For years, scientists have tried to find an answer to a puzzle. What is the evolutionary advantage for human women to survive past their reproductive years? In other words, do grandmothers matter for the survival of the species?
Grandmothers Matter for Grandchildren’s Survival:
A few years ago, scientists at the University of California, Berkeley, analyzed historical data available from four northern European countries. They found that when there were more older, presumably postmenopausal, women present, deaths due to childbirth dropped (Evolution, Medicine, and Public Health, Aug. 23, 2017). There’s no way to tell if the presence of elders caused better survival of young women in their early childbearing years. However, it does seem that grandmothers matter.
Grandmothers can also be important in helping young children survive. Initially, Finnish researchers analyzed detailed historical records for the 18th and 19th centuries in four regions of the country. These demonstrated that when maternal grandmothers were present, more children were born and they were more likely to survive (Scientific Reports, Feb. 11, 2021). Paternal relatives (the mothers’ mothers-in-law) did not seem to contribute to grandchild survival.
In a more detailed analysis, the investigators examined whether having the grandparents present in the household made a difference (Behavioral Ecology, March 27, 2023). After all, if food is limited, having more mouths to feed might not be an advantage. The biggest benefit for grandchild survival was when grandparents were alive but not living in the same household.
Infections Take Less Toll When Grandmothers Are on the Job:
In their most recent analysis, these investigators utilized historical demographic data from a dozen different regions of Finland (Proceedings of the Royal Society B, May 31, 2023). Specifically, they asked why, when grandmothers were present in a household, children were less likely to die before adulthood.
This effect was most notable for deaths due to smallpox, diarrhea or respiratory infections. Grandmothers didn’t seem to protect kids from dying of accidents or measles.
The scientists wondered if perhaps grandmothers encouraged parents to vaccinate children against smallpox. That is one medical intervention that was available in this pre-industrial period. However, no evidence supports that hypothesis. Whatever the reason, grandmothers matter because they offer life-saving assistance and knowledge when children are sick.
