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elfsI had the pleasure recently of watching the PBS Nova episode Judgement Day: Intelligent Design on Trial. The show was quite good. If you google for it, you'll find a lot of complaints about it, most of which whine that it was "biased in favor of evolution" and "didn't show the science behind ID."
Well, there's a reason for that: there is no science behind ID, and reality itself is biased in favor of evolution.
One of the things that annoyed me was the explanation of Tiktaalik. In 1999, paleontologists discovered a plain in Northern Canada that exposed a rock bed, the best date of which was exactly between the era of the fish and the emergence of the amphibians. Evolutionary theory predicted that in that rock bed one might find a transitional fossil: something with characteristics of both a fish and an amphibian.
It took four years, but they did find something like that: Tiktaalik, a fish with hefty fins allowing for motility on muddy surfaces but, more importantly, a broad head with forward-pointing eyes, very un-fish-like. The explanation for why Tiktaalik was an excellent "transitional fossil" between fish and amphibian was quite solid.
And yet, something important was missing from the discussion of Tiktaalik. Something vital.
One of the most common statements you hear from the "intelligent design" side of the argument is that, to quote Of Pandas and People, "Intelligent Design means that various forms of life began abruptly - through an intelligent agency, with their distinctive features already intact-- fish with fins and scales, birds with feathers, beaks, and wings, etc." A bizarre result of this is that the Intelligent Design yahoos, the useful idiots at the bottom of the ID intellectual foodchain, frequently write screeds (both in small-town punditocracies as well as simple letters to the editor) asking of what use is half a wing, or the partial evolution of a feather?
With questions like this, the ID people attempt to argue that there's no such thing as a "transitional" fossil form. You can't have a species halfway between a dinosaur and a bird, because, to quote from that same atrocious article I linked to above, "Imagine such a species surviving in such a miserable state over many millions of years waiting for fully-formed wings to evolve."
Tiktaalik is important not because it's a transitional form, but because it's a highly successful organism in its own right. By having a more robust undercarriage, and by having both eyes in the front, it was significantly more capable as a large organism of dragging itself to niches that prior to its emergence had probably only ever been visited by insects. The front-mounted eyes suggested that, although it had not left its icthyian nature completely behind, it was already preying upon insects its more fish-like ancestors could never have reached, and avoiding predators that were preying upon its ancestors.
Tiktaalik wasn't busy waiting for fully-formed legs to evolve. And it wasn't "miserable." (That's a value judgement, by the way. Nature Doesn't Care what we think about its day-to-day operation.) Tiktaalik ancestors didn't hope to someday have legs. Some of Tiktaalik's ancestors had stronger fins than others, and those that did found it advantageous to pull themselves up into the mud and snag a few tasty bugs. They lived longer; they had more children; stronger fins were selected. The same with the eyes; those with eyes a millimeter closer to the front found binocular vision advantageous in snagging said tasty bugs. That characteristic was selected for. Nature doesn't "want" or "wait" for these things; they happen as a consequence of living things doing what living things do within a constantly changing environment like our Earth.
While Tiktaalik happened, other fish remained in the sea, eating and breeding and following their own reproductively successful strategies. Tiktaalik found a new way to exploit a new niche. It didn't crowd out an old niche; it didn't supersede the other fishes. (Another popular whine among Creationists is "If man evolved from apes, why are there still apes?" The common and excused answer is that we didn't want the apes' niche. The horrific and true answer is that we do want their niche, we're just not done killing them all off. Evolution, even the "bad" aspects of it (again, note that's a human value judgement and Nature Doesn't Care), takes time.)
I would really have liked Nova to mention Tiktaalik's existence as a highly successful organism optimized for a specialized niche in its time and place. Tiktaalik's existence points out the vicious deception of two of the the Cdesign Proponentsists's favorite stupidities, and it would have been nice to have a biologist put the screws to ID's thumbs even harder.
Well, there's a reason for that: there is no science behind ID, and reality itself is biased in favor of evolution.
One of the things that annoyed me was the explanation of Tiktaalik. In 1999, paleontologists discovered a plain in Northern Canada that exposed a rock bed, the best date of which was exactly between the era of the fish and the emergence of the amphibians. Evolutionary theory predicted that in that rock bed one might find a transitional fossil: something with characteristics of both a fish and an amphibian.
It took four years, but they did find something like that: Tiktaalik, a fish with hefty fins allowing for motility on muddy surfaces but, more importantly, a broad head with forward-pointing eyes, very un-fish-like. The explanation for why Tiktaalik was an excellent "transitional fossil" between fish and amphibian was quite solid.
And yet, something important was missing from the discussion of Tiktaalik. Something vital.
One of the most common statements you hear from the "intelligent design" side of the argument is that, to quote Of Pandas and People, "Intelligent Design means that various forms of life began abruptly - through an intelligent agency, with their distinctive features already intact-- fish with fins and scales, birds with feathers, beaks, and wings, etc." A bizarre result of this is that the Intelligent Design yahoos, the useful idiots at the bottom of the ID intellectual foodchain, frequently write screeds (both in small-town punditocracies as well as simple letters to the editor) asking of what use is half a wing, or the partial evolution of a feather?
With questions like this, the ID people attempt to argue that there's no such thing as a "transitional" fossil form. You can't have a species halfway between a dinosaur and a bird, because, to quote from that same atrocious article I linked to above, "Imagine such a species surviving in such a miserable state over many millions of years waiting for fully-formed wings to evolve."
Tiktaalik is important not because it's a transitional form, but because it's a highly successful organism in its own right. By having a more robust undercarriage, and by having both eyes in the front, it was significantly more capable as a large organism of dragging itself to niches that prior to its emergence had probably only ever been visited by insects. The front-mounted eyes suggested that, although it had not left its icthyian nature completely behind, it was already preying upon insects its more fish-like ancestors could never have reached, and avoiding predators that were preying upon its ancestors.
Tiktaalik wasn't busy waiting for fully-formed legs to evolve. And it wasn't "miserable." (That's a value judgement, by the way. Nature Doesn't Care what we think about its day-to-day operation.) Tiktaalik ancestors didn't hope to someday have legs. Some of Tiktaalik's ancestors had stronger fins than others, and those that did found it advantageous to pull themselves up into the mud and snag a few tasty bugs. They lived longer; they had more children; stronger fins were selected. The same with the eyes; those with eyes a millimeter closer to the front found binocular vision advantageous in snagging said tasty bugs. That characteristic was selected for. Nature doesn't "want" or "wait" for these things; they happen as a consequence of living things doing what living things do within a constantly changing environment like our Earth.
While Tiktaalik happened, other fish remained in the sea, eating and breeding and following their own reproductively successful strategies. Tiktaalik found a new way to exploit a new niche. It didn't crowd out an old niche; it didn't supersede the other fishes. (Another popular whine among Creationists is "If man evolved from apes, why are there still apes?" The common and excused answer is that we didn't want the apes' niche. The horrific and true answer is that we do want their niche, we're just not done killing them all off. Evolution, even the "bad" aspects of it (again, note that's a human value judgement and Nature Doesn't Care), takes time.)
I would really have liked Nova to mention Tiktaalik's existence as a highly successful organism optimized for a specialized niche in its time and place. Tiktaalik's existence points out the vicious deception of two of the the Cdesign Proponentsists's favorite stupidities, and it would have been nice to have a biologist put the screws to ID's thumbs even harder.
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no subject
Date: 2007-11-21 02:01 pm (UTC)Half a wing? Like we don't have critters around who find gliding useful.
Half an eye? Since they seem to have evolved well over two dozen different times, i'd say that a light sensitive patch of nerve cells is a heck of a lot better than none.
... good grief, even devoid of any scientific polysyllables that must give them such headaches, you'd think the ID people would at least think their own arguments through all the way.
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Date: 2007-11-21 04:19 pm (UTC)no subject
Date: 2007-11-21 11:33 pm (UTC)This was almost certainly their original purpose. In fact if you look at the structure of feathers, they are essentially fractal designs, and it's easy to see how simple feathers might have started as a sort of fuzz of naked stalks, creating a zone of warm air against an (already warm-blooded) archosaur, and then over tens of millions of years one after another simple mutation could have caused "stuttering" and the growth of additional stalks from the stalks, until we got to the complex feathers seen on modern birds (and probably also possessed by feathery dinosaurs).
Half a wing? Like we don't have critters around who find gliding useful.
Notice how a cat flattens itself out in a long fall. Notice how some squirrels use increasingly wide membranes to first increase jump distances and then glide. The path to true flight is actually rather obvious, without any long mutational jumps required.
Half an eye? Since they seem to have evolved well over two dozen different times, i'd say that a light sensitive patch of nerve cells is a heck of a lot better than none.
Dawkins outlines this evolutionary path in great detail in Climbing Mount Improbable. The really amazing thing is that you don't even need "nerve cells" -- ANY cell able to detect light's presence and somehow communicate this to the parent organism gives that parent organism an evolutionary advantage, and once you have a tendency to produce even one such cell, even a Gouldian "random walk" will eventually result in eyes as good as the creature can profitably use.
Indeed the "eyes" argument is an emotional one. We humans happen to have one of the best visual systems among mammals, and we are very sight-centered in our mode of survival. Hence, we tend to think of vision as something exceptionally difficult to evolve: the truth is that simple vision is fairly easy to evolve. Vision at our level takes a lot of steps to reach, but all the steps are small ones.
Another thing to do with half a wing
Date: 2008-01-17 03:53 pm (UTC)There's a little-known theory called "Wing-assisted incline running" that I like better (References: http://www.sciam.com/article.cfm?id=taking-wing and http://jeb.biologists.org/cgi/content/full/206/24/4553). The researchers noticed that young ground birds (who were still unable to fly) would use their "half-wings" to help them run up inclined surfaces. It turned out that the birds were using their wings to push themselves into the ground (as opposed to away from the ground as in flight), to the point that the adults can use this technique to scale vertical surfaces. Proto-birds could have used this type of manuever to escape predators and it gives a very clear incremental progression in the evolution of wings, with each improvement being benificial (they could run up increasingly steep surfaces until their wings/muscles had evolved enough to allow flight). It has the added advantage over the gliding hypothesis that you don't need to imagine the dinosaurs climbing trees first.