tag:blogger.com,1999:blog-1812431336777691886.post3480523810252474365..comments2024-02-29T03:57:00.088-05:00Comments on The Mermaid's Tale: Everything's just the same, unless it isn'tAnne Buchananhttp://www.blogger.com/profile/09212151396672651221noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-1812431336777691886.post-27507784343722208892011-03-08T08:21:54.325-05:002011-03-08T08:21:54.325-05:00Bacteria et al. are still here, but as the post an...Bacteria et al. are still here, but as the post and Holly's Monkey poem point out, we are descended from their ancestors and they 'just happen' to look like what's here today.<br /><br />Darwin was clear about that, more so than Lamarck, and Michael Ruse wrote Monad to Man, to show the pervasive but erroneous view that evolution is 'progressive' or means progress.<br /><br />So the conservation-with-divergence raises lots of questions, and I think we're largely still guessing about the answers. Clearly it's not a rarity in some senses, but just saying 'natural selection' is a form of hand-waving, given what we know about the complexity of things at the gene level. Curious to me, at least!Ken Weisshttps://www.blogger.com/profile/02049713123559138421noreply@blogger.comtag:blogger.com,1999:blog-1812431336777691886.post-31663882559239895592011-03-08T08:03:51.286-05:002011-03-08T08:03:51.286-05:00The nested bursts of divergence would be the stand...The nested bursts of divergence would be the standard answer for the pattern of overall genetic diversity, and for reconstructing phylogenies 'cladistically' (into nested branches). That's shown, more or less for the first time, in Darwin's single figure in Origin of Species.<br /><br />But why would any member stay the same? 'Purifying selection' is the standard answer, and may be right, but it says that while some species (say, beetles) diverged in all sorts of ways, some stayed absolutely changeless (at least, in terms of the traits we can see in fossils, and by extension much besides).<br /><br />It is a challenge to understand how such selection would work, though various stories can be suggested.Ken Weisshttps://www.blogger.com/profile/02049713123559138421noreply@blogger.comtag:blogger.com,1999:blog-1812431336777691886.post-32990064430144540662011-03-08T01:16:08.442-05:002011-03-08T01:16:08.442-05:00I thought of an example of what I consider and uns...I thought of an example of what I consider and unsurprising example. Is anybody surprised that amphibians continued to thrive while amniotes exploited many habitats?<br /><br />Hmm, I also need to consider if the history of this was unlikely or is my lack of surprise about it because of my familiarity with the evidence? For example, are we merely extraordinarily lucky that we have such evidence of extant "ancestral" morphologies that made it possible for Darwin to make his discovery?James Goetzhttps://www.blogger.com/profile/02412501436355228925noreply@blogger.comtag:blogger.com,1999:blog-1812431336777691886.post-71579009688520690792011-03-08T01:00:48.526-05:002011-03-08T01:00:48.526-05:00I suppose a lot of natural history involved adapti...I suppose a lot of natural history involved adaptive radiation followed by more adaptive radiation, and so on. In many of these cases, the adaptive radiations allowed populations of ancestral morphologies to remain mostly intact due to purifying selection while other populations developed new morphologies while exploiting new niche, while this cycle kept repeating itself.<br /><br />I also suppose that in many cases populations diverged in distance and evolved new chromosomes but little morphological change, and then the divergent populations came back to the same geographical area while interbreeding was hindered, as presumed by Futuyma.<br /><br />I also noticed that most discoveries of adaptation at the DNA level had nothing to do with morphological change, so we cannot judge adaptive history merely at the morphological level.<br /><br />Perhaps I'm merely describing things without answering the question why, but I'm unsurprised by the outcome, not that I've always been unsurprised by the outcome.:)James Goetzhttps://www.blogger.com/profile/02412501436355228925noreply@blogger.com