The Five Ages of the Human Brain, Revealed

Scientists analyzing nearly 4,000 brain scans from infancy through old age have identified five major “epochs” of human brain development, each separated by dramatic turning points at roughly ages 9, 32, 66, and 83.

These findings show that the brain does not evolve gradually but instead shifts into distinct eras marked by changes in wiring efficiency, grey and white matter growth, and overall network structure.

Childhood is defined by rapid synaptic pruning, adolescence by increasing connectivity efficiency, and adulthood by long-term stability before the brain transitions into early and late ageing phases.

Researchers say these patterns may help explain why mental-health conditions often emerge during adolescence and how age-related decline takes shape, offering new insights into vulnerability, cognition, and lifelong neurological health.