LOVE! LOVE! LOVE! Why do we fall in love? What's the purpose behind this emotion? Lets try and look at it from an evolutionary perspective. For this we might need to look at the mechanics and consequences of this emotion and how it fosters a survival / breeding advantage to those species who possess this emotion.

Love at the very basic level, extends the mating ritual beyond a one off engagement between the male and female and encourages them to stick around for prolonged periods if not for a lifetime. Now this behavior suddenly confers a higher survival advantage to the offsprings as they now have two adults protecting them and providing for their needs.

Before the evolution of this emotion and as seen in reptiles, males almost always leave after the mating exercise and females take care of the eggs and offsprings. In amphibians and lower animals even females leave after the mating exercise. The basic parenting instinct evolved in reptiles and love can be seen as an adjuvant emotion further extending and strengthening this activity of parenting albeit indirectly.

Further to that, females are highly vulnerable to predators and starvation while tending to their eggs / offsprings and the emotion of love encourages the male to protect the female as well as the offsprings there by increasing their chances of survival.