Seems God was just about done creating the universe, but he had two extra things left in his bag of creations, so he decided to split them between Adam and Eve. He told the couple that one of the things he had to give away was the ability to stand up while urinating.
"It's a very handy thing", God told the couple, "I was wondering if either one of you wanted that very ability."
Adam jumped up and blurted, "Oh, give that to me! I'd love to be able to do that! It seems a sort of thing a man should do. Oh please, oh please, oh please, let me have that ability. It'd be so great! When I'm working in the garden or naming the animals, I could just stand there and let it fly. It'd be so cool, I could write my name in the sand. Oh please God, let it be me who you give that gift to, let me stand and pee, oh please..."
On and on he went like an excited little boy who had to pee. Eve just smiled and told God that if Adam really wanted that so badly, that he should have it. It seemed to be the sort of thing that would make him happy and she really wouldn't mind if Adam were the one given this ability.
And so Adam was given the ability to urinate while in a vertical position. He was happy and did celebrate by wetting down the bark on the tree nearest him, laughing with delight all the while.
"Fine," God said looking back into his bag of leftovers. "What's left here? Oh yes, brains...."