Are we really doomed to mechanical and material breakdowns in our skeletons shortly after we reach adulthood? It is true that bone loss with age in humans is nearly universal. It has been documented worldwide in both living and past populations, as well as non-human primates. And though bone loss may begin after bones fuse, it accelerates during mid-life (after age 40) and continues after mid-life in humans. Increased bone loss is concurrent with an increased risk of fracture, decreased mobility, and even in industrialized societies, increased mortality. Why do humans live long past the years when bone loss begins?