This finding established something important: the interbreeding between Neanderthals and Denisovans that Denisova 11 represented was not a unique or isolated event. Before her mother and father met—or before their lineages met—there had already been an earlier exchange. Neanderthal ancestry had entered the Denisovan population at some point in the deep past, and that ancestry persisted in the Denisovan father’s genome down to the generation that produced Denisova 11.
The implication is that Neanderthals and Denisovans were not entirely separate and parallel lineages that occasionally touched at the edges. They had been interchanging genetic material over very long timescales. The encounter that produced Denisova 11 was a documented instance of something that had happened before, in deeper time, and perhaps happened afterward too.
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## What Her Mother’s Genome Revealed
The Neanderthal portion of the Denisova 11 genome—the chromosomes inherited from the mother—also carried unexpected information.
When researchers compared the Neanderthal ancestry in Denisova 11’s genome with the genomes of Neanderthals from different locations and time periods, they found that her mother’s genome was more closely related to Neanderthals from Vindija Cave in Croatia than to the Neanderthals known from Denisova Cave itself. The Vindija Neanderthals date to approximately 55,000 years ago. The Denisova Cave Neanderthal, from a different layer, dates to approximately 120,000 years ago.
Denisova 11 lived, by best dating estimates, approximately 90,000 years ago. Her mother’s Neanderthal genome looked more like a Neanderthal from western Europe 55,000 years ago than like the Neanderthal from the same cave roughly 120,000 years ago.