Human desire has been explained scientifically. The earliest and best attempt at this was Edward O. Wilson in his book "Sociobiology". This is not some crackpot weirdo. This is a famous, legitimate scientist.
In the century leading up to 1975 C.E., people started to investigate animal behavior. Mate choice and foraging behaviour coincided perfectly with mathematical models of what an animal can do to ensure that an animal have the greatest number of copies of their genome survive after their own death (mate choice), and what an animal can do to ensure that the maximum number of calories per hour be consumed (foraging behaviour). It didn't take long for things to get deeper than that, such as explanations why so many animals do extremely bizarre mating rituals.
In the 1970's. E.O. Wilson took the heretical step of applying this school of thought to humans, and found we fit in perfectly, just like any other animal. We select mates, choose careers, gather food, manage our resources exactly the same way as even the most primitive, brainless animal , in a way that maximises our chances of reproductive success.
One of the most powerful and controversial findings of this type of thought is that many of these mathematically optimized beaviours that we evolved are emotionally driven. Love, hate, lust, hunger, courage, you name it.
This is not a satanic idea. It's a scientific idea. What's satanic about this, is to recognize that we are animals, and to realize that it is neccessary for our reproductive success to acknowlege the full spectrum of emotion, for it drives behaviour necessary for survival. The other religions suppress roughly half of our essential animal urges.
I love this idea. But I can find some problems with this theory. If so many religions teach people to supress the "negative" aspects of humanity, yet we have evolved these instincts to enhance reproduictive success/survival, then why does religion not get wiped out by natural selection?
also, wilson's idea would seem to indicate that human will and emotion is a product of our genetics and therefore evolution. Wilson personally takes this idea further than I'm willing to go, and says there is no such thing as human will, that our emotions are genetically encoded to ensure reproductive success. Our will is not our own, but what our heredity told us that it should be, and we generally cannot defy this. But I know of a thing we can do where we act despite our animal urges. one common word for this is "discipline"
of course the problems with this kind of thought are complicated by the idea that both religion and discipline, while possibly permanent global disadvantages, can temporarily improve reproductive success.
Therefore after this tortuous journey comes full circle, the final answer is that we don't know.
Not terribly useful in the end, but I find the ability to hold these thoughts is liberating.