Muxel said:
Maybe "species" isn't the word for it. If psychopaths arise statistically out of genetic recombination, then they're just a manifestation of the Law (or Overlords) of Entropy. I'd want to know, how does genetic recombination produce an organism capable of housing a soul/consciousness 50% of the time? What biological features determine the presence of soul/consciousness?
For the first question, I'd say that's just a manifestation of probability and for the second, I guess that's the 64,000 dollar question, as they say.
I suspect that there are certain genetic lines that do produce more psychopaths - that's pretty much what certain genetics studies say. But my real point was to say that you can't just eliminate psychopathology in a population by selectively getting rid of certain members or sterilizing them or whatever. Genetic mixing has been going on for so long that probably everyone has the potential, even if it is recessive or much less likely, to produce a child with such a mix of genes.
You could read Barbara Oakley's "Evil Genes" for some clues, keeping in mind the fact that she appears to carry a strong tendency herself to "authoritarianism" (witness her admiration for Rumsfeld and her belief in the neocon propaganda).
From this you will learn that there are a few well-identified genetic glitches that lead to SOME aspects of psychopathology, but they all need to express at the same time or at least in certain combinations. Then, there are diseases and/or physical traumas that can change the way the brain works that can come into play.
Another source for the dynamics of genetic "selection" and changes and mutations would be Bryant Shiller's "The 5th Option".
The bottom line is, I don't think there could ever be a genetic test that would say "this person is a psychopath" (or some other manifested psychopathology) and that's that. I don't think brain scans will do it either though both genetic tests and brain scans can contribute to an overall assessment assuming that a population could deal with the logistics of administering same.
In the end, what seems to be the only sure method is observation and experience of the person by a number of individuals who compare notes over a long period of time and possibly even set up little "tests".