Children aged 10 and 11 are sexually mature, and neither they nor society are suitably prepared for the implications of that.

This is the message of Professors Mark Hanson and Peter Gluckman, whose review of the evolution of puberty is published online this week in Trends in Endocrinology and Metabolism.

Hanson and Gluckman, who respectively head the Centre for the Developmental Origins of Health and Disease (DOHaD) at the University of Southampton, and the Liggins Institute at the University of Auckland, New Zealand, researched the age of puberty stretching back beyond the Stone Age.

They found that Paleolithic girls arrived at menarche - the first occurrence of menstruation - between seven and 13 years. This is a similar age to modern girls, which suggests that this is the evolutionarily determined age of puberty in girls.

'This would have matched the degree of psychosocial maturation necessary to function as an adult in Paleolithic society based on small groups of hunter-gatherers,' they write.

Disease and poor nutrition became more common as humans settled, causing puberty to be delayed. Modern hygiene, nutrition and medicine have allowed the age of menarche to fall to its original range.

However, today there is a mismatch between sexual maturity and psychosocial maturity, with sexual maturity occurring much earlier. This mismatch is a result of society becoming vastly more complex, with psychosocial maturity therefore taking longer to reach.

'For the first time in our 200,000 year history as a species, humans become sexually mature before becoming psychologically equipped to function as adults in society,' explains Professor Hanson.

'All our social systems work on the presumption that the two types of maturity coincide. But this is no longer the case and never will be again because we cannot change biological reality. We have to work out a new set of structures - schooling, for example - to deal with this reality.'