Your very welcome t_b. It seems clear that survival of the species depends in this instance on a strong gene pool. The idea of integrating other groups because of strengthening the population is incredible. Consider since mankind was just starting to flourish, and the knowledge of compatible DNA to produce healthy off-springs was unavailable-the question becomes why another, that is, instead of a sister, or brother-except those that want to govern, or rule and want to keep their power trip going on had other ideas.
The selection process of a mate is indeed a wonder even today!

The more health issues-drugs for fertility, sexual diseases, together with laws-that is, who and what can now be jointed-do think little Lamie should be considered too, that is, as Gene Wilder did in a Mel Brooks film dealing with bringing sheep into hotels-laws suspect dealing with discrimination were not clear at that time, hope these issues become clearer with all the recent publicity - Lamie is rather warm during the winter, and so on. These social consequences all have an effect on the population, but again as you noted, " But then again it would explain they easily manipulable nature and tendency towards lemming like serial stupidities of a violent nature." t_b, indeed, so would agree. Thank you for your in-put, always most helpful.