This week’s Science has an extensive review of the National Academy Sackler Colloquium on Evolution in Health and Medicine. Elizabeth Pennisi packs many examples into just a few paragraphs and gives a vivid sense for the excitement of the meeting and its possible future impact. She contrasts the active participation of physicians at this meeting with their near-absence at first meeting for the field, actually organized by Steven Stearns, who also edited the foundation text in the field, Evolution in Health and Disease, and, with Jacob Koella, a second edition, now available from Oxford University Press. Pennisi’s article does a fine job of emphasizing the importance of evolutionary biology for medicine, and also the many challenges faced by Dean’s who must cope with an already over-crowded curriculum.
In the same issue, Constance Holden reports on the session at the Colloquium about evolutionary approaches to schizophrenia. More on that later.
Science 10 April 2009:
News of the Week
Darwin Applies to Medical School
When George Williams and Randolph Nesse made their first pitches for Darwinian medicine in the early 1990s, they turned some heads, but not the right ones. Reviving and building on European traditions that melded medicine and evolutionary biology, the duo argued that diseases could be best understood from an evolutionary perspective. Their first meeting on the subject in 1996 attracted 60 enthusiasts but few practicing clinicians, probably because physicians couldn’t envision practical applications. “The folks who were excited about it weren’t in a position to do anything about it,” recalls anthropologist Peter Ellison of Harvard University. Although a better understanding of the evolution of drug resistance has helped shape the use of antibiotics, when it comes to evolution, “medical schools are mostly oblivious,” says Nesse, a psychiatrist at the University of Michigan, Ann Arbor.
But times may be changing. Last week, a similar meeting* in Washington, D.C., attracted dozens of physicians, including the dean of Harvard Medical School and the president of the Institute of Medicine (IOM). Several participants described new medical school programs at the University of Auckland, New Zealand, and at Johns Hopkins University in Baltimore, Maryland, involving evolutionary medicine, as well as a pending textbook. “A thoughtful strategy for the future education for health professionals would incorporate a strong evolutionary perspective,” says IOM President Harvey Feinberg.
At the meeting, researchers reported headway in understanding drug resistance through the lens of evolution. Others described progress linking past evolutionary adaptations with current health problems. For instance, anthropologist Kathleen Barnes of Johns Hopkins University has evidence that for some asthmatics, this overly energetic inflammatory response may be a holdover from the body’s successes in coping with parasitic disease.
Despite the intellectual appeal of adding evolution to the medical school curriculum, medical schools are already straining from an explosion in information and technology, and clamors for change come from many directions. “Medical schools have a lot on their plate,” says James Lupski of Baylor College of Medicine in Houston, Texas. And, notes Harvard evolutionary biologist David Haig, “Evolutionary thinking is not going to give cheap medical solutions.”
Proponents counter that evolutionary thinking can provide a fresh way of looking at the human body and a framework for organizing a deluge of new genomic information. Those new data are driving home how tightly disease is linked to evolution, says David Valle, a geneticist at Johns Hopkins University School of Medicine. He and others want to move away from viewing the human body as a generic, one-size-fits-all machine. Individuals vary not just in their genetic makeup but in their connections to the microbes in their gut and their environmental exposures. “All this must somehow be understood” to manage disease, says Diddahally R. Govindaraju, a Boston University geneticist who co-organized the meeting. With genomic data in hand, “medical students are much more equipped to understand the connections between all organisms,” he adds.
During her talk, Barnes presented several examples that suggest that how humans evolved to cope with past parasitic diseases has predisposed some of us to contemporary health problems. The malaria parasite Plasmodium vivax, for instance, depends on a surface protein called Duffy to gain entry into human red blood cells. In certain malaria-endemic areas, a mutation in the gene for Duffy, called DARC, leads to the loss of this surface protein, and malaria can’t gain a foothold. But Duffy also acts as a sponge to keep immune system messengers in check; otherwise excess immunoglobulin E (IgE), which underlies allergic asthma and other allergic reactions, may be produced. Barnes and her colleagues have found that asthma is associated with the defective Duffy gene in populations in Brazil, Columbia, and the Caribbean whose recent African ancestors lived where malaria was endemic.
Similarly, others have found asthma associated with high IgE in areas such as Egypt where schistosomiasis is common. Today, cockroach and dust mite allergens are well-established triggers for asthma, and those proteins are quite similar to the schistosomiasis worm protein tropomyosin, which sets off the IgE response. People with high IgE are most able to curb parasite infection, but there can be a downside. “Individuals who are most resistant in these [worm-ridden] environments are the ones who produce the most IgE, and they are primed to respond to the common household allergens,” says Barnes. She has traced this sensitivity to some variants of the gene for the immune system messenger interleukin 13.
“She has sophisticated evolutionary thinking that she’s applied to two different medical problems, and she has not just clinical and epidemiological data, she has the genetic underpinnings. She has the complete story,” says Nesse.
Knowing these evolutionary connections could help physicians recognize who might be at increased risk for asthma and who should take precautions to limit exposure to allergens, says Barnes.
At the beginning of the meeting, Harvard Medical School Dean Jeffrey Flier called himself agnostic about the need to incorporate evolution into medical education. But now, “I want to start to influence the medical curriculum toward that,” he announced as the meeting wrapped up. “Evolutionary biology needs to get in the queue.”
At last, says meeting co-organizer Stephen Stearns of Yale University, “we’ve gotten the attention of the medical community.”