What science tells us about the incredible shrinking childhood.
Now most researchers seem to agree on one thing: Breast budding in girls is starting earlier. The debate has shifted to what this means. Puberty, in girls, involves three events: the growth of breasts, the growth of pubic hair and a first period. Typically the changes unfold in that order, and the process takes about two years. But the data show a confounding pattern. While studies have shown that the average age of breast budding has fallen significantly since the 1970s, the average age of first period, or menarche, has remained fairly constant, dropping to only 12.5 from 12.8 years. Why would puberty be starting earlier yet ending more or less at the same time?