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.
Preface-Chapter 1Chapter Summaries & Analyses
Preface Summary
Lieberman studies the evolution of the human body, and he stresses the importance of considering future human evolution. Modern humans are “paradoxical” in that in some ways they are healthier than ever, and in some they are unhealthier. Malnutrition and infectious disease rates are lower and life expectancy is higher, but noncommunicable diseases are more prevalent. Many of these issues are caused by lifestyles, and they are straining economic and healthcare systems.
Discussions on health usually revolve around preventing or treating existing conditions, and few researchers consider human evolution as relevant. Lieberman argues that this is a mistake because evolution provides insight as to why humans are the way they are. Evolution is still taking place, particularly via culture.
Lieberman’s goal is to explore the health implications of biological and cultural evolution. He describes his explanations and methods as rigorous and fact-based, with in-text citations so that readers can easily fact-check the information. The discussion is limited, centering on a few relevant evolved traits and modern diseases, and Lieberman notes the information is subject to change as science progresses. He synopsizes his conclusion, declaring human evolution prioritizes reproduction over health. As a result, modern lifestyles create feedback loops that promote disease; however, this can be overcome with healthy diets and exercise.
Chapter 1 Summary: “Introduction”
In 2012, political conservatives used the “Mystery Monkey”—an escaped macaque living in Tampa, Florida—to promote their political agenda, asserting the macaque represented government ineptitude and the inherent desire for freedom. Lieberman counters that the situation is representative of human misunderstanding. He compares the idea that the macaque didn’t “belong” in Florida to the idea that humans aren’t adapted for modern society. Humans evolved to live in small, nomadic groups that hunt, forage, and fish for their food.
Although human lives, in some ways, are better than they have ever been, there is room for improvement. Humans face lifestyle-related threats, like climate change, overpopulation, and declining fitness, so while life expectancies are rising, so are rates of illness. Chronic diseases caused by lifestyle choices are overstressing healthcare systems and are becoming an increasing issue in developing nations. Lieberman questions whether Paleolithic, or Stone Age, lifestyles would be better.
Lieberman defines evolution as “change over time” (8), asserting it is visible and irrefutable. Evolution occurs via natural selection. Natural selection is defined by three pillars: Variation, genetic heritability, and differential reproductive success. Variation holds that individuals are genetically unique; genetic heritability says genes are passed from parent to offspring; and differential reproductive success refers to individual reproduction rates. Natural selection occurs when genetic variations impact reproductive success. Negative natural selection occurs when a genetic variation reduces or prevents reproduction; positive selection happens when a genetic variation, or adaptation, increases reproductive success and causes eventual change in the species.
Not all evolved traits are adaptations, and adaptations are beneficial within certain contexts. Skin color exemplifies this: Light skin promotes vitamin D synthesis and is adaptive in colder, darker regions, while the melanin in dark skin prevents sun damage and is adaptive in hot, sunny climates. Natural selection intensifies in difficult circumstances, and shifting conditions can impact adaptiveness. The build-up of genetic traits is similar to a palimpsest, or a document which has been re-written over and contains layers of text. He reasserts that natural selection favors reproductive success but notes that human evolutionary history is not that simple, because humans are not adapted to one particular set of circumstances.
Studying human evolution—specifically what humans are not adapted for— provides insight on modern diseases, such as type 2 diabetes, which has genetic components but is significantly impacted by lifestyle. Humans evolved to crave fatty and sugary foods when such foods were rare; thus, humans are maladapted to processed, calorie-dense diets. Such phenomena are called the mismatch hypothesis, which is a concept of evolutionary medicine—a field of medical science that examines the relationship between health and evolution. Lieberman warns the mismatch hypothesis is complex and cannot be used to claim one lifestyle or environment are ideal since humans evolved under various circumstances.
Lieberman identifies five significant evolutionary transitions: Humans evolved bipedalism, expanded diets, larger bodies and brains, slower physical development, and the capacity for social cohesion, language, and culture. Human evolution is ongoing, as is cultural evolution, which is faster, more intentional, and more widespread than biological evolution.
The two most significant cultural evolutions are the Agricultural and Industrial Revolutions, which drastically changed human lifestyles in both positive ways, like increasing reproductive success, and negative ways, like creating mismatch diseases. Interactions between biological and cultural evolution can cause mismatch feedback loops in which diseases are developed, misunderstood, and treated without consideration of evolutionary causes, thus perpetuating the diseases.
Preface-Chapter 1 Analysis
The Preface and Chapter 1 establish the purpose, context, themes, structure, and methods of The Story of the Human Body. Lieberman’s purpose is to inform readers about the health implications of biological and cultural evolution and to inspire positive social change. His purposes suggest that the book can be classified as both a science book that provides in-depth knowledge on the implications of evolution and a self-help book that provides readers with actionable steps they can take to improve their health.
The context development provides readers with the foundational scientific and ideological principles Lieberman utilizes throughout the text. Since his discussion centers on evolution, Lieberman explicitly defines evolution and natural selection. His definitions of these concepts are concise and are phrased to be irrefutable, reflecting the deep scientific consensus on evolution. Along with building the scientific context, the discussion on evolution also influences the ideological context by demonstrating the text takes a scientific approach. Two other critical contextual elements include his assertions that humans don’t “belong” in modern environments and that they are not evolved for happiness but for reproduction.
That humans don’t belong in modern environments emerges in the discussion of the Mystery Monkey. Lieberman asserts, “You and I exist about as far removed from our natural environment as the Mystery Monkey” (4). He also asserts that evolution serves to increase reproduction rates, meaning humans are not evolved to be either happy or healthy. While these ideas may seem pessimistic, Lieberman approaches them with an optimistic tone which reflects his purpose of informing individuals and inspiring change. The message emerges that, although biological evolution favors reproductive success, humans can use cultural evolution to increase their well-being.
Three primary themes emerge throughout the Preface and Chapter 1. The Evolution of the Human Body and Health is briefly introduced through Lieberman’s discussion on the importance of understanding evolution to better understand health. Evolutionary Mismatches and Modern Disease is similarly introduced with relatively few details. By alluding to these themes but not fully developing them, Lieberman creates tension intended to inspire curiosity. He balances the tension by providing a few conclusory points, including that humans did not evolve to be healthy.
This notion implicitly introduces Evolutionary Implications for Health Policies and Practices. While this theme is relegated to the last few chapters of the text, it emerges in the claim that humans are neither evolved to be healthy nor evolved for many conditions of modern life. If this is true, then poor health is not the fault of individuals, which leads to the question: If individuals are not wholly responsible for their health, who is? This question is addressed in the final chapter, in which Lieberman argues that social institutions, including governments, have a moral duty to alter the environment to better promote individual health.
Lieberman explicitly states that his method of exploration revolves on scientific discussions, and he writes that he attempts to use simple explanations that do not reduce the quality or depth of the subject. This reflects his purpose of informing readers, as well as demonstrating his academic integrity. His integrity is also emphasized through his use of in-text citations and by him encouraging readers to follow the citations so they can fact-check the information themselves. To make the material more digestible for the lay-reader, Lieberman uses repetitive structures and literary devices. The repetitive structures include rhetorical questions which appear during transitions in the discussions. The rhetorical questions introduce the coming topics and their relationship to earlier elements, and they invite the reader to critically think about the subject before reading Lieberman’s views.
Lieberman also accommodates lay-readers by using comparisons and analogies to make the scientific concepts more relatable. These structural and literary elements are used throughout the text, providing a sense of consistency that may make it easier for some readers, particularly those without a strong scientific background, to follow the discussion.
