Is there some kind of moisture in bones, because how do they run tests on them to find out if they belonged to a male or female?
Julene, 11 1/2, Vancouver, Washington

Dr. dig responds:
Quite often an expert is able to decide whether a bone belongs to a male or female human or animal simply by studying its size and shape. In the human, for example, the pelvis and the jaw can all suggest gender. Bones contain nitrogen in their protein, and this is slowly lost over time when the bone is buried in the ground. By measuring the amount of nitrogen left in a bone, it is possible to work out its age. The Piltdown Skull--a famous English archaeological hoax which many people believed to be the "missing link" between people and apes--was shown to be a modern forgery when it was subjected to nitrogen, fluorine, and uranium dating.