Have you heard the one about the mother-in-law who improves family life?
A study has found that married couples with a mother-in-law living nearby have more babies.
Furthermore, historical records show these children are also less likely to die in infancy.
The research involved analysis of 300 years of church records, the most recent of which were from 2000. Virpi Lummaa of Sheffield University, who used the data to track births, marriages and deaths in farming communities in Finland, found that sons and daughters tended to marry younger if their mother was alive. They also had more children, and left smaller gaps between babies.
Dr Lummaa proposed that as the influence was only evident when a mother-in-law lived nearby, the affected families probably benefited from an extra pair of hands, as well as the additional love and attention the children received.
Her findings showed little difference between maternal and paternal mothers-in-law - but previous research into African families suggests that a mother's mother provides the greatest benefits.
This may be due to age; as men tend to marry later than women, their mothers are also likely to be older, meaning they may be less able to help raise their grandchildren.
Grandfathers seem to make less of an impact according to the Sheffield study, which was discussed at the Euroscience 2012 conference in Dublin. 'That doesn't mean they don't do anything,' Dr Lummaa stressed. 'It just doesn't translate into better survival of their grandchildren.'
- Daily Mail