One of the most frequently used dismissals of evolutionary biology by science denialists is the assertion that it is 'only a theory.' So to is the germ theory of disease, general relativity, and atomic theory, yet special creationists tend to listen to medical advice and take antibiotics when they have a bacterial infection, accept the reality of gravitational lensing and black holes, and regard the statement that matter is composed of atoms as unproblematic. The problem of course is that special creationists fail to appreciate that in science, theory does not mean 'wild hunch or speculation', but a collection of facts, hypotheses and rules about an aspect of the natural work which has explanatory and predictive power. In other words, a scientific theory is anything other than a wild guess.
The reference to the explanatory and predictive power of theories has particular resonance with me as a medical doctor. It is hardly hyperbole to say that nothing in medicine makes sense except in the light of evolution. Genomic quirks such as the multiple shared identical genetic elements such as pseudogenes, endogenous retroviral elements, and retrotransposons at identical places in the genomes of humans and apes make no sense from a special creationist point of view, but are perfectly explicable given the reality of human-ape common ancestry.
While it is possible to be an excellent medical technician if you reject evolution (much as one can be an electronics technician and design circuits while rejecting quantum physics and quantum electrodynamics). the potential for harm - yes harm - from rejecting evolution as a medical professional is not trivial. The classic example of ignoring the reality of the evolution as a doctor comes from over-prescribning antibiotics for conditions that would self-resolve, or using them for viral infections. Inevitably, the bacteria population will be dominated by drug-resistant types, and medicine loses another antibiotic. Perhaps the most dramatic example came when a special creationist surgeon transplanted a baboon heart into an infant, an event that has just celebrated its 30th anniversary:
On October 26, 1984, Dr. Leonard L Bailey placed the heart of a baboon into the chest of Baby Fae, an infant born with a severe heart defect known as left hypoplastic heart. Baby Fae seemed to do well for a few days; then her body mounted a massive immunological attack on the foreign tissue and rejected the graft. Baby Fae's death came as no surprise to scientists and physicians familiar with the human immune system and with the scientific realities that preclude successful cross-species transplants.
Before the Baby Fae incident, Bailey, a surgeon at Loma Linda University Medical Center, spent almost a decade vainly pursuing research grants. His work in xenografts, largely unknown and unrcviewed by other professionals, had not appeared in journals and was funded by Bailey himself and his colleagues. During the seven years preceding the Baby Fae baboon transplant, he performed some 160 cross-species transplants, mostly on sheep and goats, none of whom survived more than 6 months. Although warned by a colleague at a medical conference that his research was too incomplete to risk using human subjects, Bailey went ahead.
Baby Fae was not the first human to receive a primate xenograft. In a review of xenografts, the Council of Scientific Affairs of the American Medical Association noted a rapid rejection of all baboon transplants to humans. Nevertheless, Bailey claimed that the problems of rejection could be overcome by the "immature" state of an infant's immune system. After the operation, immunologists from around the world pointed out that the part of the immune system that rejects unmatched transplants is fully mature at birth, Furthermore, there is no way to match baboon hearts to human recipients, because baboons have no antigens in common with human tissue. Bailey has always maintained that Baby Fae's death was unrelated to the species of the organ "donor." An editorial in the Journal of the American Medical Association called Bailey's claim "wishful thinking."
Bailey's use of baboons was somewhat surprising, given their relatively distant evolutionary relationship to humans compared to other primates. The reason came to light when the Times of London published an interview between Bailey and an Australian radio crew. The reporters had been forbidden to ask direct questions about the operation, so they queried Bailey on the issue of why he had chosen a baboon in view of the baboon's evolutionary distance from humans. Bailey replied, "Er, I find that difficult to answer. You see, I don't believe in evolution." It is shocking that Bailey ignored basic biological concepts in formulating a life-threatening human experiment. (Emphasis mine)
Shocking indeed. When we say that nothing in medicine makes sense except in the light of evolution, we are not indulging in hyperbole.
