Adam was hanging around the garden of Eden feeling very lonely.
So, God asked him, 'What's wrong with you?'

Adam said he didn't have anyone to talk to.

God said that He was going to make Adam a companion
and that it would be a woman.
 He said, 'This pretty lady will gather food for you, she will cook for you,
and when you discover clothing, she will wash them for you.'
 She will always agree with every decision you make, and
she will not nag you, and will always be the first
to admit she was wrong when you've had a disagreement.
 She will praise you!
She will bear your children and never ask you to get up
in the middle of the night to take care of them.
 'She will NEVER have a headache and will freely
give you love and passion whenever you need it.'
 
 Adam asked God, 'What will a woman like this cost?'

'An arm and a leg.'
 
Then Adam asked, 'What can I get for a rib?
 
Of course, the rest is history....

So a rib =