Professor Daniel Lieberman teaches Human Evolutionary Biology at Harvard. I came across his work during a series of workshops I attended with Jules Mitchell on yoga biomechanics. I have always had an interest in evolution but what motivated me to read this book is its focus on the human body, on how it developed into what it is today, and what that can teach us about health and wellbeing in our modern world.
It was enlightening to learn in details how and why our bodies are not designed for the sort of lifestyles we entertain today. For example, as a yoga practitioner I’ve known and felt for a long time that sitting on chairs most of the day is not great for our bodies. Yet this book showed me that sitting is not the problem but rather the length of time we spend on chairs over days, weeks, months and years. In other words, following Lieberman, it is the long periods of inactive sitting that perverts our ancestral inclination (and need!) to move, ultimately causing illness.
The first part takes us on a journey through the evolutionary story of the human body. We evolved to be bipedal, furless, sweaty creatures, with more fat stored in our bodies compared to other species, and we are very dependent on the use of tools. As hunter-gatherers, our diet and activity evolved along those characteristics and adapted to eat food high in fibre and low in carbohydrates, as well as to crave energy-rich foods: in other words, to be physically active creatures, but also to enjoy rest and comfort. While this stage lasted for tens of thousands of years, with the origin of farming, 10-12,000 years ago, things changed quite dramatically. We were now able to increase the quantity and the quality of food that we ate. This led to an increase in human population size, when people started surrounding themselves with their own waste products, also interacting with animals by domesticating them. This also led to the spread of infectious diseases. With the industrial revolution and modern science, we were then able to produce even more food, and there was a population explosion which continues to this day. At the same time we developed sanitation, and became able to combat many of the infectious diseases the agricultural shift had introduced.
Therefore, Lieberman argues in the second part, we now live in what seems to be the healthiest stage of human evolution, with a decline in infectious diseases and malnutrition, and a serious drop in infant mortality rates. Yet, today we die from non-infectious diseases like cancer, heart disease, osteoporosis, type 2 diabetes, autoimmune disorders and many more. From the perspective of evolutionary medicine, many of the health problems people face today are mismatch diseases, i.e. diseases that "result from our Paleolithic bodies being poorly or inadequately adapted to certain modern behaviours and conditions."* For example, Lieberman says, evidence shows that coronary heart disease used to be extremely rare during our hunter-gatherer stage. And although cancers are ancient, the rates at which people die from cancer have been rising exponentially.
One of my favourite parts of the book focuses on the feet, our most precious structure of support as bipedal creatures. Lieberman shows that we evolved to be barefoot. When shoes were first invented they were very minimal, so we could still sense the ground beneath us. Without referencing somatic practices, the author describes that fundamentally somatic act that is (or should be) standing on our feet:
"You have a rich extensive network of nerves on the bottom of your feet that provides vital information to your brain about the ground beneath you and that activates key reflexes that help you avoid injury when you sense something sharp, uneven, or hot underfoot."
However, many of the shoes we wear today are sophisticated pieces of ergonomics: sometimes comfortable, but often multi-layered, multi-padded, separating us further and further from the ground we’re meant to be feeling beneath us. This causes a variety of problems including flat feet which is almost completely nonexistent in barefoot populations. Modern shoes weaken both the foot’s sensory response to the environment, and its muscles, causing the arch to either collapse, or to not develop at all. A podiatrist will then give us an orthotic to treat this symptom, which basically replaces the natural arch of the foot, setting up a vicious circle, which Liberman calls dysevolution.
This is a crucial message in the book. Doctors and researchers focus on treating symptoms in order to save lives where immediate medical care is needed, and this is important and necessary. However, by explaining why our bodies are the way they are, evolution provides a framework for how to avoid getting sick.
We are of course still evolving now, albeit through a cultural rather than a biological evolution (although that's yet to be measured).
"Some of these novel behaviours, especially the foods we eat and the activities we do (or don’t do), make us sick. [...] Lower mortality is being replaced by higher morbidity (or ill health)."
The vast majority of humans today exist in new conditions for which our bodies were not originally adapted. Many cultural changes “have altered interactions between our genes and our environments in ways that contribute to a wide range of health problems.”
The Story of the Human Body is a popular science book written in simple language that has made me more aware of the human evolutionary past, and at the same time much more conscious about its future. What I have learnt is also affecting my yoga and movement practice (and teaching) as well as the way I approach my daily activities. I have also started investigating the development of yoga (both as posture and meditation practices) within an evolutionary framework, which I had never considered before, and I’m hoping to share some insights in due course.
I recommend this book if you're curious about the human body, if you have an interest in evolution, and/or if you are looking to change some aspects of your current lifestyle but don't quite know why you would (or should).
* All quotes from The Story of the Human Body - Evolution, Health & Disease Link to the book on the publisher's site
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