Imagine a world equally divided with three sexes Male, Female and Shemale.

[natandreita]

"The left hand of darkness" a book by Ursula Leguin:
A planet where all inhabitants are hermaphrodites.

http://en.wikipedia.org/wiki/The_Left_Hand_of_Darkness
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a planet that is always cold, and its citizens are neither female nor male: they only have gender identities or sexual urges once a month. These conditions have affected the ways that civilizations ... have developed, with the most notable effect being that there has never been a war on the planet.

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The struggle of Genly Ai (the protagonist) as he tries to understand the ways of these people and survive on this hostile planet gives Le Guin the chance to explore what life would be like without the dualities, such as summer and winter or male and female...

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The inhabitants of Gethen are sequentially hermaphroditic humans; for twenty-four days (somer) of each twenty-six day lunar cycle, they are sexually latent androgynes; and for the remaining two days (kemmer), they are male or female, as determined by pheromonal negotiation with an interested sex partner. Thus each individual can both sire and bear children.

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Le Guin developed this idea out of a desire to explore what remained basic to human nature when biological gender was no longer a factor. The Left Hand of Darkness is a significant milestone in the increasing sophistication of the treatment of sex in science fiction that developed in the late 1960s and 1970s.

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Themes - Gender

At first, a large part of the novel seems to be an exploration of a neuter society?a society in which sexual difference plays no role, although love and jealousy remain. The world of Gethen has no history of war, but Le Guin has Genly Ai's narration state that the exact reason for this is unresolved. It could be due to the Gethenians' unique biology (the absence of a deep sense of duality implied by strong gender divisions may cause the Gethenians to lack a necessary component of nationalism), or it could simply be a side effect of the planet's harsh climate, limiting warfare to small skirmishes by simple economics.

Also related is the far slower pace of technological development. The Gethenians are mentioned as having gone through a very slow-paced and gradual industrialization, with many semi-feudal social institutions left intact, rather than the breakneck industrial revolution which Earth experienced since the 18th Century. In one episode, it is specifically mentioned that a particular type of truck has been in use for centuries, almost unchanged, and that Gethenians feel no special need to improve on it and develop a more advanced model. Like the above, this may be related to the absence of a sharp male/female dichotomy, or may simply be a side-effect of Gethen's meager natural resources, which are deficient not only in pure raw materials, but also in certain forms of inspiration (Genly Ai speculates at one point that the Gethenians' failure to invent the airplane may be due to the planet's lack of birds).