Women: only female mammals who orgasm

Why is it that human females are able to orgasm but not other species of mammals?

http://en.wikipedia.org/wiki/Orgasm

>Morris proposed that orgasm might facilitate conception by exhausting the female and keeping her horizontal, thus preventing the sperm from leaking out.

>>1
WTF is that bullshit? Females from other species are able to orgasm. I've seen my dog reaching an orgasm by licking herself, and it was pretty easily noticeable. She went nuts when she hit the point. Then you have species such as dolphins or some apes which have sex just for the fun of it, and I doubt females would be willing to do it if they didn't get an orgasm in reward.

>>3

Assuming you're a guy, would you bother to have sex with a girl if men can't orgasm (but can impregnate) but women can orgasm?

>>4
And your point?  We get raped by lolis?