For a long time, it was the generic pronoun he that was used when talking about mixed-gender groups or persons with unknown gender. Most grammarians at that time agreed that he also meant she, but when it came to legislation and women's rights, suddenly he referred exclusively to men. When the question arose if women could be lawyers or presidents, he wasn't generic anymore. An early exception of that rule was a case of the US Equal Rights Party member Anna Johnson who argued that if he was inclusive, then laws describing voters as he couldn't rule out women. In this way, she registered to vote almost 30 years before the ratification of the Nineteenth Amendment to the United States Constitution that prohibited the state from denying people to vote “based on sex”.

Just as it happened with occupations, the first attempts to avoid male bias were made by incorporating women into language: instead of he, generic she appeared as well as splits such as she or he and he or she or the form s/he. Soon it became apparent that none of them were inclusive. Since the discussion on gender expanded binary, singular they was once again introduced.

Singular they is not a new phenomenon in English. As the grammarian Dennis Baron points out in his book “What's Your Pronoun. Beyond He and She” (2020), the quest of searching for a gender-neutral pronoun in English has been going on for at least 200 years, and none of the currently used options is new. Even strictly from a grammatical point of view, none of the generics are actually “right”, for example in a sentence such as “everyone forgets his password'' there is no gender agreement between the words everyone and his. Baron offers a whole list of different pronouns that English speakers have come up with during the last 200 years, but singular they particularly stands out.

Its usage dates back to the fourteenth century. Even before the rise of gender linguistics, under the prescription of a generic masculine, they was commonly used to refer to someone whose gender was unknown or irrelevant - only at that point, it was considered informal and not suitable for writing. You could still find this opinion in some manual styles, but at the same time, singular they is being increasingly recognized and accepted by respected language authorities. Students, when writing in English, use singular they consequently, and even a rather conservative Chicago Manual Style three years ago introduced they as a substitute for the generic he when referring to a person whose gender is unknown: for example, does anybody want their paper reviewed?

There are also other techniques to achieve gender neutrality in texts when it comes to generic pronouns:

• Omit the pronoun altogether. In many cases, it won't cause any significant change to the meaning of the sentence.

Example:

replace "The doctor should update the records when data is transferred to her by the insurance company" 

with "The doctor should update the records when data is transferred by the insurance company"

• Replace the pronoun with generic one.

Example:

If one fails, then one must try harder next time

• Use plural. When using this technique, pay attention to eventual slight changes in connotation.

Example:

replace A student must have passion towards his goals

with Students must have passion towards their goals. 

You can always find more strategies for gender neutrality in generic pronouns, and as discussion is evolving, further changes might occur in usage of generic pronouns.