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Featured Difficulty understanding evolution

  1. Nov 30, 2016 #1
    Hi

    I am and athiest and I believe on evolution, but there is an aspect of it that I cant get to grips with. We know evolution doesnt have a concious mind and that it is the natural blind process of survival of the fittest, based on mutations over generations that are useful to the species etc.
    The problem I have is if the human body was able to mutate, without any design at all, completely mindless mutations, why is it that our arms dont have big lumps all over them or, our ribcage have random points sticking out of each one, or an extra toe poking out the side of our foot. What I cant understand is why did only the useful organised mutations stay in the gene pool and the wierd mutations that arent needed dissapear. most of the time the answer will be "because they arent needed" but that seriously indicates thought and a concious design process. Also, how is it that the nose is where it is, why isnt it on our right shoulder or why isnt our mouth on the top of our head? and how did the throat form and lead to a stomach, an intestine grow and an entire system to releave us of our food was generated, by pure unguided mutations? same for the veins, every working part has veins fuelling it, how can that be without guidance? there are a million other examples and Im not bringing up the blind watchmaker argument or anything like that, its just im struggling to grasp how the process worked so well and left us with a very in sync complex system by pure blind mutation and survival of the fittest.

    Thanks for any help with this
     
  2. jcsd
  3. Nov 30, 2016 #2
    I used to have a friend in college in the 90's that had random points of his ribcage sticking out. He's passed on. I don't think he ever got laid. The girls didn't really pay attention to him at the keg parties.
     
  4. Nov 30, 2016 #3

    phyzguy

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    As DiracPool points out in a humorous way, only the useful organized mutations stay because the organisms that got the detrimental mutations died and didn't pass on their detrimental genes.
     
  5. Nov 30, 2016 #4
    But surely some mutations that wernt asthetically pleasing or slightly non uniform wernt always a problem for survival. Also how can a gene pool "only" have good mutations and not have some slight defects. like an organism that has produced a specific feature that helps it survive would surely down the line at some point generate and pass on bad or not needed mutations, because as we know its mindless and random. The presumption that good mutations stay and bad ones dont seems to infer mindfulness to me. Thats what im struggling to grasp

    Heres another example of why I struggle with it. We know that the human eye has developed and improved over many many generations of evolution and is an incredibly complex and useful organ. I agree it could be improved and we know that squid got a better version than we did. But lets go halfway through the development of the human eye, or whatever ancestor it formed on, so we have a half evolved eye that maybe can dipict movement of light for example. So how can it be that step after step after step it continued to evolve and be more useful and complex without developing mutations that caused errors. Surely the negative mutations would have been unimaginably more frequent than the useful ones, and would render the progress of the eyes useful evolution incredibly unlikely?
     
    Last edited by a moderator: Dec 6, 2016
  6. Nov 30, 2016 #5

    Bystander

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    Did it? Really? You're certain?
     
  7. Nov 30, 2016 #6

    jim mcnamara

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    Let me try this. You are going way off trackwith too many assumptions that are not helpful, to say the least. Let's rewind back.

    Do you have a little understanding of how computers work?
    Give computers a very simple set of rules to apply and let them run starting on a very small set of data, run them over and over. You can get lots of interesting, complex patterns.

    "Life" by a mathematician named John Conway is a program that uses a tiny set of rules. The results of running those rules produces:

    Each time the game reruns, starting from the end of the previous run, it is called a new generation. You feed the output of this generation into the next generation.

    Langston's Ant is another one of these "things". These simulations (programs implementing sets of rules) are called cellular automata.

    Evolution is like that. Simple rules allowed to run over trillions and trillions of times.
    If you got that, please come back and we'll will help you fit that into a manageable mental image. Until you get the really basic idea you will not fully understand how super simplicity creates almost boundless complexity.
     
  8. Nov 30, 2016 #7

    Drakkith

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    But it doesn't! One common misconception is that evolution is completely random. This is not the case. Each individual mutation itself is random, but remember that the result of that mutation affects the organism, possibly contributing to its survival chance (I say 'possibly' because many mutations are simply neutral). When you pair this with the fact that organisms are constantly trying to survive in an ever changing environment, you get natural selection. Natural selection is not random. A mutation that contributes to worse fitness for the organism usually leads to a lower survival and/or breeding rate and is less likely to be passed on to future generations.

    Consider a very unlucky rabbit that has multiple negative mutations. Perhaps its legs are shorter and its muscles do not work as well as they otherwise would. It has a drastically lower chance of surviving to adulthood and then breeding than its siblings do. It can't outrun a fox if its muscles barely work! So all of its harmful mutations will most likely be lost from the gene pool instead of being passed on. Conversely, if a series of mutations lead to a rabbit that is able to eat an otherwise poisonous plant, it will have another possible source of food and the chance that it and its progeny will survive increases over other rabbits.

    Neither of those two examples have anything to do with a conscious designer.

    We have inherited our basic body plan from our ancestors, who first developed a simplified version of it many millions of years ago. This body plan survived because it was useful and could be gradually modified over the eons to fit a wide range of animals. If you look at how organisms are classified, a large part of the animal kingdom are known as "Chordates". The primary features of chordates is that they have a notochord and a hollow dorsal nerve chord, the latter of which develops into the spinal cord and brain in vertebrates.

    Large deviations from this body plan are nearly impossible without severely affecting the organism's chances of survival, usually negatively. Think back to the rabbit. If one of its hind legs had grown out of its back, how could it have possibly been able to move around faster than a crawl? Such extreme negative mutations are almost always removed from the gene pool by virtue of causing the death of the organism before it can breed.

    Good mutations stay because they confer an advantage to the organism in some way. This can make the organism faster or stronger (though those traits are nearly always the result of multiple genes, not just one), able to digest a food its ancestors hadn't been able to digest, survive more easily in adverse environmental conditions (heat, cold, atmospheric changes, etc), or something else.

    Bad mutations have the opposite effect and thus have a lesser chance of being passed on. Note that bad mutations are probably much more likely to occur than good mutations. It's much easier to break something than to make it better.

    This almost certainly happened. But those errors which reduced the capabilities of the eye made it harder for the organism to survive and pass on its genes. So those mutations either weren't passed on at all, or were phased out gradually as organisms with better eyesight out-bred and out-survived them. The latter of which explains how populations of organisms all have basically the same capabilities. Even a small improvement can spread to the entire population over long periods of time simply because the organisms possessing the new trait survive more often and have more offspring.
     
  9. Nov 30, 2016 #8

    BillTre

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    Many of your questions really involve understanding of the developmental processes that underlie the formation of adult structures.
    These processes can also evolve to generate variants of these shapes in derived organisms.
    The study of the evolution of development (Evo-Devo) has been a big deal in biology for the last 20 years or so.

    And as was said before, selection removes mutations from the population pretty efficiently if they are not adaptive.
    Most mutations might be mal-adaptive and get selected out of the population, but a very small percentage might be useful to survival and reproduction and thrive in the evolving population.

    Structures in in development are often formed from "developmental fields" which are contiguous groups of cells that are being instructed in some way to develop as a group into a certain part. This signaling often done by diffusable signal molecules from groups of cells, neighboring tissues or single cells. In embryos, diffusion gradients of these molecules will often form smooth iso-concentration lines which will provide a smooth threshold for a developmental response in the cells. This makes a smoothly shaped precursor of cells which enventually form an adult structure like cartilage or bone.
    Another developmental mechanism which can generate smooth structures is differential cell adhesion. If the cells defined by the chemical thresholds above switch on different cell adhesion molecule genes, they could have stronger adhesion to themselves rather than the surrounding cells. This would cause them to minimize their adhesive free energy by making smooth surfaces for the cell group. Cells can also put specific adhesion molecules on different sides to have more complex adhesion rules driving their behavior.

    Evolution of actively moving animals has generally favored the location of environmental sensors on the head end so that the animal can best direct its forward going activities. That's adaptive and would be strongly selected for.
    There are developmental defects in people and mutations (in zebrafish) that can result in the nose being above the resulting single eye. This is the result of development not going right and usually results in death.

    The entire vertebrate digestive system arises from invaginations (infoldings) of tubes of cells from the sheet of cells covering the outside of the embryo. One tube arises from the posterior end, becomes the esophagus, stomach, and intestines. The mouth comes from another invagination at the front end and the two invaginated tubes join together. The sheets of cells separating the two tubes breaks down to make the entire continuous gastro-intestinal (GI) tract. The joining of the mouth tube to the other tube is probably due to specific adhesion molecules and signaling molecules. The different parts of the GI tract are strung together because of how they develop.

    Complex systems (either evolved or designed) are put together step by step over millions and millions of generations. Once one level of organization (such as the organization of single cells, which seems extremely complex to me) was "perfected" (meaning evolved to to an acceptable level of efficiency), then evolved structures at a higher than cellular level (such as tissues in multicellular organisms) can evolve which makes use of the already "perfected" cellular components that were previously evolved.
    The stepwise evolution and the use and modification of evolved components like this can let evolution more quickly assemble larger complex structures.
     
  10. Nov 30, 2016 #9

    BillTre

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    Here is a series of proposed stages of eye evolution.
    There are existing animals with eyes like those found in the steps of this series.
     
  11. Dec 1, 2016 #10

    Drakkith

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  12. Dec 1, 2016 #11
    Thankyou very much for all the information, this has really helped begin to address a lot of my misunderstanding. The part about developmental fields is definately something that addresses some of my deeper confusion.

    I will study all these posts in more detail a little later and see if I can try to form a better confidence in the process.

    I was thinking of buying a book like the selfish gene by richard dawkins, but im always concerned it wont talk about the inbetweens that I worry about. Do you know of any books that might be good to help me?

    Will try to respond to every post later today, thanks for some very informative responses, I think I can finally get rid of this misconception I have once I understand more about the biological processes

    Ah yes I see what you mean, we have diseases and other not so perfect trates like wisdom teeth etc. I think I meant worked well in the sense that we formed into a very complex working structure. But your point is very important because we clearly have some flaws

    This is an amazing model, yes it does make sense to me, another great response!
     
    Last edited by a moderator: Dec 6, 2016
  13. Dec 1, 2016 #13

    phinds

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    To add to what's already been said, you seem to be taking it as a matter of faith that evolution DOES get rid of bad traits when they are not directly detrimental to survival. That's apparently true only of traits that affect the ability to pass on your genes otherwise the genetic predispositions for cancer, alcoholism, and other bad things would have disappeared. And the point made by @DiracPool is a good one; features that are not detrimental to the individual but which inhibit the individual's likelihood of passing on genes, DO tend to die out.
     
  14. Dec 1, 2016 #13
    Thats a very good point, it is certainly beginning to all make sense in my head now, I didnt realise that so many of my misconceptions could be answered. I think what I had was a philosphical idea that biologists took certain things for granted or didnt look deep enough into the parts that I had problems understanding. I think ive read too many articles that simply say "because its not benificial" etc I think that has mislead me to underestimate what we do know
     
  15. Dec 1, 2016 #14

    Drakkith

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    Indeed. Many people come to the same conclusion about other types of scientists.
     
  16. Dec 2, 2016 #15

    phyzguy

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    I really recommend Dawkins" "The Blind Watchmaker" . He systematically addresses the questions you have.
     
  17. Dec 2, 2016 #16
    Thanks, I will get that book, I have always hated that argument, im sure dawkins must find it utterly irritating
     
  18. Dec 2, 2016 #17

    Ryan_m_b

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    In general a deleterious trait will be weeded out of the population over time, but not necessarily. There are many traits that might be a disadvantage in one environment but are advantageous overall in another. Sickle cell trait for example, people with it have an increased risk of various diseases but they have a greater resistance to malaria. So in areas of the world in which malaria is common the trait persists.

    This evolution simulator is a pretty good educational tool to wrap your head around the basics:
    https://www.openprocessing.org/sketch/377698

    It starts by creating 1,000 random "creatures". These creatures consist of balls connected by rods of various elasticity and behaviours. They are then sorted by their ability to run down a simulated track (click "step-by-step" to see them tested one by one or "quick generation" to skip to the results). Then ~500 of them are killed, the chance of being killed is higher for those who didn't get very far. The survivors are reproduced with variation and the test is repeated. After a while you get some really good runners thanks to the combination of mutation and a selective pressure for being a good runner.
     
  19. Dec 2, 2016 #18
    This is a really great program, doesnt work too well on my phone but it really does put things into context very nicely

    Not trying to move the goalposts as like I said im an athiest with some trouble in understanding, but heres another one I find very very hard to get my head around. There are animals that replicate the animals that hunt them, like a lizard that has what looks like 2 eyes on its back so the animal that hunts it thinks its actually one of their own species! (Forget the exact creature but it literally has markings that makes it look like its predator) how on earth can it accidentally get to that point? Its like its brain is telling its body how to evolve, like its evolutionary traits have actually learned over time. Which isnt possible. I do have trouble with these forms of evolution because they seem too clever to be chance

    Struggling to upload an example photo, but a very simplified example is a cobra thats markings on the back of its head looks like 2 eyes
     
    Last edited by a moderator: Dec 6, 2016
  20. Dec 2, 2016 #19

    Bystander

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    "Monarch/Viceroy" Batesian mimicry? "Million monkeys at a million typewriters for a million years ...."
     
  21. Dec 2, 2016 #20

    BillTre

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    Things like eyespot patterns are not unusual in nature.
    They are often thought to be adaptive because they can momentarially intimidate potential predators by making them think they are they are faced with a something that might be a threat to them (the predator).
    This can give the prey item a extra moment to get away.

    Because its adaptive, it could be selected for in the normal ways that have already been described.
     
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