How did the human heart adapt during our evolution as a species? To explore that question, Harvard cardiologist Dr. Aaron Baggish led a unique study that compared the hearts of African great apes, Mexican farmers, and American athletes. But the findings also have a practical message.
“They reinforce the importance of regular brisk walking or jogging throughout life to stay healthy as you age,” says Dr. Baggish, director of the cardiac performance lab at Harvard-affiliated Massachusetts General Hospital. The study included great apes (gorillas and chimpanzees) and four different groups of men: inactive men, endurance runners, football linemen, and Tarahumara Indians. All underwent detailed heart function studies using ultrasounds done during different activities.
Chimps vs. early humans
Chimpanzees, our closest evolutionary relatives, spend most of the day feeding and resting, interspersed with short bouts of climbing and fighting. This brief but intense exertion creates pressure in the heart’s chambers, resulting in thicker, stiffer walls. In contrast, our ancient ancestors had to hunt and gather food to survive, requiring them to walk and run long distances. As evolution progressed, early farmers relied on that same physical endurance to plow, plant, and harvest their food. As a result, human hearts evolved to have thinner walls and be more flexible. The heart’s chambers became slightly larger, and they also were able to twist slightly (similar to wringing out a towel), which helps get more blood out and back into the heart as it relaxes.
Pure of heart?
The Tarahumara Indians, who live in Copper Canyon, Mexico, are one of the few civilizations that remain largely untouched by Westernization. “They lead what anthropologists refer to as a subsistence farming lifestyle that demands lots of walking, jogging, and other movement all day long,” says Dr. Baggish.
“Their hearts represent how the heart has naturally evolved to function — the pure form of a human heart, if you will,” he says.
But your heart also adapts over your lifetime depending on what type of exercise you do — or don’t do.
The heart’s main pumping chamber, the left ventricle, reflects the type of activity a person typically does. The left ve