The evolutionary reason to stay active as you age (surprising)

My doctoral studies at the University of Pennsylvania were, on the surface, in divergent fields—anthropology and medicine. But, as I’ve discovered throughout my career, these disciplines are much more related than they may first appear. 

Take, for example, a new article written by a team of anthropologists, medical researchers, and human biologists from Harvard University.1 Together, they make the case that human beings aren’t designed to simply camp out on the couch (or the savanna) as they get older. 

In fact, this diverse group of researchers concluded that being physically active as you age directs energy toward brain and body processes that SUPPORT health…and away from processes that may compromise health.    

The article shows that humans are designed to live many decades after they stop having children. And anthropologists have long discussed what they call the “post-reproductive” role of humans in society—meaning that people are evolutionarily designed to help raise not only their children, but also their grandchildren. (I’m a living example of this, currently, with my nearly 20-month-old granddaughter.)  

Because of this important role for older generations in caring for young offspring, the human lifespan was biologically programmed to be relatively longer than that of other animals. 

Taking all of this into account, the researchers examined two pathways by which physical activity reallocates energy to improve health.  

The first involves directing excess energy away from potentially harmful health effects like excess fat storage.  

The second relates to how physical activity directs energy to the body’s repair and maintenance processes.   

The researchers describe how physical activity is stressful to the body, causing damage at the molecular, cellular, and tissue levels. But the body can actually repair this damage on its own, too—which can help it “build back stronger.”  

However, the researchers note that TOO MUCH physical activity can actually impair this repair-and-rebuild process. And they explain how moderation is key to help ensure any damage to the body doesn’t exceed the ability to fix the damage. 

Dr. Daniel E. Lieberman, the lead study author, stated: “The key is to do something, and to try to make it enjoyable so you’ll keep doing it. The good news is that you don’t need to be as active as a hunter-gatherer. Even small amounts of physical activity—just 10 or 20 minutes a day—substantially lower your risk of mortality.”2 

That finding fits right in with the science I’ve reported before, showing a total of 140 to 150 minutes per week of physical activity is optimal for health as you get older. And as I just reported on page 1, even daily housework counts toward that weekly goal. 


  1. “The active grandparent hypothesis: Physical activity and the evolution of extended human healthspans and lifespans.” PNAS December 14, 2021 118 (50) e2107621118.