especially since it the whole notion that any organism is thinking consciously about reproduction of its genes when it does what is does is, erm, not what the sociobiologists are talking about anyway.
The idea, not that I agreed at all with ravi, is that traits that end up reproducing the species are traits that are selected for.
So, if way back when, it just so happened that certain males liked to go beat the dicks off other males after sex with a woman, then it doesn't matter whether the guy was doing it because he KNEW he wanted to prevent the others from impregnating her. He could just have happened because that was instinctual for him: sex with a woman unleashed the desire to punch other men in the dick. If males without that impulse get their dicks punched out all the time, they may be too damaged to have sex, too beat up to feel like having sex, or dead or something. Thus, the men who "win" and spread their genes are the men who punch other men in the dick after sex with a woman. Even though there's no conscious thought about impregnating women, about spreading their genes around, or keeping other men from having sex with as many women as they want too.