when the extraterrestrial diaspora came there were two basic classes of emigrant, those without a eugenic plan and those with one, but the classes can be meaningfully broken down further.
those of the former class had no eugenic plan as a result of either ideology or incompetence. on the ideology end of the scale were those with faith in the haphazard fruitful multiplication that has driven human history and culture so effectively through the past, some higher power ideologies, and some ideologies of abhorrence at the implications of eugenics; these latter, the anti-eugenic ideologues, might be said to cross the line into the class of those with a eugenic plan in recognition that the antithesis is nevertheless a proposition concerning the thesis, but let them lie amongst the ideologues of the haphazard fruitful multipliers.
on the incompetence end, those who simply rashly fled, or those so clouded by other ideas or ideologies that future generations did not receive any consideration: gangs, communes, many an eloping set of lovers, much of what might be considered the professional military class and culture of humans, and organizations united around worldviews not encompassing eugenics.
among these groups, in the class lacking a eugenic plan, evolution continued to happen. that is, population growth was limited by resources, and individuals regularly – somewhat more frequently, now that much of the cosmic ray buffer of terra’s atmosphere no longer prevented genetic pointshifts, than through terrestrial history – mutated, sometimes producing beneficial traits which became normative in the population.