The Ghost of an Unknown Hominin

Science Alert has a story about the Ghost of an Unknown Hominin in Africa.  Carly Cassella writes:

The gene pool of modern West Africans contains the 'ghost' of a mysterious hominin, unlike any we've detected so far. Similar to how humans and Neanderthals once mated, new research suggests this ancient long-lost species may have once mingled with our ancestors on the African continent.

Using whole-genome data from present-day West Africans, scientists have found a small portion of genetic material that appears to come from this mysterious lineage, which is thought to have split off from the human family tree even before Neanderthals.

It is not clear to me that these necessarily represent different species. This may reflect an inter-related group of populations from a very genetically diverse population. As my advisor Fred Smith once upon a time said: “If two species interbreed on a regular basis, is it reasonable to call them different species?”

BTW, the  “Unrelated” skull in the page is the Kabwe skull from What was once Rhodesia, discovered in 1925, 400 feet down, in a mine.