Selection/Drift

Natural selection is a simple theory because it can be understood by anybody; to misunderstand it requires special training.

Graham Bell, The Masterpiece of Nature

Interest has been expressed in a thread on selection and drift, so I thought I’d start one, and offer my own 2-cent summary of the concepts.

Evolution, as commonly understood in biology, simply involves change in a lineage. Through mechanisms of change – principally, mutation and the insertion of ‘foreign’ DNA sequence – offspring frequently contain DNA sequences that do not derive by simple copying from their parent(s). This change is inevitable and, iterated, inexorable. There is no memory, no externally-stored blueprint for organisms; the specification of a species ‘floats on the breath of the population’, as Doctor Johnson wrote of the unwritten Gaelic language. Unless there is some kind of boundary blocking all possible avenues, a continuing source of variation is sufficient to keep a lineage exploring never-before-seen genetic space ad infinitum.

Among close ecological competitors (among, for example, the genetically similar members of a species), at a given locus in a finite world one individual ancestor’s genetic sequence is headed towards being the ancestor of every instance of that locus in a future population, and all the others with which it shared a population are heading for extinction. This derives from two facts: samples are more likely to deviate from the frequencies in the wider group than match them, and the probability of fixation of an allele is equal to its current frequency. The distortions on generational sampling tend to reinforce, through to extinction of all but one variant. This same tendency underlies the ecological principle of competitive exclusion between non-interbreeding competing species.

If a particular locus is invariant in a population, fixation has already happened. An original mutation, occurring in a single ancestor, has been passed to every member of the current population. Looking forwards, the mechanism of this concentration continues to operate, and so one particular individual from the present population will become the ancestor at that locus of all members of a future population. From any given starting point, a population of N diploid individuals will take a mean 4N generations to achieve fixation of one ancestor’s copy, and the probability for any diploid locus of being that copy is 1 in 2N. This doesn’t mean that large populations cannot fix neutral alleles, however – the number of mutations occurring scales with population size, so mutations will be fixed at the same rate they are generated, completely irrespective of population size. Doubling the population gives twice as many mutations taking twice as long to fix – the result is the same number of mutations being fixed per generation.

At the point of fixation, all instances of that locus descend from the same ancestor – they coalesce upon that ancestor. The case described – where there is no variation at all at the locus, ie there is just one allele – is the baseline process, the neutral case. If there is no variation, there is nothing for Natural Selection to ‘see’. The only process in operation is random genetic Drift – even though in this instance, it effects no evolutionary change because there are no variant alleles. The change occurred with the original mutation. This latter fact leads me to prefer the view of ‘descent with modification’ over the population geneticist’s ‘change in allele frequency’. It is true that allele frequency change is also evolution, the only part over which selection and drift have a role, but as far as each lineage is concerned, the change occured at the moment of mutation. The lineage changed at that point; the population changed somewhat later, when this mutation became the norm.

Suppose we could uniquely label the locus for every member of the population, in a heritable manner. Now, we have essentially created 2N alleles. If we allow them to operate neutrally, just as when there was no variation, evolution will now occur because allele frequencies must change in the population. Because our labelling has had no effect on the neutral ancestry-fixation process, the label itself will surf to fixation on this process, while all others become extinct.

If, instead of labelling every instance, we simply labelled one, we would find that it still had the same 1 in 2N chance of becoming fixed. And this is the situation for any neutral mutation: 1 in 2N neutral mutations will become fixed; the neutral mutation simply functions as a label.

So now, having laboured the neutral case, where all is Drift, we can look to introduce a differential between alleles. If a new allele consistently performs better or worse than the existing one – meaning that it enhances or hinders the survival and/or reproduction of its bearers – then Natural Selection has come into play. It is a simple and obvious and non-tautological!) truth that a consistent increase in survival/reproduction – in fitness – will tend to favour such alleles over the purely neutral case, and render fixation more likely and speedy, while a reduction will increase the likelihood and speed of elimination.

Unlike the purely neutral case, in which population size is cancelled out, the behaviour of selectable alleles is affected by population size. In smaller populations, random factors have a greater influence than in larger ones, and hence alleles may behave as effectively neutral despite possessing an advantage which would see them selected in a larger population.

Drift does not simply disappear when you start to turn up the selective ‘heat’. Drift essentially derives from random sampling, the tendency of subsets to deviate from the distribution of the complete set, and such sampling is in effect almost all the way along the continuum of selective advantage (apart from alleles that are so strongly detrimental that they never gain a foothold). Even a favourable allele can disappear through Drift, likewise a deleterious allele can become fixed through the same mechanism. But more often, progress will go with the expectation, not against it. The large-number tendency is for genomes to become enriched in advantageous alleles and impoverished in detrimental ones. Because this process is environmentally conditioned, it allows populations to adapt to their circumstances, by purging the traits that do worst in the recent environment.

There continues to be a debate about the relative importance of Selection and Drift in evolution generally, and in driving speciation among sexual forms. Only selection can be adaptive, because it is the only component that is responsive to the environment. But they both have significant contributions to make, and cannot readily be teased apart. Both tend to reduce the variation in a population, which variation is only restored by mutation, recombination or immigration.

243 thoughts on “Selection/Drift

  1. Allan Miller,

    Allan,,
    You have simply repeated the same caveat (that over time it will average out, so THEN you can know which has the advantage) as if that solves the tautology problem. Its as if you are saying, Well, yea sure, if we only did one or two runs and used the theory to define the result, sure THAT would be a circular argument, but because we are doing it much longer than that, the problem is solved. Its a red herring, you are still defining the advantageous as being the most successful and the deleterious as the least successful over time.

    So when the question is, will the advantageous mutations be the most successful over time, and the answer is, the ones that are most successful are advantageous, the answer to your question will always be confirmed.

    You even say this silly line, without realizing you are saying the same thing:

    “And you can verify that those falling in the ‘beneficial’ part of the continuum (those producing a net gain of offspring) fix much more readily than those in the ‘deleterious’ part.”

    See how you just said beneficial is the same thing as saying those that produce more offspring? And when you realize you have just said this, and then you further realize that the question evolution attempts to ask is, do beneficial mutations produce more offspring, you have already answered the question by the definition you give to beneficial.

    Good hitters always hit 60% to right field (over time, on average, over numerous repeated trials Allan!! Not just one trail, that’s the important thing you have to remember!).

    So I need to solve a mystery, Do good hitters show a pattern of where they hit it to most often. I believe so.

    And you know, guess what, my theory is correct, Good hitters really do always hit 60% to right field, because if they didn’t they wouldn’t be called good hitters, they would be bad hitters!! I have confirmed my hypothesis!

  2. Guillermoe,

    How can you know that not singing is an advantage if you don’t know the reason for singing in the first place?

    So is singing an advantage for crickets?

  3. phoodoo,

    “And you can verify that those falling in the ‘beneficial’ part of the continuum (those producing a net gain of offspring) fix much more readily than those in the ‘deleterious’ part.”

    See how you just said beneficial is the same thing as saying those that produce more offspring? And when you realize you have just said this, and then you further realize that the question evolution attempts to ask is, do beneficial mutations produce more offspring, you have already answered the question by the definition you give to beneficial.

    Oh, for fuck’s sake! Beneficial mutations produce more offspring on average by definition. But evolution is not then attempting to answer the question of whether they do or not, any more than anyone attempts to answer the question of whether individuals with greater height are taller. It is looking at the effect of various differentials upon fixation probabilities.

    In some runs of a beneficial mutation through a population, it will be lost. But if it still produces more offspring per individual on average than its alternative, it is still beneficial. Loss doesn’t prove detriment; survival doesn’t prove benefit.

    If you were to choose to define ‘good hitter’ on the basis of the percentages of field covered, you could then take a collection of such individuals and see how they perform in actual games. That’s a closer analogy. But (unlike fitness) you have chosen a definition of ‘good’ which is less likely to be correlated with actual performance. Producing more offspring (determined independently of any one trial) pretty obviously increases the likelihood of fixation in any one trial. As any 7th grader will tell you.

  4. petrushka:
    For some discussion of why I requested this thread,

    It seems this thread has drifted into becoming another battle ground in the Phoodoo wars, which I guess says something about that topic’s fitness in the TSZ ecology (so maybe the Phoodoo topic was selected?)

    But I’d still appreciate discussion of the controversy on the importance or predominance of drift versus NS as mechanisms of evolution.

    Allan M. recognizes this controversy in his original post but notes that it is difficult to tease the two apart. I take that to mean that the controversy arises due to insufficient data.

    But I take Joe F to be saying that NS is more important, since even a very small positive fitness means that fixation by NS is much more likely than by drift.

    Whereas Larry M states that it is also wrong to claim that natural selection is the predominant mechanism.

    Why the controversy? Does it come down to interpretation of “more important” or “predominance”. Or do we not have enough facts, eg on the relative frequency of mutations with fitness very near zero ?

  5. Actually, phoodoo, your inane ramblings have nothing to do with my question. I skim through them on the off chance that you have learned something, but so far, no.

  6. BruceS:

    But I’d still appreciate discussion of the controversy on the importance or predominance of drift versus NS as mechanisms of evolution.

    Allan M. recognizes this controversy in his original post but notes that it is difficult to tease the two apart.I take that to mean that the controversy arises due to insufficient data.

    But I take Joe F to be saying that NS is more important, since even a very small positive fitness means that fixation by NS is much more likely than by drift.

    Whereas Larry M states that it is also wrong to claim that natural selection is the predominant mechanism.

    Why the controversy?Does it come down to interpretation of “more important” or “predominance”.Or do we not have enough facts, eg on the relative frequency of mutations with fitness very near zero ?

    In present-day fitness measurements we do have trouble estimating selection coefficients that are small. It is hard to detect the difference between s = 0.001 and s = 0. But in terms of their long-term effects, these are very different.

    Kimura’s fixation probability formula, which I gave earlier in this thread, shows that when 4Ns is greater than 1 or less than -1 there is a noticeable effect of natural selection on the probability of fixation. N is the effective population size.

    So if a population size is, say, N = 100,000, selection coefficients as small as 0.0000025 are effective in biasing the probability of fixation up or down. We can’t do an experimental measurement with as large an experiment as nature can do, or for as long a time as nature can. In effect, nature is better-funded.

    A lot of the loose discussion of “which is more important, natural selection or genetic drift” is ill-posed and not worth it. For example, are we supposed to add up all the absolute sizes of the changes in gene frequency by genetic drift, or not? If we add them all up, genetic drift will win most of the time. But that does not answer any reasonable question since those changes partly cancel each other out.

    The sensible questions are whether natural selection is affecting fixation probabilities or distributions of gene frequerncies around their equilibrium values. And for that, our inability to measure small selection coefficients is a big source of the controversy.

  7. BruceS,

    “But I take Joe F to be saying that NS is more important, since even a very small positive fitness means that fixation by NS is much more likely than by drift.”

    This is the problem Bruce, and the one Allan doesn’t seem to get. We have no idea if small positive fitness means that fixation by NS is more likely. The reason we can’t know that is because the only definition for fitness is that fixation is more likely. Its unfalsifiable.

    Allan doesn’t even think evolution needs to ask the question of whether or not this is true, he says its true by definition.

    The premise (which has never been proven) is that some mutations are better than others, and thus increase the amount of offspring over time. That is a giant assumption, that is only true if your only definition for some mutations is that they cause more offspring.

    Are blue eyes beneficial? If you have a population of brown eyed people and blue eyed people, which one is more fit?

    The answer evolution provides is nonsense.

  8. Allan Miller,

    And Allan here is another question that Evolution indeed does need to answer, but for which it is unable. What is the reason for the increase in offspring numbers.

    Is is because of the mutation you are calling useful? Is it because of a different allele that you aren’t even measuring for. Is it for a combination of two, or three or ten, or perhaps it is luck. Is it because some mutations are simply more likely than others, is it because of none of these reasons.

    You have no idea for the reasons why some populations increase more than others. But in one case one allele is more commo0n, and then in another case another is more common, and then in a third another is more common, but if you take the average, someone has to be in the lead.

    Every conclusion you make is based on a preconceived notion that you have no way to prove. You call a mutation “beneficial” simply because it is the most recurrent in the population. And you don’t even know what caused the formation of that allele to begin with. Its one bad assumption stacked on top of another.

    Thus you have no theory, you have tons of assumption, all of which are insured by definition to be true.

  9. phoodoo:
    BruceS,

    This is the problem Bruce,

    Hi Phoodoo!

    I hope you are enjoying taking on all comers in this thread and others, as you seem to be bearing the anti-evolution burden on TSZ all by yourself these days.

    Except for RB, I guess. Not sure how much rhetorical support that is, though.

  10. phoodoo:
    BruceS,

    Well, I wish I could say that about makes it a fair fight, but that might be being a bit too generous .

    I love a good chest thump!

    I explained one story (perhaps not true, but certainly not a tautology) about where and why that kind of behavior arises in a post above.

  11. phoodoo: Thus you have no theory, you have tons of assumption, all of which are insured by definition to be true.

    Then you’ll have no trouble brining light to the darkness and providing a framework that is not based on assumption and showing everyone what they’ve been doing wrong this past, oh, 100 odd years.

    Yet you’ll never do that because you are not capable. I know it and you know it.

    Otherwise you’d take me up on my offer to explain the thing that you claim does not exist and show me up for the liar I must be!

    Of course, as my condition is that you explain the theory of ID I know you can’t do that! Yet it seems you’ll never admit it. But that does not actually matter. These conversations are here for the long term, anybody searching for your name can see how confident you are in your claims.

    So out of the two claims here, there is no theory of evolution and there is no theory of ID, only one of us is unwilling to explain the theory we hold to. I’m willing to explain the theory of evolution to you, but you are not willing to explain the theory of ID to me.

    How very unexpected. Or not…

    If there was indeed a theory of ID then you’d be able to explain it! And if there was no theory of evolution, how could I explain it?

    The fact your are even afraid to address all of this is very telling, very telling indeed!

  12. phoodoo: Well, I wish I could say that about makes it a fair fight, but that might be being a bit too generous .

    The funny thing is that you obviously get more intellectual stimulation here then at UD. I guess hanging around with the likes of Joe and KF soon becomes boring as they do nothing more then repeat the same words in slightly different arrangements each time, saying nothing new or original each time.

    So the mere fact you are here speaks volumes for how engaging Intelligent Design is. After all, how many times can the refrains of “evolution can’t do X”, “design is a mechanism” and “FSCO/I exists but can’t actually be quantified” be heard before they become boring to even the most ardent ID supporter?

    How many posts about what evolution can’t do will you read, all the while wondering when the first post about Intelligent Design will show up?

  13. phoodoo,

    the only definition for fitness is that fixation is more likely.

    That’s NOT the definition phoodoo. How many more times?

  14. I personally think it somewhat artificial to separate out selection and drift. The fundamental process is allele concentration by population resampling, which takes place irrespective of selective differentials. Selection is the biased component of that process. But evolution will occur for any value of s (save only that the non-appearance of a lethal doesn’t really count). Selection takes historical precedence, is substantially more powerful, and produces adaptation. But drift is always there, and is likely to be responsible for a substantial portion of evolution.

    One interesting question relates to the role in speciation. If we have allopatric speciation, then there is no privileged position for either selection or drift in causing biological reproductive isolation. Change is change, and any change results in divergence (homoplasy aside), regardless whether it is selected or not within one or other subpopulation. Selection speeds divergence, but the relative importance depends upon the relative proportions of mutations produced in the various ranges of selection coefficient. But with sympatry, divergent adaptations can take the place of a geographic barrier in stemming and ultimately stopping gene flow.

    A further question relates to junk DNA. A popular hypothesis, due I think to Michael Lynch, argues that the small population sizes of eukaryotes mean that the detriment of excess DNA is masked whereas larger populations expose these assumed nonzero selection coefficients more clearly, hence prokaryotes have less junk. But while there is a correlation with population size within similar organisms, I feel that the extrapolation across kingdoms is less justified. I think that mechanistic constraints, and the substantial difference between unicellular prokaryote and multicellular eukaryote energy budgets and ecology, perhaps play a greater role than population size’s effect on selection.

  15. Allan Miller,

    And yet it is all just pure speculation, more likely to be believed by those who have a worldview which favors it. Any explanation is as good as another when you can just make guesses.

  16. phoodoo,

    Whereas ID is hard science, completely independent of worldview, and chock full of the detail evolutionary theory lacks. Got it, ta.

  17. walto: I love a good chest thump!

    I explained one story (perhaps not true, but certainly not a tautology) about where and why that kind of behavior arises in a post above.

    While we are on the topic of baseball scouting, here’s a great article about why athletes and classical musicians and manufacturers are much better today than they were 50 years ago, whereas teachers and doctors are not.

  18. Allan Miller:
    I personally think it somewhat artificial to separate out selection and drift.

    Thanks to you and Joe F for your followup comments. More at Larry M’s blog from his point of view for anyone interested.

    You too Phoodoo. Larry and his crew of commenters relish a good fight with an IDist. I think.

  19. phoodoo: How can you know that not singing is an advantage if you don’t know the reason for singing in the first place?

    It’s sex, phoodoo. Cricket sex!

    So is singing an advantage for crickets?

    It depends!

  20. BruceS: While we are on the topic of baseball scouting, here’s a great article about why athletes and classical musiciansand manufacturers are much better today than they were 50 years ago, whereas teachers and doctors are not.

    Thanks for that link. FWIW, I had just the other day been discussing the issue of falling TV baseball ratings and mentioned that it seemed kind of sad that in spite of baseball and classical music skills reaching greater and greater heights, both the sport and the symphony were in free fall.

    I have a trombonist friend of almost 70 who often remarks that the N.E. Conservatory grads get better and better. And I remember when only one person in the world could play the Carter Piano Concerto: the story was that he’d perform it annually and then have a nervous breakdown that would last several months. Today lots of people can play it. But the halls are empty.

    Admittedly, I’m a contributor to this “problem”. I haven’t cared about baseball since I was a kid (and it’s slower now than ever), and I have very little interest in spending an evening at Symphony Hall.

  21. Alan Fox,

    I have actually known about these crickets long before Guillermo brought this up. To me its poses a quandary for evolution, not a reinforcement, because there are again just so many unexplainable aspects to another evolution story. How often are there males born without the ability to sing in places where singing is not a problem? Is the rate the same on this island? How did the males learn a mating strategy to overcome their lack of a call? Do they know that staying in close proximity to the males that do sing will increase their chances for reproduction. Did they learn this skill immediately? Did the females also change their behavior? How did they learn? Has this always been a secondary aspect of cricket mating? If all the singing went away, what would happen, would they stop mating? I doubt they would, so presumably its quite possible to mate without the singing so why was it so important in the first place. Cockroaches do fine without singing.

    Evolution always has these layers of problems it has to answer, and it never really can. One has to just suspend their curiosity to accept all the tenets of such a complex system can be explained by virtue of lucky accidents.

  22. Allan Miller,

    I frankly feel that is an unimportant question. If the evidence is such that evolution can not possibly explain something, that is reason enough to doubt it.

    I can understand why folks like you and Omagain would love to shift the focus of the conversation away from the deficiencies of evolution, but that is not a strong scientific position. If information came along which showed the big bang theory to be woefully inadequate to explain reality, it wouldn’t be enough to say, well, you don’t have a better idea. So let’s keep it.

  23. phoodoo:
    Yes, It is a very interesting article (Coincidentally, I am a professional athlete)

    Too bad there is no way to judge your fitness as one

  24. Sadly, if you cannot grasp the concepts of differential reproductive output or population resampling, evolution will forever be a closed book to you. You illustrate perfectly the ‘special training’ alluded to in the Bell quote with which I headed the piece.

    Does microevolution occur? If so, what are its mechanisms?

  25. Allan Miller,

    There isn’t even such a thing as genes responsible for differential reproductive output Allan, so your claim stops right there. There is simply reproductive output, and then after the fact claims about the cause.

    Until you understand that, the problems with questioning evolution will always be a closed book to you.

    Maybe you can read some of the spats between Moran, Dawkins and Coyne et al (if you can stomach it) about the causes of evolution, and why even they can’t agree.

    What’s the theory of evolution? Make up your own, because one doesn’t exist yet.

  26. phoodoo,

    There isn’t even such a thing as genes responsible for differential reproductive output Allan, so your claim stops right there. There is simply reproductive output, and then after the fact claims about the cause.

    Does microevolution occur? If so, what are its mechanisms?

  27. velikovskys,

    There is a way, a very good way. You do it by results. No one gets credit for winning until after they have won. Just like evolution. Winning of the winners.

  28. phoodoo: To me its poses a quandary for evolution, not a reinforcement, because there are again just so many unexplainable aspects to another evolution story. How often are there males born without the ability to sing in places where singing is not a problem? Is the rate the same on this island? How did the males learn a mating strategy to overcome their lack of a call? Do they know that staying in close proximity to the males that do sing will increase their chances for reproduction. Did they learn this skill immediately? Did the females also change their behavior? How did they learn? Has this always been a secondary aspect of cricket mating? If all the singing went away, what would happen, would they stop mating? I doubt they would, so presumably its quite possible to mate without the singing so why was it so important in the first place. Cockroaches do fine without singing.

    Excellent questions, phoodoo. One thing I’m sure of is that individual crickets don’t learn. There’s lots of research on crickets so maybe there are some answers.

  29. phoodoo, this is a different complaint than the one I responded to above. But it is also confused. The sort of “explanation” you’re looking for here (Why do crickets sing rather than, say, mumble sarcastic remarks in Spanish?) while it would be interesting and cool for evolutionary science to answer, isn’t something that is actually required of a theory that has from the start considered mutations to be random rather than teleological. If you want to know what the particular genetic antecedents are, science may provide this (while your fave theory can’t), but if you want to know WHY in the sense above, neither your gang (that is supposed to be able to answer questions of that type) nor the actual scientists who don’t think there need be any such “reasons” are going to give you much succor.

    It’s the IDists that need to explain why crickets sing not the scientists.

  30. Allan Miller:
    Robert Byers,

    How can you get so much wrong into one sentence?

    Indeed there is nothing simple about living organisms, and there are complex dynamics at play. Nonetheless, the principle of Natural Selection is itself simple, and unquestionably a theory of evolution.

    Certainly, without a source of variation, lineages would gradually ‘freeze’, by what amounts to wholesale inbreeding (even if mating individuals were only very distant relatives). Selection is only part of the picture.

    I don’t want to get bogged down in apologetics, but where in the Bible does it say diversity arose after Genesis?

    Selection is a small part in evolution. The great part must be the engine for biological change and so the mutation concept.
    So natural selection is not saying very much about evolution.
    selection is trivial relative to the glory of biology. It really should be called natural mutationism to emphasize the actual engine for claim origin of biology results
    You do seem to be saying selection is the engine for biology results.?!
    Selection deals after the biological processes from mutation have occurred.
    Darwin resumed minor trait differences but wrongly understood the glory of biology and so the need for radical change and so mutationism is essential.

    The bible teaches a dramatic biological change in order to bring the reality of death.
    after that everything reacts to survive and has the means. I say its in a memory of the biological entity.

  31. walto,

    I agree with Robert (although I don’t really believe in the bible) , organisms react and adjust to survive. Its a much more obvious, and explanatory description of nature.

  32. Guillermoe: But evolution is not just a trait appearing in one organism. Mutation does not explain change in a population.

    Your saying selection is more defining of what evolutionary biology is then mutations.
    The mutation is the great thing. in one organism its the only important thing. later if selection moves it into the creation of a new population is a minor point to biology. It would AGAIN require another IMPORTANT mutation to move create yet a new population again.
    So selectionism is a;most trivial in defining evolution.
    Its the mutation that only can explain the glory of molecules to men and fish to men.
    Natural selection does not explain evolution simply. Its mutationism that explains it.
    Probably also why the public misunderstands it.
    If selection has nothing of note to select on then there is no evolution.
    The mutantion is the creator of biological complexity and diversity.
    Of coarse as a creationist i insist nutations never could or did create the glory of biology.
    A very unlikely hypothesis.
    It was a creator, a disaster, and innate (memorized I think) mechanisms that create biological changes from original kinds.

  33. phoodoo,

    I agree with Robert, organisms react and adjust to survive. Its a much more obvious, and explanatory description of nature.

    You could verify this experimentally. You could take identical lineages and create populations of each, then subject them to the same conditions and see if they all ‘react and adjust to survive’, and whether any differential change derives from mutation and selection/drift. You could freeze their genomes periodically, so that when something interesting happens, you could go back and track the reasons for the change, by sequencing and by experimental verification of selective differential. Guess what? It’s been done. Your ‘much more obvious and explanatory’ (and hopelessly hand-wavy) description is not supported.

    Microevolution occurs, through the mechanisms of mutation, selection and drift. These things that you declare do not happen, happen.

  34. Robert Byers,

    Darwin resumed minor trait differences but wrongly understood the glory of biology and so the need for radical change and so mutationism is essential.

    So you’re saying evolution is true, but mutation itself provides a force that must not be underestimated, and without which evolution cannot proceed? I wouldn’t disagree!

  35. The Lenski experiment calls to mind a generalised experimental and practical everyday use of Drift (though selection can have a role). If you generate a steady state in a chemostat, where medium is added and culture removed at a rate appropriate to the growth rate of a microorganism in the culture, you can purify a cell strain – your culture eventually becomes populated entirely by descendants of one cell from your original mixed culture: microevolution, the thing that doesn’t happen.

    If there are differential growth rates between lineages cells in the original culture, then the purified strain is more likely to come from that with the greater growth rate. This simple and obvious truth, which phoodoo reassures us is an empty tautology devoid of explanatory power – purification of the strain most likely to be purified – is used as a matter of experimental routine.

  36. Allan Miller,

    What a laugh Allan, I am going to start to take you less seriously. You want to claim that experiments with E coli refute the notion of survival, and confirm the notion of evolution? How long have you had your head in the sand.

    Labs have been experimenting with bacteria with trillions of specimens. And in all that time, and in all those generations, what have we seen to show the great powers of evolution? Virtually zero. Nothing ever happens. The bacteria don’t mutate into a more sophisticated form of life, we don’t get radical change, we get bacteria, bacteria and more bacteria, essentially in the same form that it has existed for billions of years.

    Not only can we see this in the lab, but we also have a 3.5 billion year old experiment of life to look at, and what do we see? Bacteria remains unchanged, for what, 10 trillion, 100 trillion generations?

    E Coli, one of the biggest evidences against evolution ever doing anything, and Allan wants to sing the praises. Wow, you really don’t carry much skepticism with you do you?

  37. phoodoo,

    Phoodoo seems to be asking “if evolution is true, why are there still bacteria?”

    The niche, phoodoo! Remember the niche!

  38. walto: Thanks for that link.FWIW, I had just the other day been discussing the issue of falling TV baseball ratings and mentioned that it seemed kind of sad that in spite of baseball and classical music skills reaching greater and greater heights, both the sport and the symphony were in free fall.

    I have a trombonist friend of almost 70 who often remarks that the N.E. Conservatory grads get better and better.

    I recommend Play It Again, about an amateur musicians attempt to play Chopin’s Ballade #1. The author happens to be the chief editor of the Guardian and so he is dealing with Wikileaks, royal phone hacking, kidnapped reporters in the Middle East, and other humdrum matters while he learns the piece.

    Note that I have not made any fitness jokes about baseball or concerts; you may fill in your own.

  39. phoodoo: I can understand why folks like you and Omagain would love to shift the focus of the conversation away from the deficiencies of evolution, but that is not a strong scientific position.

    Yes, because by offering to explain evolution to you I’m trying to shift the conversation away from evolution!

    Did I make a claim that we understand everything there is to understand?

    No, I did not.

    Did I make a claim that I fully understand it?

    No, I did not.

    Did I make a claim that there are no differences of opinion regarding the mechanisms of evolution?

    No, I did not.

    So it is exceptionally dishonest of you to claim that I want to “to shift the focus of the conversation away from the deficiencies of evolution” and that, my friend, is against the rules of the house.

    If you would like to quote me attempting to “to shift the focus of the conversation away from the deficiencies of evolution” then please do so. If, however, you think that by asking you to explain the Theory of Intelligent Design is doing that, well, I have a quote you may be interested in:

    I can understand why phoodoo would love to shift the focus of the conversation away from the deficiencies of Intelligent Design, but that is not a strong scientific position.

    So why not talk about why Intelligent Design makes the idea of selection/drift moot as it overrides those things that don’t do anything anyway?

    Oh, that’s right, I almost forgot for a moment there…..

  40. phoodoo:
    walto,

    I agree with Robert (although I don’t really believe in the bible) , organisms react and adjust to survive.Its a much more obvious, and explanatory description of nature.

    I may have mentioned before that, many years ago, when I was slogging through every book Samuel Butler wrote whacking Darwin and supporting Lamarckianism, I set up a (very primitive–I’m no expert either in statistics or in Excel) spreadsheet, using a random number generator that I thought might show that Butler was right–that you couldn’t get from randomness to any kind of improved fitness. Admittedly, I had no clear idea what I was doing, but the result showed that I was wrong, given my assumptions and sufficient time.

    The point is, our intuitions about this stuff aren’t always right. I hope you’ll at least admit that Darwin’s theory has the advantage of simplicity: it doesn’t require anything but occasional random mutations with the vast majority of them being worthless (or worse). Any theory that requires some other force(s) as well will still need to depend on natural selection to keep the “improvements” on the planet. So “design” will have to be a more complex, less elegant theory, even if it’s true and Darwinism is false. And that means, if we can actually do without it (not based on our pre-scientific intuitions about what it makes sense to expect, but on empirical trials and correct math) we must do without it, given the apriori advantage to the simpler theory.

    I don’t claim that anything should be inferred from my own clumsy investigation except that what seems right often isn’t. I let actual scientists and statisticians do what they’re trained to do, and don’t substitute my judgment just because something seems kind of unbelievable to me. What the hell do I know? And, more importantly, here–what the hell do you know?

  41. phoodoo,

    What a laugh Allan, I am going to start to take you less seriously.

    You did before?

    You want to claim that experiments with E coli refute the notion of survival, and confirm the notion of evolution?

    No. where did you get that pairing from? Yes, it experimentally supports evolution. No, it doesn’t experimentally ‘refute the notion of survival’. (Though I confess, I don’t even know what that means).

    Labs have been experimenting with bacteria with trillions of specimens. And in all that time, and in all those generations, what have we seen to show the great powers of evolution? Virtually zero. Nothing ever happens.

    Nothing except mutation, selection and drift. Evolution, in other words.

    The bacteria don’t mutate into a more sophisticated form of life, we don’t get radical change, we get bacteria, bacteria and more bacteria, essentially in the same form that it has existed for billions of years.

    That hasn’t been the issue under discussion. The issue under discussion has been whether mutation, selection and drift are real phenomena. You have been insisting that they aren’t, don’t do anything, and anyway are tautologous (which appears to be a synonym for ‘wrong’ in your lexicon). Now you are complaining that Lenski does not have to beat back with a stick the hideous mutant beasts that crawl from his apparatus. They aren’t ‘sophisticated’ enough for you yet, after 25 years or so. Sheesh. An epic fail for the Lenski lab! 🙂

    E Coli, one of the biggest evidences against evolution ever doing anything, and Allan wants to sing the praises. Wow, you really don’t carry much skepticism with you do you?

    Wow, not congenitally predisposed to dismiss EVERYTHING about evolution much, are ya? GAs, Lenski, mathematical theory, observation, phylogenetic reconstruction … all bollocks? All of it?

  42. Incidentally, phoodoo, I brought the Lenski experiment up in direct response to your … um … theory that organisms change by ‘reacting to their environment’, not to show how much evolution can achieve in 25 years. Lenski seemed like a valid experimental test of your hypothesis, and it is simply not supported. Isn’t science fun?

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