Screen Shot 2015-02-16 at 8.43.15 AMWisconsin governor and Republican presidential hopeful Scott Walker was recently asked by a reporter during a trade mission to London whether he is comfortable with and accepts “the idea of evolution.”

Walker, the son of a Baptist minister, responded: ”For me, I’m going to punt on that . . . That’s a question that a politician shouldn’t be involved in one way or another.” He later tweeted, “Both science & my faith dictate my belief that we are created by God. I believe faith & science are compatible, & go hand in hand.”

Ann Althouse writes that there are some evolution-related questions that a public official should be expected to answer, but this poorly phrased question wasn’t one of them.

David Harsanyi points out that “the same journalists who fixate on ‘science’ that makes the faithful look like slack-jawed yokels almost inevitably ignore science that has genuine moral and policy implications.” He provides a good list of questions that liberals are rarely asked about science (e.g., Does human life begin at conception? Is a 20-week old unborn child a human being?).

When Barack Obama was a candidate for president he famously said that the question of when a human is entitled to human rights was a question “above his pay grade” (despite the fact that everyone has to answer that question). And when House Speaker Nancy Pelosi was asked “what is the moral difference between what [serial late-term abortionist] Dr. Gosnell did to a baby born alive at 23 weeks and aborting her moments before birth?” she likewise refused to answer, accusing the reporter of having an agenda. To my knowledge, Time magazine did not track down Obama or Pelosi’s high-school biology teachers to reprimand them on their non-answers, as Time recently (and bizarrely) did with Scott Walker.

But let’s return to the “idea of evolution.” Many Christians who enter the fray point out that “evolution” is an ambiguous term, and that we can distinguish between “macro-evolution” (grand-scale body-plan transformation of species) and “micro-evolution” (observable small-scale changes within a population over succeeding generations).

This is a helpful clarification, but the term is used even more elastically than that, and it’s helpful to pull it apart to note the multiple ways it can be used.

In an essay on “The Meanings of Evolution,”  Stephen C. Meyer and Michael Newton Keas explain the six ways it is often used by scientists and advocates:

1. Evolution as Change Over Time

Nature has a history; it is not static. Natural sciences deal with evolution in its first sense—change over time in the natural world—when they seek to reconstruct series of past events to tell the story of nature’s history. Astronomers study the life cycles of stars; geologists ponder the changes in the earth’s surface; paleontologists note changes in the types of life that have existed over time, as represented in the sedimentary rock record (fossil succession); biologists note ecological succession within recorded human history, which may have, for example, transformed a barren island into a mature forested island community. Although the last example has little to do with neoDarwinian evolutionary theory, it still fits within the first general sense of evolution as natural historical progression or sequence of events.

2. Evolution as Gene Frequency Change

Population geneticists study changes in the frequencies of alleles in gene pools. This very specific sense of evolution, though not without theoretical significance, is closely tied to a large collection of precise observations. The melanism studies of peppered moths, though currently contested, are among the most celebrated examples of such studies in microevolution. For the geneticist, gene frequency change is “evolution in action.”

3. Evolution as Limited Common Descent

Virtually all scientists (even many creationists) would agree that Darwin’s dozen or more famed Galapagos Island finch species are probably descended from a single continental South American finch species. Although such “evolution” did not occur during the brief time scale of the lives of scientists since Darwin (as in the case of the peppered moth), the pattern of biogeographical distribution of these birds strongly suggests to most scientists that all of these birds share a common ancestor. Evolution defined as “limited common descent” designates the scientifically uncontroversial idea that many different varieties of similar organisms within different species, genera, or even families are related by common ancestry. Note that it is possible for some scientists to accept evolution when defined in this sense without necessarily accepting evolution defined as universal common descent— that is, the idea that all organisms are related by common ancestry.

4. Evolution as a Mechanism that Produces Limited Change or Descent with Modification

The term evolution also refers to the mechanism that produces the morphological change implied by limited common descent or descent with modification through successive generations. Evolution in this sense refers chiefly to the mechanism of natural selection acting on random genetic variation or mutations. This sense of the term refers to the idea that the variation/selection mechanism can generate at least limited biological or morphological change within a population. Nearly all biologists accept the efficacy of natural selection (and associated phenomena, such as the founder effect and genetic drift) as a mechanism of speciation. Even so, many scientists now question whether such mechanisms can produce the amount of change required to account for the completely novel organs or body plans that emerge in the fossil record. Thus, almost all biologists would accept that the variation/selection mechanism can explain relatively minor variations among groups of organisms (evolution meaning #4), even if some of those biologists question the sufficiency of the mechanism (evolution meaning #6) as an explanation for the origin of the major morphological innovations in the history of life.

5. Evolution as Universal Common Descent

Many biologists commonly use the term evolution to refer to the idea that all organisms are related by common ancestry from a single living organism. Darwin represented the theory of universal common descent or universal “descent with modification” with a “branching tree” diagram, which showed all present life forms as having emerged gradually over time from one or very few original common ancestors. Darwin’s theory of biological history is often referred to as a monophyletic view because it portrays all organisms as ultimately related as a single family

6. Evolution as the “Blind Watchmaker” Thesis

The “blind watchmaker” thesis, to appropriate Richard Dawkins’s clever term, stands for the Darwinian idea that all new living forms arose as the product of unguided, purposeless, material mechanisms, chiefly natural selection acting on random variation or mutation. Evolution in this sense implies that the Darwinian mechanism of natural selection acting on random variations (and other equally naturalistic processes) completely suffices to explain the origin of novel biological forms and the appearance of design in complex organisms. Although Darwinists and neo-Darwinists admit that living organisms appear designed for a purpose, they insist that such “design” is only apparent, not real, precisely because they also affirm the complete sufficiency of unintelligent natural mechanisms (that can mimic the activity of a designing intelligence) of morphogenesis. In Darwinism, the variation/selection mechanism functions as a kind of “designer substitute.” As Dawkins summarizes the blind watchmaker thesis: “Natural selection, the blind, unconscious, automatic process which Darwin discovered and which we now know is the explanation for the existence and apparently purposeful form of all life, has no purpose in mind. It has no mind and no mind’s eye.”

The authors conclude:

what we are calling “mere evolution” (evolution #1-4) is “one of the strongest and most useful scientific theories we have,” to use NAS language. Mere evolution encompasses a vast number of specific cosmological, geological, and biological theories that “incorporate a large body of scientific facts, laws, tested hypotheses, and logical inferences.”

On the other hand, . . .  a significant minority of scientists dissent on evidential grounds from the theory of universal common descent (evolution #5), and an even greater group dissents from the blind watchmaker hypothesis (evolution #6).

As for how evolution should be taught in public schools, and how Christian politicians who have doubts about evolution #5 and #6 above should respond, I think the perspective of the Discovery Institute makes good common sense:

Far from reducing the coverage of evolution, Discovery Institute seeks to increase the coverage of evolution in textbooks. It believes that evolution should be fully and completely presented to students, and they should learn more about evolutionary theory, including its unresolved issues. The true censors are those who want to stop any discussion of the scientific weaknesses of evolutionary theory. . . .  Discovery Institute recommends that states and school districts focus on teaching students more about evolutionary theory, including telling them about some of the theory’s problems that have been discussed in peer-reviewed science journals. In other words, evolution should be taught as a scientific theory that is open to critical scrutiny, not as a sacred dogma that can’t be questioned.

Source: Stephen C. Meyer and Michael Newton Keas, “The Meanings of Evolution,”  Stephen C. Meyer and Michael Newton Keas,  in Darwin, Design, and Public Education, Rhetoric and Public Affairs, ed. John Angus Campbell and Stephen C. Meyer (East Lansing: Michigan State University Press, 2003), 135-56.