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Walt Loves Chuck
Oct. 8th, 2006 07:14 pmOne of the most prevalent criticisms of Darwin's theory of natural selection involves the origins of biological structures that have no intermediate forms.
For example, creationists often mistakenly claim eyes to be miracles that cannot have evolved. Really? In the biological world one can find several examples of "eyes," from the human eyeball, with its retinal array of photosensors gathered within the eyeball behind the focusing lens of the cornea, to the simple light-sensing single photosensor on the outer skins of microscopic creatures, to the bulbous multifaceted arrays sported by common houseflies. Starting with the single photosensitive receptor, one can easily find eyes in existing creatures that gradually increase in complexity, each increase offering an advance in visual acuity that provides a survival advantage.
One cannot say the same about wings. While one can still see half as much with half an eye, one cannot fly with half a wing.
St. George Mivart raised this very point in his book On the Genesis of Species (1871), the book's very title a direct poke a Darwin's own On the Origin of Species:
He later in his book concludes (p. 107): "It is difficult, then, to believe that the Avian limb was developed in any other way than by a comparatively sudden modification of a marked and important kind."
Darwin himself noted Mivert's observations and held them in high esteem, enough to revise later editions of The Origins of Species, discussing in these revisions ". . . organs that perform two functions, one primary, the other subsidiary, then relinquish the main use and elaborate the formerly inconspicuous operation." (Gould, Bully for Brontosaurus, 1992, p. 143) Darwin thought that wings may have originally been organs that served respiration, breathing tubes that grew into wings.
While fascinating, Darwin's breathing tube speculation was later supplanted by the theory that bird wings originally served to regulate the early bird relatives' internal body temperature:
With this theory, any planar limb apendage can serve two important functions:Tucked in, the membranes/chiton extensions/stiff scales can provide insulation Spread out, vascular and conductive surfaces increase the surface to volume ratio and shed heat.
Furthermore, flapping the surfaces moves air that can drastically increase cooling. Bees appoint workers at the entrances to hives. These workers buzz their wings, moving air into or out of the hive interior. Under this theory, that job would have been possible even before the species was able to fly!
Which brings me to some correction.
Some say he was an ardent anti-communist. Some say he held a rosy vision of America that drastically skewed from the reality. Both accusations are true.
When adapted, his stories deviated from originals with wildly improbable happy endings. His myths offered little instructional value, removing from the stories any lessons the young can use later in life. Some have said this truncation of the lessons has produced a generation or three with few coping skills for the really hard situations. Books have been written about this.
( But in his defense, I'll say this: )
For example, creationists often mistakenly claim eyes to be miracles that cannot have evolved. Really? In the biological world one can find several examples of "eyes," from the human eyeball, with its retinal array of photosensors gathered within the eyeball behind the focusing lens of the cornea, to the simple light-sensing single photosensor on the outer skins of microscopic creatures, to the bulbous multifaceted arrays sported by common houseflies. Starting with the single photosensitive receptor, one can easily find eyes in existing creatures that gradually increase in complexity, each increase offering an advance in visual acuity that provides a survival advantage.
One cannot say the same about wings. While one can still see half as much with half an eye, one cannot fly with half a wing.
St. George Mivart raised this very point in his book On the Genesis of Species (1871), the book's very title a direct poke a Darwin's own On the Origin of Species:
Natural selection utterly fails to account for the conservation and development of the minute and rudimentary beginnings, the slight and infinitesimal commencements of structures, however useful those structures may afterward become. (Mivert, 1871, p. 23)
He later in his book concludes (p. 107): "It is difficult, then, to believe that the Avian limb was developed in any other way than by a comparatively sudden modification of a marked and important kind."
Darwin himself noted Mivert's observations and held them in high esteem, enough to revise later editions of The Origins of Species, discussing in these revisions ". . . organs that perform two functions, one primary, the other subsidiary, then relinquish the main use and elaborate the formerly inconspicuous operation." (Gould, Bully for Brontosaurus, 1992, p. 143) Darwin thought that wings may have originally been organs that served respiration, breathing tubes that grew into wings.While fascinating, Darwin's breathing tube speculation was later supplanted by the theory that bird wings originally served to regulate the early bird relatives' internal body temperature:
Feathers are modified reptilian scales, and they work very well as insulating devices. Moreover, if birds evolved from dinosaurs (as most paleontologists now believe), they arose from a lineage particularly subject to problems with temperature control. Archaeopteryx is smaller than any dinosaur and probably arose from the tiniest of dinosaur lineages. Small animals, with high ratios of surface area to volume, lose heat rapidly and may require supplementary devises for thermoregulation. (Gould, ibid, p. 145).
With this theory, any planar limb apendage can serve two important functions:
Furthermore, flapping the surfaces moves air that can drastically increase cooling. Bees appoint workers at the entrances to hives. These workers buzz their wings, moving air into or out of the hive interior. Under this theory, that job would have been possible even before the species was able to fly!
Which brings me to some correction.
Some say he was an ardent anti-communist. Some say he held a rosy vision of America that drastically skewed from the reality. Both accusations are true.
When adapted, his stories deviated from originals with wildly improbable happy endings. His myths offered little instructional value, removing from the stories any lessons the young can use later in life. Some have said this truncation of the lessons has produced a generation or three with few coping skills for the really hard situations. Books have been written about this.
( But in his defense, I'll say this: )