Neurochemistry

The newspaper article Love and Human Nature arose from a lead article in the February 2006 edition of the National Geographic. The National Geographic interviewed Helen Fisher, whose research indicates that neurochemicals dictate sexual behaviour - that chemical passion lasts only a few years and is replaced by the bonding chemical oxytocin. Faced with this, the reporter, Christin Geall, felt her romantic spirit begining to wither.
Christin's response to the idea that sexuality is governed by biology is to argue that some of the best relationships are born, not only out of passion, but also out of a deeper connection with nature. That is ducking the issue. Assuming sexuality is governed by biology, what is the role of sex in love?