Most intersexuals show predominantly male or female characteristics, but they are less pronounced than for typical individuals. However, intersexuals also includes "true hermaphrodites", those with equally male and female genitals, and "pseudo-hermaphrodites", those with genitals which are closer to one sex or the other, while combining features of both; but many dislike these terms as being overly medical. Note that the term is somewhat misleading since humans who are called "true hermaphrodites" are infertile, while species that display actual hermaphrodites are fertile and able to function as males and females when reproducing.
"True hermaphroditism" is rare (some 500 reported cases in total), and the causes are partially unknown. Pseudo-hermaphroditism is much more common. Causes include various chromosomal or endocrine conditions that disrupt the normal functioning of the human sex-determination system.
Typical men have sex chromosomes XY and typical women XX. One biological definition of a male child is the presence of a Y chromosome. This definition is sometimes used for gender determination at sports events.
In some cases invidiuals are neither XX nor XY:
One of the most common cases is a fetus with XY chromosomes but where for some reason a fertile male child does not develop. In the following cases the child retains an outward male appearance:
The following further XY cases leads to pseudohermaphroditism:
Excessive in utero exposure to androgens may lead to pseudohermaphroditism in XX cases:
True hermaphrodites have both ovaries and testes, or gonads which are a combination of an ovary and testes (an ovotestis[?]). True hermaphrodites most often have XX chromosomes, but they have been known to have other chromosomal makeups as well. In the case of XX chromoses, some genes from an Y chromose has accidentally been crosed over to an X chromose.
Thus so called partial and full hermaphrodites overwhelmingly involve children with a Y chromosome. This is because without the Y chromosome there is normally no possibility for male characteristics to develop, as the necessary genes are lacking. The only exceptions are when Y chromosome genes have accidentally been crossed over to the X chromosome (extremely rare) or due to in utero exposure to androgens (very rare).
Intersexual individuals are treated in different ways by different cultures. According to some scholars, there are societies where they have been treated as a third sex[?] with a social role intermediate between those of men and women. Such claims have been questioned by other academics. In most societies, intersexed individuals have been expected to select one sex, and conform to its gender role.
Since the rise of modern medical science in Western societies, intersexuals with ambiguous external genitalia have had their genitalia surgically "corrected" to resemble either male or female genitals. But there are increasing calls for recognition of the various degrees of intersexuality as healthy variations which should not be subject to correction. Some have attacked the common Western practice of performing "corrective" surgery on the genitals of intersexuals as Western cultural equivalent of female genital mutilation. Despite the attacks on the practice, most of the medical profession still supports it. Others have claimed that the talk about third sexes represent an ideologic agenda to deride gender as social constructs, when in fact they are biological realities.
"Corrective" surgery is generally not necessary for protection of life or health, but purely for aesthetic or social purposes. It may lead to negative consequences for sexual functioning in later life, which would have been avoided without the surgery; in other cases negative consequences are avoided by surgery. Defenders of the practice argue that it is necessary for individuals to be clearly identified as male or female, for proper "social functioning". However, some individuals have been so discontented with their surgically assigned gender as to opt for sexual reassignment surgery later in life.
The writer Anne Fausto-Sterling coined the words herm (for hermaphrodite), merm (for a pseudo-hermaphrodite that most closely resembles a male), and ferm (for a pseudo-hermaphrodite that most closely resembles a female), and that these be recognized as sexes along with male and female. However, these terms are now deprecated, and their author no longer advocates their use.