Love is possibly one of our most potent evolutionary tools as it develops from nest instincts and nesting instincts are what allow young to explore the world without fatal consequences - play fighting, exploring, climbing etc are all things that without parents to look after them are more likely to lead to death from predators or other causes. Humans are possibly the most child rearing centred mammals as we look after our young far longer than they need to be looked after (come on, how many parents on here with adult children still occasionally need to bail them out of financial trouble from time to time? How many of you do it without thinking? There's that instinct right there ). This set up, which ensures education and survival for our children, is made possible through the concept of love. These emotions are there for a reason and it is a reason which has partly ensured our survival as a species - possibly more so than the much vaunted (and over rated) intelligence and opposable thumbs. But there are a lot of sunconscious things which go into deciding who we fall in love with and many of these are not obvious.

On the other hand, our close cousins, the Bonobo Chimpanzees (Chimps, Bonobos and Humans make up the three 'Chimpanzee' species in genetic terms. The concept of 'Homo sapiens' as a superior species to all is an outdated Victorian concept we appear to be stuck with - either we are a 'Pans' species or they are also 'Homo' current opinion is divided) are notoriously promiscious to the extent of having sex as a means of saying hello in some cases. Two extremes - mating for life (as many species, i.e. some gorillas, do and which humans claim to do sometimes) and casual sex as social interaction. I think we fall somewhere in the middle as a species though most of our 'mating for life' instincts could easily be explained as cultural, specifically religious, imperatives (attempts to curb the human nature for promiscuity?) rather than animal instinct. At this point in our species development it is difficult to work out how much is instinct and how much is 'education' from an artificial set of ethics imposed by ancient priests and rulers.