neanderthals
If you're european -- particularly if you're redhead, pale, freckly, or blue-eyed -- you almost certainly have Neanderthal genes in your family history. They've been recently reunderstood to be completely 'human' (albeit not the modern human we know now).
If you saw a Neanderthal walking down the street today, you wouldn't think much (and may not notice). curious stuff! Makes a lot of sense of the ancient myths, no?
More here
and still more on the neanderthal genome