Human varietal form; same species. They interbred.
Hard to say though with all the disinfo out there.
They are supposedly taller, much stronger, and not as intelligent as the modern style.
They would kill Mamoths, so it is said, using a gang band and short knives. The modern style human was said to use spears - and to have invented that.
N. used fire but differently than moderns. So we are told. FWIW
There is likely more to it than simple Neanderthal-ism
The top level of the "Roman" Church wear those tall hat which would cover the long skull
Maybe they are *already a hybrid throwback?