Gross Anatomy Meets Natural Selection

Perlman 1Evolutionary biologists focus on populations, variation and natural selection. Doctors focus on individuals, their patients and disease. Their goal is to treat their patients’ illnesses or at least to relieve their patients’ discomfort.

The tools physicians have come up with, however, have been reliably undermined by nature. Antimicrobials were going to rid the world of infectious disease. Mass production of penicillin, the first antibiotic, began in 1943; by 1947, a high percentage of Staph aureus infections had evolved resistance to it. By the mid 1970s, cancer researchers were just starting to incorporate evolutionary notions into their understanding of cancers. Now, tumor evolution, often down multiple paths, is a “foundational concept in cancer biology,” according a review in the New England Journal of Medicine.

The health care community as a whole, however, remains uncomfortable straddling the chasm between evolutionary biology and medical care. The two fields, though related, concentrate on different problems, speak different languages, and see the world in different ways.

More than 20 years ago, Robert L. Perlman, MD, PhD, professor emeritus of pediatrics and of pharmacology and physiology at the University of Chicago, began building bridges. “I did standard biomedical research for most of my career,” he explained, “but I am a physician with an interest in evolution.”

When he served as master of the biological sciences collegiate division at the University of Chicago in the 1990s, responsible for undergraduate education in biology, it soon became clear that something was missing, especially for students who were interested in the health professions.

Robert Perlman, PhD

Robert Perlman, PhD

“College students need the big picture,” he said, a framework on which to hang the details. “Evolution by natural selection – the central, unifying theory in biology – is the obvious choice.” But the two fields, medicine and biology, developed as separate disciplines. “There is very little interaction between them,” he said. “That’s unfortunate.”

To fix the problem, he began co-teaching a course in Darwinian medicine, first with Michael Wade, PhD, former chair of evolutionary biology at the University of Chicago, “who taught me about evolution at a whole new level,” then with another colleague, William Wimsatt, PhD, a philosopher of biology. The students really liked the class, Perlman said, but they might have learned more, and liked it better, with the aid of an integrated textbook.

So, Perlman wrote one – “Evolution and Medicine,” Oxford University Press, 2013. The target audience was college students. “All aspiring doctors could benefit from a solid grounding in evolutionary thinking,” Perlman said, “but it’s unrealistic to think we could shovel that approach into an already overstuffed medical curriculum.”

For undergraduates, however, this is “exactly the way we should teach biology,” he said. “It’s much more cohesive, more likely to stick in the mind than the sharply focused technical questions that attract working biologists.” Integrating evolutionary concepts into medicine has the potential to “improve our understanding of disease and, most importantly, clinical practice.”

The book examines various aspects of evolutionary theory that are relevant to medicine, interspersed with chapters on how those theories play out in specific diseases. The first few chapters lay out the basics. One focuses on human demography, disease and death. Then comes a primer on genetics, as seen from the evolutionary perspective. The next chapter looks at the emergence and persistence of cystic fibrosis.

The next six chapters follow a similar pattern, with a focus on various health challenges from the evolutionary point of view, followed by relevant examples. First is a careful look at how evolution shaped overall life-history strategies: how we allocate energy to growth and especially reproduction.

This is followed by a chapter on cancer, primarily a disease of aging, then a chapter each on host-pathogen co-evolution, sexually transmitted diseases and malaria. Finally there are two chapters on man-made problems: one with ancient origins, lactase persistence, a consequence of domesticating animals, and one on more contemporary scourges – chronic lifestyle diseases such as obesity, diabetes and hypertension.

Although helping college students was the trigger for the book, “I tried to make it accessible to any interested, intelligent adult without a scientific background,” Perlman said. His goal was to make the cross-connections between evolution and medicine interesting to “knowledgeable non scientists, non-physicians.”

The book, at 162 pages, including the index, is accessible, consistently engaging and encouragingly concise. “Maths kept to a minimum,” notes the publisher’s blurb, “so as not to interfere.”

“I loved writing it,” Perlman said. “I got really immersed in it, devoted myself to it. It just felt good. Between aging and sexually transmitted diseases, there’s something in here for everybody.”

His enthusiasm, explanatory powers and extensive background in medicine and evolutionary biology shine through. The writing is clear.

“Oh gosh, is it clear,” according to a review by Michael Ruse, FRSP, the Lucile T. Worcester Professor and Director of the History and Philosophy of Science Program at Florida State University. “This man must have been a wonderful undergraduate teacher – comprehensive, authoritative without being condescending. The author tells us that he wants to reach a broad audience … If there is any justice in this world, he will. I would hope that it might become simply standard reading for just about anyone interested in health care.”

Perlman supports that notion. “Sometimes I feel like I’m a missionary for this field,” he said. “There’s a lot of interest in evolutionary medicine among anthropologists and all sorts of biologists – especially in host-pathogen co-evolution, which is tremendously important for medicine – yet it’s not something that’s really talked about in medical circles. It hasn’t caught on the way it should. I hope to change that.”

A typical example, he said, is the development of triple therapy for HIV. This highly effective approach was designed in part around evolutionary considerations. “If you treat HIV with a single drug, you select for drug-resistant mutations,” Perlman said. But if you treat it with three drugs together, that’s much less likely to produce an organism resistant to all three. So the combination is much more effective.

“Buy and read this splendid book,” raves Ruse, the reviewer. “Then make sure that all of your students do too.”

Read a sample chapter of “Evolution & Medicine” on obesity, diabetes and hypertension at The Scientist.

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