In a 2007 edition of the venerable peer-reviewed journal Proceedings of the National Academy of Sciences, Indiana University biologist Michael Lynch makes the startling claim that no observations exist supporting the idea that natural selection has been primarily responsible for the evolution of complex multi-cellular life from earlier single-celled organisms. Lynch goes so far as to say, "It is impossible to understand evolution purely in terms of natural selection."
Now, Lynch is no creationist; he is an academic biologist who fails to find compelling evidence for natural selection, preferring instead to consider other models for evolution based on non-adaptive evolutionary processes. If Lynch is right about the lack of a firm evidentiary basis for natural selection, how do we account for the fact that natural selection has been—and continues to be—promoted as the most well-established scientific theory ever devised (or as the greatest single idea anyone has ever had, as Daniel Dennett calls it)? Is it possible that natural selection is more philosophical dogma than evidence-based science?
In the aftermath of the publication of Darwin's "On the Origin of Species" in 1859, few thinkers accepted Darwinian natural selection as the driving force of evolution (a period sometimes referred to as the eclipse of Darwinism). The list of non-selectionist thinkers reads like a "Who's Who" of turn-of-the-century biology: T. H. Huxley, Asa Gray, Hugo De Vries, William Bateson, Thomas Hunt Morgan, Francis Galton (Darwin's own cousin), and even the playwright George Bernard Shaw. Natural selection did not come to dominate evolutionary thinking until the development of population genetics in the 1920s and 1930s, leading to what is often termed the evolutionary synthesis of the 1940s which enshrined natural selection as indisputable fact.
An early champion of natural selection was the British population geneticist Ronald A. Fisher. In his classic 1930 book "The Genetical Theory of Natural Selection," Fisher dismisses the many non-Darwinian theories of evolution current at his time and writes:
The sole surviving theory is that of natural selection and it would appear impossible to avoid the conclusion that if any evolutionary phenomenon appears to be inexplicable on this theory it must be accepted at present merely as one of the facts which in the present state of knowledge seems inexplicable.
This is not a scientific statement. Fisher accepts natural selection by default and then defines away potentially contradictory evidence, rendering natural selection an unfalsifiable—and therefore unscientific—theory! But why did the biological establishment rally around this dogma rather than some other?
The modern Darwinian critic, Michael Denton, points out that the Darwinian model of evolution is the only one based on well-understood physical and natural processes—random genetic variability and natural selection. Other theories of evolution (orthogenesis, neo-Lamarckism, saltationism, intelligent design) all leave themselves open to the possibility of a metaphysical or supernatural interpretation. Denton writes, "Reject Darwinism and there is, in effect, no scientific theory of evolution." This is a key insight when viewed in the light of the work of science historian Vassiliki Betty Smocovitis.
Smocovitis argues convincingly that the enshrining of natural selection as a purely naturalistic understanding of evolution was at least in part driven by the attempt to create a modern science of biology in the early 20th century to rival physics, the paradigmatic example of true science at the time. Biology had to be divorced from its natural theology roots, cleansed of any metaphysical understandings, and set up as a rigorous empirical and quantitative discipline. Since natural selection, as Denton points out, is the evolutionary mechanism most consistent with a naturalistic understanding, it not surprisingly was enshrined as the center-piece of biology despite its ambiguous evidentiary basis.
This idea is demonstrated well in the work of noted evolutionary biologist Richard Lewontin. In a 1997 review of Carl Sagan's "The Demon Haunted World," Lewontin laments the difficulty of dispelling the irrational myths and supernatural explanations held by so many people. For Lewontin, science is the only begetter of truth and scientists by definition must commit themselves to a materialist philosophy. Lewontin continues in an oft-cited passage:
It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counterintuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door.
Science here is pronounced materialistic by definition, not because materialistic explanations are necessarily more compelling. Interestingly, another influential evolutionist appears to agree.
George Gaylord Simpson is considered one of the most influential paleontologists in history and a shaper of the modern evolutionary synthesis of the 1940s. In his classic 1944 text "Tempo and Mode in Evolution," Simpson decries the tendency of some scientists to appeal to the unknown, calling it metaphysical speculation that has no place in science. But he goes on:
The metaphysical explanation might, indeed, be true, but no hypothesis for which there can be no rigidly objective test should be accepted as a conclusion or working principle in research.
He further elaborates in a footnote:
As a matter of personal philosophy, I do not here mean to endorse an entirely mechanistic or materialistic view of the life processes. I suspect that there is a great deal in the universe that never will be explained in such terms and much that may be inexplicable on a purely physical plane.
So the scientific adherence to material causation is driven by the need to maintain the scientific integrity of biology, but it may not necessarily lead to the apprehending of truth.
In this light, can intelligent design theory be considered a valid scientific alternative to Darwinian evolution? Not if science is defined as the search for naturalistic explanations. But denying intelligent design the status of science is not tantamount to denying its potential truth value. The question of evolution's mechanism must therefore remain an open question, even if the search for an answer leaks beyond the naturalistic boundaries so firmly policed by the scientific disciplines. As even philosopher Thomas Nagel, an avowed atheist, can say:
Even if one is not drawn to the alternative of an explanation by the actions of a designer, the problems that these iconoclasts [intelligent design theorists] pose for the orthodox scientific consensus should be taken seriously. They do not deserve the scorn with which they are commonly met. It is manifestly unfair.
Fortunately, the search for truth transcends human-created academic disciplinary boundaries and much to Darwin’s chagrin, evolutionary questions may not be fully answerable by naturalistic science alone. Religion and philosophy may still have a valid place at the table. Score one for the interdisciplinarity of the liberal arts.