In this article (mostly reproduced below), Professor Victor Mair discusses the history of gendered and agendered pronouns in Chinese:
One of the first things a student learns when studying Mandarin is the third person pronoun, tā. This was originally written 他 , with “human” radical (a radical is a part of a Chinese character that imparts some semantic or linguistic information), and it stood for feminine, masculine, and neuter—“he,” “she,” and “it.” During the early 20th century, however, some bright folks—undoubtedly in emulation of European languages—thought it would be a good idea to introduce gender into the Chinese writing system, so 她 (with “female” radical) came to be used for the feminine and 它 (with “roof” radical) for the neuter. I always thought that rather odd, because no attempt was made to differentiate the three forms in speech, only in writing, hence 他, 她, and 它 were still all pronounced tā.
Well, it’s not quite right to say that no attempt was made to differentiate the three forms in pronunciation, since there was a half-hearted effort to introduce yī for feminine and tuō for neuter, but it didn’t catch on.
In any case, beyond 他, 她, and 它, there is also 牠 (with “bovine” radical) for animals, a character with a “spirit” radical, for deities, and so on. All of these were, and still are, pronounced tā. In recent years, however, there has been an attempt to get rid of the gender distinctions for the third person pronoun and go back to a genderless stage. What is most curious, though, is the manner in which this is being done, namely through Pinyin, the system by which Chinese characters are transcribed into the Roman alphabet. In other words, 他, 她, 它, 牠, and others—all pronounced tā—are now being replaced by the actual letters “ta”!
Due to the nature of the Chinese writing system (at least, possibly), it seems that Chinese speakers/writers are resorting to a more flexible form of writing. Since an unknown character gives few clues to how it is pronounced, and sometimes what it means, creating new characters is a difficult task (though clearly it happens all the time). On the other hand, pinyin (the written form that largely uses Latinate letters), indicates the sound of the words, from which meaning can be deduced. If the pronoun character that used to be gender neutral has taken on the connotation of being masculine (because of the contrast between it and the versions with additional radicals indicating gender or grammatical gender), then the pinyin version removes the character’s form and thus the gender connotation. An interesting solution to a psycholinguistic, cognitive, and sociolinguistic problem!