The suggestion that a woman’s reproductive history may affect her ability to have children in the future has been a puzzle to scientists for years.
But scientists today are saying that, believe it or not, that cockroaches, of all things, could hold the answer to why women who delay having children are less fertile than women who give birth in their teens.
In earlier research by biologists at the University of Manchester it was found that when female dusky roaches were prevented from mating they lost fertility in later life.
The roaches also became less choosy about who they mated with once they were finally let loose with the males.
Now Manchester University biologists have now turned to the mating behavior of the dusky roach, the Nauphoeta cinera, to try and find the reasons behind this.
Dr Patricia Moore from the University’s Faculty of Life Sciences says the cockroach is unusual in that it gives birth to live young, rather than laying eggs, even nurturing them in their first few hours of life.
According to Dr. Moore, the females also experience reproductive cycles and show age-related decline in fertility and provide an opportunity to examine the mechanisms by which females lose reproductive potential as they delay breeding.
Dr Moore suggests a natural biochemical reaction is to blame for the decline in the cockroaches’ fertility.
The insects which live for about a year, reach sexual maturity at six-days-old, so the biologists decided to investigate what happened if they delayed mating by two weeks.
Dr Moore says that, as they expected, the eggs that would have been fertilized had the female been allowed to mate were discarded through a natural, controlled process of cell death, called apoptosis, but they also saw that apoptosis began to occur in the cells of eggs that wouldn't yet have been used.
Dr Moore believes that there are complicated evolutionary arguments behind why perfectly healthy eggs should begin to die, and suggests that reduced fertility brought about by delayed reproduction occurs because evolution has not been able to adapt to what is an artificial situation, the cockroach is unable to refine getting rid of eggs that are no longer needed.
Moore says in humans this artificial situation is created by cultural influences that see women not giving birth until long after reaching sexual maturity.
A number of researchers have claimed that if a woman gives birth before the age of 25 it can delay her natural menopause.
The research is published in the science journal Evolution and Development.