The Secret Life of Bones

Beneath our skin lies an architectural marvel—the human skeleton—a dynamic living tissue that constantly remodels itself throughout our lives. What makes this possible are intricate biological processes that both build and break down bone matter. While we often hear about bone formation and strengthening, the equally important story of bone mineral dissolution remains largely untold.

Bone mineral is far more complex than commonly assumed. Unlike the relatively pure hydroxyapatite found in rocks, bone mineral represents a unique biological adaptation—a calcium-deficient carbonated apatite with distinctive substitutions and imperfections that make it both strong and chemically reactive ¹ .

Within living organisms, bone dissolution isn't a random process but a carefully regulated biological activity essential for skeletal health. Specialized cells called osteoclasts perform this intricate task through an impressive cellular machinery that targets aged or damaged bone tissue ⁹ .

Osteoclasts employ a sophisticated acidification mechanism to dissolve bone mineral. They produce protons through the action of carbonic anhydrase, which catalyzes the combination of carbon dioxide and water to form carbonic acid. These protons are then pumped across the cell membrane by specialized vacuolar-type ATPase proton pumps ⁹ .

When organisms die, their bones undergo entirely different dissolution processes governed by environmental conditions rather than biological regulation. This post-mortem alteration of bone, known as diagenesis, involves complex chemical and physical changes that can lead to either preservation or destruction of skeletal remains ⁶ .

Diagenetic processes begin immediately after death and proceed at rates highly variable depending on numerous factors. Extrinsic factors include temperature, moisture, soil pH, microbial activity, and water movement, while intrinsic factors include the individual's age at death, bone composition, and skeletal element involved ^{6 7} .

To understand the early stages of bone diagenesis, a comprehensive study was conducted using human ribs from six donors buried in clay soil typical of northern France. This experiment tracked chemical changes monthly over 12 months using Raman microspectroscopy—a non-destructive technique that provides detailed information about both mineral and organic components of bone simultaneously ⁶ .

The results revealed fascinating patterns of change. The mineral-to-organic ratio decreased significantly over the 12-month period, indicating progressive demineralization. Crystallinity increased consistently, suggesting that smaller, less perfect crystals were dissolving preferentially, leaving behind more mature crystals ⁶ .