Geeking Science: Grandmother Effect

Photo by Aleksandar Popovski on Unsplash (Cropped by Erin Penn)

Family Matters

Our days may come to seventy years, or eighty, if our strength endures. (Psalm 90:10)

Why do humans live past their reproductive systems? Nearly every other species continues to have the females give birth until it kills them. This maximizes population potential. Homo sapiens are fairly unique in that the females have their reproductive system turn off about the time system breakdowns will prevent viable births. Also about the time their children are having children.

The 1960s came up with the “grandmother hypothesis” after observing surviving hunting and gathering societies. Grandmothers are better at gathering and were more able to provide their children food – so those children were healthier and the children’s children were more likely to survive childhood ills. The ability to NOT have children gave an evolutionary advantage to the family, and, hence, menopause. At least that is the speculation.

Studies by Kristen Hawkes of the University of Utah done in the new millennium expand this hypothesis. She found that while a mother with one child who is good at gathering food will have a healthier child, this advantage goes away with two children. Then it is all grandmother. (The article by John Poole has a link below in the Bibliography. The article focuses on the hypothesis of how needing a larger social structure to maximize food for healthy children results in humans being social creatures from a very, very young age.)

Recently two new studies based on modern evidence came out in Current Biology. Jonathan Lambert breaks them down for NPR in “Living Near Your Grandmother Has Evolutionary Benefits.” (see the link to the article in the Bibliography).

These studies are based on the early industrial age and show how the grandmother effect continues even in more modern societies. A 30% survival rate increase between the ages of 2 to 5 when the grandmother lives with the child – nothing like expertise and wisdom. Now this bonus drops away and reverses as the grandmother passes beyond 75 and she takes more care than she gives. Death rates also spike as the grandmother passes beyond “usefulness”.

“Our days may come to seventy years, or eighty, if our strength endures.”

If you are interested in where evolution, biology, anthropology and culture meet. Dig into the full articles, and maybe hit up the Current Biology scientific studies.



Bible. Psalm 90:10.

Lambert, Jonathan. “Living Near Your Grandmother Has Evolutionary Benefits.” February 7, 2019. – Goats and Soda. (Last viewed 2/8/2019)

Poole, John. “Why Grandmothers May Hold the Key to Human Evolution.” June 7, 2018. – Goats and Soda. (Last viewed 2/8/2019)