Glancing at a woman without a ring, but with a nice smile and a nice figure, Adam stood next to the bar waiting for the right moment to walk over and introduce himself. As he sweated about how to ask the gorgeous woman to dance with him, he did not notice the sly bartender, dressed in snake skin from head to toe, slip a sleeping pill into his apple martini.

As Adam gulped down his drink, he felt rather calm, fatigued, and finally lethargic. Becoming unconscious, he did not notice the bartender slithering towards him with a needle full of estrogen, female sex hormones, at hand.

When the pill wore off, Adam found himself glancing at a man without a ring, but with a charming smile and a nice body. Adam stood next to the bar waiting....

As gay marriages were, for a brief period, legalized by San Francisco Mayor Gavin Newsom, the issue of homosexuality intensified throughout the United States.

"Not only is homosexuality a sin, but anyone who supports fags is just as guilty as they are. You are both worthy of death," stated Fred Waldron Phelps, Sr., pastor of the Westboro Baptist Church in Topeka, Kansas.

"The Scripture writers believed that all people were naturally heterosexual so they viewed homosexuality activity as unnatural," said Sister Jeannine Gramick, a Roman Catholic nun and assistant mathematics professor at College of Notre Dame in Maryland.

Homosexuals are considered "unnatural" in a religious context by some because they are believed to have chosen a sinful lifestyle. Alternatively, science suggests that homosexuality is not a choice.

A major biological argument is centered on sex hormone levels. Sex hormones (steroids) are specifically produced in the ovaries and testes. The steroids’ functions include maturing the male and female reproductive organs, the penis and vagina, respectively, and the development of sexually dimorphic characteristics that indirectly relate to copulation.

Sexual dimorphism refers to the difference in physical features among males and females of the same species. For example, male peacocks have colorful, grand tails while the females have dull brown ones. In humans, sexual dimorphism can be seen in the differences in the amount of hair and the structure of the shoulders and chest between males and females.

Some sexually dimorphic features can directly contribute to copulation while others do not. The color of a male peacock’s tail is not essential for sex because it does nothing more than attract a female’s attention. Contrarily, the shape and size of the penis and vagina do directly contribute.

There are three main types of sex hormones. They include androgens and estrogens (male and female sex hormones, respectively) and progesterone, a compound that blocks estrogen function and production.

The production of these hormones is first activated by the brain briefly in the fetus. During puberty, they are again activated, this time permanently. Fetuses secreting high levels of testosterone develop male physical characteristics while low levels contribute to female features. Although that function of sex hormones is clear, how they affect sexual preferences is still a subject of research and debate.

In 1969, a relationship between hormones and homosexuality was proposed in a prenatal hormonal theory of homosexuality by Günter Dörner, a German neuroendocrinologist. The theory stated that abnormal hormones or hormone receptors related to the brain influenced an individual’s sexual preference. Since then, much research has been done on hormone influences on sexual behavior.

"We spent much of our professional careers trying to understand this process of sexual differentiation, and what functions happen within it--male sex behavior, female sex behavior, control of ovulation, control of food intake, body weight, aggressive behavior, some aspects of maternal behavior," explained Roger Gorski, neurobiologist of University of California Los Angeles (UCLA).

For over a decade, Gorski at his UCLA laboratory, studied rats’ reaction to injection of different hormones. Six pairs of rat subjects were placed in a cage along with a female rat injected with testosterone. During their interaction, the testosterone-abundant female rat attempted to have sexual intercourse with a normal female rat, just like a male. Similarly, a castrated and estrogen-injected male rat was placed among the rat subjects. After a couple of squeaking "hi’s" and "how-are-you-doings", he bent over and waited for a rat to copulate with him, instead of the other way around.

The experiment implied that homosexuality is not a lifestyle choice but rather a physical manifestation of what is biologically occurring-that is, for rats, anyway. This study with rats may infer a similar mechanism in humans.

Experiments on zebra finches’ sexual preferences might also provide valuable insight into humans’ homosexuality. Although zebra finches are evolutionarily less related to humans than rats are, they are still a good comparison to humans because finches, like humans, mate monogamously.

In a study by Dr. Elizabeth Adkins-Regan and Cary H. Leung, behaviors of zebra finches injected with and without hormones were observed and recorded.

Dr. Adkins-Regan, a psychology professor at Cornell University, Ithaca, New York, has published numerous papers on hormonal effects on animal social behavior. Together with her postdoc, Cary Leung, she found that male finches with premature testosterone injection manifested an increased interest in females. No change was seen with an increase of estrogen in females. Blockade of androgen transmission by a drug called "aromatase inhibitor" did, however, result in a decreased preference for males, suggesting that hormone levels can in fact contribute to homosexuality. With similar mating behaviors, humans might be equally affected by sex hormones.

Although injecting hormones into humans for experimental purposes is illegal, the cause of homosexual behaviors can be tested in other ways.

One such way is through twin studies. Monozygotic twins (identical twins) differ from dizygotic twins (non-identical twins) in that the former are developed from the same fertilized egg while the latter are from two different, but synchronized eggs. Therefore, identical twins receive the same genetic information while non-identical twins do not. The logic is, if a behavior is observed more frequently in monozygotic twins than in dizygotic, then the behavior has a genetic basis. If the opposite results, then the environment is the main contributor.

Homosexuality in twins has been studied by Franz J. Kallman (1952), Leonard Heston (1968) and J.M Bailey with R.C Pillard (1991). Attention has been particularly focused on what types of twins (identical or non-identical) their subjects were. Results indicated that the chance of both twins being homosexual were higher in monozygotic twins than in dizygotic twins. The results of twin studies not only point to a genetic basis for homosexuality, but they further support the argument presented in the previously mentioned animal studies that biology can explain why some are attracted to their own sex.

According to Human Rights Campaign, a civil rights organization, there are approximately 10,456,405 lesbians and gays living in the United States alone. Although homosexuals clearly live among us, why homosexuality exists is highly debatable both in science and religion. As more research is conducted, there is increasing evidence that homosexuality is determined by hormones. With even more research, perhaps one day homosexuals will be as widely accepted as heterosexuals. Who knows, perhaps one day the creation story of Adam and Eve will be told as Adam and Evan.