On Lesley's post Peter Rollins - What is Religion? I've been trying to understand what Rollins is saying, without much success. But in the ensuing comments I claimed that love is just something that humans do - my intended implication being it is nothing to do with a god, or specifically God.
Kathryn asked, "Why do you think this [love] is something humans do? Do you think it is a genetic fluke, or is there some purpose?", and I wanted to give a more complete response than I could in a comment on Lesley's post.
It's a fluke in one sense: the sense that it just turned out that way due to evolution, without any intentionality or direct design or purpose. But that 'fluke' is not to be confused with ID critiques of evolution that say evolution relies on impossible odds. Fluke, luck, random events, whatever we might call them, have a part to play in evolution, but the theory of evolution shows that other forces, such as natural selection, play on those flukes in order to cause some change that persists.
The significant point from an evolutionary perspective is that traits that have some benefit in some sets of circumstances are more likely to survive.
Some simplistic examples to make the point and put love in context (for sexually reproductive species)...
A genetic condition (e.g. a mutation) that caused infertility would not be passed on to the next generation at all. Another mutation that didn't effect fertility but did remove sexual lust would also die out quickly in most animals (though humans, with our cognitive abailities, could overcome this). An emotion like love may not be as necessary at all for short term survival, but may be necessary in some species for greater group cohesion, or perhaps mother-infant bonding. Both fertility and lust are necessary for reproduction in sexually reproductive animals, but love isn't.
But we can still see how love can provide a greater benefit than not experiencing love, for some species.
Fertility we count as a physiological trait, love as an emotional one, but lust we see more as something of both physiological and emotional - so, where's the divide between physical trait and emotional trait? When you get down to the chemistry of what's going on in the brain they are, all three, physiological traits, each with their own contribution to the survivability of a species (along with all other influences). We have no reason to suppose that love is anything other than this, and certainly no evidence that it has any special meaning or value outside the context of humans that, using our brains, give it meaning and value. it's not something we need to associate with God, despite that fact that theists tend to raise it to the level of the divine.
Evolution doesn't have a purpose as such - and so there is no purpose for love. There is a trivial descriptive sense in which, looking back, we might use a purposive description - e.g. 'the purpose of this gene sequence was to cause that trait to emerge...' (again, a simplistic view of genes) But this isn't purpose in the sense of an agent intentionally causing some trait to appear for particular purpose of his. We are used to attributing purpose to the things we do, and we can mistakenly attribute purpose to complex causal chains that are otherwise hard to describe. It can be helpful to describe causal chains with such anthropomorphic framing of purpose - but we need to be careful that we understand that this purpose isn't real, it's a metaphor for causality.
So, there is nothing in our evolutionary past which could predict, in any reasonable sense, that love would turn out to be a trait that a particular species valued highly. There are clues available to the hindsight we have acquired through the development of the theory of evolution, based on our understanding of empathy and attachment that bond animal parents to young, and in some cases parents to each other. Insects have a very specific type of bond to their fellows nest, which is basically chemical. So, love (or its simpler animal parallel) isn't necessary for all animals to be evolutionarily successful - though for larger animals with more complex brains it may be particularly beneficial. We think it's beneficial for us - so much so we have learned to value it highly.
In this sense love is just what humans do, without it having any directive purpose. It's one of the many things we do, along with hate, fear, lust, empathy and many other traits. They all boil down to having emerged through our evolutionary history, and having been developed in our intellectual and cultural history.
Perhaps a better phrasing might be love is just what humans did in the past as a more refined development of empathy, but which we do now with more purpose and intent as we have come to appreciate it and value it.
We can reasonably explain the relationship between some of these things we do, in this simplified evolutionary context...
Personally and subjectively we like the feeling of love, and we dislike the feeling of fear. Our empathy makes us appreciate the same perspective in others, so we want love for others as well as for ourselves, and part of that is that we get additional pleasure from giving love, and even more from reciprocative love. And conversely we dislike fear, we dislike seeing fear in others, and so we want to alleviate the fear we see in others. And, on top of that we dislike seeing others cause fear, because of our empathy for the victims; and in a simple sense, just as a mother responds to defend her young with the animal equivalent of anger, so we respond with anger towards those that cause fear. These are strong innate emotional responses, honed in our history, with their origins lost in myth.
Many of our basic emotions have parallels in other animals, but have been developed into more refined concepts by us, probably because of the concurrent development of our language and our brain's ability to be more acute in our understanding of these emotions and the concepts we form about them. Just as a musician can develop a more acute sense of musical notes (an analogy Kathryn uses).
The problem is we don't often consider the simpler animal basis for our complex emotions - partly because of our ignorance of the evolutionary perspective. This ignorance was understandable for most of human history in which our reach back to the past was only ever measured in terms of a few generations. We could only develop myths out of that ignorance - ironically using the very creative imagination that later allowed us to come up with the science that helped us discover more plausible explanations.
The weight of those myths persists, and is maintained in varying degrees by a continued ignorance of the significance of what evolution is telling us, along with the willing, and sometimes not so willing, indoctrination in and bias towards those myths. Even those theists that have an understanding of evolution find it hard to accept the full implications of evolution and related ideas when they challenge their theological beliefs - they sometimes express a fear of the consequences of following the ideas through - e.g. the fear of the nihilism of atheism, in the absence of God.
To help a theist put this in perspective, consider some of the cosmological ideas that are floating around - many of which theists use as examples of how science has its own myths. In some respects our old myths parallel the current speculations about our cosmological origins - the old myths were speculations in the absence of data, just as some of our cosmological ideas are speculations in the absence of data. In some cases the mathematical theory of the latter replaces imaginative theology of the former, and so cosmologists might feel their theories have a greater legitimacy than theologies. But there may come a time, when we are better informed, when some our current cosmological speculations seem more like myths. So, this is how now atheists see theologies as outdated myths.
The deep history of religion is interesting, but I'm still largely ignorant about it. One particular book on my reading list is The Evolution of God, by Robert Wright. It appears to put the contingency of Christianity in perspective, effectively explaining the myth. It's the historical perspective that I need to know more about; and I suspect many Christians need to know more about it too, but without their own theological bias. If ever there was a case of the winners getting to write the history, theology is it - I don't think much of the history of theology sees the light of day. I don't know to what extent history of theology is taught in this respect. The book's website gives a good sampling of the book and is worth a read.