Editing Hainish Cycle (section)

=== Biolog ===

Most of the people in the tales have a common descent from the planet Hain, whose people settled many worlds. Some of them are genetically similar enough to produce children together.  The unusual hairiness of the Cetians is mentioned in ''The Word for World Is Forest'' and ''The Dispossessed''. ''[[The Telling]]'' includes the detail that the people of Chiffewar are all bald.

There are some cases of ancient biological manipulation:

* Unique among known humans, the Hainish have complete voluntary control of their fertility. In order for a Hainish man and woman to reproduce, they must both consciously choose to produce viable genetic material, which they learn to do in adolescence. The required genetic changes to the Hainish population were made in the far distant past, and apparently took many generations to accomplish.<ref>"[[#Short stories|A Man of the People (Hain)]]"</ref>
* ''The Left Hand of Darkness'' mentions that the hilfs<ref name=hilf /> of S must have been produced by human genetic manipulation by the ancient Hainish people, along with the Gethenians and the degenerate winged hominoids of Rokanan. We hear no more about the hilfs of S, unless these are the same as the small furry natives of Athshe, who are also of Hainish descent.
* The ambisexual humans of Gethen may have been produced as an adaptation to a harsh climate, or an experiment to see how people would live without gender.  Both ideas are mentioned and nothing is definitely settled.
* The degenerate winged hominoids are seen in Rocannon's World. They live in cities that require much higher technology to build than the rest of the races on Rokanan, but live in bat-like societies, hunting for humans and animals on which their larvae feed by sucking their blood.
* ''The Matter of Seggri'' tells us that the extreme gender imbalance of the people of Seggri may be another case of genetic manipulation.
* Alterrans have distinctive cat-like eyes. While normally unable to breed with Earth-humans, the latter become sufficiently genetically similar within a few centuries on their planet due to unspecified natural factors. This almost drives the Earth-descended colony to extinction due to the genetic differences between mothers and fetuses causing miscarriages. The Alterrans may be another case of genetic manipulation, or a similar natural adaptation themselves.
* The Shing of ''City of Illusions'' are not of Hainish origin and cannot interbreed with Earth-humans. They dismiss the report about the human adaptation on Alterra as impossible.