Ben Carson, retired neurosurgeon and presidential hopeful. (Photo: V. Aceveda/Wikimedia Commons)

Earlier this month, Dr. Ben Carson announced that he's running for president. Carson was previously the head of pediatric neurosurgery at Johns Hopkins Medical Institutions. He also rejects the theory of evolution. Here at Pacific Standard, his stance made us wonder: How can doctors deny evolution?

We assumed such beliefs would be unusual among doctors. After all, evolution is the foundational principle of biology, which, in turn, is the basic science that backs medicine. Ninety-eight percent of scientists, a closely related profession, accept evolution.

Unfortunately, there don't seem to be great numbers on the percentage of doctors who accept evolution. In 2007, the Jewish Theological Seminary conducted a survey on this topic, finding that 78 percent of doctors accept evolution. The seminary's polling method isn't readily available online, however, so we couldn't immediately tell what the strengths and weaknesses of the poll were. Still, when Pacific Standard talked to doctors, many didn't find their colleagues' rejection of evolution unusual. "Nope, it's not uncommon at all," says David Gorski, a surgeon and researcher at Wayne State University. Even in the national spotlight, Carson isn't the only high-profile politician-physician to doubt the well-established biology concept.

"Most physicians are not scientists. This is not a knock, but they're more akin to engineers."

All of the physicians Pacific Standard talked with, both on and off the record, had the same answer to "How is it possible?": Although doctors use many insights from biology, many don't actually need to understand or believe in evolution correctly to do their jobs.

"Most physicians are not scientists. This is not a knock, but they're more akin to engineers," Gorski says. "They take science that's already known and they apply it to a problem, the problem being making patients better."

"Routine medical care doesn't require a whole lot of thinking about underlying biology or evolution," says Gilbert Omenn, a doctor and researcher at the University of Michigan. "The why and even the how is not essential, if you have good published evidence that something works and you've seen it work in some of your patients, then it's enough to try and help your patient as best you can."

When I asked if I should worry if I had a doctor who didn't accept evolution, the consensus answer seemed to be: Not necessarily, but be cautious.

"To be honest, to do an operation, you probably don't need to understand evolution."

"I think it depends on the specialty," Gorski says. "To be honest, to do an operation, you probably don't need to understand evolution. If you're in infectious disease, however, where evolution to antibiotic resistance is a very important consideration, I would say it would not be a good thing not to accept evolution."

To be sure, a doctor could be sharp about facts in his or her own specialty and still hold anti-evolution beliefs—to which she's entitled. But, as Omenn says, "the question is what you're missing and misunderstanding if this is your starting point."

I should point out here that there are many shades of disbelief in evolution. Less extreme forms may be more or less compatible with the levels to which a doctor of a given specialty needs to understand evolution. Believing that God created humans in present form is rarer among Americans with more education, which would include doctors. Many Americans believe in some kind of "guided" evolution—perhaps some doctors do too. That said, the full form of evolutionary theory explains how all the species on Earth today arose without guidance and continue to evolve, by reacting to the pressures from each other, other species, and their environment.

So much for "How is it possible?" And answering "Why does it happen?" is an even more inexact science. One survey, published in the Journal of General Internal Medicine in 2005, found that American doctors are about as likely to be religious as the general population—which is to say, very likely. And religiosity, it's well-known, correlates with a rejection of evolution. This stands in contrast to scientists, who are much less likely than the average American adult to be religious.

Medical training presents the results of generations of scientific experiments as a list of facts to recall.

Gorski thinks this difference between doctors and scientists arises because people choose to enter the two professions for different reasons, although both start their training by taking many of the same classes in college. Would-be doctors might be motivated by a desire to help people, or to serve humanity—a tenet in many religions—while budding scientists might be more interested in how the physical world works.

Another potential culprit: the memorization-based nature of medical training, which may give a doctor-to-be the impression that biology is a made up list of facts to recall; not a process that has gathered evidence for concepts like evolution over generations of experimentation. Most medical schools offer their students the opportunity to do some research, to give them a taste of the other side, but it's clearly not enough to change their rates of acceptance of evolutionary theory.

With time, more specialties might require understanding and accepting evolution in full. "For example, in oncology, it's become very important," Gorski says. "Tumor cells undergo selective pressure as they develop and get treated. We can track that through various genomic methods we didn't have before."

Plus, an evolutionary understanding of the human body can make doctoring feel richer, Omenn thinks. The symptoms people see their doctor for—vomiting, diarrhea, or anxiety, for example—all developed to protect our evolutionary ancestors. Doctors get to see and intimately know the end product of humanity's evolution so far, in all its frailties.