What does evolution - a field that often deals with changes over many generations - have to do with preventing and treating disease in our lifetime? A lot, some scientists say. If recent recommendations are implemented, future physicians may soon be tested on evolution in medical entrance and licensing exams, says an international group of doctors and researchers.
A collection of articles in the January 26 issue of Proceedings of the National Academy of Sciences illustrates recent progress in applying evolutionary theory to a range of questions in medicine and public health, from why some people age slower and live longer than others, to why humans suffer from mental illnesses like autism and schizophrenia, to why we have higher rates of cancer than other species.
"There are many ways you can use evolution to improve medical care and medical research," said psychiatrist Randolph Nesse of the University of Michigan.
Nesse is one of a growing number of scientists who since the mid-1990s have been urging medical doctors and researchers to consider human health from an evolutionary perspective. Evolutionary training may benefit researchers in the lab, skeptics argue, but what use is evolution for everyday medical care in the clinic?
"In terms of immediate payoffs, right up at the top of the list are antibiotic resistance and cancer," said Stephen Stearns, a biologist at Yale University. Because of their rapid rates of reproduction, both bacteria and cancer cells quickly evolve resistance to the drugs we use to fight them. "Some develop resistance in just one or two years after drug release," explained Diddahally Govindaraju of the Boston University School of Medicine. "Antibiotic resistance and resistance to chemotherapy are problems that cause enormous suffering and death and also sky-high costs," added Stearns. "We can alleviate these problems if we manage the way we use chemotherapy drugs and antibiotics so as to slow or prevent the evolution of resistance."
Meanwhile in the world of infectious disease, techniques developed by evolutionary biologists - such as methods for reconstructing genetic relationships, or family trees - have been used to trace the origins of pathogens like flu, SARS, and HIV. By uncovering where these diseases came from and how they spread, public health officials can better prepare for outbreaks in the future.
Evolutionary thinking can also yield surprising medical therapies, the authors explain. Throughout much of our history, for example, humans coexisted with beneficial bacteria and intestinal worms. Reduced exposure to these bugs due to improved hygiene leaves many with immune systems that don't respond appropriately, scientists say. Research suggests we may be able to reduce our susceptibility to allergies, asthma, and many auto-immune diseases - from inflammatory bowel disease to multiple sclerosis - by giving patients "cocktails" of parasite eggs. "There are now 4000 people in a clinical trial to test the efficacy of worm eggs," said Stearns.
"It's an insight that comes right out of left field," Stearns added. "Unless you were thinking about coevolution of humans and their gut flora, you never would have thought you could treat an autoimmune disease by making the immune system think the body is inhabited by parasites."
Given the numerous ways evolutionary concepts can inform medical practice, the authors argue, it's time to transmit those lessons to those best positioned to put them to use - future physicians. Though anatomy, physiology and biochemistry have long been mainstays of medical education, evolutionary biology is largely absent from the medical school curriculum, studies find. "No medical school in the United States offers evolutionary biology as a medical science, and most have no evolution at all in the curriculum," said Nesse.