Climbing Mount Improbable, p 199 (US edition)

Jan 19, 2016

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 (US edition)

  • I’m at some disadvantage on this one. I’ve read Selfish Gene and Ancestor’s Tale but I haven’t read Climbing Mount Improbable so I don’t have the luxury of reading the whole chapter that this paragraph comes from.

    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.

    So here we have the extreme selectionist viewpoint and the extreme anti-selectionist one too. There must be plenty of middle ground then. What would that look like? Would it be that under strong selective pressure, pigs with some kind of bare minimum anatomical structure – um, I don’t know, say, wide “arms” would be the only ones left after a near extinction bottleneck event? If the environment stays the same, would those wide arms continue to come in handy to stay alive and serve them well in the mating game and then favorable mutations could build up into a successful kluge of a wing perhaps? I mean, we’ve all seen some pretty bizarre anatomical kluges in ourself and our fellow life forms on this earth. I never fail to be amazed at this stuff so I’m going to say that if the selective pressures are strong and the pigs can squeeze through the bottleneck, then if the bare minimum structure is there then pigs will fly!

    So then, would it be true that if the selective pressure if fierce and there just isn’t time for natural selection to build that kluge anatomical structure, then we would have an extinction event most likely?

    This is exactly the kind of thread where I stand to learn more than I contribute. Let’s do this thing!



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  • This is a good article on the subject Laurie.

    So much would have to change in the pig with bits developing for multi purpose use. The question of “what use is half a wing’ does not take into account the use of the other half. If pigs developed the need to jump high in order to reach food then half a wing would make it jump just a little higher than without. Most things seem to taste like chicken but what if chicken tasted like pig?

    One thing that came into my mind from your writing is; what if the bottleneck were even narrower and only pigs survived a mass extinction. What animals would develop to fill the void and exploit resources? Chances of one becoming a flyer must be quite high.



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  • Hi LaurieB,

    I have read Climbing Mount Improbable, and you hit the nail on the head.

    Although we tend to think of genetic mutation as the raw material on which natural selection works this is not the full picture. The full picture is that evolution will also work on the existing bodies. The environment will favor some replicators and, by extension, their genetic variation. Giraffe necks are probably an example.

    Of course, if that genetic variation doesn’t exist then it can’t be created by the changing environment. But, as I understand it, most modern complex organisms exist today because they have developed flexibility to deal with relatively minor changes in their environment. This must, surely, be reflected in gene variation across each species.

    Genetic drift (changes in gene frequency in the population) and sexual selection might also play a part in evolving a species to be more resilient in the face of environmental change, by chance.

    In addition, modern evolutionary theory shows us that it is more likely that a species that fills an adjacent niche will evolve into a new species in order to fill a niche ‘vacated’ by an extinction, rather than that a species will evolve to continue to survive in its altered environment. More than 99% of species that have ever existed have gone extinct. That appears to indicate that rapid and/or significant environmental change is a species destroyer.

    Your example of ‘pigs could grow wings and replace bats – if bats disappear’ is obviously a stretch because the pigs’ environment is not a niche adjacent to that of most bats. Otherwise, the principle seems to me to hold.

    Also, as Olgun pointed out, a mass extinction would leave the opportunity for pigs to give rise to intermediate species that might then replace bats.

    Hopefully, somebody who really knows this will be annoyed enough by my ignorance to chime in and correct me.

    Peace.



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  • Stephen of W

    you hit the nail on the head.

    Miracles never cease! 😉

    Your example of ‘pigs could grow wings

    Not mine really. I’ts from the book paragraph. I’d rather have worked with yeast to chimps if I had the choice!

    Hopefully, somebody who really knows this will be annoyed enough by my ignorance to chime in and correct me.

    ha. My strategy as well. Thanks. L



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  • Alan4discussion

    Well Alan, all we have to do now is get those pigs onto an island and presto! Problem solved.

    From Wikipedia, the free encyclopedia:

    Insular dwarfism, a form of phyletic dwarfism,[1] is the process and condition of the reduction in size of large animals over a number of generations[a] when their population’s range is limited to a small environment, primarily islands. This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing. This process has occurred many times throughout evolutionary history, with examples including dinosaurs, like Europasaurus, and modern animals such as elephants and their relatives. This process, and other “island genetics” artifacts, can occur not only on traditional islands, but also in other situations where an ecosystem is isolated from external resources and breeding. This can include caves, desert oases, isolated valleys and isolated mountains (“sky islands”). Insular dwarfism is one aspect of the more general “island rule”, which posits that when mainland animals colonize islands, small species tend to evolve larger bodies, and large species tend to evolve smaller bodies.



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  • 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.

    This sounds like dualistic thinking. The evolution of wings was a complex process and not easily understood. Those who want a simplistic answer would come up with the idea that pigs would “sprout” wings.

    Consider the possibility that feathers may have evolved as a response to crepuscular feeding activity in small carnivorous dinosaurs. These small rapidly moving dinosaurs lived in an oxygen rich environment and fed at the most opportunistic time of the day (dawn and dusk) when small prey were most active.

    These dinosaurs did not “sprout” wings as a response to a “need.” That would be teleological thinking. Feathers first evolved as a thermoregulatory mechanism conserving heat in these poikilothermic dinosaurs. These feathers grew longer in the forelimbs by natural selection as a response to increased ability to catch rapidly moving prey. Thus the evolution of feathers was a preadaptation in the later development of wings.

    Pigs evolved from ancestral mammals that lived in a very different environment from that of small dinosaurs. To think of pigs “sprouting” wings is absurd.



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  • True. The first selective advantage was thermoregulation but later developed as a courtship display or possibly as cryptic coloration. It appears that the eventual evolution of wings was probably far more complex than first realized.



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  • cbrown

    To think of pigs “sprouting” wings is absurd.

    I think we all realize that this is absurd. I speculate that Richard knows it to be absurd too although I shouldn’t speak for him of course when he is perfectly capable of doing so himself. I really took this to be more of a thinking exercise more than anything.

    You have mentioned before that evo-bio is your field and that means that you should take this topic very seriously, as I can see that you do, but if you don’t like the “pigs” example, then perhaps you could help us out with a better one of your choosing.

    The reason I think that the pigs example is not serious whatsoever, and why I took a light tone in my comments here is because when I read the paragraph, the first thing I thought of was the saying “when pigs fly”. Here is the wiki explanation:

    Flying pig
    From Wikipedia, the free encyclopedia

    The phrase “when pigs fly” is an adynaton—a figure of speech so hyperbolic that it describes an impossibility. The implication of such a phrase is that the circumstances in question (the adynaton, and the circumstances to which the adynaton is being applied) will never occur.

    “When pigs fly” is an adynaton, a way of saying that something will never happen. The phrase is often used for humorous effect, to scoff at over-ambition. There are numerous variations on the theme; when an individual with a reputation for failure finally succeeds, onlookers may sarcastically claim to see a flying pig. (“Hey look! A flying pig!”) [1] Other variations on the phrase include “And pigs will fly,” this one in retort to an outlandish statement.

    This sounds like dualistic thinking

    Yes, but the paragraph states clearly that he is presenting the two “extreme” sides of this. I did not take that to mean that there is a dichotomy at work here. I am assuming that we are dealing with a range instead.

    Certainly you did not take the idea seriously that we ought to move pigs to an island and check back in several generations to see if any had grown wings, did you?

    Actually, I now think that the island would need to have high mountains and cliffs to accomplish the task at hand. 😉 And how will we get their bones to be hollowed out? Hmm…

    As I said, I don’t have that book here on my shelf but if someone else does have it then I’ll just bet that Richard has included some real life examples of our flying pigs story.



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  • 13
    maria melo says:

    Well I was just testing if I could post a vídeo, that´s why didn´t say nothing about it.
    That´s brilliant lecture, that´s all I ´ll have to say afteral.
    Other easy ways of understanding so difficult subjects are welcome.
    What Prof Dawkins in this piece of text, is writing about seems to be genetic variation among a species, I guess.

    (Now a book that would explain, genetic variation among for “dumbs” seems to be this one.
    Well, i don´t have such a great library, but it certainly seems interesting according to the way this books puts the subject
    I will Google translate almost entirely the resume of the book:

    emphasized text
    “For every 100 fertilized human embryos, about 70 die before 9 months! Of these, 35 died in the first 15 days of gestation, so even before the woman knows she is pregnant. How to explain this
    number? In 1858, Darwin used the term “Natural Selection” to refer to the competition for resources between living beings of the same species. Earn the most adapted, he wrote to say that the most suitable are those that leave more offspring to future generations. In this way a grown woman ready to breed is the evolution point of view, a success story. So how to explain that reproduction occurs with so much difficulty? Even in cases where pregnancy continues to the end and that mother and son / daughter leave unscathed those nine months, explain the enormous proportion of problem pregnancies, including cases of preeclampsia and eclampsia? In other words, why pregnancy is an obstacle to …
    reproduction … one of the essential components of the “fitness” in evolutionary theory?

    Because there are so many men and women? It certainly has to do with how the X and Y chromosomes combine … but what about other species that have different ways of defining gender, such as dust mites and
    wasps? And the pollution? Did you know that can save the lives of babies?

    In this book you will find answers to these and many other questions that reveal the impact of genetic conflicts in our dayly life .Sometimes, genetic conflicts are harmful, but without them, the pregnancy tests would not work just a few days after fertilization, babies wouldn´t be so chubby at birth, nor would we have a lid for every pot!”

    Link to the book “Uma Tampa para Cada Tacho” written by Francisco Dionísio,

    http://www.biologia-evolutiva.net/livros.html

    link to the author´s profile http://cba.fc.ul.pt/members/francisco_dionisio.php



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  • Not really, in such a case, this would not deserve the name “pig”.

    I consider Alan made a point when he mentions weight/size ratio and it is only one of many physical constraint this planet should stick to. So, it seems to me that not all imaginary creatures are possible here and now. Mutations rock… …as long as chemistry allows, as long as physics allows.

    On the other hand, I share the same strategy: love to be corrected.



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  • cbrown
    Jan 20, 2016 at 3:08 pm

    True. The first selective advantage was thermoregulation but later developed as a courtship display or possibly as cryptic coloration.

    Indeed! Investigative techniques have even revealed the colours of fossil dinosaur feathers.

    http://news.nationalgeographic.com/news/2010/01/100127-dinosaur-feathers-colors-nature/

    Found in the feathers of living birds, the nano-size packets of pigment—a hundred melanosomes can fit across a human hair—were first reported in fossil bird feathers in 2008.

    That year, Yale graduate student Jakob Vinther and colleagues, using a scanning electron microscope, discovered melanosomes in the dark bands of a hundred-million-year-old feather. In 2009 Vinther’s group went on to show that another fossilized feather would have been iridescent in a living bird, due to microscopic light-refracting surfaces created by stacked melanosomes.

    These earlier findings proved it was possible for melanosomes from dinosaur times to survive in fossils.

    But until now no one had found the pigments in dinosaurs—other than birds, which many paleontologists consider to be dinosaurs. And no one had used melanosome shape and density to infer color.



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  • **

    “For every 100 fertilized human embryos, about 70 die before 9 months!
    Of these, 35 died in the first 15 days of gestation, so even before
    the woman knows she is pregnant. How to explain this number?

    **

    Whatever the cause of failed pregnancies might be, there would be selection against that cause.



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  • cbrown
    Jan 21, 2016 at 1:06 pm.

    Whatever the cause of failed pregnancies might be, there would be selection against that cause.

    . . . . Unless the cause was to reduce wasted resources on unviable or low quality embryos, in which case it would just be natural selection in action, as with sperms which fail the fertilisation race.



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  • Whatever the cause of failed pregnancies might be, there would be selection against that cause.

    Not necessarily. If the cause is due to some genetic issue with the developing individual itself (and not an issue with the mother’s ability to carry an otherwise viable pregnancy to term), then yes, natural selection would tend to remove those particular genetic issues. But failures related to the parents may not affect all pregnancies, so genes that might cause future failures (of a similar kind) may still make it into successive generations.



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  • …if its fit for purpose

    Completely agree on that.

    Thanks for sharing this article. From now on, I’ll double check every zit appearing on my chin.

    Seriously, I still think that not every mutation is guaranteed to exist. Wings sprouting on actual pigs? it may be, it may be not. Not because we imagine them it does mean the required genes could be generated. ADN is not like Borges’ Babel Library which contain all posible books (even in infinite number of volumes) ADN should (as any other molecule) observe chemistry laws. On the other hand, mutation process depends on selection to succeed specially in largely different sequences involving a long chain of organisms. This implies that some gene combinations are out of the question of being generated solely by this ‘simple’ process we call life which rely on the minimum survival time to reproduce approach.

    If a more efficient mutation generator could be devised, and again, if physicis permits, may be a winged pig could exist and piss on my stupid face.



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  • 22
    maria melo says:

    I see someone may be as interested as me to know the answer 8at leat an attempt to explain) so I really bought the book yesterday and I am reading. Later on I´ll see the answer, but it mentions Ronald Fisher made an attempt to explain.



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  • Doug
    Jan 21, 2016 at 6:41 pm

    (and not an issue with the mother’s ability to carry an otherwise viable pregnancy to term)

    Even when genetically viable, it is well known that starving mothers in refugee camps, tend to spontaneously abort. – cutting losses in the potential failure.



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  • starving mothers

    What you describe is clearly “an issue with the mother’s ability to carry an otherwise viable pregnancy to term” (albeit environmental, not genetic). My point (in response to cbrown’s comment) is that this sort of cause of a failed pregnancy would not necessarily be “selected against”, particularly if that mother eventually successfully passed on her genes.



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  • 25
    maria melo says:

    To put the question in methaphoric terms (Wright was the father of mount improbable metaphor I read now in chapter 4), could a species trapped in a low peak of the mount go down against the driving force of natural selection and choose another higher peak and evolve in a different direction ? Flight and the eye have different peaks and co-evolved simoultaneously in different species insn´t it? R. A. Fisher and J.B.Haldane, Richard Dawkins mentions, have rebutted the idea that natural selection cannot be a driven force against “extreme perfection” (what does not pleases creationists who relay on perfection- without gradual escalation).
    So could pigs develop wings?
    I love this book specially . TGD mentions again this force argument against creationist´s argument of “perfection”, “that half a wing” in more useful than none (or the argument that evolution occurs in a gradual escalation, not at once with fully developed organs let´s say).



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  • maria melo
    Jan 23, 2016 at 7:48 am

    To put the question in methaphoric terms (Wright was the father of mount improbable metaphor I read now in chapter 4), could a species trapped in a low peak of the mount go down against the driving force of natural selection and choose another higher peak and evolve in a different direction ?

    The answer is no! It could not go against the forces of natural selection.

    What it could do, is be forced down BY the forces of natural selection (such as blind cave fish losing eyes) when the environment changes, and then climb a new peak as those forces change again – (such as re-emerging into the light).



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  • Too much mutated flappy skin on a pig who lives in damp conditions will soon die out. Change the conditions and it may survive if not for flying then getting rid of heat maybe? The three possibilities to promote flight, from what I have read, is climbing, jumping and moving fast. All could be for food or escape from predators. I think I misunderstood the question at the beginning in that I thought it asked if a pig could eventually turn into something else in order to fly not remain as the pigs we know and also fly. To have wings and not be able to get off the ground because you are just to big for the atmosphere is another way to get fungal infections and insect bites that turn lethal. so natural selection would deal with any potential pigs wanting to see the world from the clouds. As I said at he very beginning, a lot has to change for pig to fly.



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  • 28
    maria melo says:

    Day of misunderstandings

    “Bats are mammals that have developed wings so they can fly”

    One way to correct this mistake would be ending the sentence with: ‘because they could fly’. May not at first make sense, but first let’s see why the ‘for’ is wrong: it would be like saying that the ancestors of bats, which did not fly, have been developing flight characteristics in order to fly – ie a ” common will “of these ancestors in survival conditions favoring the flight, it would be necessary to get up this evolution. That’s not how we understand the process, in this example or anywhere else.

    The ability to evolve requires, first of all, the existence of individual differences (variations) that are hereditary. Just as it can not make omelets without eggs, so the evolution of organisms has no where to go without these variations exist from the outset. Then, these ancestors would have to include some individuals who, by the way of the finger and the existence of a membrane between them – nothing that resembles the highly modified toes current bats or with the membrane wing that extends from the toes to tail – had some ability to fly, or more likely, just glide. And with this new feature, however limited it might be, this minority survive better than others who did not have it, this would lead to:

    1 became increasingly frequent, generation after generation, individuals capable of flying at the expense of those without this ability, and
    2 to favored capacity if it were improving more and more, as they appeared new variations advantageous in features already acquired, as other innovations that have contributed to the flight of function: muscles of the back, lightness of bone, knee rotation out, rest upside down, etc
    . [1].

    That’s how you can tell who developed wings ‘because they could fly’: the process was gradual, with successive improvements, guided not by an early end, but simply by always improved ability to survive.”

    Paulo de Oliveira
    Department of Biology, University of Évora http://www.apbe.pt/nede/os-morcegos-sao-mamiferos-que-desenvolveram-asas-para-poderem-voar/

    Interesting and useful text I post above to clear the discussion about this paragraph, (Google translated).
    So, when “half a wing” becames more useful than none so that a species with no ancestors that could fly is trapped in ” half a way” of developing wings that will become increasingly more capable of flying is a methaphoric way of saying the species is going down it´s peak (but, of course, not a driving force against the force of natural selection, just that “half a wing” gives more advantage than none, and there is enough variation and pressure to it workout).



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  • 29
    maria melo says:

    Didn´t know this paragraph has been discussed on December 2015, but I assure you that I see this site almost daily for 8 years, how come?



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  • maria melo
    Jan 23, 2016 at 10:04 am

    just that “half a wing” gives more advantage than none, and there is enough variation and pressure to it

    An interesting example of the use of “half a wing”, is in flying fish!

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

    The Exocoetidae are a family of marine fish in the order Beloniformes of class Actinopterygii. Fish of this family are known as flying fish. About 64 species are grouped in seven to nine genera. Flying fish can make powerful, self-propelled leaps out of water into air, where their long, wing-like fins enable gliding flight for considerable distances above the water’s surface. This uncommon ability is a natural defense mechanism to evade predators.

    A little jump away from predators (as used by many fish), is good. – A bigger longer jump, is better!



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