Natural Selection in one generation

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Discussion by: lukesinq

Is it possible for a mutation in a species to create a veeeery small advantage in just one generation?  For instance a mutation that makes a bird's beak slightly more curved in an advantages way, or maybe a mutation that makes some it's feathers just very slightly more colorful or something very small along those lines.  Because if not, then why would a new mutation have any increased chance of surviving natural selection if it didn't offer even the slightest advantage?

19 COMMENTS

  1. There are several answers to this, but I’ll give one. Mutations occur (sort of) randomly – in other words they do not occur in response to a need. Many mutations are bad for the organism, just a few are good, but many more are neutral – they don’t confer an advantage, nor a disadvantage. I have a pair of toes on each foot that are partly webbed – clearly, those toes didn’t separate as they should have done when I was in the womb. My mother has the same feature, so I suspect I inherited it from her. My daughter does not have it, but she may nevertheless have inherited the gene from me, even though it’s her mother’s ‘toe-separating’ instruction that has expressed in her. But she might pass on my instruction and not her mother’s if she has a child. So you can see that a mutation can persist for several (in fact, many) generations, without conferring an advantage or a disadvantage.

    But now imagine that the environment in which humans live changes over a long time, such that the mutation I carry now confers an evolutionary advantage (I can’t imagine what it might be, but this is a thought-experiment). Now humans who carry the webbed-toe instruction are at an advantage – and there might be many of them (a few dozen at least – maybe hundreds) because the mutation has probably been around for a long time.

    This is an example of evolution taking advantage of a pre-existing mutation, and your own example might be another. A slightly curved beak may be neutral as far as advantage is concerned until environmental change pulls it into the spotlight, by which time there are already a number of the mutations around.

    When our ancestors separated from the common ancestor with chimps, they were themselves ‘common ancestors’, not a different species. They just became physically separated (by the Great Rift Valley, probably) but they found themselves in an alien environment – few trees, long grass, different predators, etc. No doubt some of the group already carried mutations that were potentially useful in the new environment, but that had not been so useful before. The ability to stand up a little straighter or longer than others, for instance, would have given an advantage in spotting predators or game.

    None of this means that mutations do not continue to develop. But it does suggest that the usefulness of a particular mutation does not have to be when it first arises.

  2. I buy flowers every week ( day lilies, actually). Several blooms never open completely and are ugly in comparison to their fellow stem-mates. Whenever I see these inferior examples of the perfect blossom, I think of the mutations that are occurring all the time, in nature. This isn’t a rare event, but a regular feature when offspring of an organism are produced.

    It only takes an improvement in one particular feature of the plant/animal that makes it more likely to survive and have it’s genes passed on for that individual to be superior to it’s “rivals”. One such individual won’t change the entire species overnight, but generations with the particular modification will , and that group will be more successful.

  3. I don’t think it would. Without a context, advantage doesn’t really mean anything. If there’s no process that makes the trait (dis-)advantageous then “selection” is random. It might as well not be there, but it makes no difference if it hangs around. So it will persist by chance. If it’s only present in one organism and he gets hit by a bus before passing it down, it’s gone.

  4. I would respectfully disagree with a couple of the other replies. I think the answer to your question is a wholehearted YES! This is precisely how natural selection works: tiny mutations occur all the time and the vast majority prove to be largely neutral, but you specify that the curved beak in your example is advantageous, (by which I assume you mean that the bird will be able to survive better than its competition).

    “Surviving better” in the wild often translates as, “breeds more”, and of course some of its offspring will share the parent’s advantage so they, in their turn, will pass the newly “designed” beak on to their young.

    If the local environment is particularly harsh and difficult to survive in, I suspect the transition can be remarkably rapid. If not, however, you may have to wait for some seriously adverse conditions to weed the former shape out of the population.

    • In reply to #4 by Dom 2061:

      I would respectfully disagree with a couple of the other replies. I think the answer to your question is a wholehearted YES! This is precisely how natural selection works: tiny mutations occur all the time and the vast majority prove to be largely neutral, but you specify that the curved beak in your example is advantageous, (by which I assume you mean that the bird will be able to survive better than its competition).

      “Surviving better” in the wild often translates as, “breeds more”, and of course some of its offspring will share the parent’s advantage so they, in their turn, will pass the newly “designed” beak on to their young.

      If the local environment is particularly harsh and difficult to survive in, I suspect the transition can be remarkably rapid. If not, however, you may have to wait for some seriously adverse conditions to weed the former shape out of the population.

      Just to add to your comment – If there has been an extinction, or the habitat is a new or isolated island, the environmental opportunities for the change to benefit survival of offspring, can happen – presenting niches much more quickly than in an atmosphere of fierce competition, or of environmental stability. Even so itis unlikely to be as quick as one generation.

      An example would be Darwin’s finches in the Galapagos v their parental ancestors on the mainland.

      The other sources of very rapid speciation, is fertile hybrid polyploids where these are back-sterile so cannot breed with the parent stock,

    • Dom,
      My particular (molecular genetics) view of this question causes me to agree with you. At the molecular level, mutations are very very cool things to study. Due to a phenomenon dubbed “wobble”, many of them are, silent. However, without constant tiny changes there would be no plausible mechanism for bigger over- arching changes. I think your train of thought on this topic is the right way to go.
      crooked.

      Alan4, Great piggyback point.

      In reply to #4 by Dom 2061:

      I would respectfully disagree with a couple of the other replies. I think the answer to your question is a wholehearted YES! This is precisely how natural selection works: tiny mutations occur all the time and the vast majority prove to be largely neutral, but you specify that the curved beak in your example is advantageous, (by which I assume you mean that the bird will be able to survive better than its competition).

      “Surviving better” in the wild often translates as, “breeds more”, and of course some of its offspring will share the parent’s advantage so they, in their turn, will pass the newly “designed” beak on to their young.

      If the local environment is particularly harsh and difficult to survive in, I suspect the transition can be remarkably rapid. If not, however, you may have to wait for some seriously adverse conditions to weed the former shape out of the population.

  5. Probably not in the way you seem to be implying, i.e. across a whole species in one generation.

    Micro-evolution acts on individuals within a species, but only when it is considered collectively across a species, and across a large number of generations can its effects be discerned. Depending on the species this might be within a few years or decades (for bacteria), but for complex life forms it is likely to be centuries (at least) before changes can be detected in significant numbers of a species. Maintaining control and observation of a population (much less an entire species) and maintaining the level of measurement of a species’ attributes and characteristics is very difficult across extended time-scales. Claims by creationists that “if evolution happens why haven’t we observed it” completely overlooks this time-scale, that until very recently we haven’t known what we were looking for, or even how to look.

    Mutations are of three types, neutral (most frequently), beneficial, or harmful. Beneficial or harmful mutations give an advantage or disadvantage to an individual, but that individual may not pass on that advantage or disadvantage. The mutation just increases (or decreases) the probability that it is passed on, and it is the cumulative effect of micro-evolution across large time-scales that produces macro-evolution (new species).

    Creationists claim the while micro-evolution does exist, macro-evolution does not, and that they are two different things. This is a completely false distinction, the only difference between them is the time-scale

    Macro-evolution by Natural Selection has been observed, despite the claims of creationists, notably in the Lenski Affair, where an attempt by creationists to disprove evolution catastrophically backfired on them and gained a much wider audience than it would otherwise have had for a proof of evolution.

  6. If you want to understand Evolution, you have to understand Population genetics first. There are a lot of Mutations in every Generation (likely everey Individual has some). For example in every Generation are Birds with shorter or longer Beaks or with wider or smaller Beaks than the average, but most are around the average. So, let´s say, there is a Birdspecies on an Island living primary from the Seeds of one plant. The average Beak size of the Birds is ideal for opening these Seeds fast and with few energy. Now let´s assume, that the Wind blows some Seeds of a second Plant with bigger harder Seeds on the Island. Now, the Birds will still primary feed on the easier to crack Seeds of the primary Plant, so the newly arrived Plant can spread quickly because it´s Seeds don´t get eaten. Soon it will dominate the Fauna of the Island and the Birds will have to crack the harder Seeds of the new Plant or they will decline together with the older Plant. So, now the Birds with the Beaks, that are wider and therefore stronger than the Average get an advantage over the others, they can simply open the Seeds faster and therefore eat more Seeds than the Average. This means, they will have more offspring. This offspring will Carry their Genes for bigger beaks and the Average Beaksize of the next Generation ist bigger.
    So, some Genes for bigger Beaks were already in the Population bevore they were usefull, spreading by Coincidence, but staying in a low percentage. But with a slight Change in the Habitat they became superior an can spread very fast and so, the Birdspecies adapt within a few Generations to the Change in the Habitat.

  7. Oh, difference between natural selection and evolution. Natural selection happens all the time in one generationIf you’re a woman who hasn’t had kids before 35 or so, you’ve increased the odds of having a child with birth defects and you’re starting to get closer to menopause; you got selected out. You’re a man and wait too long, you start finding out that the allure of older men is greatly enhanced by wealth and power. Plus you’re more likely to produce offspring with defects; you’re selected out.

  8. Thanks guys. Some interesting stuff here.

    I want to rephrase my question: Just how big can one single mutation be?

    ….From some searching, I’ve found that it can create some diseases in one generation, but it’s surprisingly hard to find any more information than that. Maybe I’m just bad at google lol.

    • In reply to #13 by lukesinq:

      Thanks guys. Some interesting stuff here.

      I want to rephrase my question: Just how big can one single mutation be?

      ….From some searching, I’ve found that it can create some diseases in one generation, but it’s surprisingly hard to find any more information than that. Maybe I’m just bad at google lol.

      How big is a mutation? is an interesting question. I assume you mean one which has a big effect.

      The most noticeable effects are ones which make radical changes to their organism. I suppose the most radical, are ones which are disabling deformities or fatal.

      However, at a lesser level genes which affect the switching on or off of other genes during developments are quite radical in changing structures and appearance.

      Taking dogs as an example:-

      http://www.sciencedaily.com/releases/2010/08/100810203503.htm

      The researchers found that — in contrast to humans — many physical traits in dogs are determined by very few genetic regions. For example, a dog with version A of the “snout length” region may have a long, slender muzzle, while version B confers a more standard nose and C an abnormally short schnoz. And let’s say X, Y and Z in the “leg length” region bestow a range of heights from short to tall. That would mean that in this example an A/X dog would have a slender muzzle and short legs like a dachshund. C/Y might be a bulldog, while B/Z would be more like a Labrador. This mixing and matching of chunks of DNA is how breeders were able to come up with so many different breeds in a relatively short amount of time.

    • In reply to #13 by lukesinq:

      Thanks guys. Some interesting stuff here.

      I want to rephrase my question: Just how big can one single mutation be?

      ….From some searching, I’ve found that it can create some diseases in one generation, but it’s surprisingly hard to find any more information than that. Maybe I’m just bad at google lol.

      That´s because Mutations wich can already seen in the Phaenotype of the Individual in wich the Mutation occured (autosomal dominant and allosomal Mutations) are relatively rare. Look for Achondroplasia.

      • In reply to #15 by GerhardW:

        In reply to #13 by lukesinq:

        Thanks guys. Some interesting stuff here.

        I want to rephrase my question: Just how big can one single mutation be?

        ….From some searching, I’ve found that it can create some diseases in one generation, but it’s surprisingly hard to find any more information than that. Maybe I’m just bad at google lol.

        That´s because Mutations wich can already seen in the Phaenotype of the Individual in wich the Mutation occured (autosomal dominant and allosomal Mutations) are relatively rare. Look for Achondroplasia.

        Wow, that’s one heck of a mutation.

  9. Yes. For example, you know that Cuckoo birds lay their eggs in other birds’ nests, right? Let’s begin. Cuckoo bird eggs are famous for the large amount of variation in their colour and patterns. So it comes as no surprise that Cuckoos are also famous for the speed at which localised populations that move into a new territory quickly evolve egg colours and patterns that match those of the eggs of the host bird species. ( Note that I said ” that match ” and not ” to match “. See the crucial difference? There is no target, intelligence, or intent at work here. This is a key grammatical/conceptual point that even good evolutionists usually get wrong on TV and radio, and is an endless source of irritation to me and barrier to understanding to the public. But I digress. )

    The selection pressure is on a continuously sliding scale. Any non-matching Cuckoo eggs are identified by the host parents and removed from the nest – and the local Cuckoo gene pool – to die on the ground. The more the Cuckoo egg differs from those in the host nest, the less likely it is to survive to adulthood and reproduce. Those family lines unfortunate enough, by chance, to have severely non-matching eggs in the new territory will quickly die out ( perhaps producing no surviving eggs at all ), leaving only the matching and semi-matching eggs to grow to adulthood and produce matching and semi-matching eggs, again with some variation. And so it continues.

    In the case of the Cuckoo the change can happen extremely rapidly – like within a few generations or a few years. Do a google search on cuckoo egg evolution and be amazed.

    • In reply to #16 by Dave H:

      Yes. For example, you know that Cuckoo birds lay their eggs in other birds’ nests, right? Let’s begin. Cuckoo bird eggs are famous for the large amount of variation in their colour and patterns. So it comes as no surprise that Cuckoos are also famous for the speed at which localised populations that move into a new territory quickly evolve egg colours and patterns that match those of the eggs of the host bird species. ( Note that I said ” that match ” and not ” to match “. See the crucial difference? There is no target, intelligence, or intent at work here. This is a key grammatical/conceptual point that even good evolutionists usually get wrong on TV and radio, and is an endless source of irritation to me and barrier to understanding to the public. But I digress. )

      The selection pressure is on a continuously sliding scale. Any non-matching Cuckoo eggs are identified by the host parents and removed from the nest – and the local Cuckoo gene pool – to die on the ground. The more the Cuckoo egg differs from those in the host nest, the less likely it is to survive to adulthood and reproduce. Those family lines unfortunate enough, by chance, to have severely non-matching eggs in the new territory will quickly die out ( perhaps producing no surviving eggs at all ), leaving only the matching and semi-matching eggs to grow to adulthood and produce matching and semi-matching eggs, again with some variation. And so it continues.

      In the case of the Cuckoo the change can happen extremely rapidly – like within a few generations or a few years. Do a google search on cuckoo egg evolution and be amazed.

      Yea I’ve noticed those semantical problems while people talk about evolution. It’s takes a certain frame of mind to stay disciplined in your explanations so that people don’t misunderstand evolution as I actually did not even a year ago.

      And damn, them cuckoo birds are an interesting example lol.

      • In reply to #17 by lukesinq:

        Yea I’ve noticed those semantical problems while people talk about evolution. It’s takes a certain frame of mind to stay disciplined in your explanations so that people don’t misunderstand evolution as I actually did not even a year ago…

        As if to make my point again for me, Professor Cathy Ison, head of the National Reference Laboratory said on Radio 4 today: “This is a very clever bacteria that causes gonorrhea and it historically has always developed or acquired resistance to whichever antibiotic we’ve given it.” (BBC Radio 4 news interview, 23 April 2013.)

        No, bacteria are not clever! They are a breeding population of parasites whose members vary in their resistance to antibiotics, and when the antibiotic kills off 95% of the breeding population it leaves the remaining resistant 5% to breed, creating a next-generation population that is mostly resistant to antibiotics, again with some variation. There is no cleverness, foresight, intelligence, intent, target, goal, or purpose involved. Do these spokespeople have any idea of the damage that their silly statements and metaphors do to the public’s understanding of how evolution works?

        • In reply to #19 by Dave H:

          In reply to #17 by lukesinq:

          Yea I’ve noticed those semantical problems while people talk about evolution. It’s takes a certain frame of mind to stay disciplined in your explanations so that people don’t misunderstand evolution as I actually did not even a year ago…

          As if to make my point again…

          Yea, until recently I actually thought there was feedback system of some kind to evolution. Like some way a cat walking the forests would “know” that it needed to start adding camouflage so it wouldn’t get seen so easily. And then maybe some complex system between the brain to the skin/fur would start taking place. (That was my best guess anyways, and I didn’t bother actually looking for the real answer as that would cut into my recreational time). Luckily I took a bio class last semester which helped explain things.

          I can’t say for certain, but I would certainly hypothesize that the popular and misleading language of evolution had a big role in my misunderstanding.

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