An Evaluation of Evolution as an Explanatory Device
It is very common for scientists to claim this or that phenomenon “evolved.” How well do such statements qualify as scientific explanations? How much scientific heavy lifting is done by merely stating that things are the way they are because they evolved that way? The following recent examples can be considered representative of the evolutionary explanations to be found in scientific literature in any given week.
- Let’s be fair in our explanations: An article in Science Daily claims once again that fairness evolved (cf. 04/23/2008). Because certain brain areas light up while making ethical choices, and because children exhibit an emotional response when sensing unfairness, Steven Quartz (Caltech) stated that, “The fact that the brain has such a robust response to unfairness suggests that sensing unfairness is a basic evolved capacity.” Quartz did not specify what sort of random mutations in neurons would be able to generate an ethical sense where one did not exist before.
- Disappearing evolution: Another story on Science Daily actually used negative evidence to support evolution. “Robyn Crook from the City University of New York reports that Nautilus, the ancient living ancestors of modern cephalopods, have both long and short-term memory, despite lacking the brain structures that modern cephalopods evolved for long-term memory.” The article did not explain what the peculiar phrase “ancient living ancestors” means, but it probably did not refer to living great-great-great-great-grandparents millions of years old. The title clarified it somewhat: “Living Fossils Have Long- And Short-term Memory Despite Lacking Brain Structures Of Modern Cephalopods.” Living fossils are evolutionary conundrums (10/14/2004).
In other words, we have living representatives of a long-lost lineage of sea creatures thought to have lived 450 to 150 million years ago. Pavlov-like experiments show that these living specimens have both long-term and short-term memories. According to the evolutionary timeline, Nautilus never received the brain upgrades that squid and octopi developed for this ability. It was surprising, therefore, to see them performing so well on memory tests. “Nautilus has both short and long term memory, just like modern cephalopods, despite lacking the same brain structures.”
Wouldn’t this observation falsify the belief that the brain upgrades evolved? Neither the article nor the scientists thought so for a minute. They declared the Nautilus to be ideally suited to discover the “evolutionary pathways that led to the development of the complex coleoid [soft bodied cephalopod] brains.”
- Magnetic personalities: Birds and a number of other vertebrates, including fish, amphibians and mammals, have precision magnetic sense organs for navigation. James L. Gould, an evolutionary biologist at Princeton, sought to explore this phenomenon in an article in Current Biology.1 His surprising answer is that this improbable sense evolved independently multiple times. He commented on an earlier paper that suggested “a more specialized light-dependent compass has evolved at least twice to supplement and at least partially replace what would seem to have been a perfectly good magnetite-based strategy.”
Subsequent statements had the flavor of just-so storytelling: “Quite probably the magnetite (the densest substance synthesized biologically) was originally just a weight to pull the front of the bacterium down; subsequent evolution may then have led to the aligned chain, which is much more effective.” Again, later, he said, “The same organs are also used by these sharks and rays to detect the electrical activity of hidden prey; presumably it is from this sensory occupation that the direction-finding ability evolved.”
And finally, evolution was evoked again as the explanation in spite of negative evidence: “Although the newt’s light-dependent compass appears separately evolved, its operation and its interaction with the magnetite-based map system seems very similar to the picture emerging in birds.” Evolution even provided the paradigm for future research: “Perhaps too it will lead to a more informed understanding of the separate evolution of these two fascinating systems, and the way they conspire to enhance the mystique of animal homing and migration.” To view evolution as conspiring to do anything would seem to be a violation of Darwin’s principles of natural selection acting on random variations.
- Batting average: In another article in Current Biology,2 Michael Dickson of Caltech, discussing bat flight, used the E-word right off the bat: “Active flight has evolved within just four taxa in the history of life: insects, pterosaurs, birds and bats.” The fact that a highly improbable, complex system of organs and behaviors exists in unrelated lineages was no problem for the evolutionary angle: “Because of the multiple origins of flight, wings have long served as textbook examples of evolutionary homology and convergence.”
The spectre of just-so storytelling reappeared at the end of his article: “bats and moths are engaged in a deadly evolutionary arms race for command of the night sky,” he said. “It is intriguing to note that these creatures are nevertheless united by the laws of physics.” He gave evolutionary explanations without batting an eye.
- For the love of beetles: Bouncing off J. B. S. Haldane’s memorable quip about the creator having an “inordinate fondness for beetles,” (but see 04/26/2002), Florian Maderspacher wrote in Current Biology about beetle evolution.3 “Beetles are an amazing example of an evolutionary radiation” she wrote. This presumes that diversity is a measure of the strength of evolutionary explanations, as opposed to other possible inferences. She bluffed that the evolutionary explanation is “known” despite the conundrum of how humans and insects, presumably on vastly different branches of the evolutionary tree, share numerous genes:
It has been known that insects in general, and especially the lineage leading to Drosophila, have undergone accelerated evolution, and this was confirmed when a molecular phylogeny was constructed using the newly available data from Tribolium. Overall, Tribolium shares more genes with humans than the Dipterans do. Tribolium researchers will surely be tempted to use this finding to argue that their organism is ‘more ancestral’, ‘more representative’ or simply ‘less weird’ than Drosophila.
A full evolutionary explanation remained on back order. “Of course, expression patterns and regulatory relationships can differ considerably between Tribolium and Drosophila, but to what extent such differences are due to evolutionary drift or reflect an adaptation of the patterning system to the short- versus long-germ mode of development is not clear at present.” In fact, she ended by casting doubt on the explanatory power of evolutionary theory altogether: “The genome might thus help to focus on the species itself as a product of evolution, whose traces can be read from the genome,” she said, deferring the answer to the future. “Only much further work – now able to draw on the resource of the Tribolium genome sequence – will reveal whether the genome holds an explanation for why evolution was so fond of beetles.”
This sounds as if Haldane’s lateral swipe at creationists for failing to explain why a creator would be so fond of beetles could be tossed right back to the evolutionary biologists.
Does a scientist ever balk at the use of evolution to explain things? In a letter to the editor of PNAS June 3, John R. Skoyles (University College, London) took issue with Deborah S. Rogers and Paul Ehrlich for having written a theory of the evolution of canoe design (yes, that is canoes, as in boating). The paper had even used refined terms like positive selection and negative purifying selection in their theory of how intelligent humans designed their canoes over the centuries. Skoyles protested: “This is an insufficient foundation for inferring the existence of any particular type of process, let alone one analogous to ‘natural selection.’” He further accused them of equivocation in their use of the E-word.
Rogers and Ehrlich stood by their claim in the same issue of PNAS. They defended their use of evolutionary explanations by pointing to the many scientists who do the same thing. “This is a commonly accepted signal of negative (purifying) selection for genetic evolution and when interpreting the fossil record,” they said. “Although it does not prove that natural selection was at work, it certainly supports that inference.”
Their ending paragraph gets to the heart of the issue. What qualifies as an explanation in science?
As most scientists know, how one defines “scientific” is a complex and heavily debated topic, and one should be cautious in making ex cathedra statements about it. The degree to which our results can be generalized remains to be seen.
1. James L. Gould, “Animal Navigation: The Evolution of Magnetic Orientation,” Current Biology, Vol 18, R482-R484, 03 June 2008.
2. Michael Dickinson, “Animal Locomotion: A New Spin on Bat Flight,” Current Biology, Vol 18, R468-R470, 03 June 2008.
3. Florian Maderspacher, “Genomics: An Inordinate Fondness for Beetles,” Current Biology, Vol 18, R466-R468, 03 June 2008.
It should be clear that evolution is a modern secularist form of cultural mythology. Evolution serves the same function as the Greek gods did in explanations about phenomena the ancient Greeks did not understand. In fact, philosopher Willard van Orman Quine in 1951 stated as much by analyzing how scientists explain recalcitrant data (e.g., 10/29/2004). In his influential paper Two Dogmas of Empiricism, he asserted that Homer’s gods and modern causal references serve the same explanatory function. It’s not that Quine believed the Greek gods provided an equally good explanation; “But in point of epistemological footing the physical objects and the gods differ only in degree and not in kind,” he asserted. “Both sorts of entities enter our conception only as cultural posits. The myth of physical objects is epistemologically superior to most in that it has proved more efficacious than other myths as a device for working a manageable structure into the flux of experience.” A workable device, however, is not synonymous with a truthful or established explanation.
More radically, Bas van Fraasen has argued that a scientific explanation is nothing more than an answer to a “why” question. Why are old pictures all black and white? cartoon character Calvin asks Dad. The answer is that the pictures were taken in color, but the world was black and white then. This is just as good a scientific answer as any other, van Fraasen seems to be saying in his theory of constructive empiricism. What this implies is that scientific explanations are essentially worthless as true statements about reality. If the explanation is useful, if it gives the culture good vibes, if it shuts Calvin up for the time being, then it’s a “scientific” explanation. Science is not in the business of providing true explanations as long as it provides some value in classification, prediction and control.
If so, why should the evolutionary biologists be the only players in the game? Lots of people have answers to why-questions. The animists have their answers. The Hindus have theirs. Muslims have theirs. Jews and Christians have theirs. Why do evolutionary biologists occupy the guru chair in modern culture? The postmodern social construction theorists (now fading away) would say that the Big Science community is the dominant social force only because of the sheer exercise of power. There is nothing epistemically stronger in their approach than that of any other social group.
These and other anti-realist positions created a backlash among scientists that erupted in the “science wars” of the late 1990s. Alan Sokal, at the height of the conflict, pulled a creative hoax against the postmodernists that caused them great embarrassment. Scientists took this as a vindication of scientific realism, but how much it really did so is a matter of debate. Embarrassing one’s opponent does not necessarily prove one’s case. We have little sympathy with postmodernism and deconstruction in these commentaries. Nevertheless, even Sokal knows that one can only defend a modest form of scientific realism in this post-Quine, post-Kuhn, post-Feyerabend era. He tried to do this in a short paper with Jean Bricmont called Defense of Modest Scientific Realism. The perceptive reader will see, however, these champions of normal science “help themselves” to concepts like honesty, truth and rationality that have no foundation in physicalist assumptions.
Therein lies the crux of the problem. Evolutionists help themselves to unwarranted concepts. Believing the world to be an undirected maze of particles and forces, they nevertheless help themselves to concepts of truth, explanation, justification, empiricism and honesty. Such things cannot and could not evolve from particles. Such things only make sense if they are true, universal, necessary and certain. They only make sense if one starts with the presupposition that these things flow from an all-wise, righteous, all-powerful Creator who is real. His “I am” is the starting point for all other claims that “this is.”
Those with the Judeo-Christian worldview have a foundation for scientific explanations because they believe the Creator endowed us with senses that are in touch with reality – a reality He created, and has made known to us both in general and special revelation. It is devilishly hard to make the claim otherwise. How can an evolutionist, consistent with his worldview, have any confidence that his sensations, which pass through multiple layers of processing on the way from input to the brain, bear any trustworthy connection with nature “out there” as it really is? Sokal says there are only one or a few “non-crazy” explanations, but that is a judgment call. Whom is he calling crazy? How can he judge craziness without standards of rationality that require non-naturalistic presuppositions? How can he do that without implicitly plagiarizing the Ten Commandments?
If we slapped the hand of the evolutionist every time he helped himself to the table of philosophy of realism without paying the price of adequate presuppositions (in the right denominations), he would either have to starve or become a Christian. Only then could he have the right to taste the empirical data, digest it as science, grow and be nourished as a scientist and feel satisfied with the experience.
Switching metaphors, science needs an intelligently-designed form of purifying selection. No more hybrids should be bred from Christian presuppositions wedded to naturalistic explanations. Forcing evolutionists to argue consistent with their presuppositions will lead to their extinction. Then, evolutionary explanations will take their place in the dustbin of history along with Homer’s gods and the DODO.*