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The design debate: why evolution succeeds where the teleological argument fails – Part 3

September 4, 2011 5 comments

Evolution as an Alternative to Design

I base this claim on the fact that evolution provides a mechanism by which life, in all of its order and complexity, can be the product of sheerly physical laws. As Richard Dawkins outlined in his 1986 book “The Blind Watchmaker,” Darwin’s theory of evolution by natural selection describes how mindless natural forces can come to imitate deliberate design.

This argument begs a look into Darwin’s evolutionary theory, which was built on the three following premises. Variation, now known to arise via mutation, meant that different organisms had different traits. Heritability, now understood to occur via the transmission of genes from parent to offspring, meant that this variation would be passed on from one generation to another. Finally, differential fitness, the notion that some organisms would have more reproductive success than others, meant that some of these variants would leave more descendents than their conspecifics. Over the vast course of geologic time, this meant that those traits that increase reproductive success would be passed on more frequently than others. As a result, populations of living things would, over time, evolve to be better adapted to their surroundings.

This theory of evolution, built upon these three premises, is capable of explaining how mindless physical laws can produce the ordered complexity we see in living things. Mutation is a change in the genetic blueprints of an organism, and is capable of expanding or altering the genome in ways that can increase the complexity of an organism one step at a time. Heritability provides a means of preserving these changes across generations, allowing for evolution to operate over the span of billions of years. Finally, selection acting on differential fitness can direct this process so that organisms with the most adaptive blueprints will be more common in each subsequent generation. Sophistication and a tendency to act towards ends such as growth, survival, and reproduction, are advantageous traits for an organism to incorporate into its blueprint. Consequently, the properties of order, complexity, and purposiveness were selected for and thus evolved in living things. In this way, evolution is quite capable of creating the illusion of design.

Not only is evolution an alternative explanation for the apparent design of living things, but I believe that it is a better one. First and foremost, I base this assertion on the fact that the premises of evolutionary theory are consistent with current knowledge about the biological world. Mutation, heritability, and differential fitness are all observable facts. In addition to being founded in sound premises, evolutionary theory is also buttressed by an unshakable body of evidence gathered from numerous sources. Fossil records, for instance, provide a document of the gradual changes in the phenotypes of species over the course of millions of years. Another type of evidence comes from homologous traits, biological features that function in different ways but which have similar underlying structures. These provide evidence that many disparate organisms share common ancestry. Yet more convincing support comes from cases of biologists observing evolution in action. Take, for instance, the emergence of new and more virulent strains of viruses in response to vaccinations, the evolution of bacterial resistances to antibiotics and other medications, or recorded increases in the average body size of bird populations following harsh winters – these are all documented examples of evolution taking effect in the world around us. The list goes on, and the evidence for evolution is extensive enough to fill entire books. As such, there is no way to do it justice here. But it suffices to say that the biological world is replete with evidence that points, unequivocally, towards evolution as the scientific explanation for the characteristics of living things.

Biological evidence also directly contradicts what we would expect living things to be like if they were the product of a designer. This is because the “design” of many biological structures is rather poor. One example of this is the human knee. Our knee shares its structure with those of numerous other mammals, for whom it performs quite well. But as bipedal organisms, we humans use our knees in very different ways from our quadruped cousins. As a result, the human knee joint is highly susceptible to injury, and often becomes weakened or damaged as we age.

This affliction makes sense with an evolutionary interpretation. The structure of the human knee is probably an artifact from our evolutionary past, when the ancestors of the human species walked on four legs. And because the vulnerability of our knees takes effect as we get older, it tends to only be problematic once we are finished breeding. Consequently, there hasn’t been any strong selective pressure to alter the structure of this joint. Thus, its flaws can be understood as the result of evolutionary negligence.

However, if we assume that life was designed, then this imperfection does not make sense. An intelligent designer engineering the human knee would not have to deal with evolutionary constraints, and would certainly know better than to give us a model that begins to wear out after a few decades. If the human knee was designed, then it seems to serve as an indication of an unintelligent designer. More likely, the knee is the product of evolution. This counter to the teleological argument, known as the argument from poor design, can also be made regarding structures such as the vertebrate eye (which is inside out), and the troublesome arrangement of human wisdom teeth, among many others. As these examples go to show, the flawed design of numerous biological structures provides further evidence that evolution is a more effective explanation than intelligent design for the characteristics of living things.

One further reason for the superiority of evolution is that it is a more parsimonious explanation for life’s order and complexity than deliberate design. According to the law of parsimony, when assessing two competing explanations, the simpler one should be preferred. The proposition of a divine designer requires the existence of a complex and supremely intelligent being. Furthermore, it presumes that this being worked through supernatural means – all of which are completely unbeknownst to modern science – in order to produce ordered and complex life. These are rather considerable assumptions, and are quite beyond the scope of any empirical justification. Evolution, by contrast, assumes remarkably little. Darwin’s premises – heritability, variation, and differential fitness – were only three, and have each been empirically verified time and time again. Evolution is thus a far simpler account for the ordered complexity of living things, and it explains at least as much. Consequently, the law of parsimony rules in the favour of evolution, providing yet another way in which it is superior to the hypothesis of intelligent design.