Sperm, Sperm, Sperm, Egg, Bacon, Sausage and Sperm... sort of.

So I, in my typically dirty fashion, listened to the RadioLab show about Sperm. What are sperm, why are there so many, what’s up with paternity and why are men necessary, all that jazz.
Now, in true crazy feminist fashion, I SHOULD jump on the juicy tidbits about the sudden lack of “need” for men and extort those to no end. However, I’d like to focus on the basic facts I learned which were less about sperm and more about its relation to female organisms which it, er, eventually inhabits, which is pretty darn interesting.
Apparently, females in various species are more promiscuous than men. How crazy is that? The examples given were mostly birds, including ducks. In olden times before science, people (mostly men—ooh, those men) believed that a female of any species, really, who copulated more than once had something wrong with her, was mentally deficient or—and this they didn’t say out loud but they totally thought it—was a whore. In fact, it was proved in the 1970’s that all these slightly misogynistic conceptions (okay, so I didn’t stray TOO far from feminism) were incredibly wrong.
What fascinated me the most out of everything I learned from this show was the anatomy of a duck’s vagina. They didn’t really stay for too long on the subject, but when I heard it, I was struck. Apparently, a duck’s vagina has a regular canal-type thing to channel sperm, but only the sperm it wants—it has an off-ramp for unwanted sperm! A little road leading off to the edge of a figurative cliff for unwilling sperm receipt. It’s generally used for rape, because ducks seem to get raped. (Surprisingly, I read something about that once.) Ducks have evolved over time to be able to channel semen in either direction, as well as just developing the canals. How amazing is that?
What if female humans had a similar structure? Granted, it wouldn’t stop rape from happening, but it would definitely bring a sort of peace of mind (in a sense, because no one has peace of mind about rape) to a woman who was afraid she would get pregnant due to rape. The only downside is that a pro-choicer’s argument would become moot. Still, we can think of other things to cover for that, just imagine, though! Evolution is truly amazing.