I haven't finished this Tina Fey piece on Fresh Air yet, but as I've said, my readings of Jane Austen, and now Edith Wharton, have really taken me back to this old claim (most famously aired here and answered here) that women aren't funny. As an adult, probably the first author I found to be truly humorous was Zora Neale Hurston. Better people then me can probably cite a range of other women authors who used humor in their writing, but even in my own small forays it's clear to me that they are there. Leaving aside the desire to say something provocative, if thin, I'm thinking that a large portion of this claim originates in shrinking the range of "funny."
Suffice to say that whenever this discussion ensues, we don't really talk about literary history, we talk about Hollywood. Thus. to me, the question really isn't one of the innate humor of women, but the extent to which that humor tends to be expressed on screen. I strongly suspect that this has much more to do with the business of performance, then anything else. Asking why their isn't a female Seth Rogan, is more likely a question of structure than chromosomes.
I guess that's why I've been saddened that Austen's humor, and really Hurston's too, isn't better translated on to screen. When I think of Sense and Sensibility, I think of romance a little, but I really think of something, tonally, more in the spirit of The Royal Tenenbaums. Perhaps it's me, but it's sad that this stuff gets sort of waved off as "romance." It's sad that "romance" gets waved off, period. But that's another story.
Also part of this is on us, by which I mean people who love books. I don't think many people today think of fiction, creative nonfiction or poetry as particularly funny genres.