Neandertal and Denisovan retroviruses

Modern humans (Homo sapiens) last shared a common ancestor with two types of archaic hominins, Neandertals and Denisovans, roughly 800,000 years ago, and the population leading to modern H. sapiens separated from that leading to Neandertals and Denisovans roughly 400,000 years ago [1-4]. Genome sequences for these two types of archaic hominins have been reported [1,2]. They were determined by sequencing ancient DNAs using techniques that generated many short sequence reads. Here, we analyzed individual sequence reads used to assemble the published Neandertal and Denisovan genomes for insertions of Human Endogenous Retrovirus K (HERV-K) DNA. Virus-host DNA junctions were identified that defined 14 proviruses where modern humans contain the corresponding, empty, preintegration site. Thus, HERV-K reinfected germ lineage cells of Neandertals and Denisovans multiple times, and these events occurred around the time of or subsequent to the divergence of the archaic hominin lineages from that leading to modern humans. One of the proviruses was shared by Neandertals and Denisovans, which is consistent with the hypothesis that these archaic humans shared a common ancestor more recently than they shared one with the lineage leading to modern humans.