Book Summary – The Story of the Human Body: Evolution, Health & Disease

Today, we’re healthier than ever before in human history—we have higher life expectancy, less malnutrition, and have removed threats from diseases like smallpox, measles and the plague (which used to kill masses of people). Yet, we are getting sick from preventable diseases like osteoporosis, depression, allergies, cancer etc. In the USA alone, more than $2 trillion is spent on healthcare annually, when 70% of the illnesses are preventable.

Liberman advocates that we should understand our bodies using an evolutionary perspective, so we can develop more effective strategies to prevent and address these diseases. In this summary, we’ll outline the key ideas in the book, including an overview of (a) our biological evolution and how we came to have our present bodies, (b) our cultural evolution and how it transformed the way we live, and (c) why the mismatch between the 2 evolutions has caused many of our modern-day diseases.

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Lieberman approach to evolution is built on 2 important perspectives:
• Evolution is an ongoing process of change, rather than just a study of the past. The choices we make today will determine the future of mankind.
• Evolution is not just biological. Cultural/societal changes shape the way we live and use our bodies, and affects how our bodies continue to evolve.

Let’s take a quick look at the 2 types of evolution and how they interact.

Biological Evolution

In the book, Liberman explains, in great detail, the concept of evolution, and how modern humans (Homo Sapiens) evolved from apes. In a nutshell, there were probably 5 key transitions in our biological evolution:

Transition 1: From Apes to Bipeds. This was the biggest evolutionary step that set homonins (a subset of the apes species) apart from Chimps and Gorillas, and was probably necessitated by major climate change and the need to find increasingly-scarce food. Standing on 2 feet allowed us to forage better for fruits and save energy while traveling to find new food sources. Till today, we’re still the only non-feathered species moving on 2 legs.

Transition 2: Australopiths. About 4 million years ago, the Australopiths emerged. While they were still suited to climb trees, Australopiths started to dig for underground tubers, bulbs and roots, like potatoes and ginger, which gave them an additional food-source that was rich in water, starch and nutrients.

Transition 3: The First Hunter-Gatherers. At the dawn of the Ice Age about 2-3 million years ago, when food became even more scarce, the first hunter-gatherers emerged. They started to consume meat, cooperate, make tools and process food. This combination of behaviours was unique to the human genus–they shaped the ongoing evolution of our bodies, improved the efficiency of food digestion, and increased the amount of calories we  could absorb.

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Transition 4: Spread of Hunter-Gatherers. During the Ice Age, Hominins continued to spread  across the globe, and several sub-species of Archaic Humans emerged. Generally, we developed even bigger brains, bred faster, became fatter, and matured slower.

Transition 5: Birth of modern Homo Sapiens (H. Sapiens). By the end of the Ice Age, all Homo species had become extinct, except for H. Sapiens. What set H. Sapiens apart were our heads–our prefrontal cortex gave us new abilities to think and organize ourselves, while our vocal tract and tongue brought a leap in modern human speech.  This brought a cultural transformation about 50,000 years ago, with an explosion of new tools, weapons and art-forms.

The Story of the Human Body summary_Biological Evolution

By understanding our biological evolution over millions of years, we can understand why our bodies are designed the way they are… Why the human brain is 5x as large as other mammals (while our guts are half the size), why our bodies require more fat, why we move slower but can run long distances, and can handle tools and weapons unlike any other animals. In our full book summary, we elaborate on the key details of the transitions and how our bodies were adapted to help us survive in those environments.

Cultural Evolution

Culture is the set of learned beliefs, values, and knowledge that shape people’s thinking and behaviour. Technically, there should be 2 more transitions in our evolutionary history: the Agricultural Revolution (when we started to farm our food instead of hunting and gathering), and the Industrial Revolution (when we began to use machines to replace human work). These cultural evolutions did not create new species, but they transformed how we eat, live and use our bodies, which indirectly impacts biological evolution.

The Agricultural Revolution: Farming may seem like an old-fashioned way to live, but it’s actually a very recent phenomenon by human evolutionary standards. Farming brought more predictable food supply, but also other challenges, like a more limited range of foods & nutrients, higher risk of famine and food shortages, cavities from starchier foods, and contagion and infections.  Every major infectious disease happened after the Agricultural Revolution, and humans actually shrank in size during the revolution.

The Industrial Revolution increased the pace of transformation exponentially, with the use of fossil fuels (e.g. coal oil, gas), reorganization of economic and social institutions, and science as an essential driver. Technology significantly reduced our level of physical activity, we sleep less (and less well), and the human population exploded with progress in medicine, sanitation and food storage/safety. While we have much more variety of food than the typical farmer, almost everything we consume today is bred, harvested, processed and shipped by machines, with huge amounts of pesticides, inorganic fertilizers and antibiotics. Processed foods also contain more sugars and starches, and require less energy to break down, causing spikes in blood sugar levels that our bodies aren’t used to.

The Story of the Human Body summary_Cultural Evolution

It took millions of years for the first H. Sapiens to evolve from apes. Yet, in less than 10 generations, we’ve transformed the way we live—to a lifestyle that’s totally different from what our bodies were evolved for. This results in “mismatches” which we’ll touch on below. Check out our full book summary where we explain the changes and implications in more detail, or get the book for the full works.

Understanding Present and Future Challenges

Many of the diseases or discomforts that we face today (e.g. high blood pressure, cancer, cavities) arise from “mismatches” in our cultural and biological evolution. Mismatches basically occur when the inputs from our environment are (a) too much, (b) too little, or (c) too new for our bodies to handle. Longer life expectancy also means a growing number of people with aging-related diseases and disabilities. Our medical innovations also act as “cultural buffers” to cause “dysevolution”. For example, the overuse of antibiotics can hasten the emergence of new superbugs and bring new auto-immune diseases (e.g. Crohn’s disease).

The Story of the Human Body summary_mismatches-dysevolution

Diseases from Excess. For the first time in human history, we have too much food, most of which are processed foods with little/no fibre, and contain lots of starch and sugars. In the book and our full summary, we explain why the excess energy results in issues (e.g. obesity, Type 2 diabetes, heart diseases, and reproductive tissue cancers), and how exercise and a sound diet could make a positive difference.

Diseases of Dis-use. Our bodies need to use our limited energy budget wisely, since everything involves trade-offs, e.g. thicker leg bones are less likely to break, but need more energy to move and maintain. The body decides where to invest the energy using the “use it or lose it” concept. In the book / full summary, we elaborate on how dis-use of our body in our modern lifestyle causes issues like Osteoporosis, impacted wisdom teeth, and allergies, and what we can do about it.

Diseases of Novelty. Cultural evolution tends to favour convenience, comfort, popularity or profitability. However these may not be good for us biologically. Things that we take for granted–e.g. shoes, eyeglasses, and chairs–can be comfortable or convenient, but may actually be bad for us with excessive use. Simply by moderating our lifestyle, we can minimize the strain on our bodies, e.g. go barefoot occasionally, or balance reading/indoor activities with outdoor ones. In the book and full summary, we explain more about why this is so.

Review these ideas easily with our infographic &14-pg book summary!

Other Details in “The Story of the Human Body”

This is a very comprehensive book that covers the human body evolution and modern-day diseases in great detail. This article merely outlines some of the core ideas in the book. To truly understand our bodies’ evolution and how the mismatches occur with our modern lifestyle, do get a copy of the book or get The Story of the Human Body summary bundle for a detailed overview.

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