The findings were made after an exhaustive three-year analysis of questionnaire data from 2,710 pairs of identical and non-identical twins held in the Australian Twin Registry (ATR) (4).
After removing the influence of differences in religion, education and the effect of the baby boom, the researchers still found heritable genetic differences in three key life history traits. These are the age at which women:
started their periods
had their first baby
reached menopause
Each of these traits was found to be genetically associated with fitness - the ability of an organism to reproduce itself because it is well adapted to its environment.
Out of the three traits it is the age that women had their first baby, which is most significantly associated with reproductive fitness. This means that genes influencing an early age of reproduction in the female population will become more common. In other words, womens genes will predispose them to start reproducing earlier.
Dr Owens believes this work has identified a genetic phenomenon that is likely to have many implications in terms of how human behaviour will change over the next few hundred years.
The influence of social factors on inherited genetic change
Evolutionary biologists have long agreed that the life history of modern humans has been moulded by evolution due to selection that occurred in the past.
Hotly debated however, is whether human life history traits are still under selection, and whether changes in human culture have led to new forms of selection.
Part of the twin data analysis aimed to discover the effect that social, psychological and historical factors had on the number and timing of children born to the 2,710 pairs of twins studied.
The researchers found many of the variations in the three traits were controlled by social factors such as religion and education (5). For example, Roman Catholic women had 20 per cent higher reproductive fitness than other
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Contact: Taslima Khan
taslima.khan@ic.ac.uk
44-20-7594-6712
Imperial College London
22-Apr-2001