November 20, 2006

Cold-Blooded Miracles

Justin Katz

One could, I suppose, respond to Andrew Stuttaford's prods about an intelligent designer by wondering aloud why this sort of thing isn't an example of built-in wonder — a cold-blooded miracle, if you will:

Twice within a year the brown arole lizard has evolved changes in its body and behaviour to outwit a predator — confirming Charles Darwin’s theory on natural selection.

Changes in limb length were observed by biologists after they introduced a predator, the northern curly-tailed lizard, to islands off the Bahamas where the brown arole is found.

In the first six months the brown arole, Anolis sagrie, developed longer legs so that it could outrun its predator, Leiocephalus carinatus.

Over the second six-month period the arole changed its behaviour so that it spent far less time on the ground and longer on branches and plant stems.

After a year the surviving aroles had much shorter, stumpier legs that were more suited to clinging on to thin branches. “We showed that selection dramatically changed direction over a short time, within a single generation,” the researchers reported in the journal Science.

We live in a skeptical world, indeed, if lizards' spontaneous ability to grow or shrink their legs is not evidence of design! Sadly, upon review of the online abstract and supporting materials (PDF), it appears that the ever-intriguing evolution/miracle debate needn't be had. From the former:

We predicted that the introduction of a terrestrial predator would first select for longer-legged lizards, which are faster, but as the lizards shifted onto high twigs to avoid the predator, selection would reverse toward favoring the shorter-legged individuals better able to locomote there.

And from the latter:

For individual identification, each lizard received an island-unique pattern of colored marks by injecting elastomer (Northwest Marine Technologies) subdermally into two limb segments. In November 2003 and May 2004, we censused nearly exhaustively on each island to determine surviving individuals. ...

Selection gradients could only be calculated on islands for which some, but not all, lizards died. Because survival of marked lizards was either 0 or 100% on some islands in some of the time periods, our sample size was reduced to nine islands in the first time period and five in the second time period; those five islands were used in the repeated measures analysis. On these islands, an average of 20.6 males was measured at the start of the experiment; survival
rates were 33% and 58% in the 0-6 and 6-12 month periods.

Interest may or may not compel me to pick up a copy of the magazine with the full article in it, but it appears that Stuttaford's source was incorrect. The lizards' limb length didn't change; rather, lizards of different limb lengths survived at different rates. Gee. The only astonishing finding here, as far as I can see, is the tendency of scientists and the materialists who love them to trumpet their documentation of the obvious and treat it as if it is revolutionary new proof that God doesn't exist.

As far as evolution goes, what I'd be interested to know is whether this single generation of lizards manages to convey its adaptations to the next generation. Note that the study addressed only males. If females, for a made-up example, have to lie dormant on the ground for a time in order to lay eggs, then the species might not survive at all. Or if long-legged gals are somehow better able to mate among the "high twigs," then the evolutionary influences on leg length might cancel out.

What would be exponentially more difficult to cancel out, given human beings' capacity for split-second adaptation, is the long-legged credulity of modern skeptics.

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Thanks for the chuckle Justin. It truly is something to behold, this enchantment with the "Just So Stories". I've learned to avoid these subjects at the Corner though, because they inevitably lead to some comment by Derb that I wish I hadn't inflicted upon myself.

Posted by: rhodeymark at November 20, 2006 4:28 PM

Lamarck was disproven long ago, so of course the lizards did not grow longer legs to outrun their new predator. What occurred was that the lizards with longer legs had a greater likelihood of survival, and thus it was the long-legged lizards that were able to pass on their long-legged genes to the next generation. As the lizards who moved into the trees survived at higher rates than those that stayed on the ground, the tree-dwelling lizards with stumpier legs better suited for tree life survived at higher rates than those with legs less suited to tree life, so the stumpier-legged lizards tended to reproduce at higher rates than the less-stumpy-legged lizards, and the next geeration had stumpier legs.

The end result is that there are two separate subspecies of brown anole lizard on the islands, one with stumpy legs that lives in trees and (assuming that it survived) one with long legs that lives on the ground. I think all of this is perfectly predictable not only under Darwinian theory, but also under Intelligent Design (at least as far as I understand the theory), since the only part of the Theory of Evolution that is rejected by proponents of Intelligent Design is that there has been evolution from one species (say, a lizard) to a separate species (say, a bird).

My own position on the issue is that Darwin was correct and there was interspecies evolution, but that it is absurd to believe that unicellular organisms evolved over a billion years, eventually to become human beings, without any "guiding hand" or divine intervention.

Posted by: AuH2ORepublican at November 20, 2006 8:30 PM
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