I found information by an Anthropologist names Helen Fisher who spent the last 30 years researching love and intimate relationships. Her findings suggest the evolutionary background for love of another starts with a drive to feed ones sexual appetite, then the dopamine and serotonin changes in the brain help build a connection with another, and if the connection is reciprocal the brain has mechanisms of keeping these feelings novel and interesting. A common issue with our nuclear family idealism in America is we assume relationships are monogamous when evidence suggests our brains are capable of having the same connection with multiple people. On the bright side of things, Fisher expects divorce rates to decline due to our increasing age of marriage (studies show as couple age, divorce rates decline). Another interesting topic she presents is anti-depressants and love. Fisher explains that long-term anti-depressant use will affect dopamine and serotonin levels enough to hold back the ability to create an intimate connection and to keep that connection going in a relationship. This isn't to say she is against anti-depressants, just as long as they are short-term. I think intimate relationships are a fascinating subject because everyone at some point looks for love, but not one person goes about finding love in the exact same fashion as another. I think by finding universality, we are getting farther from understanding love because relationships are subjective, not mathematics.