Others have looked at bodily difference such as fingerprints or finger length to determine the influence of prenatal hormones. Other physiological and anatomical features have also been examined, but all of the theories proposed so far have limitations, some more serious than others. Since homosexuality is thought by many to run in families, there has also been an effort to look at genetic influence, and while some researchers have found what they think is documentation of this, there generally has been a failure to replicate the findings.

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The author of this article has argued that so far there are too many variables involved to come up with any definitive answers. Probably biological, psychological, and social dynamics are all involved, and there are too many variables to reach any final conclusions. As far as classifying any individual, sexual orientation seems best left up to the individual to define for himself or herself.

Anthropology, the first of the social science disciplines to take sexuality--and particularly homosexuality--seriously as a field of intellectual inquiry in the late nineteenth and early twentieth centuries, has achieved a new impetus in the post-Stonewall era.

Although until recently rejected by most sexologists as a distinct sexual identity, bisexuality is gradually becoming recognized and studied as such.

Beginning in the 1960s increasing numbers of ethnographers have conducted research on glbtq issues, spurred by the premise that studies of diverse sexualities are crucial to understanding human behavior and culture.

The earliest etiologies--or theories of causation--of homosexuality date from European antiquity, but the search for a universal etiology has intensified as homosexual behavior has come under the scrutiny of science.

The term "homosexuality," coined in 1869, with "heterosexuality" as its opposite, has led to a binary concept that oversimplifies the complexity of human sexual behavior.

Intersexuality (formerly referred to as hermaphroditism) is a congenital anomaly in which an individual's external genitalia or internal reproductive systems fall outside the norms for either male or female bodies.

A social role for individuals who crossed or mixed male and female characteristics was one of the most widely distributed institutions of native North America.

Sodomy laws, which provided the legal basis for police harassment of sexual minorities, were conclusively overturned by the United States Supreme Court in 2003, after more than half a century of efforts at reform.

Straight men who have sex with men do so for a number of reasons, but in general such activity is about physical release and sexual behaviors, not about attraction or desire for another man.

"Transgender" has become an umbrella term representing a political alliance between all gender variant people who do not conform to social norms for typical men and women and who suffer political oppression as a result.

Both male and female berdaches (or two-spirit persons), common among Native American tribal cultures, were characterized by gender variation sanctioned by supernatural dreams and visions.

BiNet USA is the oldest national bisexual advocacy organization in the United States, attempting to serve as a voice of bisexual and pansexual people.

Two of the most significant Supreme Court decisions regarding constitutional liberty for glbtq people are Bowers v. Hardwick (1986) and Lawrence v. Texas (2003).

Although she did not explicitly identify herself as a lesbian, Anna Freud, youngest daughter of Sigmund Freud and herself a psychoanalyst, was decidedly not heterosexual in any typical sense.

The founder of psychoanalysis and the discoverer of the unconscious, Sigmund Freud initiated a fundamental transformation in the self-understanding of Western men and women, including especially the role of sexuality.

The most important sex researcher of the twentieth century, Alfred C. Kinsey contributed groundbreaking studies of male and female sexual behavior in America.