Boneheaded
By the time they are five years old, most people have a firm grasp on the idea that calcium is the most important part of bones (among other biological things, but these are less significant). Because milk helps us gain weight and get stronger, our parents made sure we knew how important it was to drink it when we were young.
Anyone who believes that the material that makes up our bones is wood has never been educated about the human body. Our bones are made of a material called hydroxyapatite. We are opting to stay with our tried-and-true skeletons that are formed of calcium, even though the thought of tree-people is tremendously interesting.