Oldest DNA discovered; Why did "oldest" H. Sapiens not interbreed with Neanderthals and Denisovans?

[Surreal]

@Colibri

Actually, Neanderthal mitochondrial DNA, which is inherited entirely through the maternal line, has not been found in modern humans. This implies that the admixture found in the nuclear DNA of modern sapiens populations was the result of male Neanderthals mating with female sapiens (although other scenarios are possible).

Interestingly it turns out that there’s also no Neanderthal Y-chromosomes in the DNA of modern humans, so we can’t really infer anything about how they may have interbred with us:

Researchers find no trace of Neanderthal Y-chromosomes in modern humans