Quizzes & Puzzles14 mins ago
Evolutionary Biology
Can anyone tell me if there is ananimal that's evolution in any way has been affected by humans? By this i mean, when the creature is born, something in it's genetic structure would not be the way it is if humans hadn't impacted on it in sime way. Viruses are an example that would fit this, but i'm wondering about more complex organisms.
The only example i've heard of is some type of wood pigeon which had previously foraged on the canopy, but due to human factors the fruits there no longer existed, so the bird was forced to forage lower down. Now, even when there is abundance above, the birds still tend to look on the ground. I'm not sure on the details of this case, and how it was tested to make sure it wasn't just learned behaviour.
The only example i've heard of is some type of wood pigeon which had previously foraged on the canopy, but due to human factors the fruits there no longer existed, so the bird was forced to forage lower down. Now, even when there is abundance above, the birds still tend to look on the ground. I'm not sure on the details of this case, and how it was tested to make sure it wasn't just learned behaviour.
Answers
Best Answer
No best answer has yet been selected by dash_zero. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.
Clanad, there seems to be some issue over Majerus' stance in all of this. If you look back to my first post, Majerus has been quite vigorous in defending Kettlewells original research and particularly over this issue of glueing dead moths to trees... in fact he did the same thing himself, in order to demonstrate photographically the differences between the moths colouring and how they stood out against the tree bark. In fact, he defended the practice most vigorously,since it was only used to capture photographs for use with the study, and formed no part of the research findings.
Secondly, I my own readings suggest that this issue of moths setlling on tree trunks seems to have been misrepresented.... I think it was Majerus himself who I believe is acknowledged as the foremost expert in this area who designed a study to look at the moths settling habits... and found two things of major import.... the basic observation that moths will settle on ALL parts of the tree, although their is a preference for canopy/ trunk/branch juncture, and secondly that moths were observed settling on the trunk of the tree some 34% of the time... this directly contradicts the claim as quoted in your post that only 2 moths have been seen in 40 years of study! This seems a major difference, and is obviously an important one. I would be interested to know the source of the claim you made Clanad.... I will try to dig out the source I used as well.
Secondly, I my own readings suggest that this issue of moths setlling on tree trunks seems to have been misrepresented.... I think it was Majerus himself who I believe is acknowledged as the foremost expert in this area who designed a study to look at the moths settling habits... and found two things of major import.... the basic observation that moths will settle on ALL parts of the tree, although their is a preference for canopy/ trunk/branch juncture, and secondly that moths were observed settling on the trunk of the tree some 34% of the time... this directly contradicts the claim as quoted in your post that only 2 moths have been seen in 40 years of study! This seems a major difference, and is obviously an important one. I would be interested to know the source of the claim you made Clanad.... I will try to dig out the source I used as well.
I'm very sorry if I have offended you Clanad, that was certainly not my intention. i happen to enjoy our discussions and I respect your views, believe it or not, although I don't think we'll ever agree about evolution. Two points:
1. The reason it is important that we know Wells' background and motives is because he does not offer original research His aim is simply to show inconsistencies in evolution theory and use any findings as ammunition to discredit evolution in favour of a creation based model in-line with his religious beliefs. He talks to a largely non-scientific audience and his research is less than thorough.
Wells hasn't done his own studies on moths as many other people have independent to Kettlewell, e.g:
http://bsgran.people.wm.edu/Grant&Wiseman.pdf
You'll find Grant quite open about any drawbacks of his research and what one can and cannot infer from the results.
2. I remember, way back, having a discussion with you regarding evolution and you seemed to have little problem with small scale changes and that is what we are talking about with peppered moths. Crudely put, we are talking about the success of a particular coloured moth over another in avoiding detection by a predator going on to have similar looking offspring and the effects this has on local populations. It surprised me that you would argue over peppered moth research that show how small changes can stick, even if you don't share my view that the accumulations of these small changes explain bigger changes over long time scales.
If I ever represented that I don't accept small scale changes in adaptation then I've not been clear in my messaging, darwin... and my apologies for having done so. My position is: Small scale changes can occur (though not to individuals only descendants) and this can even represent some minor DNA adaptations. This, however, can never lead to speciation... what ever the current definition of that is.
I find it unique, in this particular example, that evolutionists proclaim that DNA changes leading to speciation are the results of random and, therefore, non-repeatable mutations to genetic material. Yet, even Kettlewell insists that, once the environment changed, due, primarily, to the Clean Air Act, the moths responded by yet another change reversing the earlier color difference that must have been caused by the same kind of mutation, no? if so, I think we've all a problem in understanding the cause and effect. I think it was Kettlewell or possibly Majerus that said as a parting shot something to the effect that the process observed is not understood... I'll be looking up my source material for Lazy Gun as soon as I can...
I find it unique, in this particular example, that evolutionists proclaim that DNA changes leading to speciation are the results of random and, therefore, non-repeatable mutations to genetic material. Yet, even Kettlewell insists that, once the environment changed, due, primarily, to the Clean Air Act, the moths responded by yet another change reversing the earlier color difference that must have been caused by the same kind of mutation, no? if so, I think we've all a problem in understanding the cause and effect. I think it was Kettlewell or possibly Majerus that said as a parting shot something to the effect that the process observed is not understood... I'll be looking up my source material for Lazy Gun as soon as I can...
The mutation is random upto a point. The organism does not decide to mutate, it is by chance that it does. The natural selection (which is the important part of the evolutionary process) is not at all random. Fitness means that if by chance you inherit an advantage then all things being equal you should survive to pass that advantage to your offspring (statistically speaking) In the moths, the balance shifted back and forth because the relative frequency of colour phenotype altered due to natural selection brought about by predation.
Niles Eldridge calls this the antichance element of natural selection. Just to reiterate, natural selection is distinctly non-random it is, as the name suggests, selective
Niles Eldridge calls this the antichance element of natural selection. Just to reiterate, natural selection is distinctly non-random it is, as the name suggests, selective
You've a bone to pick with Stephen Jay Gould, dawkins... he (and many others) maintain that the natural selection process of DNA mutation is so random as to never occur again. His famous statement (I paraphrase) "...if the video tape of life were re-wound it would look completely different each time"...
I'd hope that you'd at least get a glimmer of understanding about alternative views when there are so many differing expert opinions on, not only the processes, but also the definitions of processes. ..
I'd hope that you'd at least get a glimmer of understanding about alternative views when there are so many differing expert opinions on, not only the processes, but also the definitions of processes. ..
Lazy Dog, after reviewing several documents relating to Majerus' published views on Kettlewell I think this is the one on which I based most of my response: http://bsgran.people.wm.edu/melanism.pdf ...
The argument appears to come down to three major factors. The first is the validity of reviews of Kettlewell by Coyne, Sargeant, et al. Especially Coyne's interpretations of Kettlewell's methodology. Secondly, whether or not Kettlewell, inadvertently or intentionally for other concerns, introduced artificially high densities of moth populations for his study, and that the moths were put onto the trunks of trees which may not be where they actually pass the day exposed to predators. Inasmuch as the high density problem was addressed by others in follow-up studies (e.g. Clarke and Sheppard 1966, Bishop 1972),
Majerus' strongest criticism of these experiments is that Kettlewell used the wrong part of the
tree.(Excerpted form said document). Thirdly, that while it certainly is true that peppered moth caterpillars (larvae) develop different colors in response to environmental stimuli (they come to match the colors of the twigs of their host plants) (Poulton 1890), it has never been demonstrated that environmental stimuli experienced at any stage in development can induce melanism in adults (in re). This is discussed, however, by Creed et al.
The indications that Coyne may have interpolated Kittlewells findings are troubling until resolved. Majerus' does imply or outrightly states that until further work is accomplished the subject matter (Kittlewell) while deserving of respect is inconclusive...
The argument appears to come down to three major factors. The first is the validity of reviews of Kettlewell by Coyne, Sargeant, et al. Especially Coyne's interpretations of Kettlewell's methodology. Secondly, whether or not Kettlewell, inadvertently or intentionally for other concerns, introduced artificially high densities of moth populations for his study, and that the moths were put onto the trunks of trees which may not be where they actually pass the day exposed to predators. Inasmuch as the high density problem was addressed by others in follow-up studies (e.g. Clarke and Sheppard 1966, Bishop 1972),
Majerus' strongest criticism of these experiments is that Kettlewell used the wrong part of the
tree.(Excerpted form said document). Thirdly, that while it certainly is true that peppered moth caterpillars (larvae) develop different colors in response to environmental stimuli (they come to match the colors of the twigs of their host plants) (Poulton 1890), it has never been demonstrated that environmental stimuli experienced at any stage in development can induce melanism in adults (in re). This is discussed, however, by Creed et al.
The indications that Coyne may have interpolated Kittlewells findings are troubling until resolved. Majerus' does imply or outrightly states that until further work is accomplished the subject matter (Kittlewell) while deserving of respect is inconclusive...
Its LazyGun Clanad, not LazyDog :)
Thanks for the link. Reading it carefully, it is fair to say that modern researchers/reviewers do have some criticisms of the design of some of the experiments. Did you read the last comment though?
Indisputable evidence for natural selection, it was labelled. Both the rise and then and perhaps more importantly the decline of the melanic form of the peppered moth show "that no other evolutionary force can explain the direction, velocity and magnitude of the change except natural selection" (qutted from Bruce S Grants article)
You have accepted that natural selection can offer small scale changes in adaptation. You then argue that the decline in the melanic form, coinciding with reduced pollution etc somehow argues against natural selection/speciation? I am unclear why you think this is the case.... could you please restate your objection Clanad?
Thanks for the link. Reading it carefully, it is fair to say that modern researchers/reviewers do have some criticisms of the design of some of the experiments. Did you read the last comment though?
Indisputable evidence for natural selection, it was labelled. Both the rise and then and perhaps more importantly the decline of the melanic form of the peppered moth show "that no other evolutionary force can explain the direction, velocity and magnitude of the change except natural selection" (qutted from Bruce S Grants article)
You have accepted that natural selection can offer small scale changes in adaptation. You then argue that the decline in the melanic form, coinciding with reduced pollution etc somehow argues against natural selection/speciation? I am unclear why you think this is the case.... could you please restate your objection Clanad?
I certainly understand what Gould meant. First off, the quote is about rewinding the tape to the start of life and that we humans might not have developed if it was rerun. He was, of course, referring to the cambrian explosion and his theory of punctuated equilibrium, because of what he perceived that the role chance played in the rise of novel forms in the cambrian. (A view which is very controversial within evolutionary biology, but that's a different story)
Gould's argument was that contingent evolution was far more important than convergent evolution, and on that basis chance played a bigger role in evolution than suggested by other researchers. Note that he felt chance was more important than biologists in general considered it and not that evolution was by chance alone. Note also that rewinding the tape back to the start of life is a bigger step than a change of phenotype of a moth. Really that is just a selective quote, used out of context and without understanding what the quote means.
Second off (and to confirm the veracity of my opinions about Gould's words, above): Eldridge (the guy I quoted about the antichance element of natural selection in unequivocal terms) co-authored the work on the Burgess shale with Gould and supports the idea of contingency (chance) but, of course, understands and supports (just like Gould) that natural selection is the opposite of random.
Gould's argument was that contingent evolution was far more important than convergent evolution, and on that basis chance played a bigger role in evolution than suggested by other researchers. Note that he felt chance was more important than biologists in general considered it and not that evolution was by chance alone. Note also that rewinding the tape back to the start of life is a bigger step than a change of phenotype of a moth. Really that is just a selective quote, used out of context and without understanding what the quote means.
Second off (and to confirm the veracity of my opinions about Gould's words, above): Eldridge (the guy I quoted about the antichance element of natural selection in unequivocal terms) co-authored the work on the Burgess shale with Gould and supports the idea of contingency (chance) but, of course, understands and supports (just like Gould) that natural selection is the opposite of random.
I'll attempt to explain and answer both dawkins and Lazy Gun's (sorry about the typo) queries. Firstly, re: Gould... my reading of Wonderful Life..., Gould's hallmark exposition on the Burgess Shales, clearly, in my opinion, sets out his attempt to explain the sudden appearance of the body types and Phyla not in evidence in the Pre-Cambrian. In doing so, gould comes into direst conflict with a number of his colleagues, notably his mentor, Ernst Mayr. The gist of the disagreements is Gould's contention and adherence to punctuated equilibrium... Gould concluded that the sudden accelerations of changes that have certainly manifested themselves throughout the earth�s history were the result of events in which chance played the preponderant role. For Gould, the determinism in nature that is contained within the blind process of natural selection was increasingly deemphasized in his writings, in favor of the purely accidental. Gould�s �radical� contingency even excluded any notion of direction, such as evolution from the simple to the complex, for example. (Source On the Death of Gould, Walter Giberti, et al ) Gould emphatically states "Roll the clock back 570 million years, and the outcome would be entirely different..." not, in reference to beginning of life but the chance application of random mutations.
The outcry from Mayr, et al led to the occasional (and continuing) belief among some paleo-biologists that evolution actually has direction... a totally radical and, at this juncture, unacceptable thesis, since it takes away the cherished randomness neccessary in classical Darwinism... how can a totally random act ever be repeated?
The outcry from Mayr, et al led to the occasional (and continuing) belief among some paleo-biologists that evolution actually has direction... a totally radical and, at this juncture, unacceptable thesis, since it takes away the cherished randomness neccessary in classical Darwinism... how can a totally random act ever be repeated?
... and Lazy Gun... this is the crux of my position on the "plausible deniability" of evolution as the sole determing factor in speciation. If, as Darwin, posited, totally random acts of mutations are responsible for adaptations in phylogeny, how are they repeatable when the environmental factors that are supposed as the propellant towards the mutations reverse themselves? I think the writings, including Kettlewell and Majerus' on Kettlewell and including other explanations all say, in one way or another that the phenomena cannot be totally explained by the environmental factors alone. I do think that there's some fallacies in the observations and I do think there's room for interpreting Majerus' as saying Kettlewell may not have considered all available factors. Regardless, the argument against speciation due to these possible adaptive mutations is, in my view, self-evident . If an organism reverts to its original state when the environmental stressors are removed, where is the evolution towards speciation? This is observed over and over, even with Darwin's cherished finch's, no? The population numbers are too low, the reproductive cycle too long for the vast majority of organisms (save possibly the bacteria) to evolve towards anything better or different as defined by species, in my opinion. (We would have to agree, as first posited in another thread with drestie as to the definition of species in the first place)...
Thanks for your clarification Clanad.
We obviously have a fundamental difference of understanding of natural selection and its underlying mechanisms.To me, what the peppered moth story illustrates is how non random selection of a population through environmental changes can affect a population so completely and so quickly. It also illustrates that selection has no guiding principle, but merely acts on the basis of "fitness".
Speciation is far more dependant upon both underlying changes in the gene pool (be it through selection, gene drift, and/or mutation), and the nature of the environmental factors and timescale than was observed here though, in my opinion.
Your argument would seem to suggest that you think that selection for whatever reason should automatically lead to speciation if the theory is correct, and the fact that this wasn't observed in the peppered moth somehow means that evolutionary theory, at least when it comes to macro-evolution, is somehow invalidated. I would disagree, and suggest that your understanding of evolution is flawed.
We obviously have a fundamental difference of understanding of natural selection and its underlying mechanisms.To me, what the peppered moth story illustrates is how non random selection of a population through environmental changes can affect a population so completely and so quickly. It also illustrates that selection has no guiding principle, but merely acts on the basis of "fitness".
Speciation is far more dependant upon both underlying changes in the gene pool (be it through selection, gene drift, and/or mutation), and the nature of the environmental factors and timescale than was observed here though, in my opinion.
Your argument would seem to suggest that you think that selection for whatever reason should automatically lead to speciation if the theory is correct, and the fact that this wasn't observed in the peppered moth somehow means that evolutionary theory, at least when it comes to macro-evolution, is somehow invalidated. I would disagree, and suggest that your understanding of evolution is flawed.
Actually, Lazy Gun it's not my position that selection should lead to speciation. That opinion is clearly stated in my desktop copy of Darwin's opus... and to clarify once more, it's my observation that there was ;ittle if any evolution displayed in the Peppered Moth epic. At least not in accordance with classical Darwinism and not even in accordance with neoDarwinism. Stephen Jay Gould was uneasy with the lack of hard evidence for speciation and reached the conclusion that rather than interminably long periods of time required for such events, it, perhaps, occurred in short, but equally unobservable bursts... hence punctuated equilibrium. He was also a vocal opponent of convergence, stating that the randomness inherent in mutations could not be repeatable, especially in unrelated Phyla. That being the case (and he does have his disciples) it would appear to impossible that mutative effects are/were at work with the Peppered Moth, since the changes appeared to reverse themselves congruent with the Clean Air Act. Majerus' waivers in his conclusions as well... in my opinion...
I wasnt trying to misrepresent your position Clanad, rather I was saying that you believe that the Peppered moth story invalidates said theory because it did not lead to speciation. Is this not a true representation of your belief?
As for your comment suggesting that there was little evidence to support either Darwinism or neoDarwinism, I would suggest that is incorrect... Evolution is descent with modification, producing change in the morphology and function of adult living organisms. Microevolution refers to morphologic change within species, and the Peppered Moth clearly shows this both with the orginal change, and later the reversal of that change, both in response to environmental factors and selection through predation. Not every single observable change is always going to lead to speciation though, and Darwinism, NeoDarwinism, all variants on the evolutionary theme are entirely comfortable with that.
As for your comment suggesting that there was little evidence to support either Darwinism or neoDarwinism, I would suggest that is incorrect... Evolution is descent with modification, producing change in the morphology and function of adult living organisms. Microevolution refers to morphologic change within species, and the Peppered Moth clearly shows this both with the orginal change, and later the reversal of that change, both in response to environmental factors and selection through predation. Not every single observable change is always going to lead to speciation though, and Darwinism, NeoDarwinism, all variants on the evolutionary theme are entirely comfortable with that.
Clanad, I gave you a perfectly reasoned response explaining how you had misrepresented Gould and his application of randomness. I highlighted, as I have done before, that many evolutionary biologists have great problems with Gould (and Eldridge's) work on PE (but that is still besides the point). Gould did not say or believe at any time in his research or books that a random mutation of a phenotype could not happen twice.. Gould was arguing (incorrectly in many peoples view) that in the history of life chance plays a bigger role than stated by other evolutionary biologists (namely the neo-darwinists). You say so yourself 'chance played the preponderant role', preponderant role. And in any case, where does that statement say or even infer that a phenotypic mutation can't happen twice? The mutations happen all the time, natural selection sorts them out (remember Eldrdge's quote about antichance) Natural selection is the bird eating the more visible moth.
If I understand you, you are trying to argue that because Gould said 'rewind the tape and it would come out different', we should somehow conclude that Gould and 'others' thought that a random mutation to a phenotype is unrepeatably random. This is not only an incorrect assumption and unconnected to his point but also a position you do not need to argue since you believe that small scale mutations leading to small hybridisations can occur.
If I understand you, you are trying to argue that because Gould said 'rewind the tape and it would come out different', we should somehow conclude that Gould and 'others' thought that a random mutation to a phenotype is unrepeatably random. This is not only an incorrect assumption and unconnected to his point but also a position you do not need to argue since you believe that small scale mutations leading to small hybridisations can occur.
Is it not true, dawkins, that in order for speciation to occur or, in most cases, even random mutation to 'phenotypes' to actually affect the subsequent offspring, more than one "random mutation" must occur? I've not seen any writings supporting the theory that one random mutation will have much of an affect but Darwin, et al stipulates that any resultant morphological 'change' is the result of an accumulation of mutations. So, the problem represented by Gould (and I don't intend to use him singularly but as a representative of a 'popular' view point among evolutionists) is that the same series of mutations must randomly occur and the resultant shanges accumulate if you will, over a long period of time, which really is an astounding shot in the dark, don't you think? Darwin, himself, clearly enunciates the view that random changes would be responsible for the macro changes he expected to be proven by, then future, investigation. Instead, what was found was stasis being the overwhelmingly observed non-devlopment of species that appeared rapidly and left, unchanged, just as rapidly, no?
Contd
Contd
Contd.
Not to leave this in a lurch Lazy Gun, but I think we're going around in circles and it's probably as much my fault as anything. Simply put, Majerus' even alludes to the possibility the Kettlewell may not have considered all aspects of the phenomena he reported. I think the evidence shows there have always been light and dark mottled moths. The fact that environmental changes may have made one or the other more attractive to predation is not evidence of classical random mutation induced micro-evolution. I think the evidence supports this conclusion when the reversion to the predominance of one over the other occurred. There simply was not enough time for genetic differences to occur and produce a different moth, only one became predominant. Even today, there are both light and darker mottled Peppered Moths, are there not? If this is the case, where is the indicators of evolutionary force at work?
Not to leave this in a lurch Lazy Gun, but I think we're going around in circles and it's probably as much my fault as anything. Simply put, Majerus' even alludes to the possibility the Kettlewell may not have considered all aspects of the phenomena he reported. I think the evidence shows there have always been light and dark mottled moths. The fact that environmental changes may have made one or the other more attractive to predation is not evidence of classical random mutation induced micro-evolution. I think the evidence supports this conclusion when the reversion to the predominance of one over the other occurred. There simply was not enough time for genetic differences to occur and produce a different moth, only one became predominant. Even today, there are both light and darker mottled Peppered Moths, are there not? If this is the case, where is the indicators of evolutionary force at work?
Clanad
You are trying to argue about stasis and contingency(of which Gould is almost out on his own) but this is a whole new (very big) subject which I am happy to debate with you but i am trying to focus on random mutations, hybridisations and natural selection, the latter of which is the basis for all evolution (phyletic gradualism). Most people don't like Gould's work on stasis but the environment must play a significant role in shaping evolution (a middle ground is probably right). It is plain wrong to suggest that Gould did not believe in natural selection or that mutations only happen once (perhaps a misreading of Dollo's law of the irreversibility of accumulated changes (Dollo's law is also controversial by the way))
I'll try and put it more simply. In the case of the moth the phenotype is the coloration which it inherits. Without any natural selection we would expect to find a RANDOM pattern of coloration throughout a population (this would be due to random mutations and breading) natural selection works as antichance because it takes this random variation and selects for fitness (in this case the birds eat the visible moths). Subsequent breadings show patterned coloration based on natural selection (NON-RANDOM), any variation in phenotype is reduced because of predation. This can occur backwards and forward unless and until one coloration is completely bred out of the gene pool of the local population at which point the phenotype would stick. It would still be possible for a mutation of coloration to occur but would be extremely unlikely that this coloration would gain prevalence in the gene pool again unless it could establish a successful line through inheritance. Moths bred in captivity (see my earlier PDF) show an array of coloration through hybridisation because they are not subject to the natural selection process of being eaten by predators. If the birds went away random variation would return.
cont
You are trying to argue about stasis and contingency(of which Gould is almost out on his own) but this is a whole new (very big) subject which I am happy to debate with you but i am trying to focus on random mutations, hybridisations and natural selection, the latter of which is the basis for all evolution (phyletic gradualism). Most people don't like Gould's work on stasis but the environment must play a significant role in shaping evolution (a middle ground is probably right). It is plain wrong to suggest that Gould did not believe in natural selection or that mutations only happen once (perhaps a misreading of Dollo's law of the irreversibility of accumulated changes (Dollo's law is also controversial by the way))
I'll try and put it more simply. In the case of the moth the phenotype is the coloration which it inherits. Without any natural selection we would expect to find a RANDOM pattern of coloration throughout a population (this would be due to random mutations and breading) natural selection works as antichance because it takes this random variation and selects for fitness (in this case the birds eat the visible moths). Subsequent breadings show patterned coloration based on natural selection (NON-RANDOM), any variation in phenotype is reduced because of predation. This can occur backwards and forward unless and until one coloration is completely bred out of the gene pool of the local population at which point the phenotype would stick. It would still be possible for a mutation of coloration to occur but would be extremely unlikely that this coloration would gain prevalence in the gene pool again unless it could establish a successful line through inheritance. Moths bred in captivity (see my earlier PDF) show an array of coloration through hybridisation because they are not subject to the natural selection process of being eaten by predators. If the birds went away random variation would return.
cont
It is true that DNA is very good at making faithful copies of itself and mutations are rare and it is also true that environments are generally stable and this is why we don't see much change on a visible basis (Goulds stasis). But there are situations where a change in environment can show how natural selection can affect a simple change such as the coloration of a moth.
Latest Posts
Quizzes & Puzzles17 mins ago
ChatterBank110 mins ago
Crosswords179 mins ago
Body & Soul189 mins ago
