Climbing Mount Improbable, p 199

Dec 7, 2015

“Now we come to a piece of genuine uncertainty and a spectrum of opinion among biologists. At one extreme are those who feel that we can take genetic variation more-or-less for granted. If the selection pressure exists, they feel, there will always be enough genetic variation to accommodate it. The trajectory of a lineage in evolutionary space will be, in practice, determined by the tussle among selection pressures alone. At the other extreme are those who feel that available genetic variation is the important consideration determining the direction of evolution. Some even go so far as to assign natural selection a minor, subsidiary role. To take our two biologists to the point of caricature, we might imagine them disagreeing on why pigs don’t have wings. The extreme selectionist says that pigs don’t have wings because it would not be an advantage for them to have wings. The extreme anti-selectionist says that pigs might benefit from having wings, but they can’t have them because there never were mutant wing stubs for natural selection to work upon.”

-Richard Dawkins, Climbing Mount Improbable, p 199 (US edition)


Discuss!

32 comments on “Climbing Mount Improbable, p 199

  • This is a wonderful question for debate. If there was only one Mount Improbable, with a well-defined fitness gradient everywhere (no local maxima), then I would tend to agree with the selectionists. Pigs with wings would correspond to some point on the slope that had been bypassed as ineffective. But perhaps there are local maxima and maybe pigs represent one of these. It’s possible that pigs-with-wings corresponds to a higher (fitter) spot but which is on the other side of a deep (unfit) valley and the genetic variation has, so far, been insufficient to get across that valley. Given the likely reality of a solution space something like the topography of the earth, it may simply be a matter of time. Eventually, a genetic “route” will exist that allows pigs to fly. In which case the answer to the question is somewhere between the two extreme viewpoints.

    But, wait a moment. What are bats? Couldn’t we claim that we already have flying pigs and that both our selectionist and our anti-selectionist are wrong?

    [It’s been a while since I read Climbing Mount Improbable. I hope I haven’t unwittingly plagiarized Richard here].



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  • 2
    zaphod42 says:

    I suppose another position would have to be, to have wings, an evolved pig would lose its front limbs. Which, in response to the first position, are actually “wing stubs” that evolved into legs. Our, human, wing stubs evolved into hands and arms. Evidently evolutionary pressure did not select wings for pigs or man.

    Were pigs to evolve to have wings, though, they would almost certainly no longer be pigs, but rather some new animal, descended from pigs.

    Just as humans are not monkeys, but rather an animal that evolved from a common ancestor.

    Where is the difference?



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  • Why don’t any animals have wheels? They would be very useful, don’t you think?

    My guess is that the truth is somewhere in between but leaning toward the anti-selectionists.

    The basic animal body plan is a stem with a head, four appendages and possibly a tail. Two of the appendages could become wings on pigs, if selection pressure were there, but there’s no way for them to become wheels because that deviates too much from the basic plan.



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  • In a multi-cellular animal how would you fuel, repair, remove waste and enervate fully rotating parts? What muscle configuration is possible? At single cell geometries its possible and rotating parts, though not wheels become propeller-functioning flagella..



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  • I’d be shocked if either ventured those opinions; they’re mixing 2 distinctly different genii. Birds evolved from the dinosaurs, an egg laying, hollow boned species which started out as glide-flight animals between trees, and later evolved into birds with proper wings. (The flying foxes of today are a leftover from that evolution). Whereas pigs are mammals; solid boned, internal breeding species. Mammals evolved rapidly after the demise of the large dino’s, but it was still millions of years before true speciation in the mammal world became visible.
    So, both statements are ridiculous. Evolution works favourably for whatever trait increases the chance of survival, food finding capabilities and amount of offspring, which translates into natural selection. As Richard stated in one of his books: “Evolution is blind”; there is no preset trajectory to follow.



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  • Pigs don’t have wings because they don’t climb trees or steep sided cliffs. If they did and the result of falling off these high places and surviving was due to who had some sort of flappy parts that broke their fall and where also a little lighter than others.



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  • Paul
    Dec 16, 2015 at 10:26 am

    (The flying foxes of today are a leftover from that evolution).

    There are four legged mammals such as gliding squirrels which show the possibility of mammalian quadrupeds other than bats evolving flight.
    http://video.nationalgeographic.com/video/weirdest-flying-squirrel

    Whereas pigs are mammals; solid boned, internal breeding species.

    You are right to pick out the heavy bones as a contra-indication, but perhaps the biggest handicap is the large size and weight of pigs.

    Even the well adapted structure of birds only works up to certain size limits.

    Some very small animals such spiderlings, do not even need wings in order to fly.



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  • I’m not a biologist, I was an English major, but as I understand it all RNA and DNA (and the genes within the DNA) on Earth is the same thing, whether it’s in a tree, or a bat, or a pig, or a home sapien. Therefore, I think we can say for a fact that in the early stages of the evolution of life on earth, the only differentiator between species must have been the differences in local environments entirely, because the earliest genes must have been very similar to one another. At this early stage, the selectionists would be entirely right. Then genes gradually became more complex codes, the complexity of the codes in and of themselves must have played an ever greater role in the selection of themselves, to the point that phenotypes could now create or at least drastically alter their environment which in turn of course would play upon the selection of genetic traits again. Thereby, the evolutionary process itself evolved into what it is today wherein there is a push and pull, symbiotic relationship between genes and environments that means both the selectionists and the anti-selectionists are correct to some extent. Of course, there are limits to what genes can do to environments and a limit to the amount of alleles that are possible for all of the extant species to express, which is why I think that while the selectionists were probably entirely right very early on in the history of life on earth there must now be a battle going on between selectionists (environmental pressures) and anti-selectionists (genetic limitations) pressures that will last until complex life is no more.



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  • Olgun
    Dec 16, 2015 at 10:36 am

    Here are some examples of skeletons of Bat wings and other forms of hand, showing the different dimensions and weight of the bones. .

    http://ngm.nationalgeographic.com/2012/05/hands/christie-art#/4
    A bat wing may look like a sheet of skin, but within its flesh are five fingers. The bones act something like tent poles, stretching out the membranous wing so that it can catch the air and lift the bat’s body. By adjusting each finger, a bat can dodge through a forest, hover in front of a flower to feed, or slip into the mouth of a cave.



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  • I think another answer is that natural selection and the solution space available tend to favour multi-function solutions that can be easily pressed into multiple tasks – locomotion, climbing, prehensile manipulation, aerofoil, touch/test, weapon/defense. Had somehow a wheel been possible, say of hard hydroxyapatite that simply wore away at its edge and bearing, it would be hugely limited in further evolution and died out in short measure. As it is the versatile three stage pattern of one bone, two bones, many bones is the swiss army knife of designoid templates

    https://en.wikipedia.org/wiki/Swiss_Army_knife



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  • While it might be advantageous for pigs to have wings, if the genetic material for wings is not available in the current species, if the environmental pressures are too great, this could lead to the extinction of pigs, as has happened for 99% of all species that came before. Adaptation in time to save species not possible = death.



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  • Exactly right! I can see it now.

    Hold the phone….

    This symbiotic life style might be the very stepping stone from prokaryotes to eukaryotes (seemingly a prokaryote with all the guts of other prokaryotes giving it super powers). Not invaginated but conjoined somehow and coequal until one back-evolved and was then invaginated.



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  • Please change your avatar phil. The last one looked like a sympathetic intelligent you when combined with your words. This one just looks like you are just taking the piss. 🙂



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  • The need for a trait is not enough To make it appear. Natural selection can’t jump over intermediate stages. Wings, for example, couldn’t evolve from legs unless each step in between conferred an advantage. Evolution can work much faster when a trait was present in an ancestor or in an earlier developmental phase, because the necessary genes are likely already present, and just need to be expressed differently. Evolution of a new feature “from scratch” would take much longer. If there was a very strong selective pressure that could only be overcome by the rapid development or a significant new phenotype, I agree with several other contributors that the result would be extinction.



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  • It would seem a combination of opportunities would have to be involved.

    Example: The human knee is not a great solution to what we use it for….if designing from scratch, we could have come up with something more robust, etc. So, just because something might give an advantage, the genes/mutations still need to allow it.

    If something that can “fly” a bit, say a flying squirrel, could fly “better” if its bones were hollow like a bird’s, or if it had feathers instead of fur, etc…its only going to GET those advantages if somewhere in its wiring, the connections are available/develop.

    I’d be pretty sure that the hollow bones were a development that saved weight…and that saving then allowed other things…such as speed, flight, etc.

    Same with feathers…they came first, then flight later on.

    If there was some sort of environment that changed slowly enough, and encouraged flight, whatever we now call a pig might end up the ancestor of a flying thing, like a bird, instead of a swimming thing, like a whale.

    They still need to follow the existing mechanisms though unless they get a good mutation that provides a new way to do something.

    Bats, squirrels, lizards, frogs, etc, go with a membrane between limbs/digits…to get surface area. They don’t get feathers, so far at least. The bones might get lighter, they might shed excess weight elsewhere, but hollowing of the bones wasn’t in the bag of tricks to pull out and use in addition to all that.

    So the environment has to encourage or discourage something, even if that is a status quo, for natural selection to do its magic. Then, the critter has to be ABLE TO change, so that the change can be selected for or against.

    An individual having a change is random, but the evolution of the species depends upon the change’s impact on subsequent generations.



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  • Sorry folks. I’ve tried three times to replace the pic and failed. Its hiding now in some place between my gmail account a google+ account and the rdnet account. I changed my sign in to try and avoid that wretched plea for money each time and got my jokey pic for personal emails. It is still me so consider how far you want to take the disturbing thing….

    These comments will make no sense when I get it sorted…



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  • Like a lot of things in nature, it’s not an “Either / Or” question. The likely answer is a spectrum of multiple variables. Something nature is fond of using. And the final results will depend on a multitude of factors, including the above two extremes, that vary depending on the conditions, the animal in question, and sometimes, whether a new mutation lives long enough to breed instead of being digested.

    Nature abhors a straight line.



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  • The trick is to use Chrome to sign in at least once and not Firefox. Others note.

    I still need to change the pic from aging TinTin.

    I may yet torment the lot of you for your temerity.

    Hmm, the blue works though…



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  • Maybe you’re being hacked by god.

    Nah! He wouldn’t dare, or he’d be demoted further from initiating principle of physics and poetical device to historical simple semantic error.

    Its a WordPress failure again that doesn’t update the RDnet account image (in my case a Gravatar) when electing for a google sign in with an image of its own. If I could be bothered I would change the gravatar at their site, but this is too much like hard work.

    Todays invention the aging Gravatar. App ages you artificially. Perhaps if it can have access to your social diary assessing the debauchery road miles, it can produce a Dorian Grey Gravatar. Perhaps tracking your facebook status too.

    I always liked Harry Potter inventiveness over science fiction inventiveness…



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  • phil rimmer
    Dec 16, 2015 at 1:23 pm

    Had somehow a wheel been possible, say of hard hydroxyapatite that simply wore away at its edge and bearing, it would be hugely limited in further evolution and died out in short measure.

    Even with highly specialised wheels, the wheel is a particularly poor means of transport in jungles, forests, swamps, rocky areas, sand, and even grassy plains.
    It is singularly useless off-road in wet conditions, and pretty poor at manoeuvring, when compared to legs!

    I am sure there are enough examples of attempts at off-road driving, which would illustrate this.
    Large vehicles bog down.
    Small model ones can’t even make it through tall grasses.



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  • Wheels for amputee dogs (and other critters) work, but only on smooth surfaces, with humans feeding them.

    gravatar

    May I be the first to say – “Dahling, you look mahvelous*”.



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  • Avatar looks great!!!

    A salt plains tortoise breaking land spread records with ultra-fast reactions picking insects from the air as it goes. It can pick up roadkill on the way back. 🙂



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  • Actually! Why are we looking at the past when we are making more and more roads for evolution to develop the wheeled animal. Australia with long roads that hardly anyone uses would be ideal for a wheeled marsupial travelling fast looking for road kill…….. 😉



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  • Maybe I won’t torment you with more avatars. Thanks, Olgun.

    We could re-invent RoadRunner…

    Perhaps we are being unimaginative about motive power. Rockets.

    One insect squirts hot steam/acid from some chemical reaction or maybe just explosive flatulence?



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  • 32
    fadeordraw says:

    1stly, the paragraph is poorly articulated. There is a distinction between the “enough genetic variation” and “available genetic variation” explained by the pig never evolving to fly because he didn’t need to or because he didn’t have the genes in the first place to do so. While noting that these aren’t contradictory propositions (the non-fly gene pig could somehow acquire the fly gene, in either case the process remains the same), there is, 2ndly, that the significance of the unclear distinction is itself unclear. Frankly, the paragraph, without further context, has me wondering about the pursuit of angels and pinheads.



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