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Author
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Topic: How novel features evolve #2
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 56 of 402 (664177)
05-29-2012 4:39 PM
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Reply to: Message 54 by zaius137
05-29-2012 4:04 PM
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The order things happen in is: Mutation of a gene that affects hair colouration occurs in a mouse Mouse can sit on a dark rock without being eaten by predators Mouse mates and passes on its brown genes More brown mice are born and can sit on brown rocks unmolested Any beige mice born are eaten by preditors Brown mice breed Etc ie the standard theory. The question we're trying to answer here is whether we can identify the gene that changed. The guys that did the work think they have and have presented their evidence. If you think differently you have to show why.
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 54 by zaius137, posted 05-29-2012 4:04 PM | | zaius137 has replied |
| Replies to this message: | | | Message 64 by zaius137, posted 05-30-2012 8:04 PM | | Tangle has replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 63 of 402 (664236)
05-30-2012 7:59 AM
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There have been a couple of further studies by the same people on these mice that add to the evidence. This one shows that natural selection is the mechanism that matches dark mice with dark rocks and light mice with light rocks. (Sadly, I can see only the abstract)
Previous work has demonstrated that two Mc1r alleles, D and d, differ by four amino acids, and are responsible for the color polymorphism: DD and Dd genotypes are melanic whereas dd genotypes are light colored. To determine the frequency of the two Mc1r allelic classes across the dark-colored lava and neighboring light-colored granite, we sequenced the Mc1r gene in 175 individuals from a 35-km transect in the Pinacate lava region. We also sequenced two neutral mtDNA genes, COIII and ND3, in the same individuals. We found a strong correlation between Mc1r allele frequency and habitat color and no correlation between mtDNA markers and habitat color. Using estimates of migration from mtDNA haplotypes between dark- and light-colored sampling sites and Mc1r allele frequencies at each site, we estimated selection coefficients against mismatched Mc1r alleles, assuming a simple model of migration-selection balance. Habitat-dependent selection appears strong but asymmetric: selection is stronger against light mice on dark rock than against melanic mice on light rock. Together these results suggest that natural selection acts to match pocket mouse coat color to substrate color, despite high levels of gene flow between light and melanic populations.
Jun;58(6):1329-41. Ecological genetics of adaptive color polymorphism in pocket mice: geographic variation in selected and neutral genes - PubMed The writers of these papers are very confident that they have identified the genes responsible for coloration in the mice that they have studied (but not other mice in other locations) and say that the difference is 4 amino acids. How confident can we be that the allele changes are as a result of a mutation of an 'original' gene?
Life, don't talk to me about life - Marvin the Paranoid Android
| Replies to this message: | | | Message 66 by zaius137, posted 05-30-2012 8:35 PM | | Tangle has replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 78 of 402 (664327)
05-31-2012 2:49 AM
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Reply to: Message 64 by zaius137
05-30-2012 8:04 PM
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Zaius writes: I have a question; does every color change await a mutation of a gene? The first time it happens, it must do.
There must be an underlining adaptable mechanism built into the genome. Why? The theory tells us that it doesn't need one and the practice shows that it doesn't
If natural selection is the main mechanism of causation, there has to be a molecular interface between the resulting gene and environmental pressure. This interface should be discernable and explainable. As has been pointed out to you several times by all of us, natural selection is NOT the main mechanism of causation. It acts only AFTER a mutation has randomly occurred. The selection process has no connection to the mutation process.
Why is there heterozygosity of coloration remaining in the selected population of mice if say black mice are selected to be more fit? I think that's a question you have to ask yourself. If a designer was at work, he would make it so that dark mice living on dark rocks would always breed true. If the process of creation of new features/species involved random genetic error plus non-random selection, we'd expect to see what we actually see.
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 64 by zaius137, posted 05-30-2012 8:04 PM | | zaius137 has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 79 of 402 (664328)
05-31-2012 2:53 AM
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Reply to: Message 66 by zaius137
05-30-2012 8:35 PM
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Zaius writes: Thanks for your citation; was this linked in the last paper? . As it was written two years after the first, it wasn't referenced in the first paper :-;
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 66 by zaius137, posted 05-30-2012 8:35 PM | | zaius137 has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 80 of 402 (664329)
05-31-2012 4:05 AM
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I have a question for the geneticists. How do we know that the genes involved in the dark mice colouration arose from a mutation of the genes coding for light mice? ie how can we distinguish which came first and/or that both haven't always been there?
Life, don't talk to me about life - Marvin the Paranoid Android
| Replies to this message: | | | Message 83 by jar, posted 05-31-2012 9:12 AM | | Tangle has not replied | | | Message 85 by Taq, posted 05-31-2012 11:19 AM | | Tangle has replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 87 of 402 (664381)
05-31-2012 2:22 PM
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Reply to: Message 85 by Taq
05-31-2012 11:19 AM
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Thanks Taq, so we can now say with a very high level of certainty, backed up with real hard evidence, that the gene for light colouration preceded those for dark and that the dark mice genes are a mutation of the light mice genes. We can also show natural selection working on both the light and the dark mice based on their survival chances in their different environments. We have therefore demonstrated the Theory of Evolution in practice. But of course, they're still mice....
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 85 by Taq, posted 05-31-2012 11:19 AM | | Taq has replied |
| Replies to this message: | | | Message 88 by Taq, posted 05-31-2012 3:43 PM | | Tangle has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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WK writes:
I'd say that the fact that there is a different basis for melanism in the other dark population of the same species is better evidence for the dark alleles being a derived trait than the variation levels. If there was an already existing melanic trait in the species it would be reasonable to expect that it would be the selected melanic form in both populations. Presumably that means that there's a different mutation in another location in the other dark mice that does the same job. Bugger, we now need to find two smoking guns not just one. (Or God is an even bigger tease than we first thought; those fossils were only the start of the big wind up.)
Life, don't talk to me about life - Marvin the Paranoid Android
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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WK writes: Which is almost exactly what Zaius was saying in Message 48. That's fair. However, at that point it was irrelevant that there were (at least) two genes responsible for coat colouration in different populations of these mice as I thought we had found a definite mutation in the population we were looking at and had shown that it alone was dictating colour. There's still a huge amount of evidence pointing to the fact that it's a recent mutation causing the dark colour change, but we can't yet totally rule out other possibilities. Do you feel that we've got to the legal test of beyond reasonable doubt?
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 95 by Wounded King, posted 05-31-2012 7:22 PM | | Wounded King has seen this message but not replied |
| Replies to this message: | | | Message 98 by Taq, posted 06-01-2012 11:30 AM | | Tangle has replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 99 of 402 (664516)
06-01-2012 3:08 PM
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Reply to: Message 98 by Taq
06-01-2012 11:30 AM
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Yup, I'll go with that. But it's not what I was hoping to get out out of this which was direct proof that a new mutation caused a physical change to an obvious characteric which was then selected for. Very, very close though.
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 98 by Taq, posted 06-01-2012 11:30 AM | | Taq has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 101 of 402 (664618)
06-03-2012 5:21 AM
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Reply to: Message 100 by zaius137
06-02-2012 9:39 PM
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Re: Which came first?
Zaius writes:
Here is some interesting finding in fruit flies indicating a very complex interaction between genes (not just one or two as the paradigm exists) and a overall tendency to retain Heterozygosity. It's interesting work but doesn't tell us very much except that everything is far more complicated than I for one would like it to be. They conclude:
We conclude that, at least for life history characters such as development time, unconditionally advantageous alleles rarely arise, are associated with small net fitness gains or cannot fix because selection coefficients change over time You have to ask what actual selection pressure exists in these populations that would be strong enough to fix a new allele? Not much and then if there is anything it changes, it seems. The beauty of the mice example was that the selection pressure was strong and obvious, but even there, the complexity of the mechanisms involed put an irrefutable case maddeningly just out of reach. But it looks like it's getting close. ABE - as an irrelevant aside, the sheer messiness and complexity of these systems are evidence against design. Edited by Tangle, : Afterthought.
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 100 by zaius137, posted 06-02-2012 9:39 PM | | zaius137 has replied |
| Replies to this message: | | | Message 102 by zaius137, posted 06-04-2012 12:22 PM | | Tangle has replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 103 of 402 (664708)
06-04-2012 12:51 PM
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Reply to: Message 102 by zaius137
06-04-2012 12:22 PM
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Re: Which came first?
Zaius writes: Actually very strong artificial selective pressure was applied. It may be that there were high selective pressures but there's nothing in your article that tells me that. Sadly, the paper itself is not freely available and I'm not relying on an ID site to tell me what's in it. However, as I pointed out, the paper's conclusion suggest a rather different emphasis to your own.
We conclude that, at least for life history characters such as development time, unconditionally advantageous alleles rarely arise, are associated with small net fitness gains or cannot fix because selection coefficients change over time
Life, don't talk to me about life - Marvin the Paranoid Android
| This message is a reply to: | | | Message 102 by zaius137, posted 06-04-2012 12:22 PM | | zaius137 has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 106 of 402 (665371)
06-12-2012 1:30 PM
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I half heard on the radio today a geneticist arguing for genetic modification of crops. The big concern for those that care about such things is that the man-made changes will seep into 'normal' crops and before we know it we'll have frankenstein toast. The geneticist said that that was an unnecessary fear because what has actually been found is that the new genetic breeds just fade out of the genome when interbred. Now that seems counter-intuitive because a plant that is immune to a predator should have a competitive advantage. Anyone aware of this work?
Life, don't talk to me about life - Marvin the Paranoid Android
| Replies to this message: | | | Message 107 by Taq, posted 06-12-2012 2:53 PM | | Tangle has not replied |
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 109 of 402 (665497)
06-14-2012 7:24 AM
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As the conversation on the mice genes has fizzled out pending further work, would this be a good time to reappraise the nylon eating bacteria? I read a thread back in 2004 where there was still some debate about whether that was a fully convincing, new genetic mutation. Do we know more yet?
Life, don't talk to me about life - Marvin the Paranoid Android
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 114 of 402 (665527)
06-14-2012 4:32 PM
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I'm beginning to feel a little more sympathy for creationists - not much but enough to make me feel a tadge humbler. I did my zoology degree in the 70s, genetics was really only just beginning - my university only started its first dedicated degree in genetice in my second year. Evolution was of course, assumed, it was never ever questioned - it would be like questioning 2+2. But in fact we are still assuming or deducing evolution aren't we? Science has rightly been convinced beyond doubt of the fact of evolution to the extent that I'm prepared to bet (a small beer) that virtually nobody is researching an empirical proof for evolution. Getting funding for it would be as difficult as getting archaelogical funding for looking for the ark. But given the political impact of creationism in the USA, it would make a lot of sense to spend a few million finding the smoking gun. Anyway, where do we look next?
Life, don't talk to me about life - Marvin the Paranoid Android
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Tangle
Member Posts: 9504 From: UK Joined: 10-07-2011 Member Rating: 4.7
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Message 117 of 402 (665549)
06-14-2012 5:58 PM
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Genomicus, Dr A. Sure, but you're preaching to the converted with me. No giraffes in the Cambrian and molecular philogenetics provide strong evidence, as does the fossil record and so on. But this forum only exists because some people - and if the polls are true - a very sizeable number of people around the globe don't believe it and demand proof. Now we all know that they don't actually want proof and that the majority even if shown a fish turn into a dog would still deny it, but the fact remains that we still haven't shown a direct and uncontroversial mutation of a gene that provides an obvious benefit to the organism which is then selected for naturally and consequently developed a new trait in a population. Very close with the mice, lizards and nylon bugs, but still no slam dunk.
Life, don't talk to me about life - Marvin the Paranoid Android
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