Grandmother Hypothesis

 

Did you know that only two types of animal life actually outlive their fertility? Only humans and killer whales live longer than their ability to have offspring. Chimpanzees, the closest animal to a human, for example, usually die before their 50s, when they are still fertile.

Part of this is modern health care.  Not only do we live longer, but we also have a much better chance at surviving infancy.  But I think there is more at play than just better medicine.

The grandmother hypothesis is a theory to explain how a long post-fertile period (up to one third of a woman's lifespan) could confer an evolutionary advantage. One anthropologist at the University of Utah was studying a hunter-gathering group in Africa, thinking that she would uncover the origins of hunting.  Then, she noticed the many older women who seemed to be always busy, either collecting roots and plants, preparing meals, and taking care of babies and young children. It turned out that these old women played an important role in providing nutrition for the group, as much as the young male hunters and fighters. Much more important and crucial than food, though, was the role these older women played in the raising of their grandchildren.

Despite countless biological similarities, there are obviously many differences both biologically and societally. Not only do we live much longer than other mammals, our kids depend on their parents and grandparents much longer as well.  Heck, I know I still depend on my parents for support and love to this day!

By the time a chimpanzee is 7 years old, it’s gathering as much food as it will eat. But even in hunter/gatherer societies, human children pull their weight only when they are teenagers. Why would our babies be helpless for so long? That long immaturity helps make us so smart: It gives us a long amount of protected, nourished, and sheltered time to grow large brains and to use those brains to learn about the world we live in. Human beings can learn to adapt to an exceptionally wide variety of environments, and those skills of learning and culture develop in the early years of life.

Because it takes so long for us humans to mature—and it seems endless when one is dealing with a teenager!—mothers need help.  And that’s where grandmothers can help and provide such crucial assistance.  Believe it or not, in some hunter-gatherer groups, grandmothers could "relactate," actually producing milk after having already gone through menopause.

The "Grandmother Hypothesis" proposes that grandmotherhood developed directly as a result of our long childhood. In fact, grandmothers are exactly what allowed our long childhood, and the learning and culture that go with it, to emerge. In mathematical models, you can see what happens if, at first, just a few women live past menopause and use that time to support their grandchildren (who, of course, share their genes). The "grandmother trait" can rapidly take hold and spread. And the more grandmothers contribute, the longer the period of immaturity can be.

My mother, affectionately known as “GG”—Grandma Giebler—to my children, makes so much possible in our lives.  She is Edwin, Estelle, and Emerin’s primary babysitter.  She is the one my kids go to when they really, really, really want a buttered slice of bread for a snack.  She is their favorite place to ‘escape’ to for a sleepover.  Well, that’s actually a tie.  “Nana’s House” (Ellie’s parents’ house) is also high on their list.  And the kids, especially the older two, definitely keep an eye on the calendar and the clock, making sure their “GG time” is evenly balanced.

Ellie and I are so thankful and blessed to have our children’s grandparents so close to our home, and it’s always fun to see some of my patients bring their grandkids along.  In fact, sometimes if mom and dad aren’t available to bring their child to the office, it’s Grandma who does the driving, and I get to meet her as well.  Multi-generational bonding is a true blessing for us, and I know so many other families who do not take it for granted.

While it’s only the “Grandmother’s Hypothesis”, and not the "Grandmother's Law", I know that this theory is proven true in my life on a weekly basis.