Embracing Evolution: But Which Model?
November 27, 2014
Contrary to popular opinion, Charles Darwin did not invent the theory of biological evolution. But his famous work, The Origin of Species, certainly gave impetus to an idea that would quickly become orthodoxy in the scientific establishment. In his work he made several significant points that have had profound consequences for how scientists understand the natural world. Darwin did not merely suggest that change takes place over time, which, technically speaking, may be called evolution (though many would prefer to use the word "adaptation," as opposed to "evolution," to describe changes within a given species). Rather, he questioned the concept that species are immutable (i.e., cannot change).
The idea that change takes place within a species is, of course, not controversial. But Darwin went much further than that. He suggested that new species have evolved over the course of history by a process termed "descent with modification." On this model, all life forms have descended from a common ancestor. Somewhere, at some time, the inorganic (non-living) became organic (living), and from that microscopic ancestor we now have fish, land animals, birds, and human beings.
For this to happen, Darwin popularized the idea that this took place through natural selection, or what has commonly been termed "survival of the fittest." Darwin's most significant contribution to the theory of evolution was formulating the mechanism that explained the process whereby a single cell produced the variety of life found in the world today. This understanding of evolution is best described as "fully naturalistic evolution," which is how the scientific community generally understands biological evolution.
The prominent American biologist, Douglas Futuyma provides a helpful explanation of the significance of Darwin's theory:
"By coupling undirected, purposeless variation to the blind, uncaring process of natural selection, Darwin made theological or spiritual explanations of the life processes superfluous. Together with Marx's materialistic theory of history and society and Freud's attribution of human behavior to influences over which we have little control, Darwin's theory of evolution was a crucial plank in the platform of mechanism and materialism - of much of science, in short - that has since been the stage of most Western thought" (Evolutionary Biology, 2).
Futuyma draws attention to an important implication of Darwinian evolution, namely, that theological explanations for origins of life, which includes special creation, are unnecessary because the Darwinian model does not simply content itself with changes within a species, but instead explains how all species came into being in the first place.
A Christian can and should affirm that in the beginning God created basic kinds of animals, which over the years subsequently diversified. The term microevolution has been used to describe this process. So, in an example that Darwin used, a group of finches happened to migrate to an island. On the island a combination of mutation, inbreeding, and natural selection caused these finches to develop different characteristics from the ancestral population on the mainland, which is known as microevolution. Even among humans microevolution occurs. God created Adam and Eve, but from this ancestral pair we see a fair amount of diversity today.
Understood in this way evolution is not controversial. As Jonathan Wells has argued, Darwinists respond to their critics by claiming that evolution means change over time. "But," says Wells, "this is clearly an evasion. No rational person denies the reality of change, and we did not need Charles Darwin to convince us of it. If 'evolution' meant only this, it would be utterly uncontroversial" (Icons of Evolution, 5). But does microevolution provide an explanation for the processes responsible for creating life in the world as we see it today?
Darwinists answer that the creative force that produced complex animals, for example, from a single-celled predecessor over billions of years is in general the same mechanism that produces variation within animal and plant species that we witness today.
Critics of Darwinism, as well as Darwinists themselves, typically distinguish between microevolution and macroevolution, though both sides understand the magnitude of the distinction differently. Simply put, microevolution explains change within a species, but macroevolution explains the changes that occur above the level of species. Macroevolution explains how a species splits into two (i.e., speciation). One of the best-known Darwinists, Ernst Mayr, remarked that macroevolution (i.e., transspecific evolution) is an extrapolation of the events that take place within populations and species at the microevolutionary level. Thus, according to Darwinists the difference between micro- and macroevolution ought not to be exaggerated. The same processes that cause within-species evolution (microevolution) are responsible for above-species evolution (macroevolution). When the idea of speciation is added to Darwin's view of natural selection the resulting theory is seen as a sufficient explanation for the rise and diversity of life.
Natural selection occurs in order to maintain and increase the genetic fitness of a population. Individual animals with genetic defects generally do not survive to produce offspring. Darwinists use this fact to build their theory that natural selection not only maintains the genetic fitness of a population, but also provides an explanation for how a single cell - or many different cells? - produced over the course of billions of years the variety of living organisms that we see today. The mutations that sometimes take place among species are almost always harmful. However, according to Darwinists, in rare cases a mutation will prove to be an advantage and thus improve the organism's ability to survive and reproduce. If the favorable mutation spreads throughout the species it may possibly provide the basis for further improvements in succeeding generations. Speciation, via favorable mutations, can be broken down into small steps over millions of years. These steps were purposeless natural processes that did not require the belief in special creation. In Stephen Jay Gould's much-acclaimed book, Wonderful Life (New York: Norton, 1990), he suggests that evolution could not be expected to produce the same outcome. Humans may not necessarily result a second time because evolution is a purposeless/directionless force that relies on random mutations. Richard Dawkins refers to this process of natural selection as "the blind watchmaker."
The transitional or intermediate forms of life needed to accomplish the process of natural selection required, in Darwin's own words, the "accumulation of infinitesimally small inherited modifications, each profitable to the preserved being" (The Origin of the Species, 74). The fossil record did not, however, provide the empirical support that Darwin wished for. He attributed the paucity of evidence to the incompleteness of the fossil record, but hoped that later discoveries would vindicate his theory.
Unfortunately for Darwin, the fossil record did not provide the evidence to support his theory, which led Stephen Jay Gould to admit that "All paleontologists know that the fossil record contains precious little in the way of intermediate forms; transitions between major groups are characteristically abrupt. Gradualists usually extract themselves from this dilemma by invoking the extreme imperfection of the fossil record" (The Panda's Thumb, 189). Gradualism, while not supported by the fossil record, nevertheless remains the best explanation for the majority of evolutionists because they cannot think of a more plausible alternative. However, not entirely satisfied with the fossil record, Stephen Jay Gould and Niles Eldredge proposed a new theory for explaining both the fossil record and the present diversity of life called "punctuated equilibria/equilibrium." This theory provided these paleontologists with an explanation for the patterns found in the fossil record.
The theory of punctuated equilibrium, coming from such eminent evolutionists, such as Gould (who often appeared on the television show, "The Simpsons") and Eldredge, provides perhaps the most significant reason why Reformed theologians can affirm natural selection, but not natural selection in the Darwinian sense. After all, Darwin could not provide significant examples of natural selection that could be empirically tested, and so he relied on his argument by analogy. Darwinists insist that micromutations account for variability within a certain population of animals. In connection with this premise, natural selection directs evolutionary change. Ernst Mayr recognized that the Neo-Darwinian (synthetic) theory has not received universal approval from scientists. He writes:
"A well-informed minority [...] including such outstanding authorities as the geneticists Goldschmidt, the paleontologist Schindewolf, and the zoologists Jeannel, Cuénot, and Cannon, maintained until the 1950's that neither evolution within species nor geographic speciation could explain the phenomena of "macroevolution," or, as it is better called, transpecific evolution. These authors contended that the origin of new "types" and of new organs could not be explained by the known facts of genetics and systematics. As alternatives they advanced two explanations, both in conflict with the synthetic theory: saltations (the sudden origin of new types) and intrinsic (orthogenetic) trends" (Populations, Species, and Evolution, 351).
Mayr provides insight into a debate among evolutionists that maybe provides the most compelling reason why Reformed theologians, who have had little or no scientific training, should refrain from embracing the Neo-Darwinian version of origins.
Darwin's gradualist model led him to confess, "if it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down" (Origin of the Species, 142). Darwin was absolutely correct, and that explains why various prominent evolutionists have received a great deal of criticism, and at times ridicule, for suggesting that Darwin's theory of phyletic gradualism cannot explain complex structures and organisms (such as mammalian hair). The Berkeley geneticist, Richard Goldschmidt, argued that Darwin's gradualist model could only explain variation within the species boundary. Far from abandoning evolution altogether, Goldschmidt claimed speciation must have occurred through large-scale jumps called macromutations, otherwise known as "quantum evolution." This idea provided the answer to the bridgeless gap separating micro- and macroevolution. In his book, The Material Basis for Evolution, he argued for a type of "hopeful monster," a new species with the capacity to survive and propagate. Goldschmidt's theory was initially greeted with ridicule, but Stephen Jay Gould and Niles Eldredge took up his cause with their own theory of punctuated equilibrium. Eldredge describes the problem that Goldschmidt tried to address:
No wonder paleontologists shied away from evolution for so long. It never seemed to happen. Assiduous collecting up cliff faces yields zigzags, minor oscillations, and the very occasional slight accumulation of change -- over millions of years, at a rate too slow to account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the fossils did not evolve elsewhere! Evolution cannot forever be going on somewhere else. Yet that's how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution (Reinventing Darwin, 95).
In other words, Eldredge and Gould noticed two features in the fossil record that were inconsistent with Darwinian gradualism. First, most species show no directional change; and, second, new species abruptly appear in the fossil record. Natural selection cannot account for these peculiarities, argued Eldredge and Gould.
In light of these problems with the modern Darwinian synthesis, Gould asked in the title of his now (in)famous article, "Is a New and General Theory of Evolution Emerging?" In this article Gould writes:
"I well remember how the synthetic theory beguiled me with its unifying power when I was a graduate student in the mid-1960's. Since then I have been watching it slowly unravel as a universal description of evolution. The molecular assault came first, followed quickly by renewed attention to unorthodox theories of speciation and by challenges at the level of macroevolution itself. I have been reluctant to admit it - since beguiling is often forever - but if Mayr's characterization of the synthetic theory is accurate, then that theory, as a general proposition, is effectively dead, despite its persistence as text-book orthodoxy" (p. 120).
As in the case of Goldschmidt, this proposal was met with a good deal of criticism. Gradualists responded that adaptive macromutations are impossible and have nothing to do with evolution. Thus, gradualists like Dawkins, who are not persuaded by the theory of punctuated equilibria, retained their belief that evolution by micromutation is the only viable alternative. Slow, gradual evolution by a combination of mutations (not "macromutations") acting concurrently with natural selection provides the best explanation for the natural world according to the majority of Darwinists.
Punctuated equilibrium, with its claim of stasis, represents a significant departure from the standard gradualistic model that Darwin pioneered. Some scientists, even Dawkins himself, have been careful to downplay the significance of this debate. Dawkins called it a "minor dispute" that "has been blown up to give the impression that Darwinism's foundations are quivering" (A Devil's Chaplain, 199). But Dawkins is clearly downplaying the significance of this debate so that creationists will have one less weapon in their arsenal. Indeed, the debate warranted a book by philosopher of science, Kim Sterelny, titled Dawkins Vs. Gould: Survival of the Fittest (Cambridge: Icon Books, 2001). The very emergence of punctuated equilibrium (evolution by "jerks") in opposition to phyletic gradualism (evolution by "creeps") suggests that the Neo-Darwinian synthesis is far from proven.
Some Reformed theologians have perhaps been a little too eager to accept the claims of the Neo-Darwinian synthesis without understanding properly the lively debate among evolutionists on the actual mechanism of fully naturalistic evolution. Before we try to synthesize our theology with Darwinian evolution, we should at least understand the various models that we're faced with, if we insist on making a choice between the two major schools of thought.
For my part, the contrasting models above fail to persuade me that I need to baptize Darwinian evolution with certain Christian truths that are non-negotiable...because, after all, what is negotiable and non-negotiable is a slippery slope, if history tells us anything.
Pastor Mark Jones's thumbs are growing.