Genesis, missing ribs, and penis bones
But I really wanted to mention this because of a cute hypothesis that I first encountered through Daniel Quinn's Ishmael, and that is that the "rib" is actually a bone in the penis called a baculum used to help erections that most mammals have, but humans have lost. The site above gives a good explanation of this:
Most male mammals have a baculum, a bone for stiffening the penis. Humans are one of the rare exceptions, relying on hydraulics instead. Genesis 2:21-23 could refer to its removal from Adam. A baculum, unlike a rib, is associated with reproduction. The closing of flesh mentioned in Genesis 2:21 could refer to the raphe, a seam on the penis and scrotum. Biblical Hebrew has no word for penis, so another term would have to be used. The Hebrew word for "rib" has other meanings such as the supporting columns in trees, or planks in doors; it could have referred to a structural support generally (Gilbert and Zevit 2001).
If you like that interpretation of the rib, you might also like the rest of Quinn's interpretation of Genesis 2.4, the story of Cain and Abel. His thesis is basically that the story was actually written by the Semites, the nomadic herders who preceded the Hebrews, and is an account of the farmers coming out of the Caucus mountains and slaughtering the nomads in the Arabian peninsula (such as the Semites). The Semites (Abel) were the ones God chose (of course), and the angry farmers (Cain) killed them out of jealousy, and then God marked them. Because the Semites were dark and the people from the Caucuses were white, according to Quinn the "mark of Cain" is being white.
The story was part of Hebrew tradition and as such got incorporated into Genesis, but since the Hebrews were farmers it didn't make much sense. Quinn's interpretation sounds very plausible (and even likely), but it's hard to ascribe truth to anything like this. At the very least, it's quite interesting (as is the rest of his work), definitely worth checking out.