Denisova 11 is accurately described as the daughter of a Neanderthal mother and a Denisovan father. What this does not establish is that such crosses were biologically impossible, or that they were routine, or that the resulting individuals were necessarily fertile. Denisova 11 is evidence of one specific encounter. She is not a census.
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## What One Individual Can and Cannot Tell Us
The significance of Denisova 11 is genuinely substantial. At the same time, it is important to be precise about what a single individual can and cannot establish.
What Denisova 11 establishes, beyond any reasonable doubt:
Neanderthal-Denisovan interbreeding occurred. This was already suggested by the traces of Neanderthal DNA in Denisovan genomes and Denisovan DNA in Neanderthal genomes, but those were indirect signals from population-level statistics. Denisova 11 is direct and specific: here is a bone from an individual whose parents were, respectively, a Neanderthal and a Denisovan. This is not a statistical inference about ancient populations. It is the genome of a real person.
The interbreeding at this site or in this region was not a completely exceptional event. The presence of earlier Neanderthal ancestry in the father’s genome establishes that gene flow between the groups had occurred before—probably multiple times, over a long period.
What Denisova 11 does not establish:
The frequency of Neanderthal-Denisovan interbreeding across all of Eurasia and all of the time during which the groups coexisted. One documented hybrid from one cave in Siberia 90,000 years ago tells us that it happened. It does not tell us how often it happened, across what geographic range, or with what demographic consequences for either population.