What Are the Chances?

Today I was thinking about convergent evolution and wondering if anyone has ever tried to calculate the odds of the amount of convergent evolution that we see in the world today.  For those who are new to biological terms, convergent evolution is the occurrence of similar traits arising in organisms that are not closely related.  For example, the zebrafish has an eye that closely matches the human eye.  Some have even put the similarity at 97%.  In fact, eyes are a structure that have supposedly independently evolved many times throughout history (Richard Dawkins puts the number of independent evolutions of the eye at about 40).  Other examples include the similarities between tasmanian wolves (marsupials) and canines.  A broader list of examples can be found at the wiki page for convergent evolution.

So, what are the chances of 40 different eyes independently evolving?  I’m aware of no study that tackles this problem, and I’m not surprised.  The probability would most likely be so slim as to not be worth considering.

One might contend, however, that in the case of the zebrafish and humans, that it somehow shows common descent.  The argument is that certain features of the eye are highly conserved, so we might expect those features to persevere in the face of RM + NS.  But, this is such a weak argument it almost doesn’t need answering.  This argument completely ignores the fact that many of the transitional forms in between do not have those same features.  We would have to believe that these features somehow were conserved, but not expressed until zebrafish and humans both came onto the scene.  This is simply not realistic.  Once again, we find some pretty shoddy “science” used to prop up evolution.  The more likely explanation is common design.


27 responses to “What Are the Chances?

  1. Um, what the heck are you blathering about? The camera eyes of humans and fish (including zebrafish) are homologous. They are not thought to be “convergent” in any sense. They are inherited from a common fish ancestor that also had camera eyes. In fact all vertebrates have camera eyes (except for some secondary blindness in cave fish etc.).

    The classic “convergence” cases are e.g. vertebrate eyes compared to cephalopod eyes, but you are apparently so confused about what evolution actually says that you missed that.

  2. professorsmith

    Yes, and I’m sure that I’m confused about the eye evolving independently 40 times and how unlikely that is?

  3. professorsmith

    I thought that someone might bring that up.

    I’m not claiming that it disproves evolution, only asking if the calculations have been done and expressing my personal doubt about the validity of what is most likely very long odds. If we could calculate the odds and they came to less than the UPB, well, then that would be something, wouldn’t it?

    I’m pretty confident that that is exactly what we would find. Forty different, independent evolutions of the eye? The zebrafish and humans sharing 97% similarity, especially with disparate information to work with? Even hardcore materialists must admit that the possibility seems a bit low for such occurrences – and they do, else we wouldn’t have MWI-type theories.

  4. Oleg Tchernyshyov

    As pointed out by Zac Jkls, the similarity of eyes in zebrafish and humans is not an example of convergent evolition. Why even bring it up?

    Next, if we haven’t calculated the odds of eyes evolving independently several times, does that mean evolution is disproven? Of course not. Then what is the point of this post?

    Look, if you are a practicing scientist you must be aware that a scientific theory does not necessarily have an answer to every question one might pose. The force of friction, known to humans since ancient times, remains poorly understood. That doesn’t invalidate Newtonian mechanics. We have no idea why the Universe expansion is accelerating. That doesn’t mean Einstein’s relativity is wrong.

  5. professorsmith

    I would argue that if the chances of such occurrences fall outside the UPB, then we can safely say they didn’t happen in the manner described. Not have calculated the odds doesn’t invalidate evolution, it is the odds of the occurrence being so slim as to be not worth considering that would invalidate our current understanding.

    And, according to the definition of “convergent” zebrafish eyes and humans eyes are convergent, unless you wish to contend that humans and zebrafish are sufficiently closely related?

    Oh, perhaps you want to claim it isn’t convergent evolution because similar selective pressures were not applied; what with the zebrafish living in water while humans don’t? Well, then that just makes for a more difficult question for evolution to answer, with even lower possibility.

    Common design, however, does not succumb to this pitfall.

  6. Oleg Tchernyshyov

    Since we have not computed the probability, the point is moot.

    And no, zebrafish and human eyes are not considered to be an example of convergent evolution. The eyes of all verterbrates (that includes humans and fish) are presumed to have been inherited from a common ancestor.

    Cephalopod eyes would be a more appropriate example of convergent evolution. The unreversed position of the retina points to an independent evolutionary origin but otherwise the eye is quite similar to that of the vertebrates.

  7. Oleg Tchernyshyov

    Previous post has vanished. Anyway, the bottom line is vertebrate eyes are thought to have been inherited from a common ancestor, so they aren’t considered a case of convergent evolution. Cephalopod’s eyes, however, seem to have involved independently (retina is not reversed) but are still quite similar to eyes in vertebrates. That’s convergent evolution.

  8. Yeah, Prof. Smith, you need to take Biology 101. You are making a fool of yourself. You obviously don’t understand the basics of animal phylogeny (phylogeny = the tree of relationships between organisms if you didn’t know; google “tree of life”) if you think fish eyes and human eyes are supposed to be convergent. You’d be making the same mistake if you said backbones are convergent. No: backbones are a shared ancestral feature of the whole vertebrate group. So are camera eyes.

    Now you might understand why scientists get so impatient with ID. They have people coming to them, demanding that this sort of junk be taught in public schools, shouting about discrimination and oppression, when in fact it’s just cranks complaining about basic stuff they don’t even understand.

    And 97% similar? This is a meaningless statistic without stating what exactly is supposed to be 97% similar. The DNA sequence? The amino acid sequence? The morphology (where similarity is usually impossible to measure quantitatively in a rigorous way)? If you actually knew anything about biology you would know (a) that similarity numbers have to apply to something specific and (b) you would say what that something was. And if you actually knew something about science you would cite your source.

    Maybe you do know something about these topics and just got over-excited or had a bad day or something. But if so you need to admit your basic mistakes, correct them, and reformulate your argument.

  9. professorsmith

    Mr. Tchernyshyov,
    I fished your comment out of the spam filter. I don’t know why it ended up there.

    The line for zebrafish split off from what became humans over 400 MYA. The eyes that creatures possessed back then were very different from what we have now. Even the camera eye. Yes, they came from light sensitive cells that helped vision, and those may be common to all animals, but the concept of the eye and its complexity arising twice from such disparate lines is rather slim. Then, we should include the other 40 times and the chances get that much slimmer. That no one has calculated the odds (that we know of) does not make the point moot.

    Zac Jkls,
    The comments that you have left so far and the comments by one of your brethren recently have convinced me of the need to develop a comment moderation policy. Suffice it to say that you are expected to remain civil and knock off the personal attacks and insults. You might want to ask Mr. Tchernyshyov how to be civil, as he has shown a level of courtesy that you would do well to emulate.

    Further, I ask that you show me where I advocated anything in this post be taught in school. Your unfounded accusations are the sign of a weak worldview that can not tolerate dissention. If you can not argue with facts, why not just make stuff up, right? I also find it amusing that you are trying to argue over word definitions instead of acknowledging the gaping whole in your theory.

  10. I heard today that corals have light receptors. Doesn’t this say yes to design, and no to evolution?

  11. Oleg Tchernyshyov

    I am not sure why you insist that the fish and human eyes are independent of each other. Are there any specific features that suggest that (like a different retina orientation in cephalopods)? Or is it just your own conjecture?

    400 million years might seem like a long time but recall that mammals (well, marsupials) existed 125 MYA. Was that long enough to think that their eyes also evolved independently from those of humans? Where do we draw the line?

  12. professorsmith

    I had not heard that corals have light receptors, that’s cool. I would not, however claim that it constitutes an advantage for design over evolution, because I believe that the hypothesized last common ancestor between corals and other critters with eyes also had light sensitive receptors.

    Mr. Tchernyshyov,
    The evolutionary pathways of those two eyes are indeed independent from the time of the split 400 MYA. IOW, ever since that split, the two pathways have been evolving separately, yet have somehow come to very similar solutions. Four hundred millions years of “random” mutations and they come to the same result? This defies logic and probability.

  13. Oleg Tchernyshyov

    You’re assuming that the eyes have changed substantially over those 400 million years and thus differ both from the common ancestor’s eyes as well as from each other. What is the basis for this assumption?

  14. Sharks (cartilagenous fish) are more distantly related to zebrafish (which are bony fish) + humans (which are closer to each other than either is to sharks) and they have camera eyes also. The common ancestor of all bony fish had camera eyes (not just eyespots). Literally no one except Prof. Smith thinks that camera eyes developed separately in the lineages leading to zebrafish and humans. There is really no way to even begin this discussion until he admits he is wrong about this. Basically Smith is insisting that evolution says A when everyone else knows it actually says Z.

    The idea that eyes developed 40+ times independently refers to animals in general. Only one of those eye-origin events was in vertebrates — all of the other cases are invertebrates. (And recent evidence indicates that there probably was an ancestral eyespot in all bilaterian animals, and what evolved maybe a dozen or so different times was complex eyes, with the “eyespot” eyes being a primitive ancestral condition)

    Also, it is impossible to discuss Prof. Smith’s “97%” claim unless he says what, exactly, is supposed to be 97% similar, and gives a source. It’s not surprising that scientists get a little annoyed when Smith hasn’t supplied these basics.

    As for the “calculate the probability” claim, Smith is laboring under the impression that all of these eye origin events occurred by “random chance”. But he is ignoring selection. The probability of getting camera eyes multiple times is rather like the probability that puncture-proof beach balls dropped into the Grand Canyon will end up floating out at the bottom. Maybe not every beach ball would make it, but a lot of them would. Similar forces will produce similar results again and again.

  15. j a higginbotham

    I’m neither a PhD nor a biologist. The impression I get from reading these comments is that both zebrafish and human eyes come under one instance of the 40 proposed different cases of ocular genesis. But I am confused about the professor’s estimation of the probability of evolution of the eye. Surely he can’t be suggesting, as Lim Yu imputes, that it is all due to random chance and that all outcomes are equally likely. That would be just silly.

  16. professorsmith

    There’s lots to comment on, so forgive me for not hitting all of it.

    Mr. Tchernyshyov,
    We already know that human eyes have required close to 2000 mutations in order to arise. I would say that 2000 mutations in a single body part would constitute a large change.

    Mr. Yu (or Ms.? I’m not sure in the name “Lim” is a male or female name, so forgive me if I got it wrong),
    Yes, rudimentary camera eyes were around at the last common ancestor. I’ve not disputed that. And, I am not ignoring selection, however, selection needs something to work upon, and those random mutations must somehow come together in the right way and the right order. This might be feasible once, but 40 times? Also, you neglect to mention the selection pressures are/were different in each of those 40 times. Selection is not your friend in this instance, because you would have to somehow show that the selection pressures were the same, yet we know that’s not true. And, even if they were the same, the random mutations would still have to give selection the raw materials to work with.

  17. Oleg Tchernyshyov

    That’s a non sequitur. Look, you have problems at the level of definitions. As several people pointed out, you don’t understand what convergent evolution means, so any discussion of it must wait until you clear that up. You might want to start here: http://www.biology-online.org/dictionary/Convergent_evolution

  18. professorsmith

    And you are all ignoring the obvious and trying to sweep it under the rug. You want to quibble over definitions and ignore the elephant in the room. Is this what materialism has to offer? You can’t argue the facts, only what a specific word means?

  19. Oleg Tchernyshyov

    An intelligent conversation is not possible if one side ignores commonly accepted definitions. But let’s not get hung up on human and zebrafish, let’s use vertebrate and cephalopod eyes as examples of convergent evolution.

    If I understand your point correctly, you are saying something like this. It’s highly unlikely that an eye could evolve even once. It’s even less likely that an eye could evolve multiple times. I’d agree with you but you’ll have to show me an actual calculation of those probabilities. Any chance of seeing that?

  20. professorsmith

    I’m saying that I could buy it happening once, but not 40 times. Also, you’ll note the original post was asking if anyone had done the calculation, which clearly means that I don’t have it handy. Perhaps I will try to do it when I have time.

  21. If I understand your point correctly, you are saying something like this. It’s highly unlikely that an eye could evolve even once. It’s even less likely that an eye could evolve multiple times. I’d agree with you…

    Why do you think it’s highly unlikely that an eye could evolve even once?

    Even Prof. Smith agrees it could happen once. The real question is, if you admit it could happen once, why can’t it happen a bunch of times? Like I said, similar forces, similar result.

    As for calculations, read this paper. They calculate it would take less than a million years to evolve a camera eye, using standard population genetics calculations. So let’s be conservative and say that camera eyes are probable enough to evolve once every million years per lineage in the right selective environment (obviously once a lineage has eyes already it won’t evolve them again).

    Hmm. Looks like there was plenty of time available for 40 eye evolution events (and note that we still haven’t established that anyone thinks *camera* eyes evolved 40 times — someone has to look up the Mayr paper from 1970s that made that claim, and I think it might have been referring to eyespots + camera eyes).

    Game over for Prof. Smith — for a second time since he has never even shown the humility and scientific attitude to admit his mistakes on the first round. Any vaguely serious investigation into eye evolution would have turned up Nilsson & Pelger 1994. If ID advocates are scientific Prof. Smith has a weird way of showing it.

  22. professorsmith

    Mr. Yu,
    Ah, I do so love the bravado with which Darwinists pronounce victory.

    First off, I knew about the chances of evolving one eye, which is why I said I could buy it. You, of course, want to simply hide behind “similar forces, similar results” which is an argument that I have already addressed and destroyed. Thanks for playing, but it seems your claims of victory are extremely premature. I also note that you obviously didn’t read my argument against your position like a true ideologue. Next time, perhaps you will have the “humility and scientific attitude” to actually give your opponents enough respect to find out what they are saying before you stick your foot in your mouth and to actually address what they say, instead of hiding behind claims that have already been refuted.

  23. “First off, I knew about the chances of evolving one eye, which is why I said I could buy it.”

    Sure you did…that must be why you didn’t cite it.

    “You, of course, want to simply hide behind “similar forces, similar results” which is an argument that I have already addressed and destroyed.”

    And where was that? You haven’t so much as mentioned the words “similar forces” in this thread.

    “I also note that you obviously didn’t read my argument against your position like a true ideologue.”

    Thanks, since I’m not an idealogue, I’m glad I was fair to your position.


    Well, I just looked up the 1977 paper by Salvini-Plawen & Mayr which is the source of the alleged 40+ eye origination events claim.


    “Summing up the different and convergent sequences toward eye perfection in general, there are about 20 or even more independent lines of differentiation, including at least 15 case of independent attainments of photoreceptors with a distinct lens.” — p. 249, L.V. v Salvini-Plawen and E. Mayr, On the Evolution of Photoreceptors and Eyes. In: M.K. Hecht, W.C. Sterre and B. Wallace, Editors, Evolutionary Biology 10, Plenum, New York (1977), pp. 207–263.

    So we’re talking about more like 15 origins of complex camera eyes. The others in the 40+ category lack lenses.

    Look, I’m not trying to be mean, it’s just that you clearly didn’t do your homework *at all* before expounding about the downfall of evolution. Tell us, why should scientists take you seriously if you can’t get the basic biology right?

  24. professorsmith

    Yes, some random person from the internets comes here with an obvious bias shouting about how I obviously can’t know anything about biology because I disagree with it and I’m supposed to whimper in fear and kowtow to your obviously superior knowledge that you’ve demonstrated with bluster bordering on the obscene? Let this be your first warning Mr. Yu. Do not presume to put words in my mouth or decided what I do and what I don’t know based on what your expectations of what I write should be. If I don’t cite something, that doesn’t mean that I don’t know it. Second, I have dealt with your argument and if you weren’t so entrenched in your worldview you would have noticed it because it was a direct reply to you. Claiming that I have not supplied arguments when I clearly have is what got Mr. Darrell on my bad side.

  25. j a higginbotham

    How about a brief outline of how the probability of an eye forming is calculated? If you “knew about the chances of evolving one eye” then perhaps you could explain to me.

  26. professorsmith

    The argument, in short order, is that the camera eye required about 2000 mutations in order to reach the point it is at in humans. With the level of mutations per generation, the authors (if memory serves) calculated about 145,000 generations, which is within the timespan of human history. I think they over-simplified the process, but I don’t dispute that the changes that were specified in the paper are possible.

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