Much of the confusion in the evolution debate lies in the meaning of the word “evolution”. Since it can have several different meanings, and even the scientific definition of evolution can include several distinct components, it is not surprising that many confusing and confused arguments are articulated. Certainly the conversation is very difficult when conversation partners discussing evolution do not share the same definition, conflate several of the definitions, or elevate one component of evolution to be descriptive of the whole.
Dr. Allan Harvey has provided a simple overview of the various meanings of evolution. Harvey, a fellow ASA member, recently taught a 6-part course on “Science and Nature in Christian perspective” at his conservative Presbyterian church in Boulder Colorado, and the 5th essay in the series is on evolution. (Note: The entire course looks outstanding. It is presented in clear non-technical terms, and Harvey includes wise counsel on how Christians who accept the integrity of scripture should approach science. For anyone beginning this journey, I highly recommend reading through the entire series)
Harvey provides a framework that includes 6 meanings for the word evolution, and remarks on both the scientific certainty and compatibility with the Christian faith for each definition. These six meanings are:
E1. Change over time
E2. Common ancestry
E3. Evolutionary mechanisms (genetic variation, natural selection).
E4. The ability for these Evolutionary mechanisms to account (physically) for common descent.
E5. Origin of life (chemical evolution)
I have grouped these meanings into three categories: those meanings for which the scientific evidence is overwhelming and thus enjoy an extremely high degree of certainty (E1, E2, and E3), those definitions that are less certain based on the scientific evidence (E4 and E5), and those definitions whose conclusions are based on metaphysical assumptions rather than the scientific evidence(E6).
Evolution Meanings Group#1: Extremely high degree of scientific certainty
Harvey’s first three meanings for evolution (E1 – E3) are all extremely well supported by the scientific evidence. There is also, in Harvey’s view, no incompatibility between these meanings and the Christian Faith.
E-1) Change over time. This is the most basic meaning of the English word “evolution,” simply meaning that something changes with the passage of time. For example, we might talk about the evolution of popular music, or the evolution of stars. With regard to living things, this simply says that things are different than they were in the past (there used to be dinosaurs; now there aren’t). Almost nobody denies this meaning.The only opposition to E1 is in the time available for changes to occur. Young Earth Creationists (YEC) would disagree with the scientific consensus of cosmological evolution (formation of the cosmos eg. stars) because of the billions of years required for this process.
E-2) Common ancestry. This is central to what scientists usually mean by “evolution.” Common ancestry (or common descent) means that life has branched out, so dogs and wolves are distant cousins, dogs and cats are more distant cousins, and if you go back far enough dogs and fish, or dogs and trees, had a common ancestor. You can put humans in the family tree as well – related to chimpanzees, more distant from other mammals, and so forth.As I’ve commented earlier here, a shared ancestry with non-human life does not contradict the biblical claim of humanity’s creation in the image of God. As well, as Harvey points out in his 3rd essay, and as I’ve commented here, common descent does not compromise the integrity of scripture. In fact, many of the leaders in the Intelligent Design (ID) movement (eg. Michael Behe, author of The Edge of Evolution) also support common descent, even though ID is often described as anti-evolution.
E-3) Evolutionary mechanisms (genetic variation, natural selection). This refers to specific natural mechanisms (first proposed by Darwin, although in a primitive way because genetics was not yet understood) that cause species to change. Genetic variation is the fact that (due to mixing of parental genes and to mutations) children have different genes and different traits. Natural selection refers to the fact that the traits will make some children more likely to survive and pass their genes on to future generations.Note that in recent years even YEC organizations have started backing away from their opposition to the mechanism of natural selection (see here and here). They have also admitted that natural selection can lead to new species, and that “in fact, rapid speciation is an important part of the creation model”.
Evolution Meanings Group#2: Less Scientific Certainty
Harvey’s 4th and 5th meanings of evolution enjoy less scientific certainty (in fact, there is very little current evidence for E5). These definitions have historically experienced aggressive opposition from Christians (certainly more than E1-E3), but Harvey does not believe this needs to be the case.
I believe E4 is the meaning that sharply divides Christians who identify themselves as Theistic Evolutionists (TE) or Evolutionary Creationists (EC) from those who are anti-evolutionists, particularly those that are supporters of ID. Harvey’s 4th essay called “Natural Theology or a Theology of Nature” explains briefly why E4 should not really cause any conflict for Christians.
E-4) Mechanisms (E-3) account (physically) for common descent. This is typically what scientists mean by “the theory of evolution.” We know these mechanisms produce changes in species, but do they account for all the evolution (in the E-2 sense) that has happened through the history of life on Earth? Most biologists, including most Christians working in these areas, would say “yes,” but it is certainly not as 100% established as the previous meanings.
E-5) Origin of life (chemical evolution). The theory of evolution is only an explanation for the development of life from other life. How life began in the first place is a different question, but people have proposed somewhat similar theories (the technical term is ambiogenesis) of how that happened. That is an area where there is much room for doubt; some people see it as an insurmountable problem, while others think science is coming closer to good explanations.E5 is the meaning that really sparks derision among anti-evolutionists. And the lack of evidence for E5 is often used to discount the validity of E2 through E4. It is still an open question whether a “natural” origin of life theory that is supported by the scientific evidence is 3 years away, 30 years away, 300 years away, or is practically impossible. The important point is that Christians need not oppose E5 for the same reasons that E4 need not be opposed.
Evolution Meanings Group#3: Definitions based on metaphysical assumptions
Harvey’s final meaning for evolution (E6) is unrelated to science.
E-6) Evolutionism. I use that term to refer to a meaning that is not science at all, but rather an ideology that sometimes masquerades as science. This starts with the philosophical position that natural explanations exclude God (the “God of the Gaps” error discussed in Chapter 4). Since science has produced these natural explanations for life, those with this ideology claim to have pushed God out of the picture. Of course these metaphysical conclusions are not science in any way – those who advocate this meaning are simply pushing atheistic philosophy, and it is wrong to try to claim it is a result of science.
This meaning for evolution is obviously not something that can ever be accepted by a Christian. But this is the meaning that both Christian anti-evolutionists and “evangelistic anti-theist” atheists push to the forefront. They conflate evolution meanings E2 through E5 with E6, and thus state that TEs and ECs are supporting atheism, materialism, or moral relativism (anti-evolutionist claims) or are deluded and cowardly for not following the scientific evidence to its logical conclusion (anti-theist claim).
I really like how Harvey categorizes the various definitions of evolution. They are helpful both for Christians trying to understand evolution, and for those of us that are frequently engaged in the evolution / faith dialogue. I am planning to use these definitions in my own conversations. Hopefully this will allow all of us to hone in on the salient issues more quickly, and avoid talking past each other. Ok, maybe that's overly optimist, but it can't hurt to try.