Fitness effects of advantageous mutations in evolving

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flunked.jpg Ok people want more science, let’s give them what they are asking for. Most of us are familiar with the claims by creationists that most or all of the mutations are found to be detrimental. And before anyone calls this a strawman, remember that it was Ray I believe who insisted on a 100% detrimental mutation rate. In addition, ID proponents seem to take seriously Sanford’s concept of ‘genetic entropy’ which based on what I have read about his argument is a rejuvenated 2nd law of thermodynamics argument. Of course, most familiar with science would understand that most mutations are neutral and that some are detrimental and few are beneficial. However, recent research has shown that the beneficial mutation rates are much higher than originally expected.

Marianne Imhof and Christian Schlotterer report in Fitness effects of advantageous mutations in evolving Escherichia coli populations, PNAS January 30, 2001 vol. 98 no. 3 1113–1117 [read online]

The central role of beneficial mutations for adaptive processes in natural populations is well established. Thus, there has been a long-standing interest to study the nature of beneficial mutations. Their low frequency, however, has made this class of mutations almost inaccessible for systematic studies. In the absence of experimental data, the distribution of the fitness effects of beneficial mutations was assumed to resemble that of deleterious mutations. For an experimental proof of this assumption, we used a novel marker system to trace adaptive events in an evolving Escherichia coli culture and to determine the selective advantage of those beneficial mutations. Ten parallel cultures were propagated for about 1,000 generations by serial transfer, and 66 adaptive events were identified. From this data set, we estimate the rate of beneficial mutations to be 4 x 10-9 per cell and generation. Consistent with an exponential distribution of the fitness effects, we observed a large fraction of advantageous mutations with a small effect and only few with large effect. The mean selection coefficient of advantageous mutations in our experiment was 0.02.

Not to be outdone, researchers in 2007 reported on a rate which was another 1000 times faster

Evolution by natural selection is driven by the continuous generation of adaptive mutations. We measured the genomic mutation rate that generates beneficial mutations and their effects on fitness in Escherichia coli under conditions in which the effect of competition between lineages carrying different beneficial mutations is minimized. We found a rate on the order of 10-5 per genome per generation, which is 1000 times as high as previous estimates, and a mean selective advantage of 1%. Such a high rate of adaptive evolution has implications for the evolution of antibiotic resistance and pathogenicity.

Perfeito L, Fernandes L, Mota C, Gordo I Adaptive mutations in bacteria: high rate and small effects. Science. 2007 Aug 10;317(5839):813-5.

Have these e-coli bacteria no shame…

77 Comments

Behe is of course not impressed however a German blog rips Behe’s response to shreds

Behe claimed that

1) A few months ago an interesting paper in Science, “Adaptive mutations in bacteria: high rate and small effects”, by the group of Isabel Gordo demonstrated that beneficial mutations in E. coli were more frequent than had been thought. In fact, the authors remark that “We found a rate on the order of 10(-5) per genome per generation, which is 1000 times as high as previous estimates, and a mean selective advantage of 1%.” They show that the previous underestimates of the beneficial mutation rates were likely due to clonal interference — accumulation of beneficial mutations in large bacterial populations which then interfere with each other to dominate the population, making beneficial mutations seem less frequent. Does this new result mean that Darwinian evolution can construct molecular machinery much easier than thought?

No. While the result is interesting, readers of The Edge of Evolution will not be very surprised by it. As I showed for mutations that help in the human fight against malaria, many beneficial mutations actually are the result of breaking or degrading a gene. Since there are so many ways to break or degrade a gene, those sorts of beneficial mutations can happen relatively quickly. For example, there are hundreds of different mutations that degrade an enzyme abbreviated G6PD, which actually confers some resistance to malaria. Those certainly are beneficial in the circumstances. The big problem for evolution, however, is not to degrade genes (Darwinian random mutations can do that very well!) but to make the coherent, constructive changes needed to build new systems. The bottom line is that the beneficial mutations reported in the new Science paper most likely are degradatory mutations, and so don’t address the challenges outlined in The Edge of Evolution.

Can you believe this?… Beneficial mutations are degradatory mutations, Behe starts to sound more like a creationist here.

“The bottom line is that the beneficial mutations reported in the new Science paper most likely are degradatory mutations…” So who are we to believe? A peer-reviewed article in an actual science publication (the leading such publication in the country), or the opinion of an author of a non-peer-reviewed publication that has been uniformly bad-mouthed in its reviews (except in the religious and right-wing media)? Decisions, decisions…

I am somewhat confused about the concept of degradatory mutations. Yes, in case of malaria, the mutation that provides some immunity also comes at a cost (sickle cell anemia) but in the environment in question, the mutation is hardly degradatory.

I find the logic involved a bit simplistic. Let’s say, malaria goes away, would the sickle cell trait disappear as well? Well there you go, evolution in action once again.

But no worries there are many more papers undermining Behe’s ‘arguments’

I’m not sure the two results can be compared/contrasted that simply: the units seem different.

What is the conversion factor between “per cell and generation” (cell^-1 generation^-1?); to “per genome per generation”? In the surface: Since we’re talking about asexual reproduction, each genome consists of a large number of cells. Or do the authors assume that each cell has an independent genome? I don’t have access to the papers… do the authors try to reconcile the two measures?

I don’t believe that it would be necessary to use a conversion factor since in any event it is a single cell that must acquire the mutation to pass it on. I do not have the primary source, but my recollection was that there is actually a very a rare third allele that confers malaria resistance and is not harmful like sickle cell, but that because of it’s rarity natural selection will not permit it’s advance because in hybrid combinations it is less fit than the wild type or sickle cell versions.

Well I believe, as Dr. Behe has clearly pointed out, that stasis is the rule for malaria…as well as E coli and everything else he looked at!

A little more evidence for stasis you may find interesting..

There are many ancient bacterium fossils recovered from salt crystals and amber crystals that have been compared to their living descendents of today. Some bacterium fossils, in salt crystals, dating back as far as 250 million years have had their DNA recovered, sequenced and compared to their offspring of today (Vreeland RH, 2000 Nature). Scientists accomplished this using a technique called polymerase chain reaction (PCR). To the disbelieving shock of many scientists, both ancient and modern bacteria were found to have the almost exact DNA sequence.

“Almost without exception, bacteria isolated from ancient material have proven to closely resemble modern bacteria at both morphological and molecular levels.” Heather Maughan*, C. William Birky Jr., Wayne L. Nicholson, William D. Rosenzweig§ and Russell H. Vreeland ; (The Paradox of the “Ancient” Bacterium Which Contains “Modern” Protein-Coding Genes)

http://mbe.oxfordjournals.org/cgi/c[…]ll/19/9/1637

Though they do some weird contortions to try to make the evidence fit an evolutionary scenario in their paper,,,just what if the evidence from both Behe and Vreeland (not to mention the law of conservation of information by Dembski and Gitt) is correct,,,High populations of single celled organisms will exhibit stasis. Those are quite a few lines of evidence converging on that fact!

And here is a scripture I was told to give you PvM

ROMANS

1:20 For the invisible things of him since the creation of the world are clearly seen, being perceived through the things that are made, even his everlasting power and divinity; that they may be without excuse.

1:21 Because, knowing God, they didn’t glorify him as God, neither gave thanks, but became vain in their reasoning, and their senseless heart was darkened.

1:22 Professing themselves to be wise, they became fools,

1:23 and traded the glory of the incorruptible God for the likeness of an image of corruptible man, and of birds, and four-footed animals, and creeping things.

1:24 Therefore God also gave them up in the s of their hearts to uncleanness, that their bodies should be dishonored among themselves,

1:25 who exchanged the truth of God for a lie, and worshiped and served the creature rather than the Creator, who is blessed forever. Amen.

1:26 For this reason, God gave them up to vile passions. For their women changed the natural function into that which is against nature.

1:27 Likewise also the men, leaving the natural function of the woman, burned in their toward one another, men doing what is inappropriate with men, and receiving in themselves the due penalty of their error.

1:28 Even as they refused to have God in their knowledge, God gave them up to a reprobate mind, to do those things which are not fitting;

You fail to realize that they are still testing whether or not the bacteria recovered from the Permian salt crystals really are 250 million years or are, in fact, modern contaminants. Scientists are leaning toward the latter, if only because the bacteria are identified as being of the genus Bacillus, which is infamous for being omnipresent in virtually all terrestrial environments. Of course there is the possibility that those bacteria haven’t been fossilized, but, instead, have been literally living within the salt crystals, as there are bacteria that can live in porous and water-soluble rocks. … But, nonetheless, how does revived “fossil” bacteria that nearly identical genomes to their modern counterparts negate Evolutionary Biology, and if so, then how come Intelligent Design Proponents still have not been able to demonstrate the alleged descriptive power of Intelligent Design?

it was Ray I believe who insisted on a 100% detrimental mutation rate

WHO CARES?

gees, I can’t believe you are letting complete idiots dictate the content of thread contributions at this point.

sad.

Why must we continue tolerate these idiots here? They don’t want to discuss anything, let alone science, in a civilized fashion, they’re only out to ridicule and condemn those people who are fortunate enough to not share their smothering stupidity.

Born again:

Explain the origin of the designer.

That scripture in Romans given by bornagain77 is relevant to this discussion only if the writer, St. Paul, was specificially referring to the evolution/creation debate. Otherwise, it is only a useless distraction.

So bornagain77 admits these bacteria are found in salt/amber crystals formed 250 mya.

We are making progess!

That bacteria existed both billions of years ago and today is hardly a disproof of evolution. That sounds like that ludicrous argument I hear over and over, “If man came from apes, why are apes still around?”

ID proponents seem to take seriously Sanford’s concept of ‘genetic entropy’

Ichthyic got to this first, but I want to pitch in to say that it is probably damaging to fisk every odd concept that creationists Gish gallop in their attack on science. I believe someone claimed in a recent thread that there is one or two mentions of ‘genetic entropy’ on the web. Let it remain so.

Evolution describes contingent beneficial traits which may build up, enhance, block or destroy earlier mechanisms. Even when Behe tries to cherry-pick examples, he gets beaten by his abysmal reading of current research. People have gathered together many examples of beneficial mutations in malaria. Including such that also builds interactions or structures, as if there was any doubt about it.

Creationists argue from their idea of religious given species vs a strawman of religious given hierarchy for evolution. But instead of always accepting their strawmen, they should describe what ‘genetic entropy’ or ‘information’ is as regards biology, and by which mechanism IDC provides it.

They should also explain why increased ‘information’ or ‘genetic entropy’ is beneficial. Information is a relative measure, but in the most common realizations as Shannon information and algorithmic information it means increased disorder, just as increased entropy means.

Or in a biological perspective, random variation is the basic source of information. Selection decides which information is fixed in the genome as describing what worked best for survival in the current environment.

While a non-ordered genome would carry the most information, entropy and complexity, the beneficial information gives structure and so lowered entropy (by common measures) and complexity (by common measures) of the genome. That is no different from when an organism as a whole grows or maintain its structure against entropy increase.

This is exactly the opposite to creationist description, and that is why there is no need to discuss this as a serious question. Everyone laughs at their theological ideas about finetuning or anthropic arguments, and there is no reason to react differently to their theological ideas about information, complexity or entropy, all going against basic physics and not even remotely touching biology.

Let us concentrate on explaining biology instead. The last part of the post was beneficial, and even constructive. :-P

gees, I can’t believe you are letting complete idiots dictate the content of thread contributions at this point.

There I did it again.

Ichthyic got to this first, but I want to pitch in to say that it is probably damaging to fisk every odd concept that creationists Gish gallop in their attack on science. I believe someone claimed in a recent thread that there is one or two mentions of ‘genetic entropy’ on the web. Let it remain so.

That’s such a defeatist attitude. Let’s not give more credibility by showing that the concept is wrong. The whole concept of beneficial mutations as well as their distribution is an essential part of evolutionary dynamics and you seem to be worried about mentioning the term ‘genetic entropy’ and hope it will all go away? Pathetic

Let us concentrate on explaining biology instead. The last part of the post was beneficial, and even constructive. :-P

Well thank you, and the first part was beneficial as well as it showed once again the vacuity of Intelligent Design Creationism.

Well I believe, as Dr. Behe has clearly pointed out, that stasis is the rule for malaria…as well as E coli and everything else he looked at!

And you accept his claim despite the contrary facts? Are you violating St Augustine’s fair warning again?

You have been duped, don’t let it drag you down to the dark areas of ignorance.

And here is a scripture I was told to give you PvM

Are you now someone else’s messenger boy? Do you have no capability to think or act on your own?

And rather than quote mining papers, why not read them? Willing to discuss the findings? Or are you once again embarassed by repeating ignorance?

The original paper looked at a few genes and on closer examination it was found that there were significant differences. Of course, the interesting question remains, how did the DNA or these organisms survive? But the argument by BornAgain is once again based on ignorance and careless research.

Title: Fatty acid and DNA analyses of Permian bacteria isolated from ancient salt crystals reveal differences with their modern relatives Author(s): Vreeland RH, Rosenzweig WD, Lowenstein T, Satterfield C, Ventosa A Source: EXTREMOPHILES 10 (1): 71-78 FEB 2006 Document Type: Article Language: English Cited References: 29 Times Cited: 1 Abstract: The isolation of living microorganisms from primary 250-million-year-old (MYA) salt crystals has been questioned by several researchers. The most intense discussion has arisen from questions about the texture and age of the crystals used, the ability of organisms to survive 250 million years when exposed to environmental factors such as radiation and the close similarity between 16S rRNA sequences in the Permian and modern microbes. The data in this Manuscript are not meant to provide support for the antiquity of the isolated bacterial strains. Rather, the data presents several comparisons between the Permian microbes and other isolates to which they appear related. The analyses include whole cell fatty acid profiling, DNA-DNA hybridizations, ribotyping, and random amplified polymorphic DNA amplification (RAPD). These data show that the Permian strains, studied here, differ significantly From their more modern relatives. These differences are accumulating in both phenotypic and molecular areas of the cells. At the Fatty acid level the differences are approaching but have not reached separate species status. At the molecular level the variation appears to be distributed across the genome and within the gene regions flanking the highly conserved 16S rRNA itself. The data show that these bacteria are not identical and help to rule Out questions of contamination by putatively modern strains.

1:21 Because, knowing God, they didn’t glorify him as God, neither gave thanks, but became vain in their reasoning, and their senseless heart was darkened.

1:22 Professing themselves to be wise, they became fools,

Sounds appropriate a description of Intelligent Design proponents who insist that their God hides in gaps of our ignorance. So what’s your point here?

Why must we continue tolerate these idiots here? They don’t want to discuss anything, let alone science, in a civilized fashion, they’re only out to ridicule and condemn those people who are fortunate enough to not share their smothering stupidity.

Do you have any idea how ironic your statement sounds?

Ok, while I was prepared to address creationist objections and questions, it seems that there may exist a common confusion as to the relevance of these findings.

Research has found that the distribution of fitness effects of mutations peaks around zero (detrimental) and then has a distribution around 1, with some mildly detrimental and some mildly beneficial ones. I believe that the detrimental distribution is a beta one versus a gamma distribution for neutral/beneficial ones.

Understanding evolution requires one to understand the impact of the MANY parameters involved. Such as population size, distribution of fitness effects, sexual versus asexual reproduction, stable versus changing environment, selective pressures and many more. Unraveling under which circumstances evolution can be succesful and when evolution may ‘fail’ is important to understanding how the mechanisms of evolution interact with the many additional parameters to understand population dynamics.

Evolution is far more exciting than the simplistic population models we have all grown familiar to. The problem is that many seem to be unable to look beyond them.

Accumulation of beneficial mutations of small effects may allow for multigenetic changes while a single large effect beneficial mutation may sweep the genome. As such, the distribution of fitness effects can be of importance to resolving the issues raised by our critics. Should we ignore our critics ignorance or help others understand where they went wrong?

PvM

I am somewhat confused about the concept of degradatory mutations. Yes, in case of malaria, the mutation that provides some immunity also comes at a cost (sickle cell anemia) but in the environment in question, the mutation is hardly degradatory.

I don’t think Behe is arguing that they are degradatory in the sense of not being beneficial. However, in the manner of being beneficial, they come from destructive and not constructive processes and so won’t be helpful for building complex structures.

He doesn’t seem to provide any evidence that these mutations are ones that degrade (he just says it seems likely). This doesn’s stop him from concluding that they pose no challenge to his thesis.

Don Smith, FCD Wrote:

So bornagain77 admits these bacteria are found in salt/amber crystals formed 250 mya.

We are making progess!

Actually BA77 even admitted common descent like Behe. But I would not call that progress, because these people refuse to challenge YECs, or OECs that deny common descent. Even though that’s the least they can to to get some scientific credibility. We may see the increasing concessions, and the increasing “don’t ask, don’t tell” that tries to cover them up, as signs that the activists privately know that they don’t have a prayer (pun intended) at an alternative theory. But it won’t be real progress until the message reaches the public. And so far that message is fully drowned out by “sneaking in God” and “ID ‘is’ creationism.”

PvM, you wrote:

That’s such a defeatist attitude. Let’s not give more credibility by showing that the concept is wrong.

Actually there’s some valid basis for Torbjorn’s request. A recent experiment suggested that if you repeat a flawed argument for any reason, even in the context of refuting it, you tend to reinforce its standing in the minds of your readers/listeners.

That finding does help explain why we always seem to be running in mud when trying to respond to creationist lies.

That’s such a defeatist attitude. Let’s not give more credibility by showing that the concept is wrong.

I think you misunderstand me. The point I tried to make is that when a concept is barely used, newly dug up by a creationist, it makes little sense to discuss it.

The whole concept of beneficial mutations as well as their distribution is an essential part of evolutionary dynamics and you seem to be worried about mentioning the term ‘genetic entropy’ and hope it will all go away? Pathetic

Now you are accepting the creationist strawman as a basis for a discussion again. My suggestion is to cut off the problem at its base, either to point out that “information” et cetera isn’t a basic part of evolution, or that IDC use is contrary to basic physics.

I don’t understand how you jumped to your last conclusion. I discussed ‘genetic entropy’ and why it isn’t applicable. How is that “hoping it will go away”? Maybe you can conclude that I was “hoping it won’t come”, but even so I think you can observe me willing to tackle most anything that do come. :-P

And I’m sure you don’t want to imply that a lot of The Panda’s Thumb commenters are pathetic when they say the same:

One Brow Wrote:
J. Biggs Wrote:
raven Wrote:

Granted, they didn’t exactly put my proposal, but they seem to live by it.

Really, googling PT the one referring to ‘genetic entropy’ seems to be a frantic commenting nutcase with the tag “bornagain77”. Discussing one mans delusions, isn’t that a bit … pathetic?

A recent experiment suggested that if you repeat a flawed argument for any reason, even in the context of refuting it, you tend to reinforce its standing in the minds of your readers/listeners.

wolfwalker, thanks, I must admit that I forgot about that, which is highly pertinent. [I’m currently nursing my first hangover for a couple of years and my memory seems shot to pieces. I blame Halloween, a first snow fall, and the many changed plans, queues and waiting periods that ensued. Yes, I wrote the comment PvM disliked while I waited in between a few ad hoc parties. I’m just glad it came out readable. :-)]

There is also the problem when you analyze a strawman that you may accept what amounts to a contradiction, as here, for the sake of the argument. With a contradiction as basis you can prove anything. (Which of course is why they are so popular among denialists.)

So your only outs from such an analysis as I understand it is either to point out that it isn’t applicable to the subject (i.e. really refusing the strawman) or to point out a contradiction (preferably the original). Maybe it’s my hangover that speaks, but it doesn’t seem worth the head ache.

Thanks PvM for a decent thread that deals with real science. I for one find this immensely more satisfying than having to continually scroll past the nonsense that spews from the keyboards of such as Pole Greaser. (Has anyone else noted the irony of someone using that name crying about the evils of sodomy?) One of the things that this blog should legetimately do is address creationst arguments. This is not giving them control since we can choose what arguments to address and when to address them. If you don’t like this topic move to another thread or another site. I welcome the chance to discuss real science here.

As to the importance of the topic, I completely agree that data regarding the distribution of fitness values for random mutations is critical and that experiments such as these are the proper way to address the issue, at least in prokaryotes. This data is critical for any modeling of the evolutionary process. It should be remembered however, that reality is much more complex that the conditions used in these experiments. I am sure that the frequency of beneficial mutations would be even higher if the environment was more variable. Remember that fitness is not a constant and what is deleterious in one environment can be beneficial in another.

As to the objections by Behe, this guy is obviously no scientist. The results don’t conform to your ideas, well just make up some objection and claim it to be true. There is absolutely no evidence whatsoever that all, or even the majority of these mutatins are “degratory”. And even if they were, he would have to prove that virtually all of them were exclusively so in order to make his case. And of course, he hasn’t even bothered to define the term, so that would be impossible anyway. The evidence is quite clear that evolution can and did produce new structures and new functions using variation produced by random mutations. Trying to claim that it could not is not going to work. Give it up already.

As for the 250 million year old bacteria, of course they are the same as their ancestors in many ways. After all, how much did that environment change? Of course they are different from modern bacteria genetically. Drift operates even in the absence of selection. Gould showed us how long periods of stasis can preserve some features. That doesn’t mean that evolution has stopped in these lineages or in any others. As with the other studies, the genetic details reveal the processes involved. Claiming that “bacteria are still bacteria” isn’t going to get you anywhere.

Albatrossity, (or anyone who knows),

What does “separate species status” mean here:

At the Fatty acid level the differences are approaching but have not reached separate species status.

Yes Bornagain confused the 99% similarity in a single gene with the whole genome being virtually similar, as later research showed, there was at most a 70% overlap.

Thanks for posting these updates, resolving these minor myths. I can understand why Bornagain would use these examples without double checking the sources, they are quote mined on various well known creationist sites.

Will these sites correct their errors? Unlikely.

GuyeFaux: What does “separate species status” mean here:

At the Fatty acid level the differences are approaching but have not reached separate species status.

Bacteria make some weird lipids (anteiso chains, double bonds in strange places, odd numbers of carbons); different species make different combinations of these. Some bacteria make unique fatty acids; if you find these, you usually assume the presence of that species. There have been some successful efforts to detect hard-to-culture bacteria in soil and other samples using just the fatty acids in the sample, and other efforts to characterize the microbial “community” using this approach. This is a relatively new area, and there are obviously some problems with its application to multispecies communities.

But it is possible to extract fatty acids from pure cultures and compare them, using principal component analysis, in order to determine differences and similarities. If you grow the bacteria under identical conditions (to reduce the prospects of environmental influences on the fatty acid composition), this can be used with some confidence, apparently. I haven’t kept up with the field, but there are now commercial enterprises devoted to these types of analyses. So I assume there must be some sort of PCA-derived metric that allows one to say that bacteria X is a different species than bacteria Y, based on analysis of the fatty acid profiles.

hope this helps

Albatrossity Wrote:

hope this helps

It does.

So “separate species status” is “just” a statistical measure. It would be good to know what the measure is and what the threshold is. I’ll look into what these are.

GuyeFaux Wrote:

So “separate species status” is “just” a statistical measure. It would be good to know what the measure is and what the threshold is.

An interesting way to look at it, but I think I can see what the ID/Creationists would do with it.

Just as they did with archaeopteryx, they would quibble over how much deviation from the mean constitutes a new species and would claim any filled gap just creates two gaps.

Dembski would go the statistical distribution curve, convert the deviation from the mean to a probability, then take negative log to base 2 and show that “macroevolution” is impossible.

GuyeFaux:

Albatrossity Wrote:

hope this helps

It does.

So “separate species status” is “just” a statistical measure. It would be good to know what the measure is and what the threshold is. I’ll look into what these are.

Well, I’m not sure I would phrase it that way. This is just one measure that they use in this paper. Species is a debatable (and arbitrary) concept already; I’m not sure that we need to muddle it with more statistical tests :-)

I just downloaded the 2006 Extremophiles paper, and it is interesting. They compare fatty acid profiles of four strains of their putative Permian bacterial culture to two species of related bacteria (Virgibacillus marismortui and V. salexigens), all grown in the same conditions. The authors say this:

These data indicate that at the fatty acid level, the four Permian strains represent two different biotypes. Compared to more modern species, the data clearly show that these are different microbes. The data of fig. 1 show that the Permian microbes can probably best be considered as subspecies of V. marismortui

BA77, if you’ve read this far, I’d be happy to send you a copy of the paper. You know my email address; all you have to do is ask. You might be interested to know that, as the name implies, V. marismortui was isolated from the Dead Sea. I’m sure that this biblical connection can be used to your advantage somehow…

So “separate species status” is “just” a statistical measure. It would be good to know what the measure is and what the threshold is.

An interesting way to look at it, but I think I can see what the ID/Creationists would do with it.

Just to re-emphasize (not that it matters to liars) I’m only interested on what “separate species status” means w.r.t. “fatty-acid level differences” since I’ve never heard of species being delineated in this way.

Dembski would go the statistical distribution curve, convert the deviation from the mean to a probability, then take negative log to base 2 and show that “macroevolution” is impossible.

Surely the Pniversal Probability Bound has to get in there somewhere.

GuyeFaux Wrote:

Just to re-emphasize (not that it matters to liars) I’m only interested on what “separate species status” means w.r.t. “fatty-acid level differences” since I’ve never heard of species being delineated in this way.

I hope you didn’t think my comment was directed at you, GuyeFaux. I just couldn’t resist imagining what the IDiots would do with it. :-)

In fact, I would suspect that they would want to muscle their way into any scientific definition of “species” just to impress their audience that they are part of the scientific process. It’s part of their M.O.

I hope you didn’t think my comment was directed at you, GuyeFaux.

No I didn’t think that, though re-reading my comment I see the ambiguity. I certainly was not calling you a liar.

If I were an ID/Creationist, I wonder if I would be happier with lots of species with small variation, or fewer species with lots of variation. With lots of species with small variation, it’s easier to make an “evolution is never gonna get from X to Y” type of argument, since you don’t see that much variability in the population to drive evolution. On the other hand, with fewer species with lots of variation you can resort to the “they’re still just fruit-flies” type of argument. In both cases the strength of the other argument diminishes.

So I wonder which type of species is preferred.

So I wonder which type of species is preferred.

Ring species? Nah, probably not.

GuyeFaux wrote:

“If I were an ID/Creationist, I wonder if I would be happier with lots of species with small variation, or fewer species with lots of variation.”

It doesn’t really matter, since we have many examples of both patterns. And you are right, in both cases the strength of the other argument diminishes. Evolution is entirely capable of producing both patterns and many more.

I suspect that creationists would be most happy with very few species and little or no variation within species and lots of divergence between species. Indeed this was probably what most people assumed before modern genetics and taxonomy came along. Of course, we now know that this is certainly not true generally, although I would not be surprised if most people still believed it.

Indeed, many are now advocating a species definition based on genetic discontinuity. This is similar to the fatty acid idea, but more general. It also gets around the problem of asexual reproduction inherent in the biological species definition. The problem with this approach lies in determining how much discontinuity is required in order for two things to be considered different species. The answer is probably not going to be a simple one.

Indeed, many are now advocating a species definition based on genetic discontinuity. This is similar to the fatty acid idea, but more general. It also gets around the problem of asexual reproduction inherent in the biological species definition. The problem with this approach lies in determining how much discontinuity is required in order for two things to be considered different species. The answer is probably not going to be a simple one.

Yeah, in the case of asexual species, wouldn’t that make “species” just another rank like genus, family, etc., and just as arbitrary?

Henry

If you start with a simpler idea with non-living matter first, you get some idea of the complexity of how to define a “species”.

Consider things like dendritic growth of various kinds (mineral growth, the branching out of avalanches, the growth of separate icicles from water dripping off the edge of a roof, water percolating through granular material, etc.) Where to the separate branches become clearly identifiable as separate branches as the system progresses? How would one label these during the early stages?

Now think of the entire panoply of life that exists and has existed on this planet. It appears very much like “dendritic growth” if you consider the entire sweep of it. It is energy driven, and it branches into many paths, any one of which is allowed and determined by the physical conditions in the environment at the moment.

Where does one start labeling separate species? After the separate branches become distinct, there is justification for giving the branches separate names. But at the early stages of branching, we have no solid statistical measure of which way things will go, so any small “deviation” can become the focus of attention and a label for a new species.

Thus, it seems, labels early in the stages of branching are arbitrary and statistically inconclusive.

Marginally on topic–

There seem to be a lot of cases where scientists have been able to breed fertile offspring from multicelled, sexually reproducing species that are closely related but virtually never hybridize in the wild. (Coydogs, i.e., coyote-dog crosses, are an example.) This often involves tricking the females, since the sexual signals of the two species are different.

That indicates to me that the big drive behind speciation is natural selection, more than mutation. Two populations of the same species specialize in two environmental niches. Offspring which aren’t specialized for either niche are disproportionately eliminated. Mutations that change the courtship signals so that they diverge are favored, so that there are fewer intermediate offspring. The eventual divergence of the two groups until they cannot produce fertile offspring is just the result of accumulated mutations, not the driving force behind the speciation.

In the case of coydogs, the males follow the dog pattern of not helping to raise the pups, as male coyotes would. And the females give birth at one season of the year, like coyotes– but the birthing season is shifted 3 months, so the pups arrive in the dead of winter instead of the start of spring. Add to that the fact that coyotes consider dogs something good to eat, and it makes sense that two groups of animals which are interfertile and have lived together in the American Southwest for at least twelve thousand years, have never hybridized into one population.

Henry wrote:

“Yeah, in the case of asexual species, wouldn’t that make “species” just another rank like genus, family, etc., and just as arbitrary?”

Exactly. If you can’t use the biological definition of a species with asexuals, then the distinction is already arbitrary. At least using discontinuity the distinction is quantifiable, if still somewhat arbitrary.

Mike is also correct in that the process of speciation can be very difficult to predict in the early stages. Thus, a certain amount of divergence might be required in order even recognize when a new species has arisen.

Hoary also makes a good point, in that reproductive isolation can be produced by many mechanisms that do not involve genetic divergence, at least initially. So once again, the discontinuity criteria may not be useful in the early stages of speciation.

I really hate to agree with everybody, but you all make such good points. Perhaps we can find someone else to argue with later.

I really hate to agree with everybody, but you all make such good points. Perhaps we can find someone else to argue with later.

Oh, don’t worry about that - one of the anti-evolution posters will probably be here shortly. ;)

Henry

Any guesses as to how these results would impact human evolution? (i.e., can we use the relative genome sizes, etc, to estimate the beneficial mutation rate in humans or pre-humans?)

The closest I’ve seen to an attempt to do this is:

http://christianforums.com/showpost[…]postcount=31

(NB: was posted in 2005, when the 2007 report was unavailable) But I’m sure there are better estimates out there…

About this Entry

This page contains a single entry by PvM published on November 3, 2007 1:38 PM.

Allen MacNeill: RM & NS: The Creationist and ID Strawman was the previous entry in this blog.

Let there be light: Evolution is finally here is the next entry in this blog.

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