Applied to Denisova Cave, sedaDNA analysis confirmed the presence of both Neanderthal and Denisovan DNA in cave sediments from different layers and time periods, consistent with the findings from bone remains. It also demonstrated the presence of both groups in layers where no bone material had been found—suggesting that the cave’s occupation history is even more complex than the physical remains alone would indicate.
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## The Geographic Reach of Denisovan Populations
One of the most striking aspects of the Denisovan story is the mismatch between their physical fossil record and their genetic legacy. Almost all physical Denisovan remains—all but a handful—come from a single cave in Siberia. Yet the genetic signatures that Denisovans left in modern human populations are found across a geographic range stretching from East Asia to Sahul—the combined landmass of Australia, New Guinea, and surrounding islands that was connected during periods of lower sea level.
The genetic evidence, accumulated across multiple studies using modern human genomes from populations across Asia and Oceania, suggests that modern humans encountered and interbred with Denisovans not once but multiple times, in different locations. Some researchers have proposed at least two distinct Denisovan-modern human admixture events: one that contributed to East Asian populations and a separate one that contributed to populations in South and Southeast Asia and Oceania, producing the higher Denisovan ancestry found in those populations.
This geographic extent implies that Denisovans were far more widespread than their physical fossil record suggests. The cave in Siberia where almost all Denisovan bones have been found is, on this view, one endpoint of a population that ranged across continental Asia and into island Southeast Asia—an enormous territory spanning multiple climate zones, ecosystems, and geological barriers. How they managed this expansion, what ecological niches they occupied, and whether different Denisovan populations were in contact with each other across this range are questions that cannot be answered from the available evidence.