In a typical individual from a single population, both members of each chromosome pair come from the same general genetic background.

They may carry different variants at specific positions — this is normal genetic variation within a population — but the overall character of both chromosomes reflects the genetic ancestry of the population they come from.

In a first-generation hybrid, the situation is completely different.

One chromosome of each pair comes directly from one parent — in Denny’s case, her Neanderthal mother — and the other chromosome of each pair comes from the other parent — her Denisovan father.

The two chromosomes of each pair would be as genetically different from each other as representatives of two different ancient human lineages.