One might wish to check out the ON LANGUAGE column titled "All-Purpose Pronoun" by Patricia T. O'Connor & Stewart Kellerman in The New York Times Magazine of July 26, 2009, where among other things it is noted that:
"The idea that he, him and his should go both ways caught on and was widely adopted. But how, you might ask, did people refer to an anybody before then? This will surprise a few purists, but for centuries the universal pronoun was they. Writers as far back as Chaucer used it for singular and plural, masculine and feminine. Nobody seemed to mind that they, them and their were officially plural. As Merriam-Webster’s Dictionary of English Usage explains, writers were comfortable using they with an indefinite pronoun like everybody because it suggested a sexless plural."
