Robert Sapolsky makes very clear from the beginning of A Primate’s Memoir that the stress-related conditions he observed in baboons were very similar to those experienced by humans. In Chapter One of his study of these primates, referencing the ground-breaking work on causes and effects of stress, Hans Selye, Sapolsky notes that
“. . .in the years since Selye, people have documented numerous diseases that can be worsened by stress. Adult onset diabetes, muscle atrophy, high blood pressure and atherosclerosis, arrested growth, impotency, amenorrhea, depression, decalcification of bones. You name it.”
Sapolsky’s years of research on baboons in East Africa, with his focus on the mental and physical tolls taken on living tissue by stress, enabled scientists to compare the brain functions of these close cousins of homo sapiens, and the parallels are astounding. In Chapter 16, Sapolsky expands upon his findings with respect to the parallels between humans and the primates he had dedicated years of his life to studying. Noting the correlation between where a baboon ranked in its tribal or “troops” hierarchy and the state of its health, he concludes that the lower one ranked in that hierarchy the weaker its immune system and the higher the levels of bad cholesterol in its blood, contributing to the development of diseases associated with high levels of stress. In other words, the low ranking baboons suffered from higher levels of stress that caused or seriously exacerbated medical conditions not unlike those experienced by humans. Discussing the levels of good and bad cholesterol in the blood of baboons on various levels of these primates’ social hierarchy, Sapolsky noted the following:
“. . .people with major depression often have elevated basal levels of that same stress hormone that was elevated in the low-ranking [primate] males. I was finding that the hypersecretion in those baboons was due to the same constellation of changes in the brain and pituitary and adrenal glands that gave rise to the hypersecretion in depressed humans.”
The points Sapolsky makes in A Primate’s Memoir regarding the applicability of his findings for humans are centered on the brain’s reaction to stress. Baboons that ranked low within their group’s hierarchy exhibited higher levels of stress and, consequently, experienced greater rates of diseases associated among humans with high levels of stress. While the parallels regarding social hierarchy are largely irrelevant – many humans with high-level positions within corporations or inside government experience inordinately high levels of stress on a daily basis, leading to health problems – the parallels regarding the effects of stress on the body’s physical condition are unmistakable. Sapolsky’s findings are important for understanding the relationship between primates and humans, and for understanding the consequences of emotional turmoil for both categories of living creature.