“Arrhythmias are additional common causes of problems and death, and the heart can also be damaged by infections, birth defects, drugs, and faulty wiring. But atherosclerosis is by far the leading culprit, and chronically high blood pressure, hypertension, is a close second. Hypertension is a silent condition that relentlessly strains the heart, arteries, and various organs. At least 100,000 times a day, the heart forces about five liters of blood through thousands of miles of arteries that resist each squeeze, generating pressure. When we exercise, blood pressure rises temporarily, causing the heart’s muscular chambers to adapt, mostly by becoming stronger, larger, and more elastic so it can pump more blood with each stroke.30 Just as important, arteries also adapt to exercise to keep blood pressure low, primarily by expanding, multiplying, and staying elastic.31 However, when blood pressure is chronically high, the heart defends itself by developing thicker muscular walls. These thicker walls stiffen and fill with scar tissue, and eventually the heart weakens. A vicious cycle then ensues. As the heart’s ability to pump blood declines, it becomes harder to exercise and thus control high blood pressure. Blood pressure may rise as the heart progressively weakens until the failing heart cannot support or sustain a normal blood pressure. Death usually ensues. Coronary artery disease is ancient and has even been diagnosed in mummies.32 But research on nonindustrial populations provides powerful evidence that coronary artery disease and hypertension are largely evolutionary mismatches. Although many medical textbooks teach doctors that it’s normal for blood pressure to rise with age, we have known since the 1970s this is not true among hunter-gatherer populations like the San and the Hadza.33 The average blood pressure in a seventy-year-old San hunter-gatherer is 120/67, no different from a twenty-year-old. Lifelong low blood pressure also characterizes many subsistence farming populations. My colleagues Rob Shave and Aaron Baggish and I measured more than a hundred Tarahumara farmers of every age and found no difference in blood pressure between teenagers and octogenarians.34 By the same token, blood pressure can also stay normal into old age among industrialized people who eat sensibly and stay active.35”