FIGURE 4.2 Height differences Throughout childhood, boys and girls are similar in height. At puberty, girls surge ahead briefly, but then boys, on average, overtake them at about age 14. (Data from Tanner, 1978.) Recent studies suggest that sexual development and growth spurts are now beginning somewhat earlier than was the case a half-century ago (Herman-Giddens et al., 2001).

Marili Forastieri/Photodisc/Getty Images