tag:blogger.com,1999:blog-37148773.post6554373686505186809..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Stephen Matheson's Critique of Michael Behe's Edge of EvolutionLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-37148773.post-70211939796244135872008-08-29T00:27:00.000-04:002008-08-29T00:27:00.000-04:00The Lorax says,I am going to take issue with this ...The Lorax says,<BR/><BR/><I>I am going to take issue with this statement. While I think this rate has been well documented in logrithmically growing cells (where most studies have been done). Under stress, during growth in a biolfilm, or in stationary phase increased mutation frequencies have been observed, hence the whole field of adaptive mutations.</I><BR/><BR/>Assuming that you are correct, a change in mutation frequency during times of stress isn't likely to have much of an impact over millions of years of evolution. What we know from comparing nucleotide sequences (or amino acid sequences) is that the rate of change (mutation plus fixation) is roughly constant over this time frame.<BR/><BR/>That's why there's a molecular clock—the rate of fixation of neutral alleles is equal to the mutation rate.Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-13426031619340497952008-08-27T19:44:00.000-04:002008-08-27T19:44:00.000-04:00I think the rate 10-10 per nucleotide per replicat...<I>I think the rate 10-10 per nucleotide per replication has probably been pretty constant over several billion years and I doubt that it differs very much in different species.</I><BR/><BR/>I am going to take issue with this statement. While I think this rate has been well documented in logrithmically growing cells (where most studies have been done). Under stress, during growth in a biolfilm, or in stationary phase increased mutation frequencies have been observed, hence the whole field of adaptive mutations. (This is all based on work done with microbes, both bacterial and eukaryotic, but that is where mutation rates were determined anyway.The Loraxhttps://www.blogger.com/profile/13361004494346338824noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-36722926422017281152008-08-25T14:34:00.000-04:002008-08-25T14:34:00.000-04:00Hi Larry--Thanks much for the link. Re mutation r...Hi Larry--<BR/><BR/>Thanks much for the link. Re mutation rates over time, let's see if I can get you on board by explaining why I think the extrapolation is a problem for Behe. The question isn't <I>whether</I> mutation rates were wildly different in the past. It's <I>when</I>. We would postulate that the proofreading machinery – assuming it was assembled through natural processes – arose by the same general mechanisms as every other system in the cellular toolkit. And as you correctly note, that machinery is deeply conserved and therefore ancient.<BR/><BR/>But as I'll explain in my final post in the series, this is exactly the evolutionary epoch where Behe's challenge is located. He's already granted that "darwinian" mechanisms account for the diversity of species, and perhaps of families and genera. It is at the assembly of complex machinery, even before the origin of multicellularity, that he is drawing his firmest line. And this means that the proofreading systems are themselves among the machines whose origins he is pretending to explain. At the very least, the wildly complex proofreading systems had to arise in the absence of proofreading systems.<BR/><BR/>Regarding clonal interference, you got this part wrong: "that seems to increase the number of beneficial mutations..." When you read up on it, I think you'll see that it makes elegant good sense, and you'll learn that it doesn't "increase" the number of beneficial mutations. On the contrary, it <I>decreases</I> the number of beneficial mutations that can contribute to adaptation, by forcing small-effect beneficial mutations to compete with each other.Stephen Mathesonhttps://www.blogger.com/profile/05057004085073574659noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-59405143597243960502008-08-25T12:52:00.000-04:002008-08-25T12:52:00.000-04:00The clonal interference idea is recent, but seems ...The clonal interference idea is recent, but seems to have evidence behind it.<BR/><BR/>I really do believe that Behe's "argument" is anti-evolutionist. All of the truly significant changes (as he'd call them) are caused by God, with front-loading, a universe designed to produce the required mutations, or perhaps by continual intervention. The form of evolution is maintained, but the essence is creationist.<BR/><BR/>What he seems not to recognize is that, because he has absolutely no means of detecting "design" (but only makes bad calculations where he assumes non-design without reason or good cause), he has absolutely no way of determining where (Darwinian) evolution is taking place, and where "design" steps in. That is to say, he has no demonstrable reason to believe that P. falciparum is evolving due to random mutation and natural selection (plus the rest), and not because of design.<BR/><BR/>He has no basis for calculating what evolution can do because he has no independent means for distinguishing between design and evolution.<BR/><BR/><A HREF="http://geocities.com/interelectromagnetic" REL="nofollow">Glen Davidson</A>Unknownhttps://www.blogger.com/profile/15647353309370269220noreply@blogger.com