The “grandmother effect”: a crucial role in demographic evolution – Collaboration between Université de Sherbrooke and Bishop’s

The “grandmother effect”: a crucial role in demographic evolution – Collaboration between Université de Sherbrooke and Bishop’s

From a biological perspective, menopause in women is puzzling: in comparison to what is observed in other species, it occurs much earlier, and long before the end of women’s life expectancy. This led researchers from the Université de Sherbrooke and Bishop’s University to wonder if the relatively early end of reproductive capacity for women might present advantages with regard to gene transmission, by helping their daughters to establish larger families.

Their findings, which are published today in the prestigious Current Biology scientific journal, constitute new supporting evidence to the “grandmother hypothesis.”

By studying the exceptionally well-detailed demographic data available on the first French settlers in Québec between 1608 and 1799, first author Sacha Engelhardt – a postdoctoral fellow at the Université de Sherbrooke, whose work was co-supervised by Dr. Fanie Pelletier, Canada Research Chair (CRC) on Evolutionary Demography and Conservation at the Université de Sherbrooke, and Dr. Patrick Bergeron, of Bishop’s University’s Biology Department – found that having a grandmother living close to her daughters was statistically associated with more grandchildren being born, and with an increased likelihood that those grandchildren would reach maturity.

“Research results suggest grandmothers played a critical role in Québec’s preindustrial population,” Dr. Engelhardt explains. “We were very interested in looking at the geographical effect on humans’ life events, such as the age of first reproduction, how many children were born and how many children reached the age of 15, for instance.”

“In our study, women whose mothers were alive had more children, and more of those children lived to the age of 15,” explains Dr. Bergeron. “Interestingly, the “grandmother effect” decreased as the grandmother-daughter geographic distances increased, suggesting that the potential for help may be related to geographic proximity.”

“The results show that daughters with geographically close living mothers on average were able to have two more children, and that the number of children still alive by the age of 15 increased by about one on average, compared to families where the maternal grandmother had passed away,” Dr. Pelletier explains. “This is a significant evolutionary advantage, especially considering that in parts of that period, sometimes up to about a third of children born did not survive their first year.”

To access the vast amount of data on which their conclusions are based, researchers collaborated with Dr. Alain Gagnon and Dr. Lisa Dillon, of the Université de Montréal’s Programme de recherche en démographie historique to access the vast amounts of data used to reach their conclusions. The study also benefited from using the Mammouth supercomputer of the Université de Sherbrooke’s Centre for Scientific Computing to analyze the data.

The research benefited from the financial support of the Fonds de recherche nature et technologie du Québec (FQRNT), the CRC on Evolutionary Demography and Conservation the Quebec Centre for Biodiversity Science, the Social Sciences and Humanities Research Council (SSHRCC), the Canada Foundation for Innovation (CFI) and the Natural Sciences and Engineering Research Council of Canada (NSERC).

About the Université de Sherbrooke

The Université de Sherbrooke is at the core of one of the three major research centres in Québec. Recognized for its sense of innovation, UdeS is a top-tier partner for national and regional governments to favour social, cultural and economic development. It also stands out through the rapid growth of its research activities in recent years, its successful technology transfers, as well as its entrepreneurial and open innovation initiatives in partnership with industrial and social actors.

About Bishop’s University

Founded in 1843, and located in Sherbrooke, Québec, Bishop’s University is a predominantly residential, undergraduate university. Our primary concern is offering students a quality education in the fine arts, humanities, social sciences, natural sciences, business and education. The residential aspect of our small size (2,400 full-time students) encourages students to develop close relationships among themselves and with their professors, and to immerse themselves in the complete Bishop’s experience.

Dr. Patrick Bergeron
Dr. Patrick Bergeron, of Bishop’s University’s Biology Department



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