The age of menarche has fallen as child health has improved. Although there is ample evidence of delayed puberty being associated with poorer childhood nutrition, menarche is also influenced by prenatal factors. In particular, early onset of puberty is reported in children who have migrated from developing to developed countries. Evolutionary perspectives suggest that these effects can be explained by adaptive mechanisms. They also provide an explanation for the human pubertal growth spurt. In the past few decades, as puberty has advanced, biological maturation has come to precede psychosocial maturation significantly for the first time in our evolutionary history Although this developmental mismatch has considerable societal implications, care has to be taken not to medicalize contemporary early puberty inappropriately.