Non-Darwinian Evolutionary Mechanisms

Charles Darwin was never entirely satisfied with the evolutionary role he originally gave to natural selection in On the Origin of Species. He later expressed reservations about attributing too much of evolution to the action of natural selection and survival of the fittest because he became convinced that nonfunctional structures evolving without natural selection could later prove to be useful and therefore come within the range of natural selection. Darwin thought his failure to sufficiently consider the existence of structures that are neither beneficial nor injurious was one of the greatest oversights in his work. He realized that he was not able to eliminate entirely the influence of his former belief that each species had been purposely created and each structure was of some special service. He felt that anyone with this assumption in mind would naturally extend the action of natural selection too far.

Darwin's observation on the link between natural selection and a belief in the purposeful creation of species remains applicable to much of evolutionary biology today. Evolutionary approaches in anthropology and archeology are largely reduced to imagining the evolutionary advantage conferred by an adaptation, and this presumed advantage is supposed to explain why the adaptation came into existence. In a recent compendium on the evolution of great ape intelligence, for example, authors repeatedly imagined selection pressures that were supposed to have increased the intellectual ability of great apes compared with other primates. Because a larger and more complex brain was more costly, it had to be an advantage so that it could be selected to provide the advantages by which it would exist in the first place. Never, in any of these arguments, is there any empirical demonstration that such adaptations owed their origin to the past action of natural selection or that the advantages incurred had anything to do with their origin.

The appeal to imagined selection pressures is superficially very attractive because it requires no deeper understanding of biological structure beyond the constraints of imagination. As Darwin correctly identified, the mode of reasoning is scientifically problematic because it involves an explanation of the origin of a structure in terms of its purpose in servicing the organisms' future survival and reproductive success. Many modern practitioners of evolution appear to be unaware of Darwin's concerns, and with natural selection shown to have an ecological reality, it would seem to be a simple extrapolation to assume its role in evolution as well.

The use of teleological reasoning—the explanation of origin in terms of future purpose—is perhaps one of the greatest ironies of evolutionary biology. Evolution was supposed to end this kind of reasoning and yet it continues as the most popular and pervasive form of biological reasoning. Teleology makes nonsense of biology because it reverses the actual relationship between morphology and genetics by treating morphology as a response to a need that in turn determines the genetic basis for a feature's existence. This developmental relationship is the wrong way around because it is the pathways of molecular communication that produce morphology in the first place, and it is the organism's morphology that constrains what the organism can or cannot do. In what Jeffery Schwartz recently called the “vacuum theory of evolution and adaptation,” the biological structure or adaptation of an organism is sucked into a function, and the genetic foundations of this form are sucked along the way.

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