Gender and Life

Why aren't there more than two sexes?
Answered by Meredith Bower and Discovery Fit & Health
  •  Meredith Bower

    Meredith Bower

  • Discovery Fit & Health

    Discovery Fit & Health

  1. First, let's talk about the birds and the bees. Unlike humans, the sex of some species of birds and insects is determined by the presence of additional chromosomes and how an egg is fertilized. But in humans and most other species, the process of evolution has limited our biological sex options to either male or female, depending on the presence of the heterogametic 'XY' chromosome. After a human egg cell is fertilized, cells divide, either testes or ovaries are formed, and the child's sex usually becomes clear.

    There are cases however, when a member of a species is born with both male and female reproductive organs. When this occurs in humans, they are called hermaphrodites, and in some cultures these people are considered members of a distinct third sex. According to Greek mythology, Hermaphroditis, the son of the gods Aphrodite and Hermes, was fused with a nymph, giving him both male and female qualities.

    In modern, Western cultures, people labeled hermaphrodites are not always treated with god-like status. Also known as intersexed, most infants whose sexual identity is unclear at birth have endured corrective surgery to render them female (because it is an easier operation) [source: Bernhardt]. While the procedure can "fix" them to one sex physically, many intersexed people struggle with gender identity and are left with deep psychological scars.

    Meanwhile, in other parts of the world, the idea of a third sex is embraced. In one region of Indonesia for example, hermaphrodite priests are the authority figures of a society that also recognizes transgendered people, believing there are a total of five genders who must all live in harmony [source: National Geographic].

    Cultures that believe in a third sex don't think there is a third chromosome in addition to X and Y, but simply that there is something else in a person's genetic makeup that causes identification with the sex not ascribed by their genitalia.

    While many people in Western cultures still try to assign everyone to one of two sexes, it's possible that public opinion is slowly evolving to accept the idea of gender variance [source: Gender Spectrum]. As the concept of gender identity has become more widely accepted, maybe one day, so too will intersexed or hermaphrodites be universally recognized as a distinct sex.


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  2. There are mushroom species that have dozens of thousands of sexes, which gives a mushroom a lot of options when it comes to the mating game. However, because mating is so widespread within a population with lots of types of sexes, DNA mutations and defects spread much more quickly. When the number of sexes within a species is limited, they have fewer mating options, but their offspring have a greater chance of survival.

    Purpose Of Sexqa3
    (Macduff Everton/Getty Images)

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