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The Natural and the Supernatural: Alfred Russel Wallace and the Nature of Science

Michael Flannery's assessment of Alfred Russel Wallace as a prescient scientist who anticipated modern Intelligent Design theory is premised on the belief that modern evolutionary biologists have failed to explain the myriad abilities of the human mind that Wallace outlined in his day as unanswered and -- in his hyperselectionist formulation of evolutionary theory -- unanswerable.

In point of fact there are several testable hypotheses formulated by scientists -- evolutionary psychologists in particular -- that make the case that all aspects of the human mind are explicable by evolutionary theory. Flannery mentions just one -- Steven Pinker's hypothesis that cognitive niches in the evolutionary environment of our Paleolithic hominid ancestors gave rise to abstract reasoning and metaphorical thinking that enabled future humans to navigate complex social and cognitive environments found in the modern world.

In his PNAS paper Pinker outlines two processes at work: "One is that intelligence is an adaptation to a knowledge-using, socially interdependent lifestyle, the 'cognitive niche.'" And: "The second hypothesis is that humans possess an ability of metaphorical abstraction, which allows them to coopt faculties that originally evolved for physical problem-solving and social coordination, apply them to abstract subject matter, and combine them productively." Together, Pinker concludes: "These abilities can help explain the emergence of abstract cognition without supernatural or exotic evolutionary forces and are in principle testable by analyses of statistical signs of selection in the human genome." Pinker then outlines a number of ways in which the cognitive niche hypothesis has been and can continue to be tested.

In point of fact, Darwin himself addressed this larger problem of "pre-adaptation": Since evolution is not prescient or goal directed -- natural selection operates in the here-and-now and cannot anticipate what future organisms are going to need to survive in an ever-changing environment -- how did certain modern useful features come to be in an ancestral environment different from our own? In Darwin's time this was called the "problem of incipient stages." Fully formed wings are obviously an excellent adaptation for flight that provide all sorts of advantages for animals who have them; but of what use is half a wing?

For Darwinian gradualism to work, each successive stage of wing development would need to be functional, but stumpy little partial wings are not aerodynamically capable of flight. Darwin answered his critics thusly:

Although an organ may not have been originally formed for some special purpose, if it now serves for this end we are justified in saying that it is specially contrived for it. On the same principle, if a man were to make a machine for some special purpose, but were to use old wheels, springs, and pulleys, only slightly altered, the whole machine, with all its parts, might be said to be specially contrived for that purpose. Thus throughout nature almost every part of each living being has probably served, in a slightly modified condition, for diverse purposes, and has acted in the living machinery of many ancient and distinct specific forms.1
Today this solution is called exaptation, in which a feature that originally evolved for one purpose is co-opted for a different purpose.2 The incipient stages in wing evolution had uses other than for aerodynamic flight -- half wings were not poorly developed wings but well-developed something elses -- perhaps thermoregulating devices. The first feathers in the fossil record, for example, are hairlike and resemble the insulating down of modern bird chicks.3 Since modern birds probably descended from bi-pedal therapod dinosaurs, wings with feathers could have been employed for regulating heat -- holding them close to the body retains heat, stretching them out releases heat.4

So one testable hypothesis about the various aspects of the mind that so troubled Wallace is that cognitive abilities we exhibit today were employed for different purposes in our ancestral environment. In other words, they are exaptations, coopted for different uses today than that for which they originally evolved. But even if these hypotheses fail the tests, new hypotheses will take their place to be empirically verified, rejected, or refined with additional data from the natural world. This is how science operates -- the search for natural explanations for natural phenomena.

By contrast, Intelligent Design theorists offer no testable hypotheses at all, no natural explanations for natural phenomena. Instead, their answer to the mysteries of the mind is the same as that of all other mysteries of the universe: God did it. Although their narratives are gussied up in jargon-laden terms such as "irreducible complexity," "specified complexity," "complex specified information," "directed intelligence," "guided design," and of course "intelligent design," these are not causal explanations. They are just linguistic fillers for "God did it" explanations. It is nothing more than the old "God of the gap" rubric: wherever creationists find what they perceive to be a gap in scientific knowledge, this must be where God intervened into the natural world.

If they want to do science, however, they must provide testable hypothesis about how they think God (or the Intelligent Designer -- ID) did it. What forces did ID use to bring about wings, eyes, and brains? Did ID intervene in the natural world at the level of species or genus? Did ID intervene at the Cambrian explosion or before (or after)?

Did ID create the first cells and pack into their DNA the potential for future wings, eyes, and brains? Or did ID have to intervene periodically throughout the past billion years to build bodies one part at a time? And more to the point here, did ID layer cortical neurons atop older naturally evolved brain structures to enable certain primates to reason more abstractly than other primates?

The reason scientists do not take seriously the claims of Intelligent Design theorists today is the same reason that scientists did not take seriously Wallace's speculations about an "overarching intelligence" that guided evolution. As I noted previously, Wallace's hyperselectionism and hyperadaptationism blinded him to the possibilities offered in a multi-tiered evolutionary model where the concept of exaptation expands our thinking about how certain features might have evolved for reasons different from what they are used for today.

As Wallace's biographer, I hold the opinion that he was driven by his overarching scientism of which his theory of evolution as pure adaptationism was a part, and that even his spiritualism was subsumed in his scientistic worldview.5

References Cited

(1) Darwin, Charles. 1862. On the Various Contrivances by Which British and Foreign Orchids Are Fertilized by Insects, and on the Good Effects of Intercrossing. London: John Murray. p. 348.

(2) Gould, Stephen Jay and Elizabeth Vrba. 1982. "Exaptation: A Missing Term in the Science of Form." Paleobiology, 8, pp. 4-15.

(3) Prum, R. O. and A. H. Brush. 2003. "Which Came First, the Feather or the Bird: A Long-Cherished View of How and Why Feathers Evolved Has Now Been Overturned." Scientific American, March, pp. 84-93.

(4) Padian, Kevin and L. M. Chiappe. 1998. "The Origin of Birds and Their Flight." Scientific American, February, pp. 38-47.

(5) Shermer, Michael. 2002. In Darwin's Shadow: The Life and Science of Alfred Russel Wallace. New York: Oxford University Press.