We all know why we find certain people attractive and want to form relationships with them. Those special people might be more than usually compassionate, intelligent or funny -- or might be physically well-endowed in some way. And neurologists know which areas of the brain become active when we meet that special someone -- the ventral striatum, a brain area linked to the anticipation of reward.
But at a deeper level, why do we prefer some people as sexual partners to others? The answer, says a team of German scientists, can be found in fish. Sticklebacks, to be precise.
According to the theory of sexual selection, there are several reasons why animals choose between different prospective mates, as opposed to mating with random members of the opposite sex. One hypothesis says that "mate choice" functions to avoid inbreeding. If sexual partners were selected at random, there would be a high probability of mating with a close relative (a bad idea genetically, not to mention psychologically). By being choosy in mating preference, you might also be able to produce attractive offspring, or if you select a rich partner, gain access to his (or her) resources.