MANY BELIEVE THAT THE NATURAL SELECTION FORCE in humans declines to zero once reproduction is complete. But a new research investigation challenges this long-held view. Could grandparents be the secret ingredient for longevity?

In his groundbreaking On the Origin of Species, English naturalist Charles Darwin expressed the idea of natural selection. In this 1859 book, he reports the results of his research in the Pacific Islands and South America.

Natural selection is selfish; it favors traits that promote reproductive success. Selection pressure can take out deleterious genetic mutations that occur during early life and through our reproductive years.

Are you a giraffe with an especially long neck, a structure that allows you to feast on leaves others cannot access? With more food, you are more likely to survive to reproduce and pass your propensity to have a long neck on to your offspring. Your friends with shorter necks are less likely to survive to pass on their genes to future generations.

An adaptation is a physical or behavioral characteristic that helps an organism to survive in its environment.

In summary, we pass genetic mutations beneficial to our survival through reproduction. This process results in a new generation of organisms more likely to survive and reproduce.

On the other hand, once fertility stops, natural selection becomes less interested in what happens to our bodies — we become more likely to suffer from harmful mutations. For most animals, death often follows soon after fertility ceases.

The importance of elders

New research challenges the prevailing view that the natural selection force in humans must drop to zero once we complete reproduction. The secret sauce? Modern medicine? Nope. It’s grandparents.

Enter the Grandmother Hypothesis: Through their efforts, maternal grandmothers can increase their fitness by improving their grandchildren’s survival. Their daughters can have more children, and grandma’s genes are passed on to future generations.

Here’s what the researchers’ model yields:

“Elders are valuable, but only up to a point. “And not all grandmothers are worth their weight. By about their mid-seventies, hunter-gatherers and farmers end up soaking up more resources than they provide. Plus, by their mid-seventies, most of their grandkids won’t be dependents anymore, and so the circle of close kin who stand to benefit from their help is small.”

I appreciate my elders more than ever. Let’s celebrate older folks. Thank you for joining me today.