Earlier puberty & the causes?

Although still a matter of much controversy - it seems like females are reaching puberty sooner than in times past - why? An article from Britain's Daily Mail summarizes some of the hypotheses out there:

So what is the cause of precocious puberty? While experts aren't able to give a single explanation, numerous theories exist.

One is that improved nutrition is a factor, as the onset of puberty is believed to be linked to physical size.

Another theory is that the epidemic of childhood obesity is to blame: heavier girls begin their periods earlier due to an increase of the puberty-triggering hormone leptin, which is stored in fat cells.

"There is a relationship between childhood nutrition and the age that people pass through puberty,' says Mark Bellis, Professor of Public Health at Liverpool's John Moores University.

"Having a calorie-rich diet in childhood, and being obese, brings the age of puberty down."

Modern social conditions have also been touted as a contributory factor - with research suggesting that children from broken homes experience earlier puberty as the stress of a family breakdown alters the balance of growth hormones.

The arrival of a stepfather in the family home produces new and unfamiliar pheromones, chemicals which are believed to hasten the arrival of puberty.

"Single-parent families and divorce cause stress that can also change the age of puberty a little, too," says Mark Bellis.

Early puberty has even been linked to watching too much television - Italian researchers found that children who watched three hours of TV a day produced less of the sleep hormone melatonin, low levels of which play an important role in the timing of puberty.

The content of today's television may also be to blame, with young children subjected to increasingly sexualised programmes from an early age. Research has shown that watching such images produces increased hormones.

Another theory is that exposure to chemicals in the environment - which mimic the effects of hormones - is causing the drop in puberty age and disrupting the normal timing of sexual maturation.

Here are some links to articles concerning specific hypotheses:

Environmental pollutants
Obesity
TV