The Story of the Human Body

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The Story of the Human Body is a fascinating book written by Daniel E. Lieberman,  a professor of human evolutionary biology at Harvard.  Topping out at 370 pages, I wouldn’t necessarily call it a fast read, but I found it so interesting that I read it in a couple of days.  It is separated into three parts, Apes and Humans, Farming and the Industrial Revolution, and The Present, the Future.

The section on Apes and Humans described all the different species of humans that roamed the earth as they evolved from apes.  I am a science geek at heart and I found this section very interesting.  The two events that really were crucial for mankind, bipedalism and cooking with the use of fire.  Bipedalism (moving on two legs) gave humans a chance to travel farther distances to find food and shelter.  We were also able to hunt more effectively because of it.  Fire allowed us to cook food, so there was less chance of getting sick from it and it also helped make the food easier to absorb.  These two things helped our brains continue to grow and that set us apart from the great apes.

Eventually the Hunter/Gatherer way of life was mostly abandoned for the agricultural and farming lifestyle.  Lieberman suggests that this posed some problems for our paleolithic bodies in a post paleolithic world.  Now this progress was not all bad, it lead to improvements in health care, education, and sanitation that made it easier to survive.  It would be ridiculous to deny the positives that came out of this movement.  However, it has also lead to the prevalence of diseases that didn’t exist or were very rare in ancient humans.  As the author puts it, our modern lifestyle had led us to an “evolutionary mismatch” and resulted in the creation of “mismatch diseases.”  These diseases include heart disease, certain cancers, osteoporosis, type 2 diabetes, and Alzheimer’s, as well as many less severe illnesses.  There is also reason to believe that modern lifestyles have led to a host of mental illnesses, such as anxiety and depression.  Lieberman believes this evolutionary mismatch has led to dysevolution,  which is not biological evolution, but cultural evolution, because we pass on behaviors and environments that promote mismatch diseases.  The establishment of farming led to people settling down in areas with higher population density which increased the incidence of infectious disease and social stress.  We didn’t fare much better with the arrival of the Industrial Age.  While the jobs were initially physically demanding, as technology increased, so did our lack of physical activity.  The Industrial Revolution also ushered in the abundance of cheap, calorie dense food created by food producers.  These food producers could easily create the foods that mankind has always craved,  containing fat, starch, sugar and salt, and it could all be done at low cost.  While he admits that life in the Hunter/Gatherer society was not easy by any means, it is quite possible that we were more adapted to living that lifestyle.

The last section of the book discusses The Present, the Future.  He touches upon the reasons we are susceptible to the mismatch diseases.  Obesity and Metabolic syndrome can be attributed in its most simplest terms, to an excess of available energy.  We can get calorie dense food just about any time we want.  He also addresses reasons why flat feet and myopia are so common, the reason our jaws are smaller and our bones weaker.  In the last section of the book, he suggests there are four approaches we can use from this point forward to deal with this evolutionary problem.   1) Let natural selection sort the problem out. 2) Invest more in Bio-medical research and treatment.  3) Educate and empower. 4) Change the environment.  I think he sums it up nicely in one of the final paragraphs of the book:

“Like it or not, we are slightly fat, furless, bipedal primates who crave sugar, salt, fat, and starch, but we are still adapted to eating a diverse diet of fibrous fruits and vegetables, nuts, seeds, tubers, and lean meat.  We enjoy rest and relaxation, but our bodies are still those of endurance athletes evolved to walk many miles a day and often run, as well as dig, climb, and carry.  We love many comforts, but we are not well adapted to spend our days indoors in chairs, wearing supportive shoes, staring at books and screens for hours on end.  As a result, billions of people suffer from diseases of affluence, novelty, and disuse that used to be rare or unknown.  We then treat the symptoms of these diseases because it’s easier, more profitable, and more urgent than treating their causes, many of which we don’t understand anyway.  In doing so, we perpetuate a pernicious feedback loop-dysevolution-between culture and biology.” -page 366

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