the world before the flood was peopled by neandertals (also called men) and adamics (aka the sons of god). get over it.
when the lord saw that the lines had been crossed and his creation was deciding to go off the rails on the crazy train he found noah. and in doing so noah found grace in gods eyes. he was perfect in his generations. that means he didnt have any neandertal dna in him. neither did his wife. nor his three sons. all of noahs generations were clean.
but then he built an ark and gathered the animals and grabbed a wife for each of his boys. there is where we find neandertal. hams wife seems to have been pure. subsaharan blacks have no neandertal dna in them. it was shem and japheths wives that had neandertal in them.