In What Version of Evolution Do You Believe?

David Zeigler

Before the reader complains: yes, the word believe, as in taking something on faith, is appropriate to the title because it is clear that many who say they “accept” evolution do in fact believe in a version of evolution that is not empirically based. It is true that even scientists “believe” that empirical objective evidence gives the most accurate information concerning the nature of the physical universe. Though some philosophers disagree with this stance, I assure you that even the most ardent idealist looks both ways before crossing a street.

We know the term evolution can be broadly taken to mean simply change, as in the evolution of the automobile, the evolution of fashion, or the evolution of our view of evolution. But when scientists/biologists use the word evolution, it is organic evolution with common descent that comes to mind—Darwinian evolution to be precise. Today evolution is well understood to be the result of several naturalistic mechanisms such as natural selection, genetic drift, horizontal gene transfer, endosymbiosis, and others. Some in the intelligent design and creationist camps accept evolution in varying degrees, even with common descent, but always with the provision that God directed evolution (in some unexplained way) according to “his” designs for life. These believers have of course been especially active in recent decades, as they probe every possible legal opening to get their equal time in the science classroom, though they still have no scientific evidence for their positions. We know, for example, that mutations are essential to evolution over the long haul, and evidence suggests that mutations are random changes in the genome. If a supernatural being caused specific mutations to occur at “appropriate times” to bring about his desired results, how would we know? It is clear that there is no way to substantiate that particular past mutations, horizontal gene transfers, endosymbiotic events, or selective deaths of the unfit were the result of supernatural forces. More parsimoniously, they were natural occurrences requiring no special push from a god.

Surveys regularly report that over 90 percent of people believe in some form of a god or gods, and at least half that number (in the United States) say they accept evolution. It is probably a safe assumption that religious people by and large believe that humans are an important and planned part of their god’s creation. In short, a great many people who claim to accept evolution actually believe in evolution through divine guidance to create not only humans but likely most of the other life forms familiar to these believers. There is of course a major catch to this position—this is definitely not Darwinian evolution by random mutation and natural selection and therefore not the accepted scientific explanation for evolution.

Darwin’s explanation of natural selection was simple, yet for some it is singularly difficult to fully grasp in its implications. Natural selection, though not the only cause of evolution, is still agreed by most biologists to be the major agent (along with mutation) of obvious evolutionary change, and the main point of natural selection is that it adapts species to survive and achieve genetic fitness within their local environments—and nothing more. In other words, there are no long-range teleological trends or directions to evolutionary change; no goals of design, complexity, or intelligence are inherent in the evolutionary process. For some, Stephen J. Gould’s major lesson in his many eloquent writings was his continued emphasis on this important point. As he put it: “We are glorious accidents of an unpredictable process with no drive to complexity” (Gould 1996).

Other workers have also made this point: “Life is not oriented towards increasing complexity, nor is it fated to become ever more complex” (Meinesz 2008). Some disagree with this point because obviously life for the first half of Earth’s history consisted only of various microbes yet now contains blue whales and oak trees. But as has been pointed out by many, when you start out simple, one of the few paths open for innovating and adapting is to become more complex, principally by accidental gene duplications that enlarged the genomes of some lines, and in some of those lines by actual increases in structural complexity. However, some amoebas have vastly larger genomes than humans, and some multicellular lines, such as the ancestors of yeast, have simplified their morphology “back” to the unicellular level (and there are several other examples of this type of simplification having occurred). Evolution has been characterized almost as much by loss of complexity as by its increase, with much of biodiversity remaining simple for the whole scope of evolutionary history. The vast amount of biodiversity is likely to be still confined to microbes (certainly they represent the largest percent of standing biomass), so the evolved complexity of a few lines does not define a trend in evolution, only a likely consequence of life adapting to ever diverse environments. There is certainly no evidence of a drive (as Gould put it) toward complexity in the evolutionary process.

Darwinism evolved with the Neo-Darwinian Synthesis into a process of genetic change in populations, still driven mainly by natural selection. This—along with several more recently recognized phenomena such as genetic drift, neutral evolution, gene duplication, gene deletion, lateral gene transfer, and endosymbiosis—is the evolution most biologists now understand and accept (as opposed to believe). To suggest that metaphysical plans, goals, or directions affected any point in the evolution of life is a nonscientific version of evolution that obviously should not be covered in science classrooms except possibly as an example of how some people have blended their religion and science to form their hybrid “belief” in evolution—a belief that is not truly neo-Darwinian or empirically supported.

An essential point worth remembering is that natural selection is fundamentally a negative process that eliminates the relatively unfit, not a positive force selecting some preferred trait or form (Mayr 1997). Natural selection is in short a weeding out of the unfit—those less able to survive and reproduce than others of their species. Of course vast numbers of the simply unlucky are also eliminated. We may never know whether over 99 percent of the species that ever lived are extinct due to selective pressures or to bad luck (undoubtedly some of both), but either way the graveyard of species is beyond imagining. Also, across all species an average 95 percent or more of each new generation is eliminated early in life by lady luck or by selection’s harsh hand. It would seem difficult to accept that a “higher power” would use such cruel and wasteful methods for bringing us (or any species for that matter) into being. It has recently become clear that even within the human family Hominidae, our family tree was “pruned” of at least ten to fifteen species in the past five million years leaving only one (the “chosen” one?).

Given the time span we know earthly life has existed, and the incomprehensible number of generations separating us from life’s common ancestor, how many times would a god have had to step in and adjust the course of evolution to have given rise to humans or to any other of the “higher” species? The answer would likely be at a minimum somewhere in the millions. For a god to “steer” evolution from the first eukaryotic cells to any one of the more complex life forms would surely require far more “corrections” than a car would require in driving from Boston to Miami. To understand Darwinian evolution and then allow that metaphysical forces may have controlled the process to this extent is to subvert the explanatory heart of Darwinism by making the scientific unscientific.

So what about teaching evolution? In the science classroom, I believe that only our empirical understanding of evolution should be taught, because that is science, and it takes some time to explain the mechanisms and timeline of evolution. I can’t imagine how one could give equal time to the creationist/intelligent design alternatives since there is no objective evidence to present for those viewpoints. As for the strict Biblical creationist myth, all available evidence contradicts it. As for the intelligent design position that holds that a higher intelligence guided evolution over the long history of our planet to achieve certain results, while this admittedly could be the case, there is no direct evidence supporting that belief. So, as for either of these two alternative views, there is really nothing here to teach in a science classroom.

Our knowledge of evolution is a huge body of work that has been hard won by many brilliant workers. It deserves to be covered and covered well as an essential part of our children’s education. George Gaylord Simpson wrote, “I do not think that evolution is supremely important because it is my specialty. On the contrary, it is my specialty because I think it is supremely important” (Simpson 1964). If biology teachers everywhere would take this thought to heart and continue to strengthen their knowledge of evolution, the creationists would have a hard time in their efforts to chip at the empirical foundations of evolution. They are exceedingly strong foundations.


References

  • Gould, Stephen Jay. 1996. Full House. New York: Three Rivers Press.
  • Mayr, Ernst. 1997. This is Biology. Cambridge: The Belknap Press of Harvard University Press.
  • Meinesz, Alexandre. 2008. How Life Began: Evolution’s Three Geneses. University of Chicago Press.
  • Simpson, George Gaylord. 1964. This View of Life. New York: Harcourt, Brace, and World, Inc.

Before the reader complains: yes, the word believe, as in taking something on faith, is appropriate to the title because it is clear that many who say they “accept” evolution do in fact believe in a version of evolution that is not empirically based. It is true that even scientists “believe” that empirical objective evidence …

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