In the trilogy, The Sirian Revelations, Patricia Cori mentions the inhabitants of the planet Engan as one of the four alien races whose DNA was used to create mankind. They allegedly are a black skinned race. The location of the planet Engan is not given, but the planet is described as desert-like.
(Two other races are mentioned by name: the Alt and the Arien. No name is given for the fourth, yellow-skinned race).
Note that thus far I have not come across any other author who mentions these alien civilisations. Also note that several other sources mention twenty-two, not four, races that contributed to our DNA.
This information was channeled.