ASSUMPTION: A person is either male or female
Humans are assumed to be divided into two general groups, one called male and the other called female. The two groups are considered bipolar opposites, matched parts that fit together as puzzle pieces.

Reality Check
This bipolar division is based in an either/or dichotomy; one is either male or female, based on physiology and this is assumed to be immutable. Intersex people, as well as transgender people, are "disappeared" by this assumption; homosexuals are pathologized.
• Two percent of the population is not easily assigned into a simply male or female designation, but are intersexed.
• Genitalia are rarely visible publicly; assumptions about male/female sex are actually based in gender attributions of masculinity and femininity.
• Despite the bipolar divisions of male/female, man/woman, masculine/ feminine and gay/straight all aspects of human sexuality -- physiology, gender identity, gender role behavior and sexual identity -- have multiple variables and expressions
• A dual-sexed system is inherently a heterosexist one. If male and female parts are naturally paired, then it is reasonable to deduce that any male/male or female/female bonding is therefore unnatural. A bipolar sexual system infers and reinforces a heterosexual world.

ASSUMPTION: Sexual and gender identities are the same thing
The words sexual and gender identity describe the same thing and people who have non-normative sexual identities also have non-normative gender identities (and visa versa). In other words, if a biological male cross-dresses, he's gay; if a biological female acts "butch", she's a lesbian.

Reality Check
• Sexual identity is the self-perception of one's sexual orientation. It describes the direction of erotic desire, one's sexual preference and emotional attraction.
• Gender identity describes one's core experience of their own gender and has little to do with eroticism, desire or sexuality.
• Sexual and gender identities are two components of human identity and describe different phenomenon.
• Gender variant people can be homosexual or heterosexual; people of all sexual identities can be transgendered.

ASSUMPTION: Sexual and gender identities have nothing to do with one another

Reality Check

• The relationship between sexual and gender identities is extremely complex. Many people who are gay/lesbian experience confusion about their gender; many people who are gender variant express confusion about their sexual orientation.
• Changes in gender identity/presentation can create a "change" in sexual orientation i.e. a male-to-female transsexual who is heterosexually married will now be perceived to be in a lesbian relationship; a female-to-male transsexual who is in lesbian relationship will now be perceived to be in heterosexual relationship. This may present confusion for the person or his or her spouse.
• Sometimes sexual identity can change if gender identity/presentation changes i.e. a transman who used to identify as a lesbian, may find himself attracted to men, which makes him still "gay" although his gender presentation has changed; a male-to-female transsexual who was attracted to women may now find herself more attracted to men. Sometimes the desire for "same-sex" (or "opposite-sex") relationships is more salient than the preference for a partner of a particular sex.
• Same-sex is not the same thing as same-gender i.e. two females in a butch-femme relationship may be in a "same-sex" but opposite gender relationship.