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Science

How Predictable Is Evolution? 209

Posted by samzenpus
from the step-by-step dept.
sciencehabit (1205606) writes "If the clock rewound, would organisms evolve the same way they did before? Humble stick insects may hold the answer to that long-running question in biology. Through studies of these bugs, whose bodies match the leaves the insects live on, researchers have found that although groups of the bug have evolved similar appearances, they achieved that mostly via different changes in their DNA. 'I think it says that repeatability of evolution is very low,' says Andrew Hendry, an evolutionary biologist at McGill University in Montreal, Canada, who was not involved with the work."
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How Predictable Is Evolution?

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  • Repeatable as Fuck (Score:2, Interesting)

    by VortexCortex (1117377)

    Just look at how many times Eyes have independently evolved, yet they all have the same basic components.

    We put water, methane, CO2, etc. in a closed system, ran some simulated "lightning" through, and got amino acids and what not forming. Various experiments show similar (even more prominently supporting) results: Nature and physics shapes the beings that exist within it.

    There are plenty of other examples of evolution coming to similar results from different ends -- Just look at the shapes of sharks and w

    • by Your.Master (1088569) on Thursday May 15, 2014 @08:37PM (#47014237)

      This tells us that getting a sensor is repeatable. There are high-level design details of eyes that are divergent across species. The "blind spot" is a flaw in the eye design that is shared by all vertebrates, but cephalopods don't have it. Either it's very hard to mutate our way out of the flaw, or the flaw is by itself not important enough for the extraordinarily rare mutants who evolve their way past it to gain any ground on non-mutant populations.

      It's easy to think of that as an accident of fate, and eventually such accidents are bound to build up into going a different direction in response to strong selection pressures.

      I think sharks and dolphins is better than sharks and whales. That demonstrates convergent evolution -- but note that dolphins still have lungs, and sharks still have gills. They got to similar body plans but they are not fundamentally the same.

      • by cheater512 (783349) <nick@nickstallman.net> on Thursday May 15, 2014 @09:44PM (#47014603) Homepage

        Many people don't actually know they have blind spots so I'd say we don't need to fix it.

      • by agm (467017)

        This tells us that getting a sensor is repeatable. There are high-level design details of eyes that are divergent across species. The "blind spot" is a flaw in the eye design that is shared by all vertebrates, but cephalopods don't have it. Either it's very hard to mutate our way out of the flaw, or the flaw is by itself not important enough for the extraordinarily rare mutants who evolve their way past it to gain any ground on non-mutant populations.

        If an eye with no blind-spot somehow causes a person to be more likely to have offspring than a person with a blind-spotted eye then perhaps there would be selection pressure. Otherwise it won't make a bit of difference from an evolutionary point of view.

        • by Beck_Neard (3612467) on Thursday May 15, 2014 @11:49PM (#47015035)

          It's not that simple. Something like a blind spot can't just be evolved away. There needs to be a pathway from "has blind spot" to "doesn't have blind spot" that doesn't go through "vastly decreased eyesight" along the way. Otherwise evolution will stick with what it has, and no amount of selection pressure can cause it to change.

          We're vastly suboptimal in many ways. We're not perfectly tuned machines, we're cobbled-together from evolutionary scraps, and you can see it by looking at any part of our physiology. That's precisely the thing that makes intelligent design a stupid idea. Yet, we "work", and are capable of survival, and that's enough.

          • by tsa (15680)

            There are people who say that each organism is 'perfectly adapted' to its environment. I never understood them because you don't even have to look hard to find out that that is not true. Besides, if they were they would be extinct as soon as their environment changed only the tiniest bit.

            • There are many many species that fit in that exact category.

              As soon as their environment changes in the slightest, they go extinct.

              Perhaps they are end nodes of more adaptable species or perhaps they thrive by being perfectly adapted and crowd out those less perfectly adapted. But when things change, they die.

              • To be fair, though, it's possible to be perfectly adapted to your environment but also well-adapted to other environments (not that any creature is). It's also possible to be only slightly adapted to your environment but even less adapted to any other environment. Indeed, it's also possible to be well-adapted to your environment and to go extinct through just pure chance, without your environment changing at all. Darwin actually talked about that in The Origin of Species. A tree might produce hundreds of th

                • absolutely.

                  But don't overrate us. Even without humans, most species would go extinct. Just much slower. And I mean really slowly. Humans seem equivalent to a major natural disaster like an asteroid strike.

                  • by tsa (15680)

                    Yep. That's why in my opinion the efforts to save the giant panda are a waste of money and energy. The beast is at a dead end of evolution and deserved to go extinct ASAP.

                    Death to all pandas! ;)

                    Oh,and koalas. Also a useless and overrated species.

            • by invid (163714)
              The word "perfect" is meaningless outside of mathematics.
          • There needs to be a pathway from "has blind spot" to "doesn't have blind spot" that doesn't go through "vastly decreased eyesight" along the way.

            We're vastly suboptimal in many ways.

            c.f. the recurrent laryngeal nerve [wikipedia.org]. 4.5m longer than it needs to be in the giraffe, but it can't "evolve" its way to a different path.

          • yup, evolution implements the big ball of mud architectural pattern. http://www.laputan.org/mud/mud... [laputan.org]
      • Though it might not be a flaw. As Nick Lane points out, evolution is cleverer that you are. For example, the nerves that cross the front of the retina could have evolved to act as wave guides improving vision, not making it worse compared to say, the eye of an octopus which is "correct" as you might design it.
    • by Anonymous Coward

      You misinterpret the question.

      It was not "would the end results have similar function", but "would the function be achieved the same way".

      It is repeatable as any random process (i.e at the detailed level it's not).

      Look at your own examples. All of those eyes are different, and whales/sharks have some fundamental differences (the main propulsion being the most obvious)

    • by rubycodez (864176) on Thursday May 15, 2014 @08:40PM (#47014255)

      you are silly, vast differences in eyes in the animal kingdom. the spookfish eye has a side chamber with mirrors and a second retina, and works like a reflecting telescope. The Tarsier can't even move its eyes in the sockets, has to turn its head, besides night vision can see in ultraviolet but can't see color. The collosal squid has a built-in headlight, a photophore, in each eye to illuminate what it is focusing on, the dragonfly has 30,000 eyes that can see polarization of light as well as ultraviolet let, and moreover has 3 additional eyes of another type that are hypersensitive to extremely fast movements a human can't perceive. How about four-eyed fish with eyes to see in air and another pair for water?

      • by gewalker (57809)

        Don't forget lobster eyes, very cool design - lots of square mirror boxes. They are even planning an x-ray analog of them at Nasa [nasa.gov]
        And the lowly scallop has a very nice set up to about 100 reflectors 1 mm in size.

        • by rubycodez (864176) on Thursday May 15, 2014 @09:36PM (#47014575)

          also could have mentioned some bird's eyes that can see the earth's magnetic field; and goats with their horizontal rectangular pupils, which combined with the eyes position on the skull gives them a 340 degree field of vision without even having to move their eye. they can see you coming up behind them!

          • by Camael (1048726)

            I have to say as a complete layman that I find this whole discussion fascinating. I had no idea there was such a wide variety of eyes in this world.

            Which makes me wonder though why we haven't actually been seeing any/many inventions making use of these principles to augment our own vision. For example, I can see that a physical analog for the goat's vision may have some application in the field of law enforcement, or vehicle HUDs or anything for that matter where a larger field of vision would be an advant

            • by dargaud (518470)

              Which makes me wonder though why we haven't actually been seeing any/many inventions making use of these principles to augment our own vision. For example, I can see that a physical analog for the goat's vision may have some application in the field of law enforcement, or vehicle HUDs or anything for that matter where a larger field of vision would be an advantage.

              ...It's called a side mirror in your car !

          • by tsa (15680)

            My rabbits have that too and they have round pupils. They can even see you coming from above.

          • by nbritton (823086)

            also could have mentioned some bird's eyes that can see the earth's magnetic field

            Why does everyone overlook the fact that the eye is a device that leverages quantum mechanics? The simple fact that we can observe the electromagnetic spectrum is proof of this. By extension, it would be reasonable to conclude that the brain also leverages quantum mechanics.

      • The tarsier and 4 eye fish are remarkbaly cool, but they are variations on the vertebrate eye, which means they're much more similar even to each other than the various types of invertebrate eye. The interesting thing of course is that the various ranched all evolved eyes from very different starting points.

        Also if you want awesome eyes, look at the the mantis shrimp. Hyper spectral, polarisation sensitive and capable of independent depth perception (trinocular, not binocular like us mere vertebrates) with

    • by Bite The Pillow (3087109) on Thursday May 15, 2014 @08:50PM (#47014301)

      The key question is whether the same results would come from different ends, again.

      And the key evidence is that parallel evolution uses different changes from different genes to achieve the same end.

      The question that I have to ask is, if different changes result in the same end, can the follow-on changes result? Or are they stopped?

      Flippers turn into hands, but using different gene combinations - does that stop the thumb from differentiating? Or would evolutionary pressure still reward the mutant with the thumb?

      I haven't read the whole thing, but I'm not swayed on any part of the question other than someone is now thinking about this. It is far from the foregone conclusion you think it is. In fact, in your statements, it stops at the interesting point. Will eyeballs that evolved differently be able to further evolve in similar ways? Or are they forever doomed, due to their makeup of different proteins, to be different? Or is it somewhere in the middle, which sounds plausible pending further research?

      • by plover (150551) on Thursday May 15, 2014 @09:12PM (#47014433) Homepage Journal

        I think the answer is self-evident: alternate reality results would be just as diverse as species are today, and while they would bear superficially similar results, they would be "different animals." Commenters above have noted that vastly diverse organisms in a common environment still successfully evolve common features: they may have similar means of locomotion, means of food detection, means of sexual partner selection, and on and on, yet the specifics for any given species will be completely different from the other species.

        Would the appearance of an opposable thumb on a flipper cause the lengthening of the appendage into something more useful, like an arm? Maybe, because arms are a useful advantage for food gathering; or maybe not because arms aren't as hydrodynamic as flippers. Or maybe there'd be a fork with two successful species resulting. I don't think the follow on changes would stop, they just would be different changes.

        But as to the original article, why would anyone think that if we rewound the clock that a chaotic process would repeat? It's not like the universe called rand() with a common seed when it started mutating DNA.

        • But as to the original article, why would anyone think that if we rewound the clock that a chaotic process would repeat? It's not like the universe called rand() with a common seed when it started mutating DNA.

          It's a valid question, when looking to the simplest organisms such a viruses or bacteria you can observe repetition of specific adaptations when under the same environmental pressures (up to a certain point). You neutralize several strains with monoclonal antibodies or a compound against a specific protein and the escape mutants frequently show the same changes. The question is "how much of this is conserved in more complicated organisms?" It would not be the first time that an apparently chaotic process wa

        • Forgive me for trying to boil this down into more simplistic terms to understand the concept:-

          So what you're saying is that just because 2 different drivers drove from Town 1 to Town 2 (similar results), it does not necessarily mean that they took the same route. Driver A had to buy groceries, pick up his daughter, visit the video store so he drove a certain route. Driver B had to top up his gas, return a library book and buy dinner so he took a different route (evolutionary pressures). But both of them end

          • by Sique (173459)
            Actually no. Because both drivers had to use their respective route again if they drive again from Town 1 to Town 2. After some generations you would have two different tribes of drivers, one that drives along the grocery store and the kindergarden, the other one via the gas station and the library. And if the video store closes, some drivers of the first tribe cease to drive at all because it doesn't make sense to them anymore while the new hardware store causes other drivers of the first tribe to morph in
          • by plover (150551)

            That's not really a good analogy, because your drivers have "goals", and evolution doesn't drive towards goals. It selects for adaptations that work better in the organism's environment.

            Driver A isn't trying to get to Town 2. Driver A simply is trying to survive. Now, if your Driver A randomly developed a vision mutation that caused him to identify grocery store signs, that's a beneficial survival trait in his environment - he'll be big and healthy and not starving, which might make him a more successful

    • by gmuslera (3436)
      Not taking into account interaction between random changes in different species. Change is random, but natural selection is not, if your random changes make you survive and breed, they may remain enough time to become evolution of your species. But if a random change in a prey (or a predator) turns into viable a random change in a predator (or viceversa) then you could get something new, same for environmental changes. Is not a butterfly effect, but is enough to not make very predictable the course of evolu
    • by Agent0013 (828350)
      Sharks and whales are interesting in that they look similar, but are quite different. One breaths air while the other has gills to breath water. Also, the whales have a horizontal tail-fin and their propulsion motion is an up and down wave while the sharks are based on a fish body plan with a vertical tail-fin and their propulsion motion is a side to side wave.
  • by perpenso (1613749) on Thursday May 15, 2014 @08:35PM (#47014227)
    Convergent evolution suggests it is somewhat predictable, unrelated species having evolved similar solutions to similar problems. If a solution is clearly better nature will tend to go there given sufficient time and experimentation (mutation).

    The fact that a trait may be expressed by different DNA sequences doesn't really seem to undermine this. The DNA sequences are implementation details. Evolution is about solutions and environments not DNA sequences.
    • by Anonymous Coward

      The fact that you have widely different 'implementation details' solving similar problems suggests that it's NOT as deterministic a process as your'e suggesting.

      Nature exerts a strong evolutionary pressure on animals that can *sense the environment around them.* One good way of sensing the environment around you is a complex "camera eye" - but there are many ways of implementing this in multiple organisms, which means that minute variations in environment can have a large effect on evolutionary outcomes.

      If

      • by perpenso (1613749)
        Who said it is a deterministic process? Evolution is based on random mutations. All that is being suggested in that given a large number of experiments a more optimal solution tends to be found, if one exists. That similar environments can independently converge (discover) upon such a solution. Its not unlike multiple independent runs of a Monte Carlo simulation finding the same maxima.
      • by Tablizer (95088)

        One good way of sensing the environment around you is a complex "camera eye" - but there are many ways of implementing this in multiple organisms

        I wonder if an insect-like compound eye is competitive at a larger scale. It seems to me it may be more damage-resistant in that it fails incrementally (spots), where-as a single-chamber design like ours can be taken out of commission if just one part fails.

        Well, we do have 2 eyes such that we have 1 spare, but we lose stereo sensing if one goes out. In compound e

    • Re: (Score:3, Insightful)

      by richtopia (924742)
      Convergent evolution also depends on how you define two features similar. For example, the convergent evolution of oxygen carrying blood in Cephalopods could be a counter example to the prediction argument, as their blood has oxygen bind to copper.

      So both bloods were evolved to perform the same task of moving oxygen, however they use two different mechanisms to perform the task.
    • by Sockatume (732728)

      I think in this situation, by "is evolution predictable" they mean "is evolution reasonably deterministic with respect to creating a given set of genetic code given a set of starting code and a certain environment".

      The answer is "no".

  • It depends... (Score:5, Interesting)

    by radtea (464814) on Thursday May 15, 2014 @08:38PM (#47014243)

    The degree of molecular similarity in the DNA changes to achieve a particular result will depend strongly on the type of change one is looking at.

    For the case of toxin-resistance, which is much closer to the molecular level, the odds of similar changes to the DNA are much higher than for complex morphological changes.

    Molecular changes like toxin-resistance are more likely to involve a single gene that codes for a single enzyme, changing the enzyme so that the toxin is no longer metabolized in a harmful way. There are going to be a very limited number of ways to do this because it's pretty close to a one-gene/one-enzyme mapping in many cases.

    Morphological changes, on the other hand, involve a whole network of genes that are turned on over the course of development, and the network can be altered in many different ways to get to the same result. Think about it like a road network where you're used to taking a particular route to get from A to B. If a bridge goes out on your your usual route, you may choose different alternatives depending on time of day, the kind of vehicle you drive, etc. Networks create choices.

    Even then it will depend on the kind of morphological change we are talking about.

    For example, there is a lizard in Mexico, which was studied in the '80's or '90s. There were several related species living inland, and a couple of isolated species on the coast near the Yucatan peninsula. Both the coastal species had an extra cervical (neck) vertebra, and it had been assumed on the basis of this similar morphology that their evolutionary history had been a general migration to the coast, an adaptation to coastal environments that involved having a longer neck, followed by a general die-back that resulted in the two existing but separate populations.

    It turns out based on their genes the two coastal species hadn't had a common ancestor for millions or tens of millions of years, and the adaptation to coastal living had happened independently but fairly recently. In this case, because certain aspects of body plan are controlled by a highly conserved and relatively simple set of genes, the additional vertebra were the result of similar sets of genetic changes.

    Things like body width, which is what TFA is talking about, are a lot more complicated in their regulation, so more likely to be achieved via different genetic changes that have the same morphological outcome.

    I'm going to throw in a shameless plug here because it seems relevant to the topic at hand. I've just published a hard SF novel that's premised on a what-if about the role of mathematics and law-like descriptions in evolution. If you're interested in that sort of thing you should check it out: http://www.amazon.com/Darwins-... [amazon.com]

    • by wattersa (629338)

      Is your book available in print form? I only see the kindle edition. Also, it would be great if you could put your email address on your profile so I don't have to reply to your comment in order to contact you :P

  • What? (Score:5, Interesting)

    by DarwinSurvivor (1752106) on Thursday May 15, 2014 @08:38PM (#47014245)

    If I'm reading this wrong, and I hope I am, please let me know.

    ...researchers have found that although groups of the bug have evolved similar appearances, they achieved that mostly via different changes in their DNA. 'I think it says that repeatability of evolution is very low...

    I read this as "Stick bugs have reached similar appearances through different means thus the same change probably won't make the same result".

    Is this equivalent to "People can change their appearance to include a hole in the abdomen through different means (bullets and knives). Thus shooting or stabbing people are unlikely to produce holes in people"?

    It may make it more difficult to guess which DNA change caused them to look like that (without an actual DNA test), but it in no way implies that those DNA changes won't necessarily cause them to look like that.

    • Because there are multiple paths to the same result, "selecting for the same result" is not guaranteed to follow a specific path.

      That is, if evolution is driven by random mutation, where the selection of a particular path is a random result.

      • So they are saying the path (mutations) may be different even if we got the same result. Makes much more sense.

        • To be a little more precise, we don't have the same result - we have different results with the same effects.
    • Yes you are reading that wrong. What they are saying is that since you can end up with similar looking creatures that took different DNA routes to get there, it's only the results that matter and not the DNA framework.

      If you can end up with the same body style with different DNA then if you rewind the clock and started over there would be no reason to believe that you would end up with the same creatures we have today.

      • The summary was a little confusing. When they said "wound the clock back", I thought they were talking about re-implementing the same mutations and expecting a different result, not animals conforming to similar situations via different mutations.

    • Re:What? (Score:4, Insightful)

      by Anonymous Coward on Thursday May 15, 2014 @10:17PM (#47014715)

      no, a better example is - we handed the spec to a bunch of different developers...

      They each gave us wildly different code to achieve the same goal.

      If we give the same specs to other developers, we expect the same result. That the code will be wildly different each time for the same goal - so we can't predict what it will look like.

      • Ok, I think I get it now. So they're not saying we probably wouldn't end up with animals that look like they do today, but that we would likely end up with the same looking animals with different DNA than we have now. That actually makes a lot more sense.

      • Now, we watch all the original developers quit, and we hire more developers to deal with changed specs. What they do is likely to depend heavily on which version of the code we give them. If the specs are more like "Make the code do this general thing", we're likely to wind up with different-looking solutions.

  • There are humans similar to us on other Earth type planets. Dinosaurs too. Maybe even some sentient avians and aquatics?
  • by manu0601 (2221348) on Thursday May 15, 2014 @09:02PM (#47014369)

    Looking at cows, dolphins and horses genetic proximity [ucsc.edu] shows unexpected results, as cows and horses are not the closer in the trio, despite their similar features.

    That suggests environment drives evolution in a predictable way, while the genetic evolution is not. This is the really amazing point: evolution find similar solutions to similar problems, but it does so through different ways.

    • by rubycodez (864176)

      oh? what about aquatic animals(and mammals at that!) that used to be land animals, that went back to the sea?

    • This is the really amazing point: evolution find similar solutions to similar problems, but it does so through different ways.

      This is a common problem when talking about evolution. We can't help invoking metaphors of "design," even if we don't mean it -- and that clouds our understanding.

      Evolution is not "finding" anything. It is not a conscious process. If we truly believe that evolution works through random genetic mutation, that it is simply a matter of randomness and survival of random things that fit the environment better.

      If I program a robot to randomly drive around a maze, it will eventually get to the end over a lo

      • by manu0601 (2221348)

        I could say that evolution finds solution to environmental challenges like water finds the way out of a bucket.

        But let me rephrase what I find amazing : evolution leads to the same solutions for the same environmental challenges, but through different genetic setups. That suggests the optimum is always reached. This is amazing.

  • Burgess Shale (Score:3, Interesting)

    by Kittenman (971447) on Thursday May 15, 2014 @09:24PM (#47014501)
    Refer to Stephen Jay Gould and his "Wonderful Life" http://en.wikipedia.org/wiki/B... [wikipedia.org] also. Gould mentions that there were a range of various paleobiological doohickeys bopping around at the same time, and we come from one group that happened to swim better, or whatever. Next time round, we'll have five eyes.

    Well, I'm not explaining it right, but that's why there's books...
  • We need to see how things evolved on other worlds, evolving entirely independently of the life forms on this planet, which may have in some way influenced eachother, in order to even begin to gauge how predictable evolution is.
  • We know precious little about how evolution proceeded here, and we know nothing at all about how it might have proceeded elsewhere.

    We can guess that it would be carbon based, because carbon has four covalent bonds and would have been formed sooner than silicon (with 4 bonds, but lower energies) would have. Beyond that, we'd need a few dozen D20 dice to calculate the odds.

    But any real scientist knows that at some point, we have to admit WE DON'T KNOW how it might turn out. Wild-assed guesses aren't science

  • the one who is better adapted will always win. That's as predictable as it gets. Everything else is just variations on the theme.

    • by iggymanz (596061)

      no, the only criteria is survival to reproduce. "fittest" and "better adapted" have nothing to do with anything. good enough wins

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