Children are entering puberty younger.
There appears to be a racial factor: Hispanic and white boys go through puberty at an average age of 10 and African-American boys show signs of it at nine. Nearly one in 10 white boys and one in five black boys show some signs of it at the age of six.
Dr Robert Scott-Jupp, consultant paediatrician at the Royal College of Paediatrics and Child Health in London, warned: "I would be slightly alarmed if somebody read about this, noted that boys are going through puberty at six and then didn't take their child to the doctor if he showed signs of puberty at that age. It may turn out to be very early puberty, but that's very rare and it could be another condition causing it."
In the United Kingdom there is no consensus that puberty is occurring earlier in boys; the range for the first signs is still taken as nine to 14. In girls, that range is eight to 14 and this has got earlier, although not by the margin you might imagine. In the 1950s and 1960s, the average age for first period was 13 and a half; now it is 12 years and 11 months.
The racial element of the US study should also be viewed critically, Scott-Jupp said: "In any study in the US that appears to identify differences between the races, the difference usually turns out to be that black families are poorer and more socially deprived."
But the fact remains that puberty is much easier to define in girls – it is the first period – and, possibly as a result of that, there have been many more studies in which a much firmer conclusion has been reached. If it turned out in the long term that boys were also maturing faster this would not come as a tremendous surprise.
So what could be causing it? What challenges does it create? How would a mature society deal with a physiological trend like this?
Pop psychology has posited the idea that girls' early menarche (first period) is associated with an absent, distant or in some way deficient father, but this seems to be a misreading of an aside in a study that found a link between obesity and early puberty. Diet is by far the most important factor – medics and psychotherapists both say that better nutrition is the definitive change in children over the past century.
Phillip Hodson, fellow of the British Association for Counselling and Psychotherapy, said: "The best way not to go into puberty is starvation. Early puberty is about great nutrition in the classic sense of getting access to good protein, good vitamins and minerals." He underlines that earlier puberty is often accompanied by a commensurate growth in height.
One other theory "for which there is no evidence at all", Dr Scott-Jupp notes cheerfully, "is that more people being exposed to light for more hours of the day, in the form of artificial light, has an effect on brain chemistry". It makes your brain think you have been alive longer, I suppose, and that it is time you got married. This does seem a little far-fetched.
If diet is the cause, it would explain why Americans have seen results in boys faster than we have here: children there have a more calorific diet.
There are studies relating early periods to depression in adolescent girls, but the crucial anxiety hanging over the conversation is that, if children are going to go through puberty earlier, does this mean they will become sexually active earlier? Will their emotional maturity match their sexual development and, if it does not, is it realistic to expect that one can persuade them to hold off until it does?
Scott-Jupp said: "There's a tendency to confuse puberty and adolescence. Adolescence follows puberty; they're not concurrent."
Puberty is the physical change and adolescence the psychosocial transition from childhood to adulthood. Just because a boy has developed pubic hair does not mean he has made the leap. As Hodson put it: "Sorry to be vulgar – from Lego to leg-over."
Nevertheless, Hodson said, "what we have to say is that if there were very early aspects of puberty occurring, you couldn't just assume that your six-year-old who has started showing signs of puberty would become the 10-year-old that you expect. You might therefore need a better set of disciplines around his life, because he might well have the rage and the strength and the sexuality, or flashes of those things, that a much older person might have."
The idea of hypersexualised 10-year-olds worries Hodson much less than the timeless experience that children who are different get bullied. When you are 10, having a faint moustache could be as devastating for your popularity as having horns and a tail. "The mercilessness of children is well known. The difficulties are compounded in the age of the social media and the way in which people can be instantly, broadly vilified. But the anxieties of those with early puberty are dwarfed, to a degree, by the anxieties of those children who get left behind."
Scott-Jupp, likewise, focuses on pragmatic considerations above hell-in-a-handcart predictions of radically earlier sexual awakening.
"It's a practical problem for young girls who start their periods while they're still at primary school. They're not very well set up; there's not much privacy. There's the important educational aspect that girls need to be taught about puberty at an earlier age so they're not taken by surprise."
But this is politically charged – you cannot just shift the age at which education about puberty occurs; that leads inevitably to a conversation about sexual characteristics and to a conversation about sex. A UK health service-funded website and smartphone app, Respect Yourself, was slated this week for considering questions such as "what's the average age to lose your virginity" and "where can I buy a Karma Sutra? (sic)" appropriate to an audience of 13 and over (even though the answers – "17" and "a bookshop" – might not strike one as terribly controversial. I do not think the compilation of these questions is liberal, or sexualising children. I think it comprises questions they have genuinely been asked.
Signs of puberty are a pretty poor index of readiness for sexual relations, as I discovered this year through Save the Children's family planning campaign. In cultures where people still marry young – at 12, 13 or 14 – and have children as soon as they marry, the physical consequences are appalling: birth weights are pitiably low and the mortality rate of mother and baby extremely high. And this is before problems such as fistula manifest later on, in the mother's twenties, and see her socially ostracised for being incontinent.
Nature tolerates a huge grey area, which could span a decade, when you have sexual traits but are not ready for sex, or when you are ready for sex but are not ready to procreate. Socially, I think we would all prefer it if there were no ambiguity, if all the signs of puberty arrived at once on everybody's 16th birthday. Unless we are prepared to seriously limit children's portion sizes we are going to have to get used to things being a little more complicated. – © Guardian News & Media 2012
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