Too big for their brains

Peter Gluckman says the average age girls exhibit the first signs of puberty has fallen to 8, but brain development doesn't come until 16. Picture / Jane Ussher

We've all seen it. The 11-year-old girl in the midriff-baring hipster skirt, small breasts just denting her boob tube, arching her eyebrows at a group of bemused boys - and we've shuddered.

But no, says Professor Peter Gluckman. This is natural. The way it is. Over the past 50 years the average age at which girls exhibit the first signs of puberty has fallen to 8 years old. Meanwhile brain development - including how to say no - is stuck where it always has been, around 16.

This gives kids a gap of five to eight years with their hormones raging and their brains lagging way behind. The reasoning part of the brain doesn't hook up properly until they're 25, so this not-quite-mature period stretches out to age 17.

The problem is the same for boys: earlier puberty contrasted with static or even delayed brain development.

This leaves adolescents, their parents and society with a problem. Developed bodies and surging hormones crossed with a world that treats them as children on one hand and constantly reminds them of their sexuality on the other, adds up to the kind of frustration you see every weekend at the city's shopping malls. Young people demand freedom. Parents cling to control.

Worse, says Gluckman, the gap is widening. Puberty is getting earlier at the rate of a month's fall every two or three years. "The age of menarche [the first period which comes roughly three years after the first signs of puberty] has fallen by about three years in the last 100 years, if not more, meaning the average age of puberty is 12, compared with 16 for our grandmothers. That's about a month [fall] every two or three years. It may not sound like much but [in evolutionary terms] it's a dramatic difference."

Compounding all of this is the way today's youngsters are kept dependent for longer than ever before. Three or four generations ago puberty marked a rapid transition from child to adult.

"In Nelson's time a midshipman in the Navy was 12 years old. Would you put a 12-year-old in charge of a battleship?" asks Gluckman. "Two of my grandparents were in business by age 12. That doesn't happen now."

While it was possible to treat young teens as mature people hundreds of years ago, modern society needs more time to get to grips with them. "We now live with a complexity that was never required before, which is compounded by expectations and pressures that come from the impact of media," says Gluckman. "It's also possible, though not certain, that the structures of society mean it actually takes longer to mature as an adult."

In other words, faced with large social groupings (big cities), multiple influences (media, advertising, peer group and family pressures, social mores and expectations), and fast moving technology (internet, email, mobile phones, iPods), young brains may develop more slowly.

Certainly, society is giving less responsibility to young people. School lasts until we're 17 or 18. The job market is complex, meaning the training needed to get a job often extends to age 25 and even through to 30.

As Gluckman says, "For the first time in our evolutionary history biological maturation precedes, by a number of years, the age of psychosocial maturation and the age at which the individual is accepted as an adult."

This long physical and psychosocial mismatch points to future problems. Both sexes in the age group show signs of frustration. The violence, crime and car accident statistics for young males, teased into thinking they're invincible by their testosterone-driven brains are legendary. Adolescent women are showing up more in violent crime, bullying and binge-drinking statistics - and we have one of the highest teenage pregnancy rates in the world.

Says Gluckman: "We can't pretend kids can go for 10 years with their hormones raging and not have the inevitable biological responses and just deal with it, to be crude, by telling them to keep their legs crossed. Young peoples' brains and bodies are mismatched."

The question Gluckman cannot answer is how society should deal with these sexually mature but intellectually and socially immature adolescents. He is not in favour of suppressing their hormones with drugs.

Dr Sue Bagshaw, mother of four grown children, and a specialist in adolescent mental health will appear with Gluckman when he talks about evolution of the adolescent brain at the Liggins Institute next month.

The answer, says Bagshaw, also 57, is to streamline the handover of power from parents to children - and to time it right. There are two things to consider when looking for signs that your adolescents are ready for more independence. One, where are they in terms of reasoning? Are they still literal thinkers or can they talk ideas and theories? And two, where are they in their journey in terms of adult responsibilities? "Are you looking after yourself, getting yourself healthy, getting yourself money?"

She talks about how all young people and children need great warmth, high consistency and clear boundaries plus the right sort of parenting to make the transition to independence. The four typical styles of parenting are: permissive (sit anywhere you like); neglectful (is there a chair?); authoritative (sit down, shut up, listen and learn and we'll talk about it); and authoritarian (sit down, shut up, listen and learn).

The problem is that most people learn their parenting style when their kids are around 2 and need the security of "authoritarian" parenting - which needs to be modified to "authoritative" for adolescents. As Bagshaw explains, both groups are grappling with the need to separate from their parents, but in a different way and need different handling. "Two-year-olds are trying to separate from their parents physically [wanting to put their own clothes on, feed themselves] and teenagers are trying to do it emotionally.

"Authoritative is what the research says works the best with adolescents. Parents need to learn how to negotiate, how to hand over power, not too fast but not too slow - and they need to learn they're the coach on the side. Not the big dictator."

And how do you control a young person's sexuality until they're old enough to unleash it? Some societies keep them apart till they're allowed to reproduce. Others make sure they marry early, say 15. Other, mostly Western, societies ensure they take responsibility and accept contraception.

"But there's a dilemma to me," says Bagshaw. "You teach self-respect, access to contraception, but sex? Not always. I think we should delay [sex] as long as possible to give the frontal lobe time to catch up ... to be skilled enough to make good decisions."

Apart from infections and the physiological implications of young pregnancies, the real damage caused by early sex is emotional, says Bagshaw. "That happens if your brain's not in gear and you get involved and dump each other. It can be quite hurtful emotionally; you don't have the skills to do it in a less hurtful way. Friendships break up and come together and that's fine. When sex is involved that adds a totally different dimension."

The ultimate task is to help your young person become a contributing member of society, to leave the world a better place than he or she found it - and that can start before they can talk. "You've got to work yourself out of a job."

Drop in puberty back to our roots

Why the sudden drop in age before the onset of puberty? Gluckman argues that we are simply returning to our evolutionary roots. "In crude evolutionary terms, humans would have evolved to have physiological and psychological maturation at roughly the same time," he says. And if you were old enough to breed, you were mature enough to be a parent.

Puberty always related to nutrition. In Paleolithic times when we were all hunter-gatherers, life was relatively simple, short and brutal. The average life expectancy was 25, but there was enough food to go round; children who survived were well-nourished, and the average girl reached menarche at seven to 13 years.

The gradual delay in the onset of puberty began with the population explosion of 10,000 years ago when agriculture developed, people clustered into villages to work the crops and malnutrition and infection first appeared, with even more precarious childhood development and a delay in the onset of puberty.

From there, says Gluckman, social complexity grew: the development of social and power structures, kingdoms, feudal systems, tax and tithing. "The skills you needed to be an adult got more complex and that's just continued and continued, I would argue, in an exponential fashion."

The most delayed puberty was seen in the 16th-18th centuries when girls had their periods, on average, at 16 or older. Then, about 200 years ago, with the development of early science, child health started to improve and puberty started to come back. "That's accelerated over time."

With the formation of a different kind of society, the age of acceptable maturation, in psychosocial terms, rose quite rapidly, from 12 to 15 100 years ago to 20-plus years now. Meanwhile, the age of puberty has fallen from, say, age 15 to younger than than 12.

"All our systems, be it our school structure, customs and mores, need a fundamental rethink," says Gluckman. "Nutrition and child health has improved to the point where puberty may fall to younger ages. Society will get more complex, not less, so children will take a long time to accumulate the life-skills to be adults.

"The media will continue to drive messages to sell their products based on reminding kids of their sexuality and their sex maturation, which reinforces the very thing we don't want to reinforce. I think we have a fundamental problem in society. And I do not expect we can put the genie back in the bottle."

Deeper questions still wait to be answered

For Peter Gluckman, founder of the Liggins Institute and one of our most decorated biological scientists, the mismatch between psychosocial development and puberty is only a fragment of the big story - and reflects his personal urge to move on to a different kind of science.

"Puberty's a good illustration but it's a much deeper, greater, issue," he says, going on to talk about his new book. Written with a British-based colleague, Mark Hanson, and called Mismatch: Why Our Bodies No Longer Fit Our World, it is published by Oxford University Press and will be available in Britain next month and New Zealand in February.

At 57, with more grey than black in the beard, less hair on his head and dressed in comfortable corduroy, Gluckman has reached a point where he wants his intellectual effort to go into thinking through big, deep issues.

He resents spending 60 per cent of his time chasing funding for the 4-year-old Liggins Institute and looks exhausted after spending months working on the book from 10pm till 3am.

What he increasingly wants "is the time to ask the deeper question of why things happen rather than what has happened.

"We're the first people in a very long time, if ever, to ask why certain aspects of human development occurred the way they did. I take enormous pride in what we've built here. Our science is ground-breaking.

"We've done much work round the issue of how early life events have consequences for the rest of life. There's a big paradigm shift about what we're thinking about in science.

"And I must admit I'm getting nervous. We have a lot more to contribute - what if we don't have the capacity?"

Hear the facts

Evolution and the Adolescent Brain, with Professor Peter Gluckman and Dr Sue Bagshaw.
* The Liggins Institute, Wednesday, September 6, 5.30pm.
* For bookings phone (09) 373-7599 extn 86691.