Gondawa people are the In-Universe ancestors of Europeans.
It's stated In-Universe that Enisor people and Martians are respectively the ancestors of both Native Americans and Eastern Asians (for the former) and Black Africans (for the latter) so it's likely that White Europeans, though this never being stated nor implied, are descendants of Gondawa people who had survived the Enisorai - Gondawa war. Gondawa and Enisorai were not the first civilisations and the whole story already happened before.
The whole "Black people actually come from Mars but are somehow interfertile with Earth Humans", aside from sounding rather racist, makes absolutely no sense from a biological point of view… unless humanity as a whole does originate on Earth, reached space travel levels of development, but only certain human populations of predominantly (or exclusively) black phenotypes settled on Mars for long. Then society crumbled entirely on both planets and humans went their separate ways on both Earth and Mars, until Éléa's time where Mars' civilisations, descended from the colonists, were discovered again – with all knowledge of humanity's past space travel lost, everyone indeed was convinced that humanity appeared on two separate planets.