Evolution is a Big Word: The Many Theories of Evolution and Why They Matter

One of the most important things we can do for our children is to help them to think through issues deeply. It is easy to paint the world into two sides–ours and theirs–and then to say, “make sure to stay on our side.” In fact, the world is filled with numerous different positions. Some of them fall on a line, where you have a “right,””left,” and “center” position. Some of them are hard to categorize at all. One of the keys to holding a reasoned position is to understand the varieties of views on a given subject. Only then are you even able to really understand your own position. When you engage deeply with a variety of positions, even if you disagree with them, it often expands your understanding of the entire issue considerably.

Another reason to become acquainted with a range of views is to prevent yourself from being bullied by a “consensus of opinion.”  Many times when a “consensus” is formed, it is done by heaping together a large swath of diverse opinions into a single position, or by creating a category so big it is meaningless. When those positions are then picked out and examined individually, it turns out that the “consensus” is nothing of the sort, but rather a ploy to make the argument seem more sound than it is.

In the debate over origins, there has been such an effort to paint science as being decidedly evolutionary that the actual interesting details of the question get lost. What does one mean by evolution? Is evolution a sequence or a mechanism? If it is a mechanism, what is the mechanism? If two people disagree on both the sequence and the mechanism, to what extent should their opinions be taken to represent the same idea? Might there be fascinating ideas which are not being heard simply because they are being pushed into the background of the overly generalized term “evolution?”

In this article, my goal is to show a sampling of the diverse opinions on the subject of evolution so you can see the varieties of understandings there are. This will hopefully help elucidate the issues at hand more fully, as well as help you see how wide a stroke one needs to make in order to speak of a “consensus” on the issue. As a creationist, understanding these views has helped me develop my own comprehension of creation, adaptation, and evolution. Unfortunately, each position can only be stated briefly, but I have provided a bibliography at the end of the article to help you if you wish to investigate these ideas further.

Evolution by Natural Selection

This is the standard view most people think of when they hear the term “evolution.”  This is the theory posited by Darwin –that evolution proceeds by accidental changes (now called mutations), and that the beneficial changes are kept and amplified by the process of natural selection. Natural selection is simply a mechanical process of differential survival; the fit ones will survive and thrive, and the unfit will not. There is no forward-looking purpose, only the ability to thrive and produce offspring in the present environment. This combination of mutation and selection is then capable of producing the entire diversity of life-forms over extremely long periods of time. This view is essentially the “textbook” view of evolution.

Front-loaded Evolution

This view says that evolution is not a product of happenstance, or even selection, but instead claims that evolution proceeded by having all of the necessary information to diversify pre-encoded in the earliest ancestor(s). From there, the diversity of life evolves from the information already encoded within the original genome(s). To imagine this, think of the installation program for your computer’s operating system. The installer is one program that contains all the information necessary to generate all the other programs on your computer. The programs on your computer were all designed—none of them arose through natural selection—but they did all come from a single source when you installed them on your computer: the installation program. There are many variations on front-loaded evolution, too. Some views are minimalistic; they view a minimal front-loading process, where only the basic outlines of future systems are present.  Other views are more maximal; they posit that much of the coding for future organisms was already present in the original ancestors.

Evolutionary Developmental Biology (Evo-Devo)

In this view, evolution progresses based on developmental switches and modules. Life is like a grab bag of components that all work together. Organs, body parts, and body plans do not really “evolve” so much as they are switched on, switched off, reorganized, and tweaked. The evolution of life is basically the continual reorganization of highly complex gene regulatory networks. In addition, many parts of the organism are not even specified by genetics, but rather are found through exploration. For instance, nerves and blood vessels build themselves out based on feedback from the surrounding tissues. Essentially, they “feel out” the path they need to follow. Therefore, recombining different types of body plans, organs, and tissues is not as difficult as one might think, because many of the connecting systems will be able to adapt to the basic structural changes automatically.

Evolution by Natural Genetic Engineering

In this view, cells are equipped with systems that enable them to adapt. That is, when a cell faces a challenge, it does not passively wait for a mutation to happen, and then passively wait to see if it is improved or killed by it. Instead, cells are equipped with systems which allow them to respond to external stress by modifying their own genome in ways which are likely to be beneficial. It then deploys those modifications. If it is unsuccessful, then it tries again. Therefore, evolution is an active, not a passive, process within the cell. The process involves enzymes, DNA sequences, and regulatory networks which work together to evolve an organism in response to changing environmental conditions.

Somatic Selection

Somatic selection is similar to Natural Genetic Engineering, but is more applicable to multicellular organisms. In somatic selection, evolution proceeds by performing “evolutionary experiments” in your body cells (called somatic cells)—in other words, mutating in response to environmental stress. Then, when an experiment is successful, it transmits the modified genetic code to your sex cells (called gametes). With this method, evolution can happen relatively quickly even on organisms that do not reproduce often, because the body can perform numerous simultaneous evolutionary experiments in somatic cells, select the results it wants, and then transmit the modified DNA to the gametes for future generations.

Structuralist / Platonic Evolution

This theory of evolution focuses on the numerous examples of “convergent evolution” that are found in nature—organs and systems which are not related evolutionarily, but still function in largely similar ways. One striking example of an evolutionary convergence is in the vertebrate eye and the cephalopod eye (cephalopods include the octopus). While these two types of eyes have some important differences, the similarities in structure and function are striking. The structuralists therefore ask what processes would cause evolution to build the same structure in two different lineages in two radically different environments. What the structuralists propose is that the actual range of biological possibilities is fairly small. Physics and chemistry limit the available organizations, structures, and biochemistry such that there are only a set number of routes that evolution could take. As such, the same structures evolve over and over again because those are the only ones which could be evolved.

Biological Self-Organization

Self-organization is actually two phenomena rolled into one concept. The first is the ability for simple rules to establish complex, coordinated behavior. This can be seen in many areas of life. For example, the code to create a complex picture on a computer screen does not have to be complex itself –the code may in fact be very simple.  Likewise, following a few simple traffic rules keeps everyone on the street coordinated without crashing into each other. Basically, by following simple, local rules, complex large-scale patterns can emerge. The individual participants need only follow their rules, and can ignore the large-scale pattern which will happen automatically. The second phenomenon is that chaotic systems exhibit patterns which are not always predictable just by looking at the pieces. Therefore, self-organization theorists think that metabolic systems essentially come into existence all at once when the right pieces are together. Evolution involves switching from one self-organizational pattern to another. Since the large-scale patterns emerge from local rules, small changes in the rules can lead to immediate, and large, evolutionary changes.

Multilevel Evolution

This is kind of a “meta” view of evolution. Basically, it proposes that evolution on different scales has fundamentally different causes. That is, microevolution and macroevolution (and some add mesoevolution) are fundamentally different processes, and they have fundamentally different causes and mechanisms. For instance, some multilevel evolutionists think that natural selection might be the cause for microevolution, evo-devo might be the cause for mesoevolution, and that there is an as-yet undiscovered cause for macroevolution.

Epigenetic Evolution

In epigenetic evolution, the genetics of an organism are not as important as how the genes are read. Thus, the factors which control the expression of genes are as important, or perhaps more important, than the genes themselves. Epigenetics also differs from genetics in that lifestyle choices of the parent can affect the biology of the offspring in profound ways.

Evolution by Symbiogenesis

This view says that evolution primarily proceeds by the creation of new symbiotic relationships between organisms. In this view, changes to the genome are of secondary importance. The primary driver in biological change is the changing ecological relationships an organism has with other organisms. This view is most well-known for its speculations on the origin of cellular organs (such as mitochondria), which it claims are actually separate bacterial organisms that are now in permanent symbiotic relationships with the rest of the cell.

Teleological Selection

This is similar to natural selection. Rather than selection being a process which is blind to the future results of selective action, this view holds that selection can be forward-looking. Therefore, selection can, in fact, select for configurations which will only have meaning or usefulness in the future. Proponents of this view hold that most discussions of natural selection do not make sense on their own unless teleological selection is presumed. For instance, much of evolutionary literature talks about things which were “selected for” such and such a purpose. The term “selected for” does not make sense if selection is blind to future purposes, but makes perfect sense in the context of teleological selection.

Concluding Remarks

Two things are interesting concerning this list.  First of all, since evolution is a different subject from the question of the origin of life, none of these ideas in their basic form are necessarily incompatible with special creation (that many organisms were separately created by God at the beginning). The question of a universal common ancestor is actually a question about the origin of life, not its evolution. Therefore, one can be a creationist and still agree or disagree with any given mechanism of evolution. It is only the questions of how far these mechanisms are able to proceed, and how far they have actually proceeded, which could be in conflict with special creation. Second, while different schools of thought in biology emphasize different theories of evolution, they are not entirely incompatible with each other. However, what is heavily disputed and debated is the amount of evolution that is possible with each theory. One theory may be very well proven for certain kinds of changes, but not proven at all for others. It is good for someone pursuing research to take an idea and see how far it will go. However, it is good for the rest of us to critically examine the results and decide for ourselves how well-founded those ideas are, and to what extent they apply.

Resources

For those interested in pursuing some of these ideas further, here is a reading list. You should know, however, that most of these works are antagonistic to special creation.  Nonetheless, they provide excellent discussions in the variety of views of how life changes over time.