Body by Darwin: How Evolution Shapes Our Health and Transforms Medicine

by Jeremy Taylor

Overview

This exploration of cutting-edge evolutionary medicine and how our body’s performance is shaped by its past “covers fascinating territory” (Publishers Weekly).

We think of medical science and doctors as focused on treating conditions—whether it’s a cough or an aching back. But the sicknesses and complaints that cause us to seek medical attention actually have deeper origins than the superficial germs and behaviors we regularly fault. In fact, as Jeremy Taylor shows in Body by Darwin, we can trace the roots of many medical conditions through our evolutionary history, revealing what has made us susceptible to certain illnesses and ailments over time and how we can use that knowledge to help treat or prevent problems in the future.

In Body by Darwin, Taylor examines the evolutionary origins of some of our most common and serious health issues. To begin, he looks at the hygiene hypothesis, which argues that our obsession with anti-bacterial cleanliness, particularly at a young age, may be making us more vulnerable to autoimmune and allergic diseases. He also discusses diseases of the eye, the medical consequences of bipedalism as they relate to all those aches and pains in our backs and knees, the rise of Alzheimer’s disease, and how cancers become so malignant that they kill us despite the toxic chemotherapy we throw at them. Taylor explains why it helps to think about heart disease in relation to the demands of an ever-growing, dense, muscular pump that requires increasing amounts of nutrients, and he discusses how walking upright and giving birth to ever larger babies led to a problematic compromise in the design of the female spine and pelvis. Throughout, he not only explores the impact of evolution on human form and function, but integrates science with stories from actual patients and doctors, closely examining the implications for our health.

“Seven vivid true stories dramatically describing patients and their doctors discovering evolutionary explanations for diseases. More than just the perfect book club book, it advances the field of evolutionary medicine.” —Randolph M. Nesse, coauthor of Why We Get Sick

Product Details

ISBN-13:	9780226059914
Publisher:	University of Chicago Press
Publication date:	12/22/2022
Sold by:	Barnes & Noble
Format:	eBook
Pages:	261
Sales rank:	64,738
File size:	1 MB

About the Author

Jeremy Taylor was previously a senior producer and director for BBC Television, and he has made numerous science films for the Discovery Channel and Learning Channel, among others. He is also the author of Not a Chimp: The Hunt to Find the Genes that Make Us Human. He lives in London.

Read an Excerpt

Body by Darwin

How Evolution Shapes Our Health and Transforms Medicine

---

By Jeremy Taylor

The University of Chicago Press

Copyright © 2015 Jeremy Taylor
All rights reserved.
ISBN: 978-0-226-05991-4

---

CHAPTER 1

Absent Friends

How the Hygiene Hypothesis Explains Allergies and Autoimmune Diseases

Throughout the 1990s the Johnson family was being ripped apart by the increasingly violent, self-abusive, uncontrollable behavior of their son Lawrence. He was a very disturbed child and would become highly agitated, smash himself in the face, bang his head against walls, try to gouge out his eyes, and bite his arms until he bled. At age two and a half, he was diagnosed with autism, and as he got older, things got worse. If traffic lights failed to change according to his inner timetable as he passed them while walking down the street, he would explode with rage. He could not deal with crowded places like restaurants or movie theaters, and frequently had to be physically restrained from hurting himself. His doctors tried anti-depressive medication, anti-seizure drugs, anti-psychotics, and lithium, among others, to no avail.

His parents were at their wits' end. But because Lawrence's father, Stewart, is an active, coping, problem-solving sort of man, he tried to think his way through his son's illness and became a self-taught scholar on autism. A clue soon emerged. "We noticed that when Lawrence had a fever, all that would go away. And it was true 100 percent of the time. If his temperature went up and he had a fever from a cold, flu, or sinus infection, he would stop hitting himself, he would be calm, he was like a different child. We talked to other parents with autistic kids, and they all said the same thing."

Was it simply the lethargy of feeling poorly that damped down Lawrence's bad behavior? Some scientists have suggested that fever changes neural transmission in the brain, while others have invoked changes in the immune system. No one knew for sure. But everybody who either had to live with Lawrence or care for him said the same thing: "We're very happy when he gets sick, because life is wonderful!" However, whenever his fever subsided, the frightening behavior returned. By 2005, when Lawrence was fifteen, Stewart and his wife decided they could no longer take care of Lawrence on their own. While Lawrence was away at a specialized summer school, they reluctantly applied to have him taken into care for the rest of his life. "Lawrence was going to go and be somebody else's problem because he was killing our whole family."

It was at that precise moment, with Lawrence's dismal future decided, that they received a phone call from summer camp. They feared the worst. "But they said, 'We don't know what's going on, but Lawrence is behaving completely normally. He's fine, he's not freaking out, he's not hitting himself, he's not throwing his food, he's participating in all the activities, he's interacting....'" Stewart drove up to the camp to find his son perfectly calm, engaged with the other children, and pleased to see him. They got into the car for the two-hour drive home, and Lawrence announced that he wanted to go out for dinner. He hadn't been to a restaurant in two or three years. "But now he wants to go to this place that's extremely noisy and crowded, which is a place we'd normally cross the street to avoid. He would normally never wait in line, but we waited forty-five minutes, we got served, he ate, we had a wonderful dinner!"

Stewart drove the family home, his mind whirling. Later that night he was helping Lawrence get undressed for bed when he noticed that he was completely covered in chigger bites from his thighs to his ankles. Chiggers, biting mite larvae, are very common in the summertime where the family lived, and Lawrence had been bitten by the chiggers in the long grass of summer camp. What could be the link between chigger bites and the total remission of Lawrence's autistic symptoms? It drove Stewart back into the literature to discover that chiggers elicit a very powerful immune response as they drill into the skin and release saliva to digest host tissue. They then drop off, leaving a patch of hardened scar tissue that itches for days until the immune reaction subsides. For ten days, while Lawrence's immune system fought the chigger infection instead of him, they had a wonderful time, but as the bites faded and the itching stopped, he returned to his violent and self-destructive behavior. "I immediately said, 'That's it. I've seen enough. There's an answer here. At least some part of my son's symptoms are an aberrant immune response.'"

Stewart knew that his son's physician, autism expert Dr. Eric Hollander of the Albert Einstein College of Medicine in New York, had done research showing that there was nine times the incidence of autoimmune disease in the first-order relatives of autistic children, compared to those of normal children. Lawrence has a peanut allergy; Stewart suffers from myasthenia gravis, an autoimmune disorder that causes fatigue and weakened muscles; and his wife is asthmatic. His family medical history was consistent with research that links autism to autoimmunity and allergy. Back in 1971, researchers at Johns Hopkins University reported on a family study where the youngest son in the family had a multiple diagnosis of autism, Addison's disease (an autoimmune condition affecting the adrenal glands), and candidiasis (infection with the opportunistic yeast, Candida albicans). The next older brother had hypoparathyroidism, which can have autoimmune origins, Addison's disease, candidiasis, and type 1 diabetes. The next older brother had hypothyroidism, Addison's disease, candidiasis, and alopecia totalis — an autoimmune condition that causes the loss of all head hair. The oldest son, and firstborn, was symptom-free, like his parents.

In 2003 Thayne Sweeten, from Indiana University School of Medicine, reported that the rate of autoimmune disorders in the families of children with autism was even higher than in the relatives of children with autoimmune diseases. Disorders included hypothyroidism, Hashimoto's thyroiditis (where the thyroid gland is attacked by autoantibodies and immune cells), and rheumatic fever. Sweeten said that the finding of increased autoimmune illness in grandmothers, uncles, mothers, and brothers of autistic children "suggests a possible mother-to-son transmission of susceptibility to autoimmune diseases in the families of autistics," and speculated that autoimmunity or chronic immune system activation could account for some of the biochemical anomalies seen in autistic individuals, including high uric acid levels and iron-deficiency anemia, which are also seen in autoimmune disorders. Research conducted on Danish children between 1993 and 2004 by Dr. Hjördis Atladóttir agreed with Sweeten by finding higher rates of autism in children born to mothers who suffered from celiac disease (where you cannot tolerate gluten). The study also linked autism to a family history of type 1 diabetes and to children whose mothers suffered from rheumatoid arthritis.

Chiggers, remission of autism, and autoimmunity all began to come together in Stewart Johnson's forensic mind. If immune disorder — a hyperactive immune system — was causing his son's autism, he needed something to damp it down. His research led him to the work of Joel Weinstock, David Elliott, and colleagues, then at the University of Iowa. Weinstock's group had reported success in medical trials where they had treated a small number of patients with Crohn's disease, an autoimmune inflammatory bowel disorder, with the eggs of an intestinal parasite — the pig whipworm. They had treated one group of twenty-nine patients with 2,500 live whipworm (Trichuris suis) eggs, delivered via a tube into their stomach, every three weeks for twenty-four weeks. By the end of the treatment period, 79 percent of the patients had responded dramatically; the whipworm eggs had driven their Crohn's disease into remission. "I was impressed," says Stewart. "These were real scientists doing real work and getting results; this was not fringe stuff. It certainly looked good for Crohn's, so I thought, 'Maybe I'm right with this.' So I wrote all this up and did a sort of mini research paper with references, and I gave it to Eric Hollander."

Hollander was intrigued. "Stewart is a very smart guy and he'd done a lot of intense research and he just pulled out the literature and we talked it over. It seemed like a plausible hypothesis and a reasonable thing to try." Hollander obtained the necessary clearance to administer the treatment and helped Stewart with the task of importing the whipworm eggs from Germany. They began with a low dose, for fear of side effects. Stewart took the eggs as well — he wasn't about to foist a seemingly bizarre treatment on his son that he was not prepared to share. The initial results were extremely disappointing. They only saw the "good" Lawrence for four noncontiguous days during the whole twenty-four weeks of treatment. Stewart rang the manufacturers and they told him that the results were actually predictive of someone who ultimately does respond and will respond better at a higher dose. So they went to the same level that Weinstock had set for his Crohn's patients — 2,500 eggs per treatment. Within eight days Lawrence's symptoms completely evaporated, and they have stayed away ever since. The old Lawrence only briefly returned four times when they experimented by taking him off the eggs for a few days. So far, as long as he keeps taking the eggs, his autism symptoms appear to be kept at bay.

Stewart Johnson had discovered the hygiene hypothesis, which links the bacteria, fungi, and helminths (parasitic worms) in our guts, on our skin, and in our airways and vaginas, and a host of autoimmune and allergic diseases. There is mounting evidence that the composition of all these organisms, living on us and inside us — collectively known as our microbiota — can offer protection against a formidable list of autoimmune diseases, including the inflammatory bowel diseases Crohn's disease and ulcerative colitis, type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and, as we have seen, mental health. Some studies suggest that they can also protect against a comparable list of common atopic or allergic illnesses like eczema; food, pollen, and pet allergies; hay fever, rhinitis, and asthma. Nevertheless, it cannot be stressed strongly enough that autism is a complex, multi-factorial illness and that the therapeutic application of all the science associated with the hygiene hypothesis, for a variety of autoimmune and allergic diseases, is still very much in its infancy and largely unproven — Lawrence Johnson's treatment, for instance, is a one-off experiment, not the result of tried-and-tested medicine. But much of the research is compelling, and if it can translate into medical therapy, it could represent, within a few years, nothing short of a revolution in medicine.

Dramatic improvements in hygiene, sanitation, and water quality from late Victorian times to the present day, allied to extensive use of antibiotics and population-wide vaccination, have raised the quality of life and life expectancy throughout the developed world. But, perplexingly, post-industrial society — while largely eradicating epidemics of polio, whooping cough, dysentery, measles, and many other potentially lethal or debilitating infections — has fallen prey to new, major growing epidemics of autoimmune and allergic disease. Take bowel disease for example. According to Weinstock's research, prior to the twentieth century, inflammatory bowel disease (IBD) was largely unknown. Between 1884 and 1909, hospitals in London were averaging two cases of ulcerative colitis per year at most, and Crohn's disease only became recognized in 1932. But during the second half of the twentieth century, IBD gained in scope and prevalence. Currently, IBD in the United States affects between 1 and 1.7 million people. The current estimate is that 2.2 million people in Western Europe and the United Kingdom have IBD. Although once thought to have stabilized, the incidence of Crohn's disease continues to gradually rise in England, France, and Sweden. IBD is less prevalent in Eastern Europe, Asia, Africa, and South America. However, as countries in these regions develop socioeconomically, IBD increases. Moreover, when people move from a country with a low prevalence to a country with high prevalence of IBD, their children acquire a higher risk of developing IBD.

Although type 1 diabetes has been around for centuries, it also is on the rise — and too fast for genetic change to be implicated. This guilt-by-association link between affluent, hygienic, Westernized countries and the rise of autoimmunity also extends to multiple sclerosis (MS), which has a low incidence in tropical regions that increases as you move north of the equator. In the United States, prevalence is twice as high north of parallel 37 than below. Infectious agents, genetics, and vitamin D levels have all been implicated, but, intriguingly, adult immigrants leaving Europe for South Africa have a threefold higher risk of developing multiple sclerosis than those migrating at age fifteen or less, suggesting a protective environmental effect in the adoptive country, operating only on the young. The opposite trend is seen among the children of immigrants to the United Kingdom from India, Africa, and the Caribbean (all regions of low prevalence), where the risk of developing MS is higher than among their parents but similar to children born in the UK. Jorge Correale, a neurologist from Buenos Aires, points out that MS is rising steadily in all developed nations. In Germany, the incidence of MS doubled between 1969 and 1986, he says, while MS has increased twenty-nine-fold in Mexico since 1970, in line with steadily improving living standards. Correale also reports a fascinating inverse relationship between MS and the distribution of a very common intestinal parasitic whipworm, Trichuris trichiura, which used to be extremely common in the southern United States and still is common throughout the developing world. MS prevalence, he explains, falls steeply once a critical threshold of 10 percent of the population infected is reached. In a similar way, common atopic diseases like eczema and asthma are relatively rare in the developing world, whereas levels of helminth infection are relatively high.

Weinstock recalls how the "penny dropped" for him while ruminating in his seat on an aircraft waiting interminably for takeoff from Chicago's O'Hare Airport. He was thinking of cause and effect — I do something and then something happens. He suddenly realized that the answer to the conundrum of rising levels of bowel disorder and other autoimmune diseases lay in "what doesn't happen but used to." In other words, it wasn't about what new aspects of our environment could be contributing to autoimmunity but what had been taken away from our modern environment that might leave us open to it. "In the historical environment we had filthy streets — horse dung was a major feature — and many people walked barefoot or were poorly shod. But now we have built roads and sidewalks and we wear proper shoes, and so our ability to transmit these organisms from one another went down lower and lower. Then we cleaned up the food supply, the water ... everything got clean. As a result worms disappeared. And when you look at the incidence of deworming from population to population and the rise of immune-mediated diseases, you find that they are inversely related. That's a negative correlation, it doesn't prove that worms are effective — but it is a smoking gun."

Modern sanitation has proved disastrous to most helminths, says Weinstock. Indoor plumbing and modern sewage treatment spirit away their eggs before they can spread infection, as do frequent baths and laundered clothing. Cleaning fluids disinfect utensils and domestic surfaces, blocking their transmission. Sidewalks and shoes obstruct the common hookworms Necator americanus, Ancylostoma duodenale, and Strongyloides stercoralis, while modern food processing kills Diphyllobothrium, Taenia, and Trichinella larva. These changes have all but eradicated helminths from industrialized countries. Until the 1960s, trichinosis was endemic in the northeastern and western United States through the eating of contaminated pork. There are now less than twenty-five cases a year. Removal of these parasites has undoubtedly reduced a huge amount of morbidity in the population, but the baby has been sluiced away with the bathwater — the protection afforded by these organisms has gone with it. A classic example of this two-edged sword effect comes today from East Africa. Educational learning specialists looking at achievement in Kenyan schools had assumed that lack of textbooks and flip charts were the major factors holding pupils back but discovered, to their surprise, that helminth gut parasites were much more important. Huge deworming programs have since almost eradicated bilharzia and hookworm, and exam results have consequently risen dramatically. However, the unwanted byproduct of deworming has been a dramatic rise in eczema and other allergies among Kenyan and Ugandan children. In tropical Africa the irritation of these skin conditions often goes untreated, and constant rubbing and scratching of the sores leaves children open to infection and septicemia.

(Continues...)

---

Excerpted from Body by Darwin by Jeremy Taylor. Copyright © 2015 Jeremy Taylor. Excerpted by permission of The University of Chicago Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

---

Table of Contents

Introduction
 
ABSENT FRIENDS
How the Hygiene Hypothesis Explains Allergies and Autoimmune Diseases
 
A FINE ROMANCE
How Evolutionary Theory Explains Infertility and Diseases of Pregnancy
 
THE DOWNSIDE OF UPRIGHT
The Relationship between Bipedalism and Orthopedic Illnesses
 
DIY EYE
How Developmental Biology Cures Blindness and Rebuts Creationism
 
HOPEFUL MONSTERS
Why Cancer Is Almost Impossible to Cure
 
A PROBLEM WITH THE PLUMBING
Why the Evolution of Coronary Arteries Makes Us Prone to Heart Attacks
 
THREE SCORE YEARS—AND THEN?
How Evolution Is Breathing New Life into Moribund
 
Dementia Research
 
Acknowledgments
 
Suggestions for Further Reading

Editorial Reviews

09/14/2015
Taylor (Not a Chimp), a science writer and former BBC producer and director, celebrates the work of Charles Darwin and his successors in this densely packed survey of modern ailments with an evolutionary twist. “The value of thinking in evolutionary terms is that it acts like a forensic tool to ask fundamental questions that allow us to reframe illness in a different way that might then lead to new answers,” Taylor says. He applies this approach to asthma, autoimmune disorders, backache, preeclampsia, diseases of the eye and heart, diabetes, cancer, and Alzheimer’s disease, among many others. Taylor gives credit to researchers looking at human evolution to explain modern medical terrain, even though their research is often met with skepticism and discomfort. Though his book’s scientific content is firmly directed at medical practitioners and researchers, Taylor balances the text with humanizing case studies, including a father whose work on immunity and the human microbiome helped spare his autistic son from life in an institution, and the “heretical band of scientists” looking for guidance from evolution as they race to relieve the agony of Alzheimer’s sufferers. Taylor covers fascinating territory, and readers willing to wade into its technical aspects will find much to ponder. (Nov.)

Publishers Weekly

Drawing on complicated science, interviews, and current research, Taylor describes the body as an evolutionary collection of compromises, leaving the human species susceptible to degeneration and illness. . . . One anthropologist describes evolution as 'a tinker not an engineer.’ Understanding how this tinkerer has molded the body provides greater insight into the ways our health works and fails.” 

Booklist

Body by Darwin packages cutting edge science into seven vivid true stories dramatically describing patients and their doctors discovering evolutionary explanations for diseases. More than just the perfect book club book, it advances the field of evolutionary medicine. I will use it in my classes and give copies to my friends.

Randolph M. Nesse

There is a wealth of information in Taylor’s book, and . . . those who commit time and thought to Body by Darwin will come away with a new understanding and appreciation of our bodies and how and why they work.”

Washington Independent Review of Books

"This is a fantastic book that I found hard to put down. Taylor has tackled some of the primary health concerns for many of us in industrialized nations, including allergies, hypertension, cardiovascular disease, Alzheimer’s disease, and back and knee problems that result from a lifetime of walking on two legs. Each chapter begins with a story of someone who is afflicted with one of these health challenges, drawing attention to real lives in ways that are compelling, and the thoroughness with which each topic is developed sets this book apart from most others that I have read on evolutionary medicine.” 

Wenda Trevathan

“Body by Darwin attempts to trace the evolutionary history of many common medical issues, including heart disease, miscarriage, dementia, cancer, and back pain, with an eye toward what evolution can tell people about the possible origins of these problems and, ultimately, strategies for treatment.  . . . Taylor succeeds in drawing provocative connections between health and evolution that add an important perspective to how people should think about the theory and practice of modern medicine. Recommended.”
 

Choice

Taylor has accomplished the difficult feat of appealing to the general reader in a book aimed also at medical professionals. Doctors really do need to imbibe Darwinism, not just as the explanation for all life but as a message of direct importance to medicine itself.

Richard Dawkins

Taylor is often eager to demonstrate that the human body is for the most part a remarkably well-adapted structure. . . . Taylor does a fine job of raising provocative questions and pointing the reader toward the ways in which evolutionary biology has been enhancing medical science.”
 

Wall Street Journal

“Taylor is often eager to demonstrate that the human body is for the most part a remarkably well-adapted structure. . . . Taylor does a fine job of raising provocative questions and pointing the reader toward the ways in which evolutionary biology has been enhancing medical science.”
 

Wall Street Journal

“Drawing on complicated science, interviews, and current research, Taylor describes the body as an evolutionary collection of compromises, leaving the human species susceptible to degeneration and illness. . . . One anthropologist describes evolution as 'a tinker not an engineer.’ Understanding how this tinkerer has molded the body provides greater insight into the ways our health works and fails.” 

Booklist