Isolated and Defended

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Modern humans settled on the islands of today’s Papua New Guinea some 50,000 years ago, where they later interbred with the Denisovan hominids that occupied Asia for tens of thousands of years.

While the Denisovans became extinct, their DNA is present in modern-day Papua New Guineans and has aided them in their survival, Live Science reported.

A new genetic study found that highlanders and lowlanders in the island nation evolved distinct mutations to adapt to their different environments.

“New Guineans are unique as they have been isolated since they settled in New Guinea more than 50,000 years ago,” said co-senior study author François-Xavier Ricaut.

Ricaut and his colleagues explained that Papua New Guinea is predominately mountainous and challenging for the locals, adding that infectious diseases are responsible for at least 40 percent of deaths – particularly in lower altitudes.

To thrive, the populations had to find ways to adjust to their surroundings – with Ricaut hailing the island nation as a “fantastic cocktail” to study genetic adaptation

The research team studied genomes of 54 highlanders living up to 8,900 feet above sea level, and 74 lowlanders inhabiting areas less than 330 feet above sea level.

Their findings showed that lowlanders had peculiar mutations – probably inherited from the Denisovans – that boosted the number of immune cells in their blood. Highlanders, on the other hand, had more red blood cells to help reduce hypoxia at high altitudes.

The authors believe that the Denisovan DNA influences the function of the GBP2 protein, which helps the body fight dangerous microbes only found in the lowlands. Consequently, these genes were selected during evolution to help populations survive infectious diseases in lower altitudes.

The study team will now investigate how these mutations contributed to changes in the blood of Papua New Guineas.