New evidence suggests that natural selection is leading women to have their first child at earlier ages. This is shown to be an inherited evolutionary change that is taking place despite the influence of social factors such as religion and education.
The findings, by a team of British, Australian and American scientists, show for the first time that both genetic and social factors, such as religion and education, are having a profound effect on the timing of human reproduction. These factors are influencing human evolution to a greater extent than at any time in the pre-history of humans.
Writing in the latest edition of the journal Evolution (1), the researchers reveal that women who reproduce earlier in their lives have higher Darwinian fitness (2). They show that this trend is being passed on from generation to generation through natural selection - the process where successful genes pass on to successive generations through evolution.
These findings are different from previous studies of pre-industrialised populations (3), where the age at women start their periods is the best predictor of the number of children that they will eventually produce.
The differences in behaviour are probably due to changes in society that occurred along side industrialisation, such as freely available contraception for women and better healthcare and nutrition for children.
Dr Ian Owens of the Department of Biology and Biochemistry at Imperial College, an author on the paper, described the significance of their research:
The most important finding is that changes in society, such as freely-available birth control for women and eradication of several important childhood diseases, which have taken place in the last 20 to 30 years will probably lead to genetic changes in humans through evolution.
We can say this because the sorts of factors that we found that are associated with reproduction now arent the same ones that people had found in pre-industrial pop
'"/>
Contact: Taslima Khan
taslima.khan@ic.ac.uk
44-20-7594-6712
Imperial College London
22-Apr-2001