In 2014, Nature published a study that found a variation of a gene, which regulates hemoglobin and is present in modern Tibetans, was inherited from Denisovans. The genetic hand-me-down is likely what made it possible for people to live at 13,000 feet or more above sea level in the oxygen-sparse air of the Himalayas.

Today, however, applying a new data-modeling method to more than 5,600 genomes from modern populations, researchers identified surprising new details about interbreeding between H. sapiens and Denisovans: It appears different populations of the two hominins interbred multiple times.