A couple weeks ago an article in The Economist made the claim that love is just a chemical addiction. That's not quite all that it went on to say, however. While this looks bad for true romantics, the conclusions those who read the whole article will find will show something much more in favor of some thoughts I've long had and that I think Christians should be excited to see scientific support for.
Prairie voles release oxytocin and vasopressin during sex. Scientists have discovered that blocking this release leads to promiscuity among voles, but otherwise they mate for life. These hormones have something to do with their monogamy. Montane voles, on the other hand, do not release these hormones during sex and do not mate for life. When artificially stimulated with these hormones on the occasion of sex, they still do not mate for life. They don't have receptors in their brains for these hormones. Other than that difference, these voles are pretty much genetically the same. That means monogamy in higher animals is not a result of more complex brains or higher-order thought processes. It's a result of the ability to receive these hormones and only that ability. (They even did genetic manipulation on these voles to give the montane voles the gene for the receptors, and that did the trick, whereas removing it from prairie voles removed their ability to form a monogamous bond).
That's the bad news for romantics. We already know that animals in general continue to eat, drink, and have sex because it feels good. These activities produce dopamine in the brain. What people have often thought is that such animal desires can be sublimated by higher emotions like romantic love or higher thought processes like rationally belief formation (e.g. knowledge that unprotected sex can lead to disease or unwanted pregnancy). This research finds a chemical basis for at least the stuff we have called romantic love. The vasopressin and oxytocin lead to an association between sex and a particular partner. For mice this association is with the smell of the mate. There's an olfactory "image" (so to speak -- think Daredevil) of the mouse's partner, and that image is associated with intense pleasure.
Humans also release oxytocin and vasopressin during sex. A study in the UK linked higher levels of these hormones in brains of students who said they were madly in love. There are similar hormonal differences involving friendship, however, and this involved a much larger area of the brain. Also, the hormones associated with what these students were calling love was focused on the part of the brain that we already know has to do with gut intuitions and narcotics. Other strong emotions involve different parts of the brain.