tag:blogger.com,1999:blog-28755195.post3710878926549234416..comments2023-09-25T04:26:51.568-06:00Comments on The Barefoot Bum: Dialectical materialism and evolutionLarry Hamelinhttp://www.blogger.com/profile/08788697573946266404noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-28755195.post-54076493095262667762009-12-05T12:24:34.585-07:002009-12-05T12:24:34.585-07:00Is it fair to say that your overarching point abou...Is it fair to say that your overarching point about biological evolution is that the proximate substrates upon which natural selection acts possess no mechanism for altering themselves purposefully to promote desired heritable selective advantages? If so, you are surely correct.Comrade PhysioProfhttp://physioprof.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-28755195.post-31334028815845878862009-12-05T11:30:30.659-07:002009-12-05T11:30:30.659-07:00There are some biochemical mechanisms that impleme...<i>There are some biochemical mechanisms that implement heritable variation that are, themselves, subject to natural selection. </i><br /><br />You are of course correct in pointing out that the actual dialectical processes happen at multiple levels. But what I mean to say here is that each specific variation is uncorrelated to its outcome when the variation actually occurs. Even with higher level selection forces at work, no organism changes (or fails to change) its heritable variation <i>because of</i> the expected effect of that variation on the phenotype of the offspring.<br /><br /><i>It is now well-established that there are so-called "epigenetic" mechanisms for the transmission of acquired variation from parents to offspring through the germ line (i.e., sperm and egg).</i><br /><br />Indeed. The wording should have been "... exhibit <b>predominantly</b> Mendelian variation..."<br /><br />However, it's instructive to consider that when epigenetically transmitted information <i>is</i> correlated with selection, it doesn't generate evolutionary novelty or nearly as much complex emergent behavior.<br /><br />Furthermore variation in epigenetic <i>mechanisms</i> is also uncorrelated with future selection.<br /><br />There are of course many features, characteristics and dynamic processes in biology that are directly correlated with selection. But those processes have <i>evolved</i>; they <i>all</i> rest on a fundamental "substrate" of dialectical materialism.Larry Hamelinhttps://www.blogger.com/profile/08788697573946266404noreply@blogger.comtag:blogger.com,1999:blog-28755195.post-41006549146587283882009-12-05T11:14:32.733-07:002009-12-05T11:14:32.733-07:00Very interesting post, dude. Here are a few clarif...Very interesting post, dude. Here are a few clarifications:<br /><br /><i>Because heritable variation is uncorrelated with natural selection, these two elements are in true dialectical contradiction*.<br /></i><br />This isn't 100% true. There are some biochemical mechanisms that implement heritable variation that are, themselves, subject to natural selection. This means that organisms can actually adapt via natural selection the nature and rate of heritable genetic variation to best suit environmental conditions.<br /><br /><i>It's instructive to consider Mendelian (established at conception) vs. Lamarkian (acquired during life) variation. It happens to be the case that terrestrial organisms exhibit Mendelian variation, but we might have exhibited Lamarkian variation.<br /></i><br />Again this is not 100% correct. It is now well-established that there are so-called "epigenetic" mechanisms for the transmission of acquired variation from parents to offspring through the germ line (i.e., sperm and egg).<br /><br />The way this works is that during the life of the parent, certain environmental or physiological influences can alter the patterns of chemical modification of nucleotides in the DNA of the chromosomes, or of amino acids in the histone proteins of the chromosomes, in the sperm or eggs. These chemical modifications--mostly methylation and acetylation--are passed on to the progeny, can be copied as chromosomes replicate and cells divide, and influence gene expression in the progeny.Comrade PhysioProfhttp://physioprof.wordpress.com/noreply@blogger.com