Evolutionary biologists often sound like naughty pants boys. They delve into salacious subjects and present a worldview that appears at first glance to be openly hostile to traditional morality and institutions deemed to be sacred, like marriage.
And yet, when one looks at the divorce rate in the United States, not to mention the number of unhappy marriages that continue on for years, it might be well that these scientists are stirring up trouble. Grasping the logic of human evolution can help us understand where our desires come from, and why in many instances our natural proclivities don't sync up well with our cultural institutions.
It may seem crass to some that our behaviors are all motivated by our desire to eat things, mate with things, and not get killed. And yet, if we truly want to come to terms with both our fears and our desires we would be wise to listen to the evolutionary biologists.