Eugenics are the practice of isolating negative genes, and preserving positive ones, whether through natural or social selection. Several attempts have been made, throughout history, to do such, with human intervention - all were short-lived, but none succeeded. Such methods toward
eugenics are: genocide, bioengineering or genetic manipulation, and
selective breeding.
Through natural selection, random or adaptive mutations occur. If positive, in theory, the traits should prosper. If negative, or not beneficial, however, they should fade away, if the family possessing these genes doesn't die away before then.
With human intervention, this is accelerated - the isolation of carriers of certain DNA can be achieved without blood shed, simply if no other group interbreeds, or if such a group discontinues
populating. However, more macabre means can be undertaken to reach this, such as genocide. Still, yet, there are further, and possibly more promising methods, such as genetic manipulation, for carriers of such a trait could be "cured," rather than phased out, or exterminated, altogether.
Examples in history, involving humans, include: murder, en mass, of American Indians; the Holocaust (1933 - 1945); the Balkans
ethnic cleansing (Bosnia, Kosovo, primarilly);
Rwanda; Sudan; etc.
Ahh, eugenics - something that hasn't happened for quite a while. However,
I feel it should. This could, quite possibly, benefit the human race, for without
dumbshits, we should prosper much longer. Unfortunately, though, it seems the degenerates breed more, and faster, than do the good ones among humanity. 'Tis a shame, truly. Have no misconceptions, however, as I don't wish for races to be
exterminated, but rather, unfavorable genes removed.