High altitude environments are one of the most demanding habitats in which humans have ever lived. This difficulty is mainly due to hypoxia: oxygen is less available to human tissues at high altitude. However, several populations worldwide have successfully settled at high altitude for thousands of years, and even display physical traits to counteract hypoxic conditions. A new study, published in the PLOS ONE journal, showed that Papua New Guinean highlanders may also show similar adaptive traits as a result of living at altitude for 20,000 years.