The importance of grandmothers in the lives of their grandchildren is underlined in a study published today. But the research showed that it was only granddaughters who were likely to do better with their paternal grandmothers involved in their early lives. In contrast, the presence of paternal grandmothers had a detrimental effect on the survival of their grandsons. The discovery supports the idea that grandmothers have played an important role in human evolution and could explain why human females – alone among the animal kingdom – live well beyond their reproductive age. Molly Fox of Cambridge University and her colleagues tested out the idea by analysing the birth and death records of seven populations in Asia, North America, Europe and Africa who had lived in different periods going back to the 17th century. They looked at infant mortality in the first three years of life and found that it differed depending on whether paternal or maternal grandmothers were present in a grandchild’s early life. ‘The presence of a paternal grandmother in all seven of the populations had a harmful effect on grandsons because her presence was linked with an increase in mortality,’ Ms Fox said. […]