So God goes to Adam not to long after the creation and says, "You know Adam I think your ready for a mate."
"A mate?" replies Adam
"Oh you'll love this" says God, "You'll go out hunt and gather come back to cave she'll have a fire going warm meal ready for you."
Adam says, "Well that sounds good."
"Oh there's more, maybe you'll get some urges she'll take care of you. Couple kids might come along, she'll take care of them you won't have to do a thing."
"Well I like the sound of that" replies Adam, "But what's that going to cost me?"
"An arm and a leg." says God
"What can I get for a rib?"