A new study has revealed that the interaction between extended family members is dependent on whether they are related through the mother or the father. The study also showed that maternal grandparents are generally more attached to their grandchildren than paternal grandparents.
This, says author Thomas Pollet and colleagues at Newcastle University and the University of Antwerp, Belgium, is because maternal grandparents go the extra mile for their grandkids when it comes to maintaining contact with them.
The findings revealed that for grandparents living within 19.5 miles (30 km) of their grandchildren, over 30pct of the maternal grandmothers had contact daily or a few times a week.
Around 25pct of the maternal grandfathers had contact daily or a few times a week. In contrast, only around 15 pct of the paternal grandmothers and little more than 15pct of the paternal grandfathers would have contact daily or a few times a week.
Mr Pollet said that people ensure that they meet their maternal family members during festive seasons.
"As the festive period approaches, we can still see that family get-togethers are integral to the celebrations. Many people will be going the extra mile to ensure they meet up - and we've found that's particularly important if family members are related through mothers," he said.
The researchers found even after divorce maternal grandparents make an extra effort.
"Even in families where there has been divorce, we found consistent differences - grandparents on your mother's side make the extra effort," he added.
"We believe there are psychological mechanisms at play because throughout history, women are always related by maternity whereas men can never be wholly certain they are the biological father to their children," said Pollet.
Family members related through mothers (matrilineal kin) are predicted to matter more than those related through fathers (patrilineal kin).
The study conducted over 800 grandparents from a representative Dutch sample revealed that maternal grandmothers might go an extra mile to visit their grandchildren.
The research is published in the latest edition of the journal Evolutionary Psychology.