For better or worse science is encroaching there too, in to the study of morality at any rate. See http://www.amazon.com/The-Moral-Animal-Evolutionary-Psycholo... for example.

An ad hominem attack with a dash of appeal to authority...enlightening. If you require proof of sexuality's impact on human behavior, I recommend reviewing the extant literature. Here are some examples:

1. http://www.amazon.com/Red-Queen-Evolution-Human-Nature/dp/00...

2. http://www.amazon.com/Moral-Animal-Science-Evolutionary-Psyc...

I wonder why you were initially downvoted? Anyway, to quote from Williams: "I see no reason why a conscious motive need be involved. It is necessary that help provided to others be occasionally reciprocated if it is to be favored by natural selection. It is not necessary that either the giver or the receiver be aware of this. ... Simply stated, an individual who maximizes his friendships and minimizes his antagonisms will have an evolutionary advantage, and selection should favor those characters that promote the optimization of personal relationships."

Robert Trivers expanded this idea and you can read his paper, "The Evolution of Reciprocal Altruism", here: http://www.cdnresearch.net/pubs/others/trivers_1971_recip.pd... Since then the evidence has continued to grow in support of the idea (at least in primates--birds and fish that Trivers suggest don't have as much evidence).

http://lesswrong.com/lw/kw/the_tragedy_of_group_selectionism... is a nice post on why group selection theories tend to be wrong by default and why you shouldn't really pay attention to them when they come up.

For people interested in evolutionary psychology I recommend Robert Wright's The Moral Animal, which does a good job covering the history of the field and offering explanations for a variety of behaviors. http://www.amazon.com/Moral-Animal-Science-Evolutionary-Psyc...

This isn't a question of a high-level personality trait, but a question about the low-level firmware in our heads. The standard myth that we all grow up with is that everyone is born as a blank slate, and the child's environment shapes the person from scratch. This is only partially true, there's a whole lot about our nature that is simply fixed in stone (ok, neurons really) before we even take our first breath. Two obvious examples are the innate human calls of crying and laughter. The weird thing is that most of the rest of our minds are pre-determined by biological evolution too.

<insert shock, awe, indignation, cries of "What, I'm not even at all like my identical twin brother!", etc here>

There's far less variation between people than we normally think; a whole lot of us is dictated by the low-level firmware we're born with. We're just acutely sensitive to the relatively minor differences between us, just like you can tell faces apart even though they're all basically the same.

If you're saying is that the relative weights vary between people, so while one person might be very comforted by touch another wouldn't care for it much, I agree with that. But this is just the small amount of variation between different people, the small amount that isn't fixed and can vary person-to-person. This is just a difference-in-degree, not a difference-in-kind. I doubt you can find someone who reacts to touch by immediately beginning to juggle knives or by sneezing. Now that would provide some evidence for the whole blank-slate hypothesis.

Evolutionary Psychology is fascinating stuff. As I said in another thread: "EvPsych basically makes one important observation and asks the natural question leading from it: Just like our eyes and hands, our minds have also been developed in response to evolutionary pressures. What were these pressures and how do they account for the features we see in ourselves, like language, love, laughter, crying, etc?" A good pop-sci book on the subject is The Moral Animal by Robert Wright: http://www.amazon.com/Moral-Animal-Science-Evolutionary-Psyc...