Presumably this hypothesis is meant to explain why there is this observed asymmetry in the type of Neanderthal DNA we find in modern human populations that contain them, which is entirely autosomal. With none in the mitochondrial form, which is exclusively passed down along the female line, and also none in the Y-chromosome form, which is exclusively passed down along the male line. Without weighing on the validity o…
Autosomal region is what acquires most ancestral dna as it's the one which recombines.