When Bones Keep Growing: What Adolescent Hands Reveal About Human Development

Human growth is often narrated as a clean arc. Childhood stretches into adolescence, adolescence closes with puberty, and adulthood arrives with a skeleton that has settled into its final form. It is a comforting story. It is also wrong.

Placement of metacarpal total length and width measurements for the MC2 (A) and MC3 (B). Blue lines represent guides used to find the total lengths and perpendicular midpoints. The dark purple line indicates the total width at the midpoint; the yellow line indicates the medullary width at the midpoint, measured along the same line as the total width.

A new longitudinal study¹ of adolescents and young adults shows that even after the hormonal storms of puberty have passed, the human skeleton continues to quietly remodel itself. The evidence comes not from dramatic changes in stature or limb length, but from the slow thickening of cortical bone in the metacarpals, the slender bones that form the framework of the hand. These changes extend well into the late teenage years and beyond, challenging assumptions that have shaped biological anthropology, forensic science, and interpretations of the fossil record.