Modern Papuans’ immune system likely evolved with a little help from the Denisovans, a mysterious human ancestor who interbred with ancient humans, according to a new study led by Irene Gallego Romero, PhD, of the University of Melbourne, Australia, published December 8, 2022 in the open-access journal PLOS Genetics. The article is titled “Denisovan Introgression Has Shaped the Immune System of Present-Day Papuans.” Papuans, the indigenous peoples of New Guinea Island, owe up to 5% of their genome to Denisovans, an extinct group closely related to Neanderthals, who are known only by their DNA and sparse remains in Siberia and Tibet. To better understand the significance of this genetic contribution, researchers searched the genomes of 56 Papuan individuals to see if they carried Denisovan or Neanderthal DNA sequences, and then predicted how those sequences might affect the functioning of different types of cells.