'Twixt sex and reproduction

Reproductive function in women is dependent on production by the hypothalamus of gonadotropin releasing hormone (discussed on WebPage 3). GnRH is very sensitive to body weight.

The physiological result of this sensitivity is that the improvement in human nutrition that's taken place in many societies in the last 100 years has produced an important lowering in the age at menarche from 15 to 16 years old in the mid-nineteenth century (and still today in primitive societies) to 12 to 13 in today's developed societies today.

At the same time, the need for enculturation of our young is raising even further the age at which emotional and educational maturity are reached.

This counter-K-selective long-term trend in age at menarche has increased further the gap between the ages of physical and mental maturity for adolescents -- a gap that's already had clear and deep social consequences in the West.

Biology seems always to have been destined to play havoc with nineteenth century morals and twentieth century ideals. I explore the implications in an essay published in 1999 in the Medical Journal of Australia, called Sex, reproduction and impregnation: by 2099 we won't confuse them.