Two studies expand insights into Denisovan ancestry and population history in East Asia

 

In a pair of studies, researchers provide evidence that expands our understanding of modern humans in eastern Asia and their interactions with their most elusive cousins, the Denisovans. While admixture between humans and Denisovans is widely recognized, physical remains of the archaic hominin species are exceedingly rare. What's more, ancient genomic evidence from early modern humans in eastern Asia, which would capture the nature of admixture events between the two species and inform on humans' timing and movement into and across Asia, is lacking. Recently, the fragment of a jawbone, which is suspected to be of Denisovan origin, was recovered from the Baishiya Karst Cave (BKC) located high on the Tibetan Plateau. However, the bone is poorly dated and its Denisovan origin is tenuous. Here, Dongju Zhang and colleagues describe the stratigraphy and chronology of BKC and report on sedimentary DNA analyses, which reveal long-term Denisovan occupation of the cave. Zhang et al. extracted genetic material from cave sediments and identified Denisovan mitochondrial DNA (mtDNA) within them. 

The findings indicate that Denisovans occupied the high-altitude cave as early as 100,000 years ago, and possibly as recently as 45,000 years ago, as well as at a point in-between. Such long-term occupation of high-altitude regions suggests that Denisovan admixture could have contributed to the high-altitude adaptations that allowed modern humans to colonize the Tibetan Plateau. 

In another study, Diyendo Massilani and colleagues present the genome recovered from a 34,000-year-old skullcap discovered in the Salkhit Valley in eastern Mongolia. Ancestry modeling of the new genome with regards to other Pleistocene individuals suggests relatively recent Denisovan admixture, perhaps within 1,000 years before the Salkhit individual lived. According to Massilani et al., the Denisovan ancestry identified here, as well as that identified in another 40,000-year-old individual found near Beijing, likely derived from the same admixture events that contributed to present-day mainland Asians. They are, however, distinct from the Denisovan DNA contributions to present-day Australasians. These findings provide a reference point in the early history of modern humans in eastern Eurasia - a region that has lacked genomic evidence.