Criticisms of Evolutionary Theory made by Creationists Two major criticisms frequently made by creationists against Evolution are that (1) Evolution is “just” a theory and (2) that Evolution is an “entirely random” process. Different versions of these two criticisms show up repeatedly in various creationist writings, but both are without merit because they represent a complete misunderstanding (or willful mischaracterization) of what they claim to criticize. Criticism 1. Evolution is “just” a theory. The statement that evolution is “just” a theory displays a complete misunderstanding of what a scientific theory is. In common speech a theory is often not much more than a hunch or a half-baked idea about something. In contrast, 1 scientific theory is a broad, overarching explanation for major aspects of the natural world that has been extensively tested over time and has withstood being falsified. All scientific theories are backed by an enormous amount of evidence gathered over a long period of time. Other examples of scientific theories include: Gravity Plate tectonics Germ theory Evolutionary theory is overwhelmingly accepted by scientists because it explains a vast number of observations about biology ranging from the behavior of organisms to the fact that organisms share a common genetic code. Criticism 2. Evolution is an entirely random process. A second misleading criticism that creationists often make is that Evolution is an “entirely random” process. You will often hear creationists make an argument like the following. “The human eye (or any complex biological structure you care to choose) is so complex that it could not have come about just by chance. The odds of an eye assembling itself are about the same as a hurricane hitting a junkyard and assembling a jetliner.” This argument is clearly ridiculous and deliberately misinterprets the process of natural selection. The process of evolution by natural selection includes two components one of which is random and the second that is not. Component 1. Mutation is a random process. Changes in the DNA occur as a result of chance events such as exposure to mutagens, errors in DNA copying and errors in the duplication of chromosomes. We can estimate the rates at which we expect mutations to occur based on analysis of genomes , but when and where particular changes occur in the DNA is not predictable. Mutations are important to the process of evolution because they sometimes result in changes in an organisms’ phenotype (physical appearance and capabilities), which produces variation in a population that selection can choose. Component 2. Selection, however, is completely non-random. In each generation the organisms that survive best and produce the most offspring leave behind the most copies of their genes. As a result. the gene pool changes over time as beneficial mutations are favored by selection and become more common, while at the same time less beneficial mutations are selected against and disappear. The consequences of selection are that organisms accumulate beneficial mutations over time Natural Selection results in the spread of mutations that increase the survival and reproduction of the organisms that possess them. Convergent evolution demonstrates that evolution is non-random Similar body forms have evolved in distantly related groups in response to the same selection pressures. For example, salmon (which are bony fish), sharks (which are cartilaginous fish), dolphins (mammals), and penguins (birds) are not closely related to each other. However, all of these organisms possess similar adaptations for swimming efficiently in water. All of them are very streamlined and all have fins for stabilization and movement . The Scientific Method All societies have or had creation myths that invoke the action of supernatural forces to explain the origins of life and the history of the earth. Ideas invoking the role of gods and divine actions are supernatural (i.e., beyond nature – super means beyond). By definition supernatural explanations are untestable as they are not subjects to the laws of nature. Because they can never be tested, supernatural explanations are unscientific. Creationism because it tries to invoke a supernatural designer is clearly not science. Regardless of whether creationists call what they do “creation science” or “intelligent design” it is religion masquerading as science. Early history of scientific thought The early Greeks were among the first to develop natural philosophy to explain the world. Natural philosophers aimed to develop sets of physical laws to explain the world around them and how it worked. The Greeks’ approach of trying to explain the world using only natural phenomena is sometimes called Methodological Naturalism. Methodological because this strategy provides a procedure or method for scientifically explaining the world and natural because it focused on nature. An early example of methodological naturalism is Anaximander’s cosmology. He proposed the earth is a disk surrounded by huge wheels on which the moon and sun rotate around the earth. His explanation is mechanistic because it invokes a natural (although incorrect) mechanism to explain the presence and movement of celestial objects. Aristotle was the first Greek philosopher to emphasize observation and the testing of ideas to explain those observations (i.e., hypothesis testing). The Greeks also emphasized the importance of logic in moving from observations to general principles. “The Scientific Method” Today, scientists use what is commonly referred to as “The Scientific Method” or “the Hypotheticodeductive method.” There are several steps in the process, but the key element that separates the scientific method from other approaches to trying to understand the world is that the scientific method requires the testing and potential falsification of ideas. An explanation of something that is not testable is not scientific. Use of the scientific method begins with an observation , which is usually followed immediately by a question. An observation is something that you can see, measure, sense or in some other way monitor or detect. For example, “the sky is blue” is an observation. Similarly, “Peacocks have long tails” is an observation. This leads naturally to the questions: “Why is the sky blue?” and “Why do peacocks have long tails?” Let’s address the question of “Why do peacocks have long tails?” What we are trying to do is come up with an explanation for this. We deduce a possible explanation for the long tail in peacocks by considering what we know about peacocks. We know for example that peacocks fly poorly, whereas peahens fly much better. We also know that peacocks lose their long tail (they molt the tail feathers) outside the breeding season. It seems unlikely then that the long tail increases a peacock’s chances of survival. We know that peacocks display their tails to peahens during the breeding season. Thus, considering all this information we come up with the hypothesis that “Peacocks possess long tails because it increases their chances of reproducing.” Notice, I said we deduced a hypothesis. This involved us taking a lot of information and coming up with an “educated guess” about what a good hypothesis might be. The process of deduction involves creativity and intuition and often the ability to put facts together in a novel way. A scientific hypothesis possesses two essential traits it is both tentative and testable. A hypothesis is tentative because we put it forward realizing that if we acquire additional information we may have to change the hypothesis in the future. Of course, as we said earlier to be scientific a hypothesis must be testable. Therefore a good definition of a Hypothesis is: A hypothesis a tentative, testable explanation for our observations. We must now test our hypothesis. To do this we must make predictions based on our hypothesis and then using these we design an experiment. A prediction is an “IF-THEN” statement. And takes the basis form: IF our hypothesis is true THEN something else logically follows from it. For example, the following predictions are based on our hypothesis IF peacocks possess long tails because it increases their chances of reproducing THEN males with longer tails will mate more often than males with shorter tails. IF peacocks possess long tails because it increases their chances of reproducing THEN a male’s reproductive success will decline if we cut his tail IF peacocks possess long tails because it increases their chances of reproducing THEN a male’s reproductive success will increase if we make his tail longer. We can carry out an experiment to test these predictions. To do this we take a group of peacocks (all individually marked so we know who is who) measure their tails and then assign them randomly to four groups (A, B, C and D). We then allow females to visit the males and have the males display to the females. The females then either reject the male or allow the male to mate. We thus gather data on the frequency of male mating success. We could then run a correlation analysis in which we plot tail length against male mating success. A negative correlation would cause us to reject our first hypothesis; a positive correlation would be consistent with our first hypothesis. Unfortunately, a correlational study like this just allows us to document an association between the two variables (tail length and mating success). It does not show than one causes the other. A better approach would be a manipulative experiment where we alter the trait (tail length) we’re interested in and see how it affects our results. So using our four groups of birds we do the following manipulations Group A: Tails shortened by cutting them. Group B: Tails lengthened by gluing on extra feathers from group A males Group C: Tails uncut Croup D: Tails cut and glued back to original length. [Groups C and D are control groups for comparison with our manipulated groups] We repeat the experiment we did before where we allow all the males the opportunity to display to female and record how successful they are. We can also compare our before and after data for each male too. If we discovered that males with lengthened tails had higher mating success than males with shorter tails, that would be consistent with our hypothesis. Similarly, if males with longer tails had more mating success than they had before their tail was lengthened, that would also be consistent with our hypothesis. Similarly, if we discovered males with shortened tails had reduced mating success than before that would also be consistent with our hypothesis. However, if we found that males with shorter tails had increased mating success then we would reject our hypothesis. If we rejected our hypothesis we would then have to come up with a new hypothesis and repeat the process. So to summarize the scientific method involves the following steps Observation/Question Hypothesis – testable, tentative explanation for our observations/answer to our question Predictions – develop specific statements that must be true if hypothesis is correct. Take if-then format. Experimentally test predictions. Assessment of results - reject hypothesis or tentatively accept it pending further testing Repeat as necessary. Note that deduction not the mere accumulation of more and more facts or observations. The process by which we might come up with general laws through accumulating more and more facts is called induction. The problem with induction is that adding more and more observations can never prove something is true. Recall the example from the Prothero reading about the inductive statement “all swans are white.” Observing more and more white swans could not prove the statement true, but observing one black swan proves it false.