"The above figure is from a preprint (updated from last year), Recovering signals of ghost archaic introgression in African populations."
That is the sole reference to the word "ghost" in the entire article. One would properly wonder WTF the author thinks he is talking about.
The word "species" appears just once, referring to the title of another article. One would wonder WTF you think you are talking about.
And just because you babble something over and over, that does not make it right or even sensible. All mankind is a single species. You apparently have no clue about what the word means.