祖父母在身边有利于保护人类物种的生存

　　They dote on their grandchildren, offer a treasure trove of wisdom and provide an invaluable babysitting service.

　　But it seems grandparents have a more crucial role – survival of the species.

　　Their practical and financial support helps keep youngsters fit and healthy, while their love and ability to listen helps children and teens get through difficult periods such as the divorce of their parents.

　　The conclusions come from Swiss and Australian researchers who analysed previous studies from around the world to pin down the role of grandparents. Several studies have linked grandmothers, in particular, with survival of the species.

　　A maternal grandmother, a child's mother's mother, is particularly nurturing. This could be because they can be more certain than any other grandparent that the child is part of their genetic line, with DNA that has not been tainted by affairs, and so worth the investment.

　　Maternal grandfathers produce the second highest level of care, followed by paternal grandmothers. Paternal grandfathers generally show the least interest, the journal Psychological Science reports.

　　University of Western Australia researcher David Coall said grandparents may also be motivated by the thought of having someone to take care of them when they grow old. If this is the case, they will shower their attention on the grandchildren whose parents are most likely to reciprocate in the future. Children don't just benefit from better physical health if a grandparent is around – the emotional support can also be of huge value.