Clearly everyone knows that there is an attraction between the sexes. Men however largely start as females, and gradually change during their development into males. That men have breasts (which can be larger than some girls') is an example of this - though generally men's breasts do not develop, while girls' usually go on to do so. Thus we may assume that the general programming of our brains is for the attraction to be for males. While in the males certain functions are changed during his development, and there will be a switch in his Basic Attraction Brain Area to be attracted to females.
That these switch-overs sometimes do not occur properly is evidenced in men who 'remain' attracted to men, or where the switch is only partial and a man can be attracted to both. With the changes that must be made to organs which also may not occur properly, and with changes occurring in girls when they should not, it is reckoned there are several dozen different sexes in humans. The sex right in the middle of this spectrum looks like a woman - but where nothing has developed at all - and he is actually a man in chromosomes. Possibly that the switch over in attraction is liable to weaken it is the reason girls beautify themselves more than men with clothes and make-up.
The diagram represents the Brain Area within the oval which controls the Basic Attraction, of a girl for men. The Stick Figure on the left represents a man, to which the Brain Area causes the girl to be drawn to - represented by the green arrow. The girl will not be attracted to all men but only some. Some information has been found about this. Computer methods have been used to stack a large number of pictures of girls' faces to produce an average. The result is generally regarded as a beautiful face - which suggests that men's Basic Attraction Areas are programmed towards the blue print for our species.