The Human Brain as an Argument for Intelligent Design
At Why Evolution Is True, Jerry Coyne critiques Alfred Russell Wallace's argument, made likewise by Polkinghorne and Beale, that the human brain -- in "conferring abilities far beyond those needed to survive in our ancestral environments" -- indicates that something other than blind natural selection is going on.
In Coyne's summary:
With Wallace, Polkie and Beale see the brain's ability to do math as something inexplicable by natural selection. Ergo Jebus.Coyne produces a quote from Wallace that assume a relationship between brain size and aptitude. He comments:
Wallace's mistake, which should be obvious, is that we have no assurance that the human brain really is larger than it needs to be, even in the so-called "savages" whom Wallace encountered on his travels. Humans aren't just gorillas: we can speak, learn, and have sophisticated mental programs for sussing out the thoughts of others and figuring out how to relate to others in small groups. We've mastered fire, which according to Richard Wrangham freed up our brain to become more complex under real selection pressures.Coyne makes two basic errors here: one, he fails to understand the historical context of Wallace's comments; the other is he simply misses Wallace's real point.
And once we have a complex brain, capable of learning, speaking, and working out strategies to hunt and to live in small social groups, it becomes capable of doing things beyond what it evolved for. In other words, chess, math, and building spacecraft are what Steve Gould called exaptations: those features that can be used in a beneficial way but evolved for other reasons. Once the brain crossed a certain threshold of complexity, these things became possible, but those abilities are epiphenomena.
To begin with, in correlating brain size to aptitude Wallace was merely following the best science of his day, something Darwin was in full agreement with. "The belief that there exists in man some close relation between the size of the brain and the development of the intellectual faculties," wrote Darwin in Chapter 2 of Descent of Man, "is supported by the comparison of skulls of savage and civilized races, of ancient and modern people, and by the analogy of the whole vertebrate series."
Darwin approvingly cited the work of his contemporary, physician/craniologist Joseph Barnard Davis, who had himself amassed a collection of some 1700 crania, and noted that Europeans had a cranial capacity of 92.3, Americans 87.5, Asiatics 87.1, and Australians 81.9 cubic inches. For Darwin cranial capacity and brain size served as evidence for European superiority, whereas Wallace (who himself had lived among the native peoples of two hemispheres for nearly 12 years) saw the similarity of brains among all races as giving evidence of inherent equality.
But this leads to the second point Coyne appears to miss. Wallace argued that by Darwin's own principle of natural selection, an attribute's utility should be the chief determining factor. For Wallace, then, the very equality of all peoples led to an important question: what explains that equality? It surely couldn't be its advantage in affording Homo sapiens survival since abstract reasoning, mathematical ability, artistic and musical abilities have little or no role in survival.
Coyne wants to suggest as an answer that "once we have a complex brain, capable of learning, speaking, and working out strategies to hunt and to live in small social groups, it becomes capable of doing things beyond what it evolved for." But this begs the question. What would have driven brain complexity beyond mere survival? Why develop speaking or extraordinary learning capacities or complex social units when sheer stealth or speed or agility would have sufficed?
Perhaps Coyne is referring to development by excipient stages, whereby attributes originally developed for one purpose are then developed for quite another. Since I've dealt with this elsewhere, I'll not repeat its problems here.
The argument in Polkinghorne and Beale's book (which I have not read) that Coyne brings up shows how prescient and persistent Wallace's observations -- regarding the special qualities of the human mind -- really are. Could that be because all Darwinian explanations thus far offered have failed and given little more than a promissory note of future discovery?
The best detailed examination of this issue is surely not from Coyne or any Darwinist but from James Le Fanu in his book Why Us?