Help me understand this!

32


Discussion by: ElBeto

I've heard this question asked about evolution a few times, I don't know the answer, and I've come to RDF for an answer to it.

When we talk about Everyone knows that evolution occurs by 1) a process of random mutations being passed on to the next generations, followed by 2) a sorting out of the inadequate from the adaquate by the process of natural selection. It is known that favorable muations are the ones that allow an organism to survive and reproduce. If an organism has a mutation that is hinders it survival and reproduction, it will leave the animal weaker and ultimately eliminate the bearers of that mutation from the gene pool. 

The question i need answered is what happens to mutations that neither hinder an animals' ability to survive and thrive, nor confer upon it any competitive advantage? Are they somehow deleted? Suppose over many generations my offspring developed a small claw underneath the upper arm. It would be useless. They couldn't use it for finding food, finding a mate, or fighting off predators. But the fact that it is not stopping them from doing any of those things means it should be passed on through the generations, right?

The question is why when we look at highly developed animals do we not see a bunch of useless things alongside the many necessary ones? Wouldn't you think it would be easier to randomly mutate a "neutral" attribute than one that might actually be good for something.

Example: Wouldn't one expect horned animals to have developed maybe a small horn growing out of the back of it's head pointing the wrong direction before it recieved two pointing forward that allow it to charge enemies successfully? Maybe they just chewed on grass unassertively and ran like hell when trouble came around while carrying around a stupid looking and ineffectual horn prior to recieving "combat" horns?

It's a thought that has made me think and all my thinking has yielded nothing so I am asking some people who may know.

P.S. It's hard to ask these questions in day to day life and tough to find time to do my own research so this internet tool is very cool.

32 COMMENTS

  1. Well – even such a thing as an extra claw on the lower arm will not be completely “neutral” in terms of evolution:

    It takes xtra energy to grow and maintain – which is a (slight) disadvantage. Or it may get in the way of mating (extra claws and scratches during mating may not be appreciated…), which will may reduce repeat matings with the same partner. Something sticking out there may also be prone to injuries and thus infections.

    It may also be actually useful for something in which case it is an advantage. Sounds like it might help stop the owner from sliding down surfaces by providing grip.

    Whatever the (dis)advantage for the “initial mutant” (I’m sure there’s better phrase for that, but bear with me), the mutation will be expressed in different ratios in subsequent generations depending on whether the gene is dominant or recessive. There will be much less evolutional “pressure” for recessive genes than dominant genes.

    A truly random mutation should survive randomly – but it still has to compete for “room” in the gene with other mutations that occur. Even other random ones. If a different mutation in the same place in the gene happens to be an advantage, the “neural” mutation should eventually be out-competed by the “positive” mutation.

    The example of an a whole claw or extra horns sounds a bit contrived too – don’t these things evolve over time? I’m sure that e.g. horns didn’t suddenly spring into existence, but rather grew bigger over many generations….

  2. ” The question i need answered is what happens to mutations that neither hinder an animals’ ability to survive and thrive, nor confer upon it any competitive advantage “

    Mutations happen at the genetic level and an ” extra claw ” mutation seems rather unlikely. Mutations, insertion, deletions and the like, can be neutral. One hydrophobic type amino acid substituted for another type hydrophobic amino acid by some germ line mutation will be doing the same job and be invisible to selection.

    ” Example: Wouldn’t one expect horned animals to have developed maybe a small horn growing out of the back of it’s head pointing the wrong direction before it recieved two pointing forward that allow it to charge enemies successfully? “

    Hardly. Horns cost. and that would hardly be neutral in effect. Remember, populations evolve, individuals are selected. So, any ” horns ” as you describe would be selected out and never make it into the populational gene pool.

    Are you male? You have, seemingly, ( keeping it simple ) useless nipples. Invisible to natural selection and due to normal human development. That kind of thing escapes the notice of natural selection because od human sexual development and the low to no cost of superfluous nipples. Invisible to natural selection.

    I am sure other will chime in here also. Perhaps crookedshoes will see this and comment.

    • In reply to #2 by Neodarwinian:

      Are you male? You have, seemingly, ( keeping it simple ) useless nipples. Invisible to natural selection and due to normal human development. That kind of thing escapes the notice of natural selection because of human sexual development and the low to no cost of superfluous nipples. Invisible to natural selection.

      I think sometimes it is just simpler to keep the sexes the same or similar. I asked my doctor why evolution would make prostate glands so erogenous. His answer was that because the female analog was, and there was no pressing need to remove the feature in the male.

  3. @OP – The question i need answered is what happens to mutations that neither hinder an animals’ ability to survive and thrive, nor confer upon it any competitive advantage? Are they somehow deleted?

    There is always an energy cost to an organism in growing any feature, so unused features are are drain on resources which competitors do not have, thus such growth is a disadvantage.

    Genetic changes which cause such abnormalities would be selected against, and any mutations inhibiting their development would be selected for.

    An example of this is cave dwelling animals (fish etc) which have lost their eyes – having no use for them in the darkness of caves, but requiring resources to be put into growing them if offspring retain that feature. Any mutation disabling eye growth is therefore selected for in long-term darkness.

  4. Some mutations genuinely are neutral (or near to it), e.g. changes to a gene that don’t alter the protein it produces. Genuinely neutral mutations’ frequencies change in a random manner called genetic drift. However, even at the molecular level you might not get true neutrality. Slightly deleterious genes have a nonzero probability of becoming universal (this probability negatively correlates with population size); see here.

  5. The question i need answered is what happens to mutations that neither hinder an animals’ ability to survive and thrive, nor confer upon it any competitive advantage?

    Then it’s of no relevance to the mechanism of natural selection, at least unless its status changes over generations from neutral to either beneficial or disadvantageous. Other evolutionary mechanisms, such as genetic drift, will act on it. The most interesting consequence of neutral mutations is the concept of the genetic clock, which can be used to measure when two different lineages separated from each other. However, the theory is too complex to describe here in detail, so I suggest you read The Ancestor’s Tale for a good description of it.

    The question is why when we look at highly developed animals do we not see a bunch of useless things alongside the many necessary ones?

    Most neutral mutations aren’t expressed any higher than the cellular level, but they are probably more common than you realize either way. Humans alone can sometimes be born with extra ribs, extra fingers, longer digits, more crooked teeth, differently coloured eyes and hair, various ear shapes, tongue-rolling abilities, etc. These features are largely unimportant, though that’s not to say they could never come under natural selection.

    Among animals, there are melanistic leopards, polydactyly in horses, differently coloured furs among domestic cats and dogs, etc. I daresay further investigation would yield more, but it’s hard to say unless you actually look, since people tend to assume other animals all look the same compared with humans.

    Really, though, I don’t see the reason for the problem you’re experiencing. If it’s not relevant to natural selection, then by definition it’s at the mercy of things such as genetic drift, in which a gene can vanish or dominate a gene pool simply due to the draw of the genetic lottery generation after generation.

  6. Can I suggest being a little wary of posts by ElBeto. This is the second (the first was “Reproduction. Help me understand” on 17th June) and again has the feel of coming from the Creationist Book of Devastating Arguments. Reading both threads only makes this seem stronger. So, given that this might be an anti-evolutionist attempt to trip people up (“Look what the Richard Dawkins website said…”) can I suggest we exercise caution until we know more about ElBeto.

    That said, I’ll add a few things. Offspring would be very unlikely to develop a small claw under their arms for a number of reasons. (This is a dreadfully poor example, but rather typical of the creationist “crockaduck” type of argument.) Firstly, there is nothing in the region of the underarm that is likely to give rise to a mutation such as the beginning of a claw in any case – natural selection needs something to work on and mutations are minute changes in what is already there. Secondly, even if one did develop, it would ‘cost’ something in terms of energy to produce and maintain and thus be a disadvantage overall. Thirdly, since it would most likely be seen as a ‘freak’ occurrence by others of the species, it probably would have a distinct disadvantage to reproduction, because the creature with the claw under its arm might be less attractive to potential mates. In each of these cases, the mutation would not be neutral, it would be disadvantageous. But there might just conceivably be a use for a claw under the arm, in which case natural selection would tend to preserve it – but of course that would no longer be a neutral feature, either.

    I have a pair of toes on each foot that is partly webbed (about up to the first knuckle). They are the result of a neutral mutation passed to me by my mother, who has a similar feature. What happens is that our fingers and toes first emerge webbed (presumably following genetic instructions that go back to our amphibian ancestors – or even before that) but another genetic instruction separates the webbing before we are born. Clearly this did not work well in my case and it’s the result of an old mutation that has been passed down through my mother’s side of the family. That is a realistic case of a neutral mutation that is nevertheless observable. It will eventually die out as descendants who have the mutation interbreed with the much larger group that don’t. If my daughter carries the mutant gene, she doesn’t express it since she has no webbed toes. She has no children yet, so we can’t yet see if any of them will express it.

    • In reply to #6 by Pabmusic:

      Can I suggest being a little wary of posts by ElBeto. This is the second (the first was “Reproduction. Help me understand” on 17th June) and again has the feel of coming from the Creationist Book of Devastating Arguments. Reading both threads only makes this seem stronger. So, given that this mi…

      ” but another genetic instruction separates the webbing before we are born. Clearly this did not work well in my case “

      Sounds like apoptosis pooped out here!

      ” Can I suggest being a little wary of posts by ElBeto “

      Possibly so as the questions he asked are a bit ill posed. I have not heard from him before, and we are not hearing any protestations now.

      Do you have that former post of his to link to?

    • In reply to #6 by Pabmusic:

      Can I suggest being a little wary of posts by ElBeto. This is the second (the first was “Reproduction. Help me understand” on 17th June) and again has the feel of coming from the Creationist Book of Devastating Arguments.

      I have to say I agree with you. Looking at that old thread, this ElBeto doesn’t engage in the thread in anyway. Which means one of two things. One, they are simply trolling or two, someone on RD.net is having some fun with us. I’m more inclined to the former rather than later.

      ElBeto would also appear lazy. The Talk Orgins website has plenty of information on the subject of evolution and there are many books, one by the person whom this site is named after. I have no qualms answering genuine questions but what’s being asked by this person is fairly basic and easy to find the answers for.

      As to give a simple question to the answer. Your example of physical mutations, such as an extra claw or horn are not uncommon and happens on all species, including humans. In most cases these mutations are not harmful for the species, however no mutation that is not ‘useful’ will be maintained. In other words, the mutations you describe might pop up from time to time but will never be a part of that species as it isn’t a useful adaptation. It costs too much to keep such a mutation ‘just because’ so you typically will only have these physical mutations happening rarely. Even if the species with this mutation breeds it is only a possibility that the offspring will have the mutation as well.

      In most cases any extreme mutations often leads to an early death or not being desirable in mating. Which is why these mutations often don’t stick around. You need only look at humans and see the various genetic disorders around and often you find those with extreme disorders die early and those with undesirable effects typically don’t breed. Sorry to be harsh here.

      The last thing to understand is that you are a mutation. We carry the same information of the previous generation, just slightly different. This is the basis of evolution. We are all genetically modified versions of the previous generation and so on down the line. Richard Dawkins – The Magic of Reality shows this well. Maybe download the app?

  7. Apologies for some not taking your questions seriously. And also for a very long response. But this is a great question. It gets to the essence of what is life. There isn’t a short answer to that.

    An alternative example of how and why some genetically determined things are retained or not might be functional aspects rather than structural. There’s a lot more going on inside living organisms than it appears on the surface.

    You might be interested to acquire some understanding of how proteins operate in molecular biology. You don’t need to comprehend the details, just the general principles and scope and scale of what’s occurring over time.

    It didn’t make much sense to me at first because I found organic chemistry a bit dull during high school. Tended to focus on the industrial miracles of nylon etc. I ended up with a telecoms technology & economics background and years later I stumbled across a description of molecular cellular processes as operating at radio frequency. I’d probably been told this at school but it was meaningless until I’d studied radio tech.

    Everything these complex folded protein ‘nanobots’ or tiny molecular machines does inside a cell occurs at a very high clock rate. Plus there are billions of them interacting in an incredibly complex industrial economy where energy is the prevailing intra-cellular currency for every transaction. The amount of energy expended maintaining this level of complex operations is prodigious. So you can think of life as being the very most concentrated form of energy combined with information. Any molecular biology protein operations that don’t produce a positive return on investment, within a very high discount rate timeframe, aren’t highly valued in an ‘economics of life’ sense. So they would impose substantial and potentially detrimental opportunity costs on an organism, which would be likely to impede the cell’s survival in the long run.

    Environments are dynamic over time and living organisms have evolved mechanisms to suppress unused capabilities, and to eventually abandon these capabilities entirely. Over time this makes those organisms more efficient in their particular circumstances and environment, but at the expense of being less robust to the extent that those lost capabilities might possibly one day become useful again as the environment changes. Those capabilities might be needed more quickly than could possibly arise via normal evolutionary pressures. So the trade-off for abandoning currently unused capabilities is greater efficiency versus risk of extinction. The organisms that we see around today are the result of a positive selection bias. They tend to be the ones that are a little less than highly efficient, by retaining some redundant cellular processes and other bits and pieces, at the expense of not having yet gone extinct. Therefore you’d expect to see at least some useless functions retained.

    There are many more genetically dependent functional aspects of cellular molecular biology than the emergent macroscopic structural properties of organisms, like horns or appendages. These things are visually obvious so we rate them as being very important, but most of the complexity of life is invisibly microscopic inside the cell. The rest of life (e.g. our bodies, minds, communities, etc.) is essentially just a tiny bit of extra complexity to facilitate cellular or genetic replication of some particular cells, being our eggs.

    Genes specify proteins via a complex template and assembly process. Most proteins produced play a role in cellular processes and most gene-related activity is involved with maintaining this stock of proteins. There is a fine balance between maintaining sufficient operational proteins and the rate of damage and decay of those proteins. Making new proteins involves large numbers of other proteins in very complex process pathways with incredibly complex molecular protein machinery. This takes considerable energy, pretty much most of the energy an organism absorbs and expends. The essential functions of living organisms are the continual replication of proteins (because they are so tiny and fragile) and the continual process of acquiring resources to assemble these new proteins and to accumulate sufficient stores of energy to power all these processes. More superficially obvious things like locomotion, neural activity, and thermal stability also take energy, as does storing fibrous carbohydrates in structural form to provide the framework for plants. E.g. tree trunks, branches etc. – which can one day burn or turn to coal and later release those huge amounts of stored energy. Most protein-related energy is dissipated through the myriad of high frequency economics transactions of the cell. The energy is converted to heat, movement, and information complexity. We don’t normally appreciate how much energy is involved because we don’t tend to employ large organisms (other than dead or fossilised trees) as industrial energy sources. (Though we do exploit very long dead micro-organisms in the form of oil reserves.) But much of the purpose of eating other organisms for food is to acquire energy, along with nutrients, to fund the protein transactions of our cells.

    Life is mostly about the incessant replication of protein components exploiting available energy and nutrients – including available protein components like amino acids. Most living things assemble these protein subunits. But animals like humans also obtain many of those subunits ‘pre-fabricated’ as a side effect of routinely consuming other organisms for food energy. It’s expensive (costly in energy resources) to maintain the complex functional processes that produce all amino acids from scratch. Seeing as many are around for free anyway in our food, then the gene expression for some amino acid construction may become suppressed (to conserve energy) for those apparently seldom or never used processes. Eventually, after a very long time, genes which are hardly ever expressed might drift into dysfunction after they become damaged via copy errors and environmental disruption over many generations. So the genes (and associated capabilities) are lost to the organism’s descendants.

    Reproduction of the entire organism, along with its genetic code, is not only just a process of maintaining or increasing the population of an organism, it also plays a role in maintaining the structural integrity of the genes that control crucial physiological processes in organisms. The idea being that random damage impacting genes that would result in some significant process failing to function in the offspring would cause those offspring to die or fail to thrive to the point of reproduction. So only good copies of genes lead to successful offspring. It’s literally a chicken and egg situation where organisms are alive because they have good genes. But the only way to tell if genes are good is to use them to make an organism and see if they live and reproduce successfully. Genes that become damaged but which are not normally expressed don’t get filtered via this strategy of reproduction as a means of genetic data integrity validation. So those unused aspects of an organism’s internal processes become increasingly likely to be degraded or lost across many generational reproduction cycles.

    There are even processes within organisms that ensure there is a ‘reasonable’ extent of random copying errors – without which there could be no effective filtering and discarding of unnecessary (and otherwise potentially energy wasting) cellular processes.

    Wasting energy for an organism is not all that different from simply not having enough food. i.e. It’s just the other side of starvation risk. So there is a strong likelihood of organisms in their species history experiencing selection pressure that filters out ‘unnecessary’ attributes. But the process is haphazard. An organism may retain otherwise useless features that simply aren’t really a significant energy handicap.

    The introduction of changes to genes might be random at the individual level. But at the statistical level of a great many organisms reproducing across very many generations it is not random. It’s not purposeful or intentional either. That’s what’s special (and sometimes confusing) about life and evolution. It’s not even ‘increasing’ complexity either. It’s more about fluctuations in complexity across many generations. Generally you’d expect things to get more complex over time. But organisms could evolve to become simpler as well as more complex.

    As genes become disused and corrupt they aren’t usually expelled from the genome. The gene recording capacity of DNA molecules is enormous. And since life arose there hasn’t been much of an issue with running out of space yet. It’s like a library with virtually unlimited stack storage. You can’t easily get at the redundant information but it isn’t entirely discarded. Living things tend to leave at accumulated informational clutter in their genetic structure that depends on the path the organism has evolved along. Evidence of such disused genes can be derived from this clutter and can now be used to indicate very distant evolutionary pathways from many millions of years ago. So even this apparently useless information is of some value – though to another species very distant in time (i.e. modern humans) and may contribute to increasing the likelihood of our own species’ survival, despite our relatively high efficiency and complexity, and the associated risk of extinction.

    • In reply to #9 by Pete H:

      Apologies for some not taking your questions seriously. And also for a very long response. But this is a great question. It gets to the essence of what is life. There isn’t a short answer to that.

      An alternative example of how and why some genetically determined things are retained or not might be…

      ” Apologies for some not taking your questions seriously.”

      I do not need you to apologize for me and if you read the answers here you would have found that even those who are suspicious of this poster gave serious answers.

  8. In reply to #14 by Smill:

    In reply to post 13. I’m not sure male nipples are useless, actually. Don’t you hold onto your useless clutter at home, and isn’t that because one day it might become useful again? A bit like pseudogenes?

    Well, nothing is actually holding on to anything. Natural selection doesn’t think about this, nor does it make decisions. If as a fact there is no significant cost involved in producing and maintaining nipples, they will not disappear (unless something else acts on them – sexual selection, for instance).

  9. Something as distinctive as a claw is never going to evolve over many generations if it does not provide any advantage. The reason why features evolve over many generations into something that appears designed is that each tiny incremental change along that route bestows an advantage. That’s how it eventually gets honed into something distinctive that clearly serves a purpose, such as a claw.

    If something starting as, say, a small lump were to evolve by pure chance over many generations without bestowing either an advantage or disadvantage, it would not end up looking like something like a claw that ought to serve a purpose. There’s an infinite number of random shapes that evolution could produce through chance mutations. So to end up with a distinctive claw that never served a purpose really would be like a wind blowing through a junkyard and making a Boeing 747.

    Natural selection takes evolution on a road through the random chaos.

  10. It does theoretically happen all the time. it doesn’t lead to changes in phenotype but mutated genes that are no better or worse than their originators at replicating will spread through populations. so the idea of a new claw is not really to be considered because it will take a lot of specific mutations, and nature acting upon them to create something like a new claw so by definition it wouldn’t happen by random chance.

    The thing to consider is maybe very few mutations are advantageous or deleterous, they just happen, and get taken up and spread through populations. you could easily have a situation where two poulations of the same species arise where one has the mutation and the other doesn’t and there would be no difference between them. other mutations can accumulate with no real effect on the species, some might have an effect that leads to a phenotypic change that makes no difference, say eye colour.

    what matters is not the individual mutations so much as the selection, and that’s not genetic but environmental. it’s a bit of a red herring to say “genes for..” as it can suggest purpose that isn’t there. the purpose can be as random as the mutation, for example a gene might give its owner some resistance to a particular toxin that doesn’t exist in its environment, but environmental changes may lead to a change in flora so that that particular toxin becomes more common and makes it into the food chain. then the mutated population might survive while their otherwise identical cousins on the other side of the river all mysteriously die out. it’s only then that the random mutation can be considered an advantage.

    simlarly, a mutation that has no real effect other than eye colour, might suddenly become selected for in sexual selection. maybe the small group with purple eyes happen to also be very fit in other ways and that eye colour becomes an accidental indicator of fitness, increasing in the population until animals without purple eyes become disadvantaged by numbers.

    it’s important to think in terms of genes, not phenotypes. nowadays genes are related to phenotypes, in particular in how they’re named based on what happens if a specific gene is disabled in an organism, but that won’t give you the whole story of what that gene means to the population, or indeed how it first arose.

    genetic drift is the term used for when genes spread through populations without any evolutionary pressure, but it could be seen like rolling the dice for when pressure comes along in the future

    • In reply to #18 by SaganTheCat:

      It does theoretically happen all the time. it doesn’t lead to changes in phenotype but mutated genes that are no better or worse than their originators at replicating will spread through populations.

      . . .. . .then the mutated population might survive while their otherwise identical cousins on the other side of the river all mysteriously die out. it’s only then that the random mutation can be considered an advantage.

      An example of this in humans, is white skin in northern latitudes, where weak sunlight produces vitamin D, but this is blocked in these latitudes in those with black UV-blocking skin, which is better adapted to the tropics. The white skin of course burns more readily in the tropical sun.

      Likewise the mutant gene for red/ginger hair also creates a sensitivity to sunburn, so was originally prevalent in the cloudy wet areas of Scotland!

  11. To a mole that lives underground and is always in darkness, it’s own fur or skin color might be irrelevant to its ability to survive and reproduce. But over time a given breeding population’s fur color may change by a process called genetic drift, where by pure chance genes for darker or lighter fur (for instance), might become more dominant.

    I don’t know anything about the color of mole rats, and I made up the example as an illustration of a genetic mutation that is expressed in the organism without affecting its survival.

  12. In reply to #14 by Smill:

    In reply to post 13. I’m not sure male nipples are useless, actually. Don’t you hold onto your useless clutter at home, and isn’t that because one day it might become useful again? A bit like pseudogenes?

    ” You have, seemingly, ( keeping it simple ) useless nipples.”

    We could go into male lactation here and much more, but simple, though not too simple, is best here.

  13. In reply to #22 by Smill:

    In reply to Neodarwinian, post 21. Actually, I was hoping for a comment on ‘pseudogenes’ tacked onto the end. Just anything, anything you can explain to me at all. Fingers crossed. : )

    Example:

    Your vitamin C synthesis gene(s) is a pseudogene. A gene that became full of deleterious mutations because it became invisible to natural selection. We, that is our ancestors, started eating so much vitamin C laden fruit that when the usual mutations cropped up in the gene(s) here they were not weeded out by natural selection and they ( also called ghost genes ) are now just there is the genome of individuals. So, I don’t see them becoming useful again as the protein they code for is probably useless ( even if it was even read–doubt that transcription factors would have any interest in binding to a promoter region here ) and quickly cut into the constituent amino acids for reuse, though I am not sure of that last part.

  14. First thing that crossed my mind is that aesthetically non pleasing traits would be weeded out. As would non symmetrical traits. Of course as well as this at least with the vertebrates their is a blue print that can only be modified. A claw in the arm would probably be one mutation too far: )

  15. Well if they really are wanting to try for a soundbite…

    The question is why when we look at highly developed animals do we not see a bunch of useless things alongside the many necessary ones?

    You mean like appendices, earlobes, goosebumbs, third eyelids…

    Wouldn’t you think it would be easier to randomly mutate a “neutral” attribute than one that might actually be good for something.

    Yes. But when that happens the resulting beneficial organ from the neutral one just gets labelled by IDiots as ‘Irreducibly Complex’

  16. Sorry for being late to the party. However, please ponder the following.

    Why the hell can you roll your tongue? Does it confer survival? Do women go crazy for a man who can roll his tongue?

    What about your widow’s peak? Is it paramount to survival?

    My two index fingers curve apart when I hold them adjacent to one another. I also have hair on my mid fingers. Do they giva advantage?

    I have ear wax that is kind of sticky. there are people who have ear wax the is kind of dry. Anything here?

    Cross your arms like you are mad at a child. Now, reverse the one that is on top. Do the same thing by crossing your fingers like when you are playing “here’s the church, here’s the steeple.”…. These preferences are genetically underpinned and have absolutely NO bearing on survival nor do they represent a disadvantage.

    The fact is, we could sit here and do this all day. Human beings have a myriad of these neutral mutations. All species do. You just have to look at them and kind of think…. “now, what is totally trivial about this organism that is also controlled genetically?”

    • In reply to #26 by crookedshoes:

      Sorry for being late to the party. However, please ponder the following.

      Why the hell can you roll your tongue? Does it confer survival? Do women go crazy for a man who can roll his tongue?

      What about your widow’s peak? Is it paramount to survival?

      My two index fingers curve apart when I hold…

      About time!!

      By the way, nice list!

      • Thanks, I am out of synch as far as my computer time is concerned.

        Add to the list:

        free vs. attached earlobes

        dimples

        freckles

        hair on the top of your feet

        cleft chin

        etc….etc…etc….

        In reply to #27 by Neodarwinian:

        In reply to #26 by crookedshoes:

        Sorry for being late to the party. However, please ponder the following.

        Why the hell can you roll your tongue? Does it confer survival? Do women go crazy for a man who can roll his tongue?

        What about your widow’s peak? Is it paramount to survival?

        My two ind…

    • In reply to #28 by roxyrox:

      Transexuals might find male nipples handy.

      That would be an example of acclamation to the standard default sex in humans. Quite useful considering the circumstances though!

  17. If there is a God I’m going to do him for professional negligence as a designer, because the human body is a most negligent collection of patches, defects, failure modes and dead ends of any fuctional device…If you apply Sod’s law (90% of everything is crud) it should give an idea as to the level of background noise in natural selection!

    Your thinking hasn’t yeilded nothing, it’s lead you to investigate further. (Job 38:11 is written to oppose this sort of behaviour, of course…)

  18. Your question may have already been well answered, but I thought I might give my two cents too. Many mutations are neutral, and the truth is that many characteristics of organisms are likely non-adaptive. Such neutral mutations generally reach fixation in a population at a far slower rate than beneficial or deleterious mutations do. When such mutations do reach fixation it is likely due to genetic drift (random processes that eliminate diversity).
    On the other hand, growing unnecessary structures as in the examples given in the question would likely have negative fitness consequences. Claws and horns require, at least, an investment in energy to produce. However, the existence of vestigial structures (artefacts of ancestral structures no longer used) do suggest that if a structure is not necessary, but not highly related to survival or reproduction, than it can persist. Frankly, being ticklish, I wouldn’t mind having some defensive armpit claws.

  19. Remember that random mutation of genes is not intentional, there is no designer behind it with an understanding of “good” or “better”. It just mutates randomly without a plan. I would assume that if it does not hinder reproduction and survival in any way then it may or may not be manifested based on its dominance or recessiveness.

  20. “Wouldn’t one expect horned animals to have developed maybe a small horn growing out of the back of it’s head pointing the wrong direction before it received two pointing forward that allow it to charge enemies successfully?”
    One answer to this example is that the enemy is actually any other males of the same species with horns sticking out the front, not just predators. I don’t think the poor fella with the backward horn is going to win many dates, so his mutation will most likely disappear through lack of success with his females.

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