Definition
Childhood adversity refers to stress, deprivation, neglect, and trauma experienced early in life — when the brain is still under construction. Because development is a sequence of sensitive periods, the timing of a hardship matters as much as its severity.
Sapolsky treats early experience as one of the deepest layers of behavioral explanation. To understand why an adult behaves as they do in a charged moment, he asks what their adolescence and childhood were like — and, before that, what their fetal environment supplied. Adversity at those stages tilts the trajectory of the brain itself.
Why it matters
How it works
Early adversity often acts through the stress response. Sustained childhood stress keeps glucocorticoids elevated during the very window when brain circuits are forming. The result is a brain calibrated for a dangerous world: a more reactive amygdala, a slower-developing prefrontal cortex, and an altered hippocampus. Epigenetic marks can lock parts of this calibration in, so an adaptation to early hardship persists long after the hardship is gone.