It looks like there are zero traces of Y-DNA from Neanderthal males present in modern day males. The reason could be that Neanderthal males were killed of by modern human males. Female mtDNA however descending from Neanderthal females is present in many. The claims of some “scientists” that there was no female mtDNA in modern humans is false.
I have previously discussed that here:
However:
If this is correct…
… there could have been Rh incompatibility issues when Neanderthal females “mated” with Sapiens males.