Its use is not exactly clear: sometimes it is used to refer to the Edain of the First Age, other times it is only applied to Bëor, Marach and contemporaries, and in yet other places it is used to refer to those peoples the Edain are descended from.
If the third meaning is adopted, it can be said that the so-called Middle Men of Middle-earth (the Rohirrim, Men of Dale, etc.) are also descendants from the Atanatari, like the Edain (or later Dúnedain).