I think that statement needs qualifying.
For that I'll refer here:
http://slashdot.org/comments.p...
In modern English "female" refers to gender.
That is not correct and I can prove it. I don't know which dictionary you prefer, but in the US, Merriam-Webster pretty much sets the standard for English:
http://www.merriam-webster.com...
If you're British, then Oxford sets your standard:
http://www.oxforddictionaries....
Both dictionaries seem to agree that female refers to the sex that can bear young or lay eggs. The person wouldn't fully meet that definition (and in fact still carries organs that are part of the male reproductive system, such as the prostate.)
Biological sex is not binary
The definition for male may not be, but in terms of female, the definition is pretty straightforward: Must be capable of laying eggs or bearing offspring. In most non-mammalian species, there isn't XY chromosome (reptiles, birds, and fish for example have ZW instead) but there's still a common trait for females: capable of bearing offspring or laying eggs.
Now if you want to look at the extreme and one off examples where a human has XXY (or any other variation) it still boils down to being capable of bearing offspring or laying eggs. If that person can not, or if they can't produce male gametes, then they really aren't either sex.
As far as the cultural impact of everything I've said above: Culturally a person might identify as man or woman, and whichever they choose is their choice of course, however it isn't possible to change one's sex (or at least, the technology doesn't exist.)
That also being said, even if the technology comes along that allows females to produce male sperm or males to bear offspring or lay eggs, that doesn't change the anatomy of a person's brain.