Why do bog acids react differently with the bones of the body than they do with organs, hair, and skin?

Bog acid, also called humic acid, has a remarkable ability for preserving bodies for thousands of years. Throughout Northern Europe, many people have either been buried in bog or have fallen into a sinkhole and their bodies become preserved in the unique chemistry of the bog. Bogs are essentially layers upon layers of muddy, rotted peat moss, which retains a lot of acidic moisture. In this anaerobic, acid environment, the hair, skin, and organs of a human body are essentially pickled! Depending on the acidic content of the bog, bones may be dissolved while the hair, skin, and organs remain in tact. Bones are comprised of primarily collagen and mineral, and the calcium and phosphorous contained in bone are easily dissolved by acids. So while the soft tissues are preserved by the humic acid, the bones are eaten away! Sometimes bog mummies are uncovered looking very flat or shriveled because there is no longer any skeletal structure filling out the soft tissue.