Our closest relatives are chimpanzees and gorillas. In some ways, however, we are very different. Humans are world-class endurance athletes, built for long sustained moderate exercise. We can walk and run for very long distances. Our primate relatives, on the other hand, are strength and power athletes. They can climb up and down trees and grapple during fights, but they seldom do any long-duration exercise.
Researchers at Harvard University compared the heart structure of chimps against several groups of humans and published their findings in the Proceedings of the National Academy of Sciences of the USA. A summary article by Gretchen Reynolds appeared in The New York Times.
The hearts of the chimps and gorillas are rounded in shape with thick walls. They are suited for short bursts of maximal activity. They tend to operate at a high-sustained blood pressure level. Most human hearts are more elongated and thin walled. They can twist and pump greater volume of blood and operate at a sustained lower pressure.
The hearts of four groups of men were scanned for the study. They included distance runners, football players at Harvard, hardworking Mexican farmers, and sedentary, but healthy, young men. The runners and farmers had hearts very different from the chimps. The football players who did a lot of weight work and the sedentary men had hearts that showed similarities to the chimp hearts. They were rounded, thick walled, stiffer and had higher operating pressure.
Cardiac muscle is very plastic and adapts to the workload placed on it. Without steady, regular, aerobically based exercise, hearts develop into a subtly “chimpanzee-like phenotype,” in the words of the scientists. When we evolved away from the apes, our bodies changed to allow long duration exercise necessary for hunting and gathering. Our hearts also changed in response to the needs.
In present times, when we do not get the type of exercise we were designed for, our hearts begin to rapidly remodel themselves. The exact health effect of this aping of the heart is yet undetermined. A thicker, stiffer, less supple heart operating at a higher-pressure level does not seem ideal. This is yet another reason to keep up the aerobic exercise.