Why do girls have periods and guys don't ?

Why do girls have periods and guys don't ?
O Kaay....
Because guys don't have eggs, ovaries, fallopian tubes or a uterus.
because they don't have a female sexual organ.and god didn't make it that way. moonraven
how old r u?????? oh we'll i will answer this anyways..(sigh) Boys don't have ovaries and which means they don't have any eggs..... A period is when an egg hasn't benn used!!!
Hi. I don't know if this is ture or not. But I'm 17 and my mother is very religious. I asked her this question about 2 two days before thanksgiving back in november. And she told me that back in the olden times when it was just Adam and Eve and when eve bit into the forbidden fruit, God placed a curse on her and that all females will be cursed with what she'd have.
It's something like that. I wasn't really listening to her. But like I said, I don't know if it's true or not. And then my older sister told me that it's just old blood that your body doesn't need anymore.
it was a cruel joke played on us.