Ability to interbreed does not necessarily make two animals members of the same species. At best one can conclude that it is highly probable that they are members of the same genus. But sometimes even different genera can interbreed (given the opportunity). An example might be the African and Asian elephants mentioned above. If the overall DNA is close enough and number of chromosomes match they can likely interbreed and produce a hybrid. Human classifications are constructs that do not determine the breeding capabilities of organisms, although breeding capabilities may be used in defining classifications.
There is plenty of scientific evidence to support a hypothesis that negroids are a different species (or even a separate genus between homo and pan) – even more so than for many other animal classifications such as chimpanzees, elephants, and others that are broken down into different species and genera – if consistent taxonomic principles were applied.
However, since about 1950 this cannot even be discussed by scientists without destroying their careers. James Watson, Nobel prize winning discoverer of DNA, certainly understood the implications of his and subsequent work by others.
He was villified by the media and the scientific community for merely hinting that SSAs were different and unlikely to succeed.
Of course this is all kind of meaningless. In reality, they are what they are regardless of how labeled and classified. The problem is the leftist/liberal/PC rejection of truth and suppression of open discussion of anything contrary to their preconceived ideology.