A quick read of a dictionary (http://dictionary.reference.com/browse/his) says that his is "the possessive form of he", and the second definition of "he" is "anyone (without reference to sex)". That's also what I got taught in middle/high school.
Sorry if I'm just missing something and this is a stupid question.
That's why some people push towards the use of the singular they (http://en.wikipedia.org/wiki/Singular_they) That may eventually change the language for all.
For example, consider the following headline 'What you can tell about a doctor from the sort of shoes he wears.' You're probably not picturing any women's shoes when you read that.
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If I could flip a switch, I would make it so that "their" or something similar was a gender-neutral pronoun, so that we can avoid both sounding sexist and sounding awkward. On the other hand, languages probably have a lot of cultural baggage associated with it that are outdated. But these are artifacts of the history of the languages intertwined with the past cultures that used it; we don't tacitly embrace the old connotations that they had simply by using it in this day and age.
Singular "they" is perfectly good, perfectly historic English (there have been countless HN threads on this, with copious citations) and it's only a matter of time till the convention goes back to being generally accepted and eliminates the pronoun gender problem [1]. In the meantime, let's restrain ourselves from having flamewars about it.
1. Which we only have because of meddling 18th and 19th-century prescriptivist grammarians in the first place. Thanks, meddling prescriptivist grammarians!
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...
I don't think "his" and "her" are sexist per se, though men tend to use the former and women the latter when referring to a theoretical or nongendered person or whatever. "His or her" everyone seems to agree is bulky, and fringe-use alternatives like "zyr" or something don't have nearly the mindspace to suggest as a reasonable alternative.
Any evidence to support that assertion? If one isn't comfortable using the neutral pronouns - identical as they are with the masculine pronouns in English - the tendency is to use [singular] "they" or "his or her" IME (anecdotal as that is). I don't find women generally choose to use feminine pronouns more unless they're trying to make a point in doing so.
Example: suppose there is a sentence "Each Cub Scout must build and light a fire in order to gain his backwoodsman badge". People, myself included, will tend towards saying "gain their backwoodsman badge" rather than choosing to say "his backwoodsman badge" or "her backwoodsman badge" according to the speakers sex. Of course some people will also get upset about the gender neutrality of words that end "man".
On this article, the hedline led me to think that there was something distinctive about the distribution of female names that made it far easier to guess (not tell) someone's age if they were female rather than male.
A better headline that more accurately reflected the actual content, avoided unnecessary gender classification and grammatical ambiguities would have been 'How to guess Americans' ages from their names.'
There's also precedent with thou and you although that evolution was a bit more complicated and isn't quite the same thing.
It specifically mentions that girls names are generally more constrained in time, so the technique they use works better on women.
Forcing the use of "her" instead of "his" is just as sexist. If we want to improve the mental model of the listener (reader) through the use of language, then we should make a conscious effort to be correct instead of argumentative, and say "his or her" or "their".
Edit: it's not ambiguous. The person in the title is a hypothetical single person. Whoever wrote the headline decided that the person they made up was feminine.