There have been a number of pieces lately questioning the widespread claims that puberty has been getting earlier due to chemicals such as Bisphenol A. I suspect these critics are correct.
There is a an easy to read piece about the issue here.
No one disputes, by the way, that the age of first period, or menarche, declined from about ages 14-15 to 12-13 between 1900 and 1960. Some critics, and again, I suspect they are right, suggest that the sexual revolution was largely driven by this earlier decline in the age of puberty and not by the social factors often given the credit.
More Rob Roy tomorrow by the way.