There’s no biological reason for grandparents to exist, say scientists

IF you are a doting granny or grandad, this may come as a surprise.

Scientists said yesterday they can find no plausible biological reason to explain why grandparents exist.

Of course, we all know grandparents provide love and support for their children and grandchildren – and perhaps the occasional treat.

But from a strictly scientific point of view it is a mystery why humans have evolved to live past 50. In most animals there is no reason to stay alive once they have reproduced and the next generation has been raised.

Grandmothers pose a particular puzzle – and biologists have long been perplexed as to why older women carry on after 50 when they cannot have children.

Scientists at Edinburgh University said the unusually long lives of humans was an ‘evolutionary puzzle’ and that ‘natural selection cannot directly favour continued living in post-menopausal women or elderly men’. Writing in the journal Nature Ecology and Evolution, the authors examined theories that a grandmother’s role as a babysitter helps younger family members to thrive – perhaps giving more time for the younger generation to hunt and forage during prehistoric times.

For men, it has previously been suggested that genes for long life are passed on by older dads, gradually increasing human lifespan.

But in what is claimed to be the first attempt to assess these theories, the team said neither held up. They analysed family records of people born in Utah from 1860 to 1899, where the early, mainly Mormon settlers had no birth control – meaning the results reflect natural fertility. Scientists were surprised to find no genetic link between male longevity and the ability to father a child. They also found no evidence that having grandparents around led to children having better survival chances.

However, they suggest genes that keep men healthy in young life have the bonus effect of keeping them healthy in old age.

Dr Jacob Moorad, of the University of Edinburgh’s School of Biological Sciences, said: ‘Why we live beyond 50 has long puzzled scientists ... we are no closer to explaining why women live far beyond menopause.’