Everything in human nature can be explained by Darwinian evolution. I recommend that you read some of the interesting books by Desmond Morris, who specialized in works on human evolution. A more advanced book which explains the origin and evolution of all living forms is Richard Dawkins' masterpiece The Selfish Gene. Men who are not attracted towards women will be very unlikely to reproduce, and their genes will die out; whereas men who are attracted towards women will be likely to reproduce, and their offspring will include males who are attracted towards women in the same way as their fathers. Over the millenia men will evolve who are very strongly attracted towards women (and women will evolve who are very strongly attracted towards men). According to Richard Dawkins, everything in biology can be explained by genes reproducing genes via the various living species the genes create. Successful special (like ours) are successful in reproduction.
♦ REASONS FOR PHYSICAL ATTRACTION BETWEEN MALE AD FEMALE :-
♣ ACCORDING TO YOUR question as explained by darwin it is law of nature that all the animals tries to keep themselves on this earth for long time and it is only possible through generation OR reproduction.
it is the only way they can preserve themselves from getting extinct.
so, for this purpose of reproduction it is very important of mating between male and female and it is only possible due to sex sensation, desire and attraction.
♦ this types of sex desire varies in different persons due to genes.
♦ attraction is just a medium for sex or reproduction.
these types of attraction may be on different parts, genetic organs, symmetry body shape, posture etc.
this type of sex desire is common in puberty and ages of youth due certain hormonal secreation. OR in another words we can say it is like evolution or adaption by organisms to make the process of reproduction easier and frequent as they could prevent their species for future
♦ GENES are also responsible for such desire, and attraction of sex.