Thinking Out of the Box: The Intriguing Field of Darwinian Medicine
Winter has arrived, and Cornell University student Julie DeMichele sits stiffly in a hardback chair of a packed lecture hall. In an attempt to begin her statistics exam, she looks at question one, but her eyes blur, and she braces herself for a muffled sneeze. She grabs a tissue to stop her nose from running. Behind her, someone coughs. Why did she have to get sick now? Why were her eyes tearing, or her nose running? Why were the symptoms of this cold, a non-life threatening disease, so unbearable? She wished that she had taken Sudafed® earlier this morning. Then at least, she would have been able to concentrate on her exam instead of whether she was going to have enough tissues.
Ironically, if DeMichele had taken Cornell's Neurobiology 221 class, or read psychiatrist Randolph M. Nesse and evolutionary biologist George C. Williams's book Why We Get Sick, she might not have been so annoyed at her cold's symptoms and might have actually venerated their existence.
Within the last few decades, the birth of a new field of science called Darwinian medicine has led evolutionary biologists, doctors, and undergraduate students to reexamine disease, symptoms of disease and other imperfections of the human body, to better understand the purpose of their existence.
Established in the mid-1980's, researchers of Darwinian medicine study symptoms such as DeMichele's runny nose, and ask why our bodies have developed these inconveniences, and what could be their possible benefit. Such an approach of looking at symptoms of disease varies from our traditional medical perspective by answering why' instead of how'.
According to evolutionary biologist Paul Sherman, traditional medicine usually first asks the question how: how do our bodies produce this gelatinous liquid that often leaves us with soiled shirtsleeves, and then immediately looks for a quick fix for the symptom. Sudafed® may dry up the mucus membranes that produce runny noses, but can it help people get better? Maybe.
A Darwinian medicine practitioner focuses on the question of whether a runny nose is an evolutionary, evolved-defense mechanism that is in fact protecting the body from acquiring a more serious viral or bacterial infection. Choosing to take Sudafed® may actually hinder the body from fighting minor infection, and instead may leave the body susceptible to catching a more serious disease such as the flu.
According to Sherman, this approach of stepping back and examining our vulnerabilities to disease from an evolutionary perspective has the potential of not only furthering our understanding of the human body, and why it behaves the way that it does, but it offers traditional doctors more options when deciding how to treat their patients. Instead of always instructing patients to take Tylenol® or aspirin to reduce a fever, they may recommend honoring the fever and letting it run its course, Sherman says.
In Nesse and Williams' book Why We Get Sick: The New Science of Darwinian Medicine, the authors state that "fever is an adaptation shaped by natural selection specifically to fight infection," rather than a defect. Both scientists emphasize that this difference is crucial. A fever's benefits are two-fold: increased body temperature makes the body inhospitable for bacteria to survive and reproduce effectively, yet at same time, increases the rate of bodily functions which are responsible for combating infectious diseases (i.e. white cell production). Suppressing a fever, or any other evolutionary adaptation that may have been naturally selected as a defense against infection (i.e. coughs, diarrhea, runny noses, morning sickness, or pain from tissue or muscle damage), may prevent the human body from effectively combating the pathogen or condition. What could have been a two-day fever or cold may turn into one that lasts a week; or the worse case scenario, may actually permit a life-threatening pathogen to invade an already weakened immune system, the authors said.
For Cornell University senior and neurobiology major Brian Allen, the first time he was exposed to this complimentary method of examining disease and imperfections of the human body, he was instantly captivated. He remembers sitting in Cornell University's Uris Hall Auditorium his sophomore year, when Professor Sherman began to lecture about morning sickness (NVP) in Neurobiology 221- a course that examines animal behavior from an evolutionary perspective. He told the class that despite NVP's apparent discomforts, NVP is Mother Nature's way of protecting expectant mothers and fetuses from food-borne illness, and also shielding the fetus from chemicals that can deform fetal organs at the most critical time in development.
Allen recalls at first being blown away, and then wondered why nobody had come up with this way of examining disease earlier. "Everyone knows about NVP: its symptoms, when it occurs and what it does to the body, but nobody has ever questioned why," he said.
Allen never thought it would be possible to find a scientific subject that would really open his mind and make him think outside the box. He always figured he would have to turn to philosophy. Yet he realized that who ever said never say never' was right.
Historically, humans have tried to understand science through reductionalism- breaking disease down to the molecular level. The science behind Darwinian medicine takes a step in the opposite direction. We are starting to look at why behaviors evolved, and are getting people to think differently, Allen says.
For Allen, all it took was two lectures on Darwinian medicine to fuel his desire to pursue a research project of his own. Paring up with Sherman, Allen's own research is building upon two of Sherman's previous research findings.
In 1998, Cornell University biologists proved that the traditional use of spices not only has the ability to make food taste good, but that it can provide protection from food borne microbes, especially in hot climates where food spoilage was rampant. Jennifer Billing and Sherman reported upon spices' anti-microbial properties in the March 1998 issue of the Quarterly Review of Biology.
Building upon this finding, in June of 2001, Sherman and Cornell undergraduate student Geoffrey A. Hash reported in an issue of Evolution and Human Behavior why vegetable-based recipes in 36 countries around the world are less spicy than meat-based dishes in the same societies. "Meat-based recipes that were developed over centuries in hot climates need all the help they can get from antimicrobial spices, whereas food-borne pathogens are less of a problem in plant-based foods," says Sherman.
Allen is now taking this research one step further. By the end of this year, he hopes to discover: 1) How the types of spices used on different types of meat and vegetables vary with their susceptibility to disease infestation, 2) Why the ubiquitous mineral, salt, so prevalent in most mealtime dishes; and 3) How elevation and climate changes alter spice use within the same country.
Although Darwinian medicine is still considered to be a science in its infancy, research opportunities are endless. In Nesse and Williams' book Why We Get Sick, the first chapter lists six categories of evolutionary explanations of disease. Each category, attempts to demonstrate the logic that lies behind Darwinian medicine, and the vast terrain of discovery that still lies ahead.
These categories include defenses, infection, novel environments, genes, design compromises, and evolutionary legacies. In each category underlies the essential question why. "Darwinian medicine is not a specialty yet," Sherman says. "What we're looking at is probably a twenty-to thirty-year horizon before everybody in the world picks up on it."
According to Sherman, negative attitudes towards this field and its potential contribution to the medical realm are minimal. Yet in the light of new ideas, inexorable skeptics do lurk and some criticism has developed. Most of these negative attitudes stem form a misunderstanding about what Darwinian medicine is and how it functions, says Sherman.
A small number of people have tried to lump this field with the myriad of recent alternative medicine practices now out there. "But Darwinian medicine is not just another alternative medicine scheme, and to reach this conclusion shows a lack of basic understanding," Sherman says.
The misunderstanding arises from failing to recognize that traditional medicine analyzes disease on a different level than Darwinian medicine. Traditional medicine looks at proximate explanations of disease which answer what?' and how?' questions about structure and mechanism; while Darwinian medicine looks at ultimate explanations and asks why' questions about origins and functions before determining what action, if any, to take.
Neither level of analysis is correct, or better than the other, says Sherman. "Levels of analysis in science are not mutually exclusive, but are complementary," he says. To clarify this critical argument, Sherman points to his computer, which lies hidden under numerous papers and folders in his office.
"If I were to take off the outer cover that encloses the hard drive, would you be able to describe what switch does what, how each part works, and then be able to fix it if it were broken? Or, what if I wanted to know why people use computers, or why a hard cover existed over all that wiring? Can you see the difference in these types of questions? Is there a right one? A correct one? Nope. Each set of questions compliments each other," says Sherman, who believes that as soon as the majority of individuals grasp this concept of different levels of analysis, traditional medicine stands only to benefit from Darwinian medicine's insights and research results.
Unfortunately, Darwinian medicine's relevance to traditional medicine is not the only issue being challenged. Cornell undergraduate Gabriel Bloom, whose research is attempting to explain both the distribution of Lactose mal-absorption in humans, and determine what evolutionary factors led to this non-random pattern of lactose tolerant and intolerant individuals, has faced another type of criticism.
Some scientists have commented that Bloom's research methods do not stand up to the rigors of the scientific method. Although Bloom recognizes that differences do exists, she assures those apprehensive of her results that hypothesis testing still remains at the core of her research method. "Specific experimental design protocols for Darwinian medicine research have yet to be established," she says.
The main difference between Bloom's research method and standard scientific methods comes from how she acquires and evaluates data. Often the resources already available and the historic records already tabulated dictate how she will prove or disprove her hypothesis. "I have found that the paths I have started on have often mutated due to the lack of reliable information in one area, but sufficient data in another," says Bloom.
In the realm of science, this method does not make Bloom's conclusions any less valid. In actuality, her conclusions aid further developments in Darwinian medicine. It is essential that scientific research methods remain flexible in order to incorporate this new and expanding field.
The potential contributions this new field brings to traditional medical practices seem limitless for now. Darwinian medicine might foster even deeper doctor-patient relationships than those that generally exist today in traditional medicine practices.
Due to the birth of Darwinian medicine, deciding how to treat or manage a cold may never be as simple as DeMichele wanting to swallow a few Sudafed. Darwinian medicine is not necessarily going to offer alternatives that cure diseases or even relieve associated discomforts; yet it may re-educate the public that sometimes they need to let diseases run their courses instead of treating the short-term discomforts. As Ness and Williams state, "Trying to determine the evolutionary origins of diseases is much more than a fascinating intellectual pursuit; it is also a vital yet underused tool in our quest to understand, prevent, and treat disease."