Reproduction speeds up ageing

Reproduction speeds up the ageing process, however those that reproduce later in life will live longer, according to recent report in Science.

Dr Carla Sgro, Postdoctoral Research Fellow at the University of Queensland Department of Zoology and Entomology, working with Dr Linda Partridge, of University College London Department of Biology, studied the effects of reproduction in the fruit fly Drosophila melanogaster at various stages of life.

"We were aware from previous studies that reproduction decreases life expectancy but were unsure about the reasons," said Dr Sgro.

"This study shows that it is reproduction early in life that does the damage. However, the effects are not immediate. Early reproduction has impacts that are only apparent in increased mortality rates at advanced ages."

Dr Sgro selectively bred different strains of fruit fly that either started reproducing early in life or late in life. The strain that started breeding earlier had reduced life expectancy.

To confirm that the cause of earlier death was due to reproduction early in life, both strains were made infertile so that they did not reproduce at all. Both strains of sterile flies then had similar life expectancies.

"Reduced life expectancy is not solely related to the wear and tear on the body caused by reproduction. Instead, early reproduction starts genetic processes which are beneficial at first, but impose a toll later on which result in the flies reaching their full life span earlier," said Dr Sgro.

Although the work was done in fruit flies that have an average life span of around 40 days in the laboratory, studies of human mortality statistics support the idea that higher rates of reproduction early in life lead to earlier deaths.

For more information contact Dr Carla Sgro, UQ Department of Zoology and Entomology (telephone 07 3365 9191) or Jan King at UQ Communications (07 3365 1120).