. The Denisovan DNA was likely acquired through interbreeding between Homo sapiens and Denisovans more than 50,000 years ago, and has been preserved due to the island nation's isolation.