Science has looked at the genetics in like 2006 to prove once and for all Neanderthals were not human. Some religious groups claim that they were deformed humans as it bypasses the need to explain a species with intellect, communication, rituals, trade, tools, homes, jewellery..... Etc etc not mentioned in the bible.....
Your chap is suffering an education from the uneducated. The JW's have taught both and even that they don't exist, so of course he is confused. He needs to choose better teachers.