Fact or Fiction: Adam's Rib

And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof; And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man. Genesis 2:21-22 (King James Version)

I was asked recently whether it was true that women had a different number of ribs than men.

You may have heard this one before: Men have fewer ribs than women, either by a single rib or a pair. This notion follows from the biblical account of creation, whereby Eve was created from one of Adam's ribs and is used to support a literal interpretation of Genesis. But is it true?

The typical adult human skeleton has 206 bones and this number is the same for men and women. Of these, the ribs account for 24 (2 x 12). Seven of these pairs are connected to the sternum by cartilage, 3 are connected to the cartilage of the ribs above and 2 pairs, called floating ribs, are not attached to the sternum at all. These numbers are the same for men and women.

There are abnormalities that can alter the number of ribs. One such abnormality is a cervical rib which can cause thoracic outlet syndrome. A cervical rib is an extra rib arising from the seventh cervical vertebra, above the first rib ("normal" ribs are joined to the thoracic vertebrae). They are present in about 0.5% of the population. One large study of 10,000 radiographs looking at congenital rib abnormalities showed that women more often have cervical ribs, with a rate of about a 2.5 to 1 compared to males. This may be a reason for the propagation of the idea that females have more ribs than males, but in the typical, normal skeleton males and females have the same number of ribs.