Sex

Many species of living things exist in two or more forms called sexes that combine genetic material in order to reproduce. This is called sexual reproduction. Typically, a species will have two sexes, called male and female (the female being the one that produces the larger gamete). Fungi and some other organisms exist in more than two sexes, but still reproduce in pairs (any two differing sexes may reproduce). Some species, like earthworms or geckos, are capable of both sexual and asexual reproduction.

The word sex is also used to refer to sexual intercourse, the physical acts related to sexual reproduction, but this article will discuss the concept of sex defined above.

In mammals, birds, and many other species, sex is determined by the sex chromosomes, whose alleles are called X and Y. Males typically have one of each (XY), while females typically have two X chromosomes (XX). Since all individuals have at least one X, the Y chromosome is generally reduced, and is absent in some forms, this pattern admitting some considerable variation. In other forms, sex may be determined by various other sex-determination systems, including ones controlled by environmental factors like temperature, or by age. Many animals are hermaphroditic - that is, individuals may have both male and female parts.

By the 1930s social scientists had discovered that there is much variation across time and space in human understandings of sex and sexuality, and in normative behavior for human males and females. In the 1960s social scientists began distinguishing between "sex" and "gender" in oreder to describe such variation intelligibly and accurately. "Sex" refers to the biological division into male and female, while "gender" refers to social status and roles assigned to people on the basis of sex.

The suggestion has been made that the two sexes are not discrete, but rather a continuum, along which lie many intermediate positions -- the intersexuals. Some have argued that the division of human beings into male and female is a social construction, and that in reality there are at least five sexes (male, female, merm, ferm and herm), although the first two are the most common. Advocates for intersexual people have stated that this theory is wrong, confusing and unhelpful to the interests of intersexual people. The originator of this theory, Anne Fausto-Sterling has stated that she no longer advocates it.

See also: evolution, gender and sexuality studies, human sexuality, sex organ, the assembly language mnemonic SEX, Autosome, Hermaphrodite,