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Politics : Evolution -- Ignore unavailable to you. Want to Upgrade?

To: Tunica Albuginea who wrote (662)	9/16/1999 3:48:00 PM
From: TigerPaw	Respond to of 69300

Here's just one example You keep trotting out this article, so I suppose that means you think it supports your point. The article is a report that someone has an opinion with just the following example: The standard textbook example of natural selection involves a species of finches in the Galapagos, whose beaks have been measured over many years. In 1997 a drought killed most of the finches, and the survivors had beaks slightly larger than before. The probable explanation was that larger-beaked birds had an advantage in eating the last tough seeds that remained. Okay, so far so good. Larger beaks for the last seed is a working hypothesis. There can be other hypotheses, I propose that the ones with larger beaks were more related, cousins if you will, and shared a family characteristic just as many human families may have a dimple in the chin. They happened to live near each other which was near the best remaining food and water source. The larger beak was irrelevant in their differential survival. Okay, now we have two proposals that attempt to explain the facts. What's next? You have to gather more facts. There are a couple of things you could try to look for in my proposal. Did the birds actually live near each other? Could try to DNA test bird droppings to see what area those birds lived in. I can't get more info from the article so lets assume that the last hard seed hypothesis is the more correct. A few years later there was a flood, and after that the beak size went back to normal. Nothing new had appeared, and there was no directional change of any kind. This is exactly what we would expect according to the theory of Punctuated Equilibrium. Those birds that survived contained a lot of genes. A surprisingly small number of birds would contain nearly all the gene pool as did the original population before the drought. These birds went through only one selection event, once the pressure was off they chicks could survive again with smaller beaks (In fact a slightly smaller beak was probably optimal which is why the original population had it in the first place). When those birds breed again and those old chromosomes start pairing, the chicks are as likely to get a gene set that was present but not expressed in the parent, as they are to look just like a clone of the parent. This is the equilibrium part of the theory. A gene pool larger than that contained in any individual is preserved by the group. Large scale changes in chromosomes are reduced, thereby increasing the likelyhood that any male of that species can mate successfully with any female ( If the female says yes, and he buys her dinner... ). impressive example of natural selection Yes, as modified by Gould and Eldridge. TP