[astine]

The dinosaur to birds comparison isn't a particularly good one. Birds are cladistally dinosaurs, that is, the common ancestor of all birds was a dinosaur. In that sense, there are no birds that are not also dinosaurs.

That's not true with modern humans and neanderthals. A tiny amount of their dna remains in some human populations, but neanderthals are not the common ancestor of all humans. We are all descended from early homo sapiens and the tiny amount of neanderthal dna that persists is totally swamped by the homo sapiens dna.