A unique study that compared the hearts of African great apes, native Central Americans, and American athletes sheds new light on the evolution and adaptability of the human heart. 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 the study’s senior author Dr. Aaron L. Baggish, director of the cardiac performance lab at Harvard-affiliated Massachusetts General Hospital.
Published Oct. 1, 2019, in Proceedings of the National Academy of Sciences, 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 heart function studies using ultrasounds done during various activities. The groups were specifically chosen to offer clues to heart function from an evolutionary perspective, says Dr. Baggish, whose collaborators include his friend and running partner Daniel Lieberman, professor of human evolutionary biology at Harvard, and Dr. Robert Shave, an exercise physiologist from the University of British Columbia.
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.
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 ventricles of the endurance runners were longer, larger, and more elastic than average (and therefore able to cope with large volumes of blood). The hearts of the football linemen, on the other hand, were more adapted to short, intense bouts of exercise that reflects their strength training. The walls of their left ventricles were thicker and less flexible, allowing them to cope better with pressure rather than volume.
However, the group of men who didn’t exercise ended up being the most important part of the story with respect to health lessons, says Dr. Baggish. These men, all in their 20s and 30s, didn’t have any traditional heart disease risk factors, such as high blood pressure. But their untrained hearts appeared more ape-like, with thicker and less flexible walls.
“If you don’t do any physical activity, you don’t push large amounts of blood through your heart and blood vessels on a daily basis. Both the heart and blood vessels start to stiffen,” explains Dr. Baggish. It creates a vicious circle: the less you move, the less you’ll be able to do the type of exercise that keeps you healthy.
Exercise to prevent high blood pressure
The new findings suggest that the process of developing high blood pressure is set in motion years before it is first detected in a doctor’s office, he says. Unfortunately, only about 20% of American adults get the recommended 150 minutes per week of moderate-intensity physical activity. And about a third of adults have high blood pressure.
Even though it’s better to exercise throughout life, it’s never too late to start. For many people, changing from being sedentary to being active is hard and requires a real behavioral shift. “But the more we can help people understand the underlying causes and implications of their choices, the better off we are,” says Dr. Baggish.
Bible verses for today’s meditation and inspiration: Matthew E. McLaren
Whoever claims to love God yet hates a brother or sister is a liar. For whoever does not love their brother and sister, whom they have seen, cannot love God, whom they have not seen. 1 John 4:20 NIV
Since you are precious and honored in my sight, and because I love you, I will give people in exchange for you, nations in exchange for your life. Isaiah 43:4 NIV
However, as it is written: What no eye has seen, what no ear has heard, and what no human mind has conceived — the things God has prepared for those who love him. 1 Corinthians 2:9 NIV
Let no debt remain outstanding, except the continuing debt to love one another, for whoever loves others has fulfilled the law. Romans 13:8 NIV
See what great love the Father has lavished on us, that we should be called children of God! And that is what we are! The reason the world does not know us is that it did not know him. 1 John 3:1 NIV
There is no fear in love. But perfect love drives out fear, because fear has to do with punishment. The one who fears is not made perfect in love. 1 John 4:18 NIV
May the Lord make your love increase and overflow for each other and for everyone else, just as ours does for you. 1 Thessalonians 3:12 NIV
Whoever pursues righteousness and love finds life, prosperity and honor. Proverbs 21:21 NIV
Instead, speaking the truth in love, we will grow to become in every respect the mature body of him who is the head, that is, Christ. Ephesians 4:15 NIV
Hatred stirs up conflict, but love covers over all wrongs. Proverbs 10:12 NIV
For I am convinced that neither death nor life, neither angels nor demons, neither the present nor the future, nor any powers, neither height nor depth, nor anything else in all creation, will be able to separate us from the love of God that is in Christ Jesus our Lord. Romans 8:38-39 NIV
The second is this: ‘Love your neighbor as yourself.’ There is no commandment greater than these. Mark 12:31 NIV
I love the Lord, for he heard my voice; he heard my cry for mercy. Because he turned his ear to me,
I will call on him as long as I live. Psalm 116:1-2 NIV
Whoever does not love does not know God, because God is love. 1 John 4:8 NIV
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