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Zachriel



Posts: 2598
Joined: Sep. 2006

(Permalink) Posted: April 10 2007,21:40   

great_ape  
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Aquiesce, Joseph, your statements contain so many empirical and philosophical points that I must take issue with that I don’t even know where to begin to address them.

I have the same problem. Sometimes I just pick a random sentence.

great_ape  
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I do suspect gradualism predominates, but I am not necessarily wedded to that stance. Certainly I believe in gradual changes in *nonfunctional* molecular regions; there is much empirical evidence towards that end.

But as for what occurs at the time of speciations in functional DNA and in bone morphology, how fast it occurs, etc. I really don’t know. That is why I refrain from writing any lengthy defense of gradualism. Right now, as a molecular biologist, I simply think gradualism is the more conservative stance. Yet I can certainly understand how folks like Gould, from a palentological perspective, might arrive at a different position. I can tell you that there are active research projects going on concerning how reproductive barriers form between populations; studies that directly address how rapidly biological speciation could conceivably occur.

Once species are isolated reproductively they continue on their own, independent, evolutionary trajectories. Just how fast they can substantially change subsequently is another fascinating question for which I have no good answer. I will venture an educated guess, though…To quote from a former computer science professor of mine, the best answer will be “it depends.”  

Watch out Great_Ape! You are being nuanced, and you know that means trouble.

Consider a finished tabletop. Smooth, right? But if rub your hand across it, maybe you'll feel a bit of roughness. A magnifying glass might reveal coarseness in the grain. A microscope and you'll find great ridges and vast canyons.

As a first-order approximation, evolution is gradual. Eukaryotes to metazoans to vertebrates to fish to amphibians to reptiles to dinosaurs to birds taking eons of time. But as we look closer and closer, we start to notice that evolution moves at an uneven pace, most of the time slowly, sometimes very rapidly such as with adaptive radiation into new niches. If we look even closer, at the species level, we think we can even discern small discontinuities (perhaps observational artifacts). And of course, at the very finest levels, mutations are discrete events.

So what is "gradual"? After millions of years of evolutionary divergence, humans and other apes still strongly resemble one another, and human evolution is considered quite rapid in the scheme of things.

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