How so? That they weren't intelligent enough to keep their genes pure? Couldn't they have been dominant but also a minority so they were willingly diluted away?

How so? That they weren't intelligent enough to keep their genes pure? Couldn't they have been dominant but also a minority so they were willingly diluted away? I wonder if the Neanderthal genes we have are more from men or women? Perhaps that would show which direction any conquest and raping happened in.