In the trilogy, The Sirian Revelations, Patricia Cori mentions the Alt as one of the four alien races whose DNA was used to create mankind. The Alt allegedly are a red skinned race from the Pleiades.
(Two other races are mentioned by name: the Engan 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. This information was channeled.