Instincts

Almost all animals exhibit some or the other kind of "natural instincts" and i cannot but wonder whether humans also posses some kind of definitive instincts. Of course there are some common ones like survival. But unlike animals we go about our lives based on rational or reasoned out decisions(mostly), thats how we are so different from those lot.

There are many noticeable instincts in humans that i find particularly interesting. Especially those which are gender specific. Last week i was hearing some random musings of a radio jockey who put forward a topic for listners' opinion, it was something like - what is the most annoying thing about your partner that you cant really understand. A man called up and said he was fed up of his wife's and daughter's mania for buying numerous pairs of footwear! I couldn't help but laugh at first but then it struck to me it was a very common truth. Its not like all the women in the world were told to do so but still they all(most) would rather own 10 pairs of cheap attractive footwear rather than 2 pairs of expensive ones. This conundrum extends to many other preferences such as liking for pink color, attraction towards stuffed toys, allure of infinite lil colorful artifacts of jewellery, readiness to burst into tears etc. etc..

Men are not left behind either. We are well known for not liking the above mentioned things, craze for cars/bikes, penchant for loud and so called metal music, allergy to emotional pangs(very debatable), using tools, tendency to heat up and burst into physical interaction and common notion that they are more lewd/lecherous etc. etc..

I do not deny that many of these points are highly debatable, but we cant also overlook these common prejudices. Many may claim that these characteristics are are cliched and don't exist much nowadays. Neverthless my question is whether these things come wired in our brains since birth (or more precisely etched in our genes) or do we acquire these by observing the world around us?
Most of these even transcend borders, cultures and nations; hence should not be proximity based developments.

But if I were to say these features(if i may) come inbuilt in genders, then how can I account for the anomalies which exist? are they damaged ? neurally, or genetically perhaps?
Looking at the larger picture, does everything that doesnt fit into our current classification considered defective? take for example homosexual people, are they wired differently than a heterosexual ones?

This has drifted me away to a thought that all that we know today as explainable facts by science is just an insignificant fraction of something much bigger than we can ever imagine. An equation we think that explains a set of phenomenon might just be a particular case of a unfathomable general equation. Believe me I am more scared than you are reading this. Mathematics sucks!On this bombshell I will wrap up this post before I blow up my teeny weeny brain.