Could we be evolve to be fertile for longer?
The increase in women become mums later in life may lead to women being fertile for longer, researchers have suggested.
With many women waiting until they’re older to have babies, it’s just those with longer lasting fertility genes that will successfully become older mums. This could mean the average fertility span will get longer as their genes pass on to their children, reports the Telegraph.
In the past, women would marry young and if widowed were too old to get re-married, so early motherhood was favoured. But today, women don’t settle down and try to fall pregnant until they’re older. This trend might lead to fertility starting to favour older women, the University of Sheffield’s study indicates.
The study analysed the survival and marriage histories of 1,591 women, using 18th and 19th century Finnish records - a time when marriage was the norm. It seems having children young was pretty standard, and a limited portion of the population had the opportunity to have children at older ages because of the high chance of becoming a widow.
In our society though, women don’t start families as young because they tend to settle down later, said Duncan Gillespie, from the Department of Animal and Plant Sciences at the University of Sheffield.
"As a result of this, the natural selection maintaining young-age fertility might weaken and the relative strength of natural selection on old-age fertility could increase, something that could potentially lead to improvements in old-age fertility over many generations,” explained Duncan.
"Now family-building appears to be increasingly postponed to older ages, when relatively few women in our evolutionary past would have had the opportunity to reproduce.
"As a result, this could lead to future evolutionary improvements in old-age female fertility.”