[AnotherUnixGeek]

Growth accelerators in our food chain? Chemicals in our water? Seems to me that 50 years ago girls did not enter puberty until their early teems.

Childhood obesity. The body requires a certain amount of weight and fat before puberty begins, and obese kids are meeting those conditions earlier and earlier in their childhoods.

[roses of sharon]

Yes, and it has been reported for years that serious gymnasts have delayed onset of puberty/menstruation.

Diet and exercise...body fat is the most likely explanation.