Belyaev's hypothesis was that all of the other traits common to domestication, everything from changes in facial structure and skin/fur markings to increased empathy with and receptivity to communication signals from other species, might be gene-linked to one single trait: aggressiveness. So he grabbed wild members of two species, one of which has been domesticated before (more or less) and one which had long been held to be undomesticable, the rat and the fox. And before breeding age, he separated each generation of offspring into two groups, only allowing those that showed the most tendency towards aggression to breed with each other, and only allowing those with the least tendency towards aggression to breed with each other. And in a scant 40 generations of each, his hypothesis was completely borne out. His bred-for-non-aggression foxes have more dog-like muzzles, have floppier ears, have patches of white or other colors in their fur, show substantially less fear of human beings, will tolerate be walked on leashes, and unlike feral foxes, can figure out that a human researcher is pointing towards a place where food is hidden. The results in rats were even more striking. Randomly caught Siberian wild rats, in as few as 40 generations, split into almost two entirely different species to look at their behavior: one as tame as any other rats bred as pets, and the other insanely dangerously psychopathic. Indeed, the rats bred only with other aggressive rats are so aggressive that the lab treats them as a biohazard, for fear of what would happen if their attack-anything-on-sight genes were to spread into the wild rodent gene pool.
So it's amazing that, despite literal threat of death for his work, a scientist in the Soviet Union was able to duplicate a feat not seen since the stone ages. But the work that's being done with the breeds he created is potentially even more earth-shaking. Right now, researchers are studying the genetic sequences of the tame versus psychotic rats, and of offspring between the two, to try to isolate the gene for aggression. Preliminary research suggests that it may, in fact, be as simple as one gene that regulates the nervous system's sensitivity to fear; it was, in fact, one of Belyaev's last hypotheses that he had accidentally selected not so much for reduced aggression but for reduced fear of others, that the aggressive behavior he was looking for in youthful animals to select them out might have accidentally been more about aggression towards our species, not their own.
What's the earth-shaking part, if it turns out to be true? Belyaev also noted that many of the same differences between his tame versus aggressive foxes, and tame versus aggressive rats, are also similar to the differences between human beings and chimpanzees. Belyaev hypothesized that the fork between our ancestors and the ancestors of the great apes happened when either conditions or a change in preferences caused one or more pre-human tribes to deny the most aggressive males access to women. When Robert Anton Wilson (and others) referred in their writings to human beings as "domesticated primates," it may well be that they were unintentionally exactly and literally right. Which is why researchers hope to find out, once they've identified the gene sequence(s) that mark domestication in rats, if those same gene sequences match the ones that mark the difference between humans and apes.
I've spent two weeks trying to think about the historical, social, cultural, and (gods forbid) even political policy implications of such a finding. My mind recoils, rebounds in horror from thinking about it very long. I can't get any farther than realizing the implication that 40 generations, let's say as little as 700 years, of cultural preference by women for less cooperative, more aggressive men, or for more fear or caution in general, could be enough to breed an entire species of dangerous, literally inhuman, psychopaths. Is it essential to our survival as a species that we identify bullies before puberty and render them sterile, incapable of passing on their undomesticated genes? Is a winner-take-all economic system, one that rewards the most successful psychopaths, those with the most fear of their competition and the least inclination to cooperate, with greater attractiveness and reproductive success, sufficient to produce a competitive subspecies of near-humans as dangerous as Belyaev's psychotic rats? Is this, gods forbid, exactly what's happened to the global upper class? We're talking about not merely the potential to meddle with the very definition of "human being," we're looking at the possibility that science will show us an almost absolute need to do so if we're going to survive as a species. And I can only think about that for a few minutes at a time before my brain forces me to think about something else, or pass out.