The first derivative of human height growth velocity charts. The 3rd, 50th, and 97th percentile of first derivatives for both boys (solid lines) and girls (thin lines) were calculated from the US CDC 2000 data (http://www.cdc.gov/growthcharts). The upper part indicates the four pre-adult life-history stages: infancy (I), with its decelerating growth velocity, the stable growth of childhood (C), the decelerating growth of juvenility (J), and the up and down of growth velocity during adolescence (A).