Originally Posted by archetypal fool

This theory might break down, however, if the animal we're talking about has the visual accuracy and conceptual understanding of identity to distinguish between itself and others in the populations (take early man, for example). An interesting side affect of sharing our genes with our offspring is that they will always look at least 1/2 like us. If 'Jim Bob' notices that his offspring look nothing like him, then in beast-like fashion, he would likely rid himself of that offspring. In such a case, in attractive males, polygamy would not be a favorable trait. This could also be an explanation why we are so good at catching very subtle differences in others' faces. Dawkins goes into it a lot more, but I can't remember more of the points he made for polygamy/monogamy/cheating/etc...