tag:blogger.com,1999:blog-37148773.post7370062993318080934..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Why are most biologists adaptationists?Larry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger70125tag:blogger.com,1999:blog-37148773.post-84880518211767945582017-01-23T11:04:27.170-05:002017-01-23T11:04:27.170-05:00I agree with you that relatives stasis is just the...I agree with you that relatives stasis is just the buffer effect seen in large populations. I agree that species can evolve to be different in an unchanging environment (new mutations, result of hybridization, etc.) and also that environments may not be as unchanging to the organisms as they appear to be to us (especially if we're looking at the fossil record). See oscillating variation in Galapagos finches, for example.<br /><br />I do think that speciation is often associated with small populations either at the margins of a range or left behind as the large population moves. Uneven cladogenesis, one might say. That speciation may be associated with PE at the time of species or afterwards if the new species succeeds and spreads, when no only does it have different mutations than in the parental species, but it changes the environment (competative interactions, etc.).<br /><br />Normally when you say something I disagree with, I figure I have to learn a lot quickly because I'm wrong. However, the importance of small populations seems to fit with what I see in the world. Therefore, in this case I figure that either you're wrong or (more likely) I've communicated badly so we wouldn't actually disagree if I could make clear what I think with all the appropriate qualifications. <br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-50831350532410169382017-01-23T08:33:12.214-05:002017-01-23T08:33:12.214-05:00S Johnson,
Yes. That's why I wrote "pheno...S Johnson,<br />Yes. That's why I wrote "phenotype" and "phenotypic" as necessary. I did not mean genetic stasis.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-17359902454624364732017-01-23T08:11:09.162-05:002017-01-23T08:11:09.162-05:00@bwilson295
The important thing about PE is that ...@bwilson295<br /><br />The important thing about PE is that change is associated with speciation by splitting (cladogenesis). In most cases the daughter species come to occupy the same environment as the parent species. This suggests that the environment is not playing a role in the speciation event. Furthermore, speciation in one lineage is not correlated with speciation in other lineages found in the same location suggesting that environmental change is not driving speciation. <br /><br />The number of species in the same environment is always increasing by splitting but after over time some species go extinct. This led to development of species sorting as a higher level analogy to population genetics.<br /><br />The idea that evolution must be linked to environmental change is undoubtedly true in many instances but the link is often exaggerated. Species still evolve in an unchanging environment. In order to explain stasis this way you have to make the assumption that all species are perfectly adapted to their current environment so they don't change unless the environment changes. That's an unreasonable assumption. <br /><br />It's better to explain relative stasis as just the buffer effect seen in large populations. Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-32855966350358357572017-01-23T01:15:43.442-05:002017-01-23T01:15:43.442-05:00The claim by Gould and Eldredge that big evolution...The claim by Gould and Eldredge that big evolutionary changes happen in small populations makes sense to me. <br /><br />In little populations, genetic changes can be pretty random. Neutral or somewhat harmful traits can become fixed. Odd combinations of alleles can come about. If the small population survives (it probably won't) it may become quite different from its parent population, in unpredictable ways. Its environment is likely to be different from that occupied by the main population from which it arose, too, so selection pressures, to the extent they can operate, will be different.<br /><br />Big population have a certain inertia. Yes, any slightly beneficial allele is likely to become common, but also it will shift range with the conditions it's adapted to, so neither selection nor drift will easily or quickly move it from its current adaptive peak.<br /><br />Consider a cold-adapted plant as the ice-age ends. Main population shifts range north. Small populations are left on north-facing slopes, in coastal bogs, and in other cold pockets. There's a lot of genetic diversity in the newly isolated populations, though that will fall with time. New mutations, of course, aren't shared with the parent population.<br /><br />What happens to the little populations? Mostly they go extinct, either because of bad luck or because inbreeding causes too many harmful alleles to come together. In some, harmful alleles are lost and the plants hang on for centuries if the habitat remains stable, in (apparent) stasis. Sometimes the parent population migrates back while interbreeding is still possible, and the potentially distinctive population is lost. And sometimes, sometimes, the genetic changes in this small population cause it to change in ways that leave it more or less well adapted to a different set of conditions than its parent population. It may hang on and stay small, or spread widely. <br /><br />How small are the isolated populations? I've worked with ones of 20 or less (census, not effective populations) and many of a few hundred to a thousand. Some isolated in the last 200 years, some for thousands of years. <br /><br />I think small populations are key to rapid or big evolutionary changes.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-10828677178859737602017-01-23T00:46:10.330-05:002017-01-23T00:46:10.330-05:00I would expect stasis in many organisms for long p...I would expect stasis in many organisms for long periods of time. Mutations change, but if the environment stays similar, most variations will die out and the population won't change. When the environment changes cyclically (ice ages vs. not, El Nino vs. not years etc.), selection pushes organisms a little this way and a little back; from any moderately long view, that will look like stasis. And when the environment changes in a consistent but slow way, populations may well migrate, staying in conditions to which they are well adapted, rather than change.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-520452111082854732017-01-22T23:20:24.217-05:002017-01-22T23:20:24.217-05:00rich lawler: since I don't post a lot here, it...rich lawler: since I don't post a lot here, it will be easy to skip my posts. <br /><br />photosynthesis: "Nothing in evolutionary theory demands that species can never show stasis." Strictly speaking, beneficial mutations, neutral and nearly-neutral mutations, random genetic drift, recombination, etc. do strongly imply constant evolution in the sense of change in gene frequencies, so these normal processes of evolution do argue against stasis. And the presumed power of natural selection to optimize the body plan suggests that changes in environment (which includes other organisms also changine) will modify morphology (or phenotype or whatever you wish to call it.) I have often thought a popularization of evolutionary theory should be entitled "All Flesh Is Grass."<br /><br />It's hard to tell though whether the statement was about evolution as multiplication of species. Or whether the tacit assumption is that drift, neutral etc. aren't really parts of modern evolutionary theory.S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-35095628207289165072017-01-22T22:16:11.023-05:002017-01-22T22:16:11.023-05:00photosynthesis,
“Stasis means that some organisms...photosynthesis,<br /><br />“Stasis means that some organisms keep a phenotype for quite a while. Nothing in evolutionary theory demands that species can never show stasis.”<br /><br />That isn’t exactly accurate. It is a problem. The paper opens and closes noticing that it is a problem. Some kind of theoretical accommodation has to be made to explain why some things stay stable for tens of millions of years, while others, like whales, are supposed to have raced from Pakicetus to a fully marine animal in just four million*.<br /><br />I can sympathize with your embarrassment and anger. (It’s a religious deal, like someone pointing out to a muslim that the prophet Muhammed didn’t record any prophecies.) But I wouldn’t worry about it if I were you. Like rich lawler says, “Stasis has never been a problem for evolutionary theory”. That isn’t because it isn’t. It is because evolutionary theory is fiercely protected, and problems are not allowed. But, they can be easily solved by dropping a suitable adjective in front of ‘selection’, or by just using your imagination.<br /><br />I know the term is somewhat taboo, but how do ‘living fossils’ fit in your worldview?<br /><br />*http://news.nationalgeographic.com/news/2011/11/111116-antarctica-whales-oldest-evolution-animals-science/ txpiperhttps://www.blogger.com/profile/03645156881353741058noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-56951550105662699182017-01-22T21:01:45.807-05:002017-01-22T21:01:45.807-05:00S. Johnson: I have no idea what you're on abou...S. Johnson: I have no idea what you're on about. I can't really understand the main points you are trying to make in almost every post you write. Sorry. rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-69549957537240399952017-01-22T12:50:17.233-05:002017-01-22T12:50:17.233-05:00txpiper,
"I've read it more than once.&q...txpiper,<br /><br /><i>"I've read it more than once."</i><br /><br />No, you didn't read it. Had you read it, you would not have said that "fossils didn't cooperate," since the article mentions many examples of fossils "cooperating." It also mentions that the "problem" they're talking about is understanding the <b>tempo</b> of phenotypic changes in evolution, as I explained to you. Not only that, they explain potential solutions to this "problem."<br /><br /><i>"Stasis is an ongoing problem because it means that things don’t evolve."</i><br /><br />Stasis means that some organisms keep a phenotype for quite a while. Nothing in evolutionary theory demands that species can never show stasis. Only your idiocy and ignorance demands such a thing. Why did you link to that paper if you didn't read it? Did you think I would not read it either? Are you really that stupid?<br /><br /><i>"The closing statement says:"</i><br /><br />I read the whole thing. You just looked for the word "problem" and didn't care to check what they might be talking about. Sad news to you: they don't mean what you thought they meant.<br /><br />Learn to read. That would save you some embarrassment. Also read the other answers offered to you above.<br /><br />Why do you insist on looking like an illiterate buffoon? Do you really think that you, looking like an idiot, will convince anybody here that you might as well be right?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-76654289710183431302017-01-22T12:22:40.932-05:002017-01-22T12:22:40.932-05:00I should clarify to Simon that I wasn't talkin...I should clarify to Simon that I wasn't talking about PE when I was bringing up the Estes/Arnold paper. Obviously, my second paragraph I do bring up PE. <br /><br />My apologies. rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-50922628361285993042017-01-22T10:13:51.542-05:002017-01-22T10:13:51.542-05:00Rich Lawler "The fossil record is rife with e...Rich Lawler "The fossil record is rife with examples of gradualism (e.g., the slow dental evolution of early Adapids)..." <br /><br />And there are the classic charts of the progression of man from ape to modern human. Or the equivalent for the evolution of the modern horse. Given the reserve with which we should treat those poularizations, I think lay people should be very cautious in claiming continuous evolution of phenotypes leading to multiplication of species. <br /><br />But more to the point, the kind of adaptationism on hand as the topic of discussion is one which sees natural selection as the pervasive and powerful, so much so that all traits are conceived to be adaptive. Despite the occasional concession that mutation, random genetic drift etc. do exist, they are in practice never to be considered. <br /><br />It seems to me this kind of adaptationism implies a nearly universal sequence of gradual changes in morphology as part of the multiplication of species. It also seems to me that adaptationism of a less imperial kind says that natural selection is the primary force conserving the phenotype despite mutation, random genetic drift etc. This kind natural selection, as the agent of stasis and protector of adaptations, instead of the agent of change, the creator of new species, does indeed seem to be a "well-documented present-day evolutionary mechanism...) I don't think the charge against PE that it posits some magical past processes is true at all. S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-34499633454278537462017-01-22T09:15:28.373-05:002017-01-22T09:15:28.373-05:00I'm not handwaving about how sample sizes in t...I'm not handwaving about how sample sizes in the fossil record influences our interpretations of rates of change...plenty has been written about it--a simple google scholar search will demonstrate that (e.g., work by Pete Wagner). <br /><br />I also wasn't talking about PE, and nor were Estes/Arnold (they bring it up only to say that their moving optimum model accounts for both bursts of change and stasis) but apparently you were. rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-58872015128037024022017-01-22T08:18:15.914-05:002017-01-22T08:18:15.914-05:00ISTM that the determination that the selection coe...ISTM that the determination that the selection coefficient definitively takes any value - which would include zero - is on rather shaky ground. It's a reasonable null hypothesis against which to check departures. But it is damned hard to measure with the accuracy required to distinguish zero, or even the effectively neutral zone - to confirm the null, rather than to fail to reject it - within the confidence limits chosen. AllanMillerhttps://www.blogger.com/profile/05955231828424156641noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-43629212734381228592017-01-21T21:18:35.214-05:002017-01-21T21:18:35.214-05:00The Estes & Arnold paper does not address the ...The Estes & Arnold paper does not address the central issue, which is that the distribution of rates of change is bimodal for a wide range of taxa and quantitative traits. It is worth noting that referring to the incompleteness of the fossil record often amounts to nothing more than handwaving, unless there is a concrete discussion on how it affects observations. In this particular case it is worth noting that if the underlying rate distribution is bimodal (i.e. PE holds) then the observed distribution will tend to become unimodal as sampling gets worse. The reverse isn't true - an underlying unimodal distribution stays unimodal. The idea that the PE pattern observed for many taxa is an artifact of incomplete preservation is nonsense for this reason - but you could have the appearance of gradualism due to a lack of fossils. Adapidae have just 60 occurences (PaleoDB querry, just now), while paleozoic brachiopods have 133,527. That's a tad more. PE is generally found for taxa that are sexually reproducing and have an extensive and comparably excellent fossil record. It's not found for taxa that have shoddy records. There's no equivalence here, just like you can't say "well, there are papers with large sample sizes and long durations demonstrating a link between smoking and lung cancer, but I compared 10 smokers to 10 non-smokers over a 2 year period and found no significant health effects, so I guess the issue is wide open. And anyway there's never enough data, so maybe the studies that found a link between smoking and cancer have too little statistical power". Anonymoushttps://www.blogger.com/profile/04521153536420798640noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-21002596622130677022017-01-21T20:43:58.042-05:002017-01-21T20:43:58.042-05:00Do runners have more babies?
Do runners have more babies?<br />Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-51584739083347300282017-01-21T19:21:12.882-05:002017-01-21T19:21:12.882-05:00I am not seeing my post appear, so I will repeat i...I am not seeing my post appear, so I will repeat it. Morton's toe, whichnis the condition of having the second toe the longest, is thought to cause various running injuries. For instance, it can supposedly cause too much pressure on the second toe when running.<br /><br />I am not a doctor so I qualified all this, but you can find this referenced online and I learned about it in an old book I have on common running injuries.<br /><br />Here are some lay people talking about it on a running site.<br /><br />http://community.runnersworld.com/topic/morton-s-toe-morton-s-foot<br /><br />The point being that sometimes small morphological differences can matter. Actually, as a layperson I wonder why Morton's toe wasn't selected out back when being able to run long distances might have mattered.Donaldhttps://www.blogger.com/profile/12097924170959207117noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-37347160666365620542017-01-21T13:45:42.016-05:002017-01-21T13:45:42.016-05:00Stasis has never been a problem for evolutionary t...Stasis has never been a problem for evolutionary theory and doesn't imply that things don't evolve (since a population held at an optimum by stabilizing selection or some other mechanism will still accumulate neutral mutations). An excellent analysis of stasis in the fossil record is by Estes/Arnold in Am. Nat. 2007. They show how a moving optimum can explain many different patterns of morphological evolution in the fossil record, particularly stasis. <br /><br />The fossil record is rife with examples of gradualism (e.g., the slow dental evolution of early Adapids), and punctuation (e.g., Paleozoic brachiopods). There is no "rule" about fossils and how they should evolve, so there is no need to invoke generalizations as if the past was some mysterious magical thing to which well-documented present-day evolutionary mechanisms don't pertain. But certainly one contributing factor to debates about fossil evolution is simply the incompleteness of their record. Several people have written about this.rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-65502872475554458372017-01-21T13:11:01.986-05:002017-01-21T13:11:01.986-05:00Thanks for the response, makes sense. And I agree...Thanks for the response, makes sense. And I agree, sexual selection gets soundly abused, particularly when applied to human mate choice (i.e., the Ev-Psych nonsense). rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-69996676617254757532017-01-19T13:28:46.453-05:002017-01-19T13:28:46.453-05:00@rich lawler,
No, they didn't mention sexual ...@rich lawler,<br /><br />No, they didn't mention sexual selection. I made that up. <br /><br />It is, however, the fall-back position for adaptationists when all other explanations don't make sense. Problem is, they can't decided whether men prefer women who can role their tongues or reject them! In other words, |s| must be greater than zero but the sign is tricky. :-)<br />Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-26870744624301094862017-01-19T10:21:44.402-05:002017-01-19T10:21:44.402-05:00It's been awhile since I (re)read Gould/Lewont...It's been awhile since I (re)read Gould/Lewontin, but did they really mention sexual selection? (your point 7). <br /><br />I do remember that the Clutton-Brock/Harvey paper that preceded Gould/Lewontin's paper at the same conference made more use of sexual selection as an explanatory concept for putative adaptations. rich lawlerhttps://www.blogger.com/profile/13353965284524429553noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-30297312677061262322017-01-18T18:03:20.771-05:002017-01-18T18:03:20.771-05:00From what I understand, the fossil record for many...From what I understand, the fossil record for many species tends to show a geologically slow change in morphology. And, as a result, it is technically correct to speak of "chronospecies," since species in paleontology are morphological defined, rather than by observation of interbreeding as per the biological species concept held by Mayr et al. Apparently that's why it's so common for discussions of ancient organisms to speak most often of genera, rather than species? The thing is, it is not at all clear to me that this kind of evolution (and surely it is evolution too) doesn't demonstrate random genetic drift on a species wide scale (rather than in isolated populations.) At any rate, it seems to me the adaptationists should be able to see natural selection at work here too. As far as I know that's not the case at all.S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-59802189821440909012017-01-18T17:55:54.130-05:002017-01-18T17:55:54.130-05:00Adaptationism never rests. Since natural selection...Adaptationism never rests. Since natural selection is all powerful, the zebra's stripes must be adaptive. https://whyevolutionistrue.wordpress.com/2017/01/18/the-secret-of-zebra-stripes-solved-or-so-scientists-say/<br /><br />It is unclear to me why the possibility that horses outside Africa aren't striped because stripes didn't happen to be a trait of ancestral populations. Nor is it clear how it's been demonstrated that striped horses were selected over unstriped horses. That seems to suggest that the differential reproduction from being bitten less (not at all?) is so great that stripe were fixed in African populations. Nor is it all clear that biting flies in other continents were so much less of a detriment to reproduction. All I'm really getting from this is that evolutionary biologists have a rock hard conviction that all traits are adaptive because of natural selection.S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-19671026749778906822017-01-18T09:11:55.991-05:002017-01-18T09:11:55.991-05:00@Corneel
Thank you. I will study it, although I t...@Corneel<br /><br />Thank you. I will study it, although I think I have seen it before. I have also looked at Wikipedia, and written a comment to by own blog, that I referred to above. Do you have specific comments to my blog, so give them there. I am now writing a new blog post that includes randomness, so stay tuned. Misconceptions in evolution theorieshttps://www.blogger.com/profile/02221854011348738166noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-83911798506961886772017-01-18T08:13:53.783-05:002017-01-18T08:13:53.783-05:00@Jarle Kotsbak
In my understanding, macro evoluti...@Jarle Kotsbak<br /><br />In my understanding, macro evolution refers to evolutionary processes at or above the species level, such as mass extinctions, adaptive radiation and such. <br /><br />I note that our dependable host <a href="http://bioinfo.med.utoronto.ca/Evolution_by_Accident/Macroevolution.html" rel="nofollow">has already written an essay on it</a>. <br /><br />Under this definition, adaptation should simply be subsumed under the heading of evolution.Corneelhttps://www.blogger.com/profile/02884855837357720225noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-50716749758350283822017-01-18T06:47:25.846-05:002017-01-18T06:47:25.846-05:00@Corneel
You are right. There are different defin...@Corneel<br /><br />You are right. There are different definitions and different terms in use. I know Stephen J Gould used those terms. But I am not sure he used these terms in the same way as I use adaptation and evolution. As I have understood his definition, macroevolution is changes that can be detected by fossil records, while he saw e.g. the evolution of an eye as microevolution. But maybe you have another definition? Misconceptions in evolution theorieshttps://www.blogger.com/profile/02221854011348738166noreply@blogger.com