The Science of Lust

Most people think that being attracted to someone signifies nothing more than what can be seen at face value. These people would be wrong. There is much more occurring biologically than a person is aware of when the are attracted. There is a science to attraction, lust, and even love. Many factors are involved in choosing a suitable companion.
Females are naturally more picky than men in choosing a mate because a woman must choose a male who has positive biological values. A woman must choose to mate with a man who has physical attributes that will allow her offspring to succeed. She ideally would find a man who is physically fit, has a strong immune system, good genetics, and is able to protect and care for her and the child during pregnancy. However, men can compensate physical attributes and genetics with the ability to give a woman security and stability. This is why wealthy and comparatively unattractive men have more options for a companion than his less wealthy counterpart.
The body has certain ways of achieving this. One example is sweat. On the surface of skin live microbial organisms. These organisms can indicate the immunities that a person has. When a man sweats, a woman can smell how biologically beneficial mating with him would be. Although on a concious level a woman does not enjoy the smell, on an unconscious level the receptors in the brain are receiving signals evaluating his immune system. If a man has immunities that the woman does not, she will dislike the smell less. In a blind study, women were found to detest the smell of close relative's sweat more than other males, this is due to similar immune systems and is a evolutionary safeguard to prevent incest.
Men view mates differently. A man's goal is to spread his seed as much as possible to raise his likelihood of fathering a child. This is why men generally do not mind the smell of any woman's sweat. This is also why men are more attracted to women when they are ovulating. In a study, men were asked to judge a woman's appearance and were found to rank women highest when they were ovulating and second highest when they were menstruating. A man will see a woman's face as more symmetrical and thus more attractive when she is ovulating. Men believe that a waist to hip ratio of .61 is the most attractive. This indicates wide childbearing hips and a slender, fit waist. Men will fight each other in order to further their line. The shape of the penis lends itself to pushing out other men's sperm during intercourse. Jealousy is evolutionary.
Men and women will be compatible when they are similar. A successful couple will most likely be a couple that has the most in common. Men and women of similar attractiveness, intelligence, and means will generally be compatible mates. The saying that "opposites attract" is generally false.
The brain, hormones, and chemical levels all contribute to the level of attractiveness that you feel for a person. When two people become compatible mates, the brain chemistry changes. In scans of the brain, a person in different stages of mating will undergo chemical changes. A person in the attraction stage will be different than a person in young love will be different than a person in a long term relationship.
Labels and cultural differences in long term relationships do not have large effects on happiness. One study shows that people who regularly attend parties in which they sleep with other individual's spouses are no more or less happy than conventional, monogamous couples. The idea of one person sexually monogamous with one other person is not evolutionarily logical. This lowers the chance of conception and it is not the norm in all cultures. More cultures, past and present, have practiced consensual non-monogamy than monogamous cultures.