62 pages • 2 hours read
Daniel LiebermanThe Story of the Human Body
Nonfiction | Book | Adult | Published in 2013A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Themes
The Evolution of the Human Body and Health
The evolution of the human body and health appears throughout the text, and the theme’s development aligns with the parts of the text. Lieberman introduces and develops the theme by exploring biological evolution, then he discusses how cultural evolution impacted human bodies and health during the Neolithic, and he concludes the theme by discussing the modern health implications of human biology.
Human evolution took place over millions of years and included innumerable changes, but Lieberman identifies several physical alterations that are more significant and relevant to the conversation on modern health—bipedalism, diet diversification, larger bodies and brains, slower physical development, and enhanced social capabilities. Each of these traits were developed through natural selection, meaning they improved human reproduction rates but not necessarily their overall health. For instance, while bipedalism allowed humans the use of their hands, it also resulted in decreased strength and climbing abilities, higher rates of back problems, and more discomfort and instability during pregnancy. Thus, bipedalism, like many biological characteristics, increased humans’ ability to procreate but did not improve their health.
In Part 2, Lieberman discusses how the Agricultural Revolution and the Industrial Revolution drastically altered human culture and environments. Adaptions are only adaptations under certain contexts, and these radical shifts in environment changed the context of human biological traits. Part 3 expands upon this idea by discussing specific health conditions which arise from the adaptations becoming maladaptive in modern environments. One of the most frequently noted disparities involves human’s capacity for storing fat. The ability to store more fat compared to other apes likely evolved in response to the brain’s energy demands and to fuel endurance activities.
When these traits emerged, hominins were living hunter-gatherer lifestyles, meaning they took in relatively few calories and expended large amounts of energy. Sometimes they took in more energy than they expended, and sometimes they did not, but the processes were often balanced over long periods of time. The Agricultural and Industrial Revolutions changed the context of increased fat storage. Humans had access to more calories, and they had fewer reasons to consistently practice endurance activities. Lieberman emphasizes both the prevalence of high calorie foods—“natural selection never prepared us to cope with endless seasons of plenty, let alone fast-food restaurants” (119)—and of physical inactivity—“[c]ountless other devices, such as electric can openers, remote controls, electric razors, and suitcases on wheels have reduced, calorie by calorie, the amount of energy we expend to exist” (218).
The biological evolution of humans thus favored reproduction over health, and the shifts in cultural context have further impacted human health negatively. Through these ideas, Lieberman demonstrates that natural selection cannot promote health and longevity, so humans must use intentional cultural evolution to promote health.
Evolutionary Mismatches and Modern Disease
The link between evolutionary mismatches and modern disease emerges at the intersection of biological and cultural evolution. Biological evolution led to the development of modern human biology, and while such evolution is ongoing, it has been surpassed by cultural evolution, which operates at wider scales and faster paces. Not only does cultural evolution cause mismatch diseases, but cultural practices also create barriers to recognizing, preventing, and properly treating mismatch conditions through cultural buffering and dysevolution. As explained in The Evolution of the Human Body and Health, adaptations are only adaptive within certain contexts, and when the context changes—such as occurred during the Agricultural and Industrial Revolutions—beneficial traits can become harmful. This is the foundational principle of the mismatch hypothesis.
Mismatch diseases share common features. They have obscured or complex causes, they do not interfere with reproduction, and their causes are culturally valuable. While Lieberman holds that many mismatch diseases can be prevented, he does not blame individuals for contracting such diseases, partly because the process is not as simple as lifestyle choices resulting in inevitable mismatch disease development. Many mismatch diseases have genetic components that may not be fully understood, and the genetic components are further complicated by epigenetic changes, which occur when environmental conditions alter genetic expression. Humans are unable to control their environments, particularly their in-utero and childhood environments. Long-term studies of the Dutch famine (1944-1945) demonstrate this: “People who were in utero during this intense famine had significantly higher rates of health problems as adults including heart disease, type 2 diabetes, and kidney disease” (261). The complexity of these diseases makes them difficult to address.
The cultural values associated with mismatch diseases are visible through cultural buffering and dysevolution. Cultural buffering occurs when certain practices address the complications of mismatch diseases, which prevents natural selection from creating evolutionary changes that would otherwise address issues. Eyeglasses are an apt example of this process. Modern lifestyles, particularly reading and spending more time inside, have contributed to increasing rates of myopia. Instead of identifying the cause of myopia and trying to prevent the condition, the cultural response was to create and normalize the use of eyeglasses. The eyeglasses act as a buffer by addressing the symptoms of myopia and negating the need to address the causes by attaching cultural value to both the causes and the cultural buffer—i.e., both reading, and the use of eyeglasses, are considered culturally valuable. This results in dysevolution, or the cultural perpetuation of mismatch conditions.
Myopia is a relatively minor problem, but many mismatch diseases have much more significant health consequences, like type 2 diabetes, which is perpetuated by the normalization of unhealthy diets and by treatment plans which do not address the underlying causes of the disease. The purpose of examining mismatch diseases, their causes, and their accompanying cultural values is to both inform readers so they can understand and potentially avoid mismatch diseases, and to inspire social changes that would prevent or more effectively mitigate such conditions.
Evolutionary Implications for Health Practices and Policies
The theme of evolutionary implications for health practices and policies emerges first implicitly through the discussions of the impacts of biological and cultural evolution, and then explicitly in the final four chapters of the book, where Lieberman criticizes modern cultural practices and calls for societal change.
The implicit exploration of the theme is covered during the development of The Evolution of the Human Body and Health and Evolutionary Mismatches and Modern Disease. Together, these two themes imply that individuals should not be held accountable for mismatch diseases, which are a side effect of modernity. With individuals absolved of guilt, Lieberman redirects the conversation and targets culture as the underlying cause of numerous diseases. If culture can create the conditions in which diseases emerge, he argues, then culture can prevent or better manage mismatch diseases.
Before directly addressing the need for cultural change, which is a controversial topic, Lieberman garners support by identifying corruptions and logical fallacies embedded in cultural practices. He demonstrates that government does not always act in ways that are beneficial to individual citizens: “Most states sponsor gambling to generate revenue in spite of the social costs from gambling-related addiction and corruption” (319). Such ideas demonstrate how modern policies and practices may have cultural value while harming individuals. To further argue his case, Lieberman mentions the economic costs of mismatch diseases:
The United States, for example, spends more than two trillion dollars a year on health care, nearly 20 percent of the country’s gross domestic product, and it is estimated that approximately 70 percent of the illnesses we treat are preventable (350).
Lieberman uses a variety of arguments to appeal to a wide audience: People who value socialist policies will likely support increased public health efforts, while people who value capitalism and individualism may be swayed to favor increased regulation if it will prevent them from incurring the financial costs of mismatch diseases.
After establishing the need for cultural change, Lieberman explores various approaches to enact the alterations. While he proposes four potential solutions—natural selection, biomedical research, public health measures, and cultural change—he largely discredits the first three and stresses the concept of intentionally changing culture through “soft paternalism.” Soft paternalism is the idea that both regulation and personal freedom can coexist. Current examples of soft paternalism include the warning labels on alcohol and alcohol restrictions: Adults are free to consume alcohol, but they are warned in advance of the dangers, and they are barred from performing certain activities, like driving, while under the influence.
Lieberman suggests society should increase and expand such regulations. He asserts that doing so may decrease the prevalence of mismatch diseases and may have other positive effects, such as reducing the amount of money spent on mitigating preventable diseases.
