This turns out to be a little harder to dig up from HN Search than I thought, so I've made a list of some of my favorite links on the topic. If you find any other high-quality ones, please let me know—there are several I couldn't easily find again in five minutes. I know Language Log has had many good posts about it.

There are many memorable details in this history, such as that the first English grammarian to prescribe generic 'he' was a successful female entrepreneur (who ironically was mostly an anti-prescriptivist), and that the name of another was the delightfully apropos Sir Charles Coote.

http://www.siu-voss.net/Androcentrism_in_prescriptive_gramma...

http://www.nytimes.com/2009/07/26/magazine/26FOB-onlanguage-...

http://www.damninteresting.com/when-they-became-him/

http://motivatedgrammar.wordpress.com/2009/09/10/singular-th...

http://itre.cis.upenn.edu/~myl/languagelog/archives/002748.h...

http://www.crossmyt.com/hc/linghebr/sgtheirl.html

http://www.crossmyt.com/hc/linghebr/austhlis.html