In an article for National Geographic, "Your Inner Feather," Carl Zimmer writes: "Feathers started out as simple filaments, turning to fuzz, and then diversifying into a lot of different forms — including the ones that eventually let birds take to the air." Touting a study in Molecular Biology, Zimmer points out that even humans have nearly all of the genetic requirements for feathers. How can this be?
"It may seem strange to consider the fact that you, as a mammal, have all the known genes required to pattern a feather, and yet you do not look like Big Bird. The reason for this discrepancy," Zimmer insists, "is that genes can do different jobs." This conclusion was derived from scientists looking at the "genetic recipe for feathers written in the DNA of birds." This molecular "cookbook" is apparently very old, and "evolution was tinkering with the same [genetic] toolkit" in developing feathers.
What is interesting in Zimmer’s account is how it is festooned with teleological language. Though he presumably believes evolution is a wholly unguided process, fueled by randomness, his word choices suggest the opposite — "cookbook," "recipe,"� "tinkering" — these are all suggestive of instructions, purpose, and intentionality. Cookbooks and recipes are simply instructions that need to be followed to achieve a desired result, and "tinkering" implies a "tinkerer." How all this happened by purely Darwinian processes is unclear, and indeed the filament-to-fuzz-to-feather narrative is subsumed in the fuzzy thinking often accompanying these evolutionary just-so stories. Questions of precisely how and why some filaments turned to hair and others to feathers, often under very similar selective pressures, are answered with vague speculations and hand waving.
Now, the question isn’t whether or not feathers "evolved" or even whether or not feathers are the product of complex genetic messaging over an extremely long period of time, but whether or not feathers can be explained by the unguided processes of Darwinian evolution alone. One central figure in the history of biology, Alfred Russel Wallace (1823-1913), thought not. The co-discoverer of natural selection obviously embraced evolution but it was intelligent evolution. In The World of Life, Wallace pointed to the feather (among other things) as demonstrating the guidance of a purposeful intellect in life’s development (pp. vi-vii):
I first endeavour to show . . . by a careful consideration of the structure of the bird’s feather [and certain other features of nature] �. . . the absolute necessity for an organising and directive Life-Principle in order to account for the very possibility of these complex outgrowths. I argue, that they necessarily imply first, a Creative Power, which so constituted matter as to render these marvels possible; next, a directive Mind which is demanded at every step of what we term growth, and often look upon as so simple and natural a process as to require no explanation; and, lastly, an ultimate Purpose, in the very existence of the whole vast life-world in all its long course of evolution throughout the eons of geological time.
Of course Wallace didn’t have the advantage of our modern knowledge about molecular biology or genetics, but he was probably much closer to an accurate appraisal of the developmental processes resulting in the feather than the Darwinian reliance upon blind, unguided chance and necessity. Zimmer himself can’t talk about the feather without invoking strongly teleological language.
The historical connection to understanding feather development isn’t from Darwin to the neo-Darwinian synthesis � la Dobzhansky, Huxley, and Mayr, but from Wallace to our emerging understanding of irreducible complexity, information theory, and intelligent design via Michael Behe, Stephen Meyer, Michael Denton, and William Dembski. As Darwinians continue down their scientific cul-de-sac, others are blazing more fruitful paths.
Photo source: Leandro Amato/Flickr.