What is the Mechanism of Natural Selection for Evolution?

Discussion in 'Biology & Genetics' started by matthew809, Feb 22, 2014.

  1. Grumpy Curmudgeon of Lucidity Valued Senior Member


    The DNA we have in common with a Banana is doing exactly the same job in Bananas as it does for us. That DNA developed before either us or bananas existed and it did it's job so well that there is no evolutionary pressure for those particular genes to ever change and they are spread throughout life. We have those genes in common with almost all life and mutation in those genes is almost always fatal to the organism.

    But Natural Selection is not random. Mutations to an individual's DNA are tested by whether that organism survives to reproduce(and thereby continue that mutation in their offspring, preserving it). Fatal mutations kill that organism before it can pass on that mutation into the gene pool. Only those mutations that do not prevent reproduction are passed on. That is the first stage of testing, survival to reproduce. But even non-lethal mutations are tested by the struggle for reproduction(what we call our lives), if that non-lethal mutation confers a better ability to survive and reproduce it will be preserved(by the survival of more offspring who have that particular mutation), while one that is neutral will survive less often, and those non-lethal mutations that hinder reproduction or even reduce it just a little bit will become less common in the gene pool. All by the simple act of reproduction(a simple, binary, pass/fail test, the outcome of which is not random). That is Natural Selection, mutations tested by whether they assist or prohibit survival to reproduce. Those that survive pass their genes on, those that don't reproduce do not. Genes that assist in survival are preserved, those that don't are eliminated. Nothing random about the process.


    Demonstrably false.

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    Each of these "eyes" can be seen in Nature, from light sensitive patches of skin to the camera eye they all give an evolutionary advantage, each improvement, however small, being preserved and passed to the next generation. Give it a few billion generations and you have your eyes coming from incremental improvements applied to the original heat sensitive patch of cells. This is undeniable for those who know the facts, only those who have an agenda deny it. Your objections are not based in science, they are based on your beliefs about your god. There is no such thing as Irreducible Complexity in evolution, it is bogus pseudo-scientific babble.


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  3. exchemist Valued Senior Member

    Furthermore, is it not the case that the eye has evolved independently several times, as in molluscs like the squid, in vertebrates such as fish, reptiles and mammals, and again separately, the compound eye of arthropods? One of many fascinating examples of convergent evolution.
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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Not sure what you mean. Yes being able to gain information from things too distant to touch is a great survival aid and has thus been evolved independently more than 10 times.

    One quick eample is the occtupus (and some related creatures) God, the "intelligent designer" loved them more than man as He put the photo sensitive cells in their eyes as the front part of the retina, not behind a layers of nerves fanning out from the "blind spot" and not behind all the retinal blood vessels as in man.

    One set of slow moving insects has only a single photo sensitive cell in each eye. It is up on a short "stick" which has fibers attaching it to muscles. I.e. it moves to different locations in the focal plane to "scan" the image, much like the elctron beam in old CRT televations, "painted" the 2D array of phosphors on the inside of the vacuum tube face made "successive still pictures"

    One thing bad about evolution is the "designs" can get trapped by choices made millions of years earlier. For example, the ancestor of the giraffe was not with long neck. One of the important facial nerves passed below a bone that later evolved to be the "collar bone" - I. e. is down on the shoulder part of the giraffe. The path of nerve signal produced by touch to that part of the giraffe's face, which is only 10 or so centimeters from the brain target area is not only ~10cm, but twice the length of the giraffe's long neck. I.e. the nerve's path still must go below that collar bone. Evolution can only proceed by tiny changes - not in one generation make any big change, like a nerve switching from one side of a bone to the other side.

    Thus, never will a baby be born with the photo cells of the retina up front - first thing the light strikes as that would be "discrete step" change that evolution can not do.
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  7. Grumpy Curmudgeon of Lucidity Valued Senior Member


    A child inherits one half of it's genes from each parent. Each parent has two halves to contribute, therefore there are at least four completely different sets that each child could have, thus four different children are possible from each reproduction event. That is sexual variation(inheritance)and has virtually nothing to do with Natural selection as a whole, it is an additional type of variation caused by mixing, not mutation. Populations of individuals evolve(we call it the gene pool for a reason)not individuals or even mated pairs. The genome contains all the sexual variations, it is not just the genes of an individual.


    True, but the reptiles and mammals got their eyes from the fish, mollusks evolved their eyes by an entirely different source. Insects are a separate line altogether. Being able to sense light or see your predator or prey makes any improvement of the eyes prime evolutionary material. Even the least improvement by mutation will be selected to survive(IE they will have more offspring).


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  8. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    OK - I'm coming out of the closet: Both the scientists and the religious have it wrong. Evolution did not evolve creatures, God made them but He was not an "intelligent designer" - rather a stupid one just learning. Our universe was his first "homework" assignment in beginning level of "divinity school." He made all the land creatures first with lots of stupid design flaws, but learned and did better when he got around to making sea creatures. Did not get the octopus's retina backwards, no fish has a head nerve going all the way back to the tail before retuning to the nearby brain as the giraffe does, etc. for dozens of other obvious errors known in land creatures.

    I hear he got a grade of D- but was given chance to do another universe as he did learn on his first messed up attempt.
  9. Trippy ALEA IACTA EST Staff Member

    The tenet of the lazy creator is one of the tenets of the First Church of Bacchus (revised).
  10. wellwisher Banned Banned

    Instead of thinking at the term "intelligent design", as derogatory religious buzz words, think of this term, in the context of a design engineer, who is designing and building something that is both practical and beautiful, such as a sports car. An intelligent design will require very low maintenance costs due to the way the designs fits together like glove.

    An intelligent design would be the product of imagination, reason, and practical skills, that combine many diverse elements into an integrated whole that combines form with function. An intelligent design, would not be a design that did not require thought, planning, and anticipation. It would not be a design that just randomly appears after throwing a bunch of things in the air, a bunch of times until the design appears. That is not intelligent but shows lack of intelligences. This second approach implies lack of understanding being traded for luck.

    The term intelligent design, in this context, as applied to a theory of life and evolution, would require a logical explanation and not a random throw things in the air, mishmash approach. Evolution, as is, is not the most intelligent design since it depends too much on throwing stuff in the air and consulting a statical oracle to solve problems.

    In anyone seeks to be more rational and systematic, so the design is more intelligent, this makes the caretakers of the miss mash approach get insulting with the term, " intelligence design". The two words mean rational planning and anticipation, with this approach considered a derogatory taboo. The reason is, this approach would make the mishmash look dumb.

    For example, water is critical to life. There is no example of life, anyone can show, that has life without water. All other solvents have been tried with life and none of theses could maintain integrated life. Beyond the global, enzymes and the DNA will not work without water. All of life stops, if we remove the water and in the case of the seed, will return when water is added.

    Water is so important, yet it is not rationally included in the random, throw the dice design of evolution. The reason this design is randon, is because it leaves out an important variable that accounts of 9 of 10 molecules in life. That is not an intelligent design.

    From the religious context of intelligent design, it assumes God created life. If God is God, one would not expect a dumb approach. One would expect he would show an approach that beyond the smartest human approach. This raises the bar very high and encourages some humans to not just settle for throwing stuff in the air, since a monkey can do that. It requires more logical thinking and planning to climb that ladder. Water is a prime example, of the caretakers of the traditions not planning very well and needing random to fill in this variable with an approximation.
  11. spidergoat Liddle' Dick Tater Valued Senior Member

    And yet the physical structure of life shows no evidence of planning. Indeed it looks exactly as it should if it were adapted gradually from from existing parts.
  12. Write4U Valued Senior Member

    No organism is exactly the same, so the question is kinda moot and it comes down to small advantages and someties luck that produce a "line". But OTOH, think of the billions of organisms that did not make it, even if they had some advantageous traits. Natural selection is selection by default. The last man standing (or hiding) gets to procreate.

    By the law of averages, the best adapted are the most likely to survive and procreate. Darwin discovered two lizard which were practically identical except for color. Turn out the color of the lizard inabiting a rocklike territory was darker and more drab, while the very same, but brightly green colored lizard lived in the forest. Same species adapted to their immediate environment.
  13. matthew809 Registered Senior Member

    By design, all species have a randomly-controlled built-in flexibility of characteristics within a given range. In these cases, mutation is not the cause of change, even for such diverse variation within species. This built-in flexibility has it's limits though(as any sort of professional breeder can tell you), because it is intended for assisting in relatively minor adaptation, not evolutionary change. So when we talk about evolutionary changes, we must be sure that we are not simply talking about a result of these built-in limited variations allowed by DNA instruction, but rather a result of unintended mutations.

    So my point is that micro-evolution(a misnomer BTW) is different than macro-evolution, whether you like those terms or not. They have completely different causes; one does not imply the other. The problem with purveyors of evolution is that they lump both types of "evolution" together, thereby confusing everybody(even themselves apparently), to the point where anyone who would dare to specify one type or the other is labeled a crackpot. That is not science, it is politics.

    I am not arguing here that macro-evolution doesn't exist, only that it still needs to be proven. Micro-evolution does not prove macro-evolution. Natural selection is touted as proof of evolution, but it has only been observed to cause micro-evolution. In order to use natural selection as a means to explain macro-evolution, you have some serious explaining to do.

    In reality, mutations which may be mildly beneficial would have no more influence on survivability and reproduction than the status quo. Therefore all mutations must be considered neutral in that regard. I have serious doubt that a neutral mutation could come to dominate the gene pool full of other equally neutral configurations of biology. Even if a mutation manages to persist to the future generation without resistance, the law of probability would exact the reverse mutation in time.

    In order for evolution to achieve the level of life we have on planet Earth right now, mutations would have to be a lot more abundant, more persistent, and a lot less neutral than they appear to be.
  14. matthew809 Registered Senior Member


    The DNA may be unique, but it is not an evolution because the language of DNA did not evolve. The language is the same, but the sentence structure is different. The DNA of the parents only combined because that it exactly what it was pre-programmed to do. The DNA language is beyond any mere application of it. The DNA language of life is static.

    In other words, even though a species may change in time, it is still the same as it always was.
  15. Write4U Valued Senior Member

    That is incorrect. How can something be the same as it always was when it has changed? You mean the same building blocks? Well, true, but all species share the same basic building blocks, so that is not a valid argument. Many different species share the same DNA. It must be so, because all living things started as a single celled organism that was able to duplicate through DNA instructions. We all still have that DNA from that single celled organism.

    Before we overthink the term "evolution" we should begin with its defiition, IMO.


    Evolution includes mutation as well as refinement of inherited traits.
    Humans evolved from a hominid ancestor by a mutation of the fusion of two chromosomes into a single chromosome (which is why we have one pair less chromosomes than other great apes). But we retained 98% of our shared DNA without any change.

    Actually the word "evolution" is a generic term meaning "change", not "staying the same".
  16. Grumpy Curmudgeon of Lucidity Valued Senior Member


    All evolution takes place within the DNA of the genes, in fact, all evolution occurs within the DNA of the sexual gametes alone. Mutations within any other cell do not get passed to the next generation. That is the ONLY evolution there is, no matter if the thing being coded for is "micro" or "macro"(whatever that's supposed to mean). There is just evolution. The organism with the new code is tested by survival, if it fails the organism dies, eliminating those genes from the pool. "Macroevolution" and "microevolution" are non-sense words with no meaning in the study of evolution other than as a description of the "largeness" of the change, I guess. A tiny change to a single protein in a cell can have much more of an effect on an organism than if their nose is twice as long as any other of that organism.

    They are in no way designed, nor are they random. If the trait is selectable it has served a survival purpose in the past of that genome. An example is a heavy coat of fur. This is a selectable trait that is tied to the seasons, as well as the climate. Polar bears and Kodiak bears are the same species and interbreed in some circumstances. Where they live determines both the thickness and color of their fur, the trigger is pulled during the pregnancy, the conditions during that time can cause dark furred cubs to be born to Polar bears and vice verse. That is an evolved trait, but the change is a selection of another evolved trait, triggered by conditions during gestation. The change is therefore not an evolutionary one. There will always be a range of traits in any population, new mutations constantly being tested is evolution, selection among common traits is not.

    And this...

    ...is just garbage. Evolution has been observed in the lab, in the wild and in forced experimentation. The Nylon Bug only eats specific chemical wastes associated with the manufacture of nylon, no other organism can do so. Nylon has only existed since the 1940s. Therefore the Nylon eating bacteria is a new species that evolved in only a few decades. And many mutations are fatal, not neutral. They are definitely selected against because that organism has no children to pass that mutation to. Neutral ones never become dominate(we have many eye colors, for example), while advantageous mutations cause more children to be born to those who have it. Slow, sloppy, undesigned, but highly effective over time, every trait you possess evolved the same way. You just don't realize just how long it took. Man has been here about a million years, it took 4-500 million years to go from one celled bacteria to man, but it took 3 billion years to go from the first self replicating molecules to bacteria. Most of the hardest parts happened in those first 3 billion years.


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  17. Arne Saknussemm trying to figure it all out Valued Senior Member

    Thank you Grumpy for your tireless efforts to explain The Facts of Evolution and Natural Selection to the hard-headed. You do not go unappreciated.

    Grumpy: :grumble:

    Me: :bravo:

    The Hard Heads: :wallbang:
  18. Write4U Valued Senior Member

    I am always amazed at the conflicting assumptions of theists. On one hand they believe with certainty in an almost impossible concept of an omnipotent supernatural entity which has the ability and motivation to create stuff (including humans) at will, yet a proven function of nature (biological evolution) is just "impossible" according to holy scripture.

    God exists and is perfect, but nature is limited in it's functions and even then it functions only at the micro level, never at macro level, because it is impossible to get a new different kind from an older kind.

    "Each according to its kind, forever, so it is written, so it shall be!"

  19. billvon Valued Senior Member

    That's like saying Shakespeare is the same as The Daily Show script because they both use exactly the same twenty-six letters. They can never be any different; the letters are static and always mean the same thing.

    Is microerosion (roads washing out) different than macroerosion (the Grand Canyon?) After all, it's a much bigger change.

    One is a lot of the other. Look at the slow, gradual evolution of land animals to whales. Each step tiny, but a million tiny steps gets you from a land animal to a sperm whale.

    Then they are not beneficial, by definition.

    Not if most/all the organisms without the mutation died. Which, of course, is how evolution works

    They are abundant, persistent and common. One such experiment:
    The E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988. The populations reached the milestone of 50,000 generations in February 2010.

    Since the experiment's inception, Lenski and his colleagues have reported a wide array of genetic changes; some evolutionary adaptations have occurred in all 12 populations, while others have only appeared in one or a few populations. One particularly striking adaption was the evolution of a strain of E. coli that was able to use citric acid as a carbon source in an aerobic environment.
    . . . The populations are regularly screened for changes in mean fitness, and supplemental experiments are regularly performed to study interesting developments in the populations. As of October 2012, the E. coli populations have been under study for over 56,000 generations, and are thought to have undergone enough spontaneous mutations that every possible single point mutation in the E. coli genome has occurred multiple times.
  20. Trippy ALEA IACTA EST Staff Member

    Penicillin resistance evolved through a mutation - a malformation of the particular enzyme that Penicillin targets. The mutation was harmless, and under ordinary circumstances offered no survival advantage, however, once evolutionary pressure - in the form of penicllin was applied...
  21. Aqueous Id flat Earth skeptic Valued Senior Member

    Intelligent design is the hopeless proposition that myth outweighs reality.

    Heritable traits are deterministic. Mutations are random. The rest is mumbo jumbo.

    Incorrect. In humans the range of "characteristics" includes extensive genetic anomalies that naturally abort in the very early stages of ebryoic development.

    No such maxim exists. Some genetic anomalies are "within the range" and others are "outside the range".

    There is no such thing as "built-in flexibilty". There are intrinsics, like the laws of chemistry. Equilibrium dictates what can and can not happen during embryonic development, for example.

    The universe is governed by laws, not intent.

    No, when we talk about changes in the phenotype we immediately recognize that they are adaptations to selective pressure. The rest is superstitious nonsense.

    It's mostly a talking point for religious fanatics. It has little value to science.

    They have little or no value to biology. They are nearly entirely rooted in the lexicon of Creationism.

    This statement has no scientific value.

    The only thing being purveyed is myth over reality. The rest is science, which cares not one whit about this gashing of teeth and rending of garments.

    Pseudoscience represents something even worse than confusion. It's a deliberate intent to prey on vulnerable minds.

    Crackpots are known for purveying pseudoscience. It's the defense mechanism at its worst. Much harder is to pick up a book and actually learn enough biology to pass a college entrance exam. At that point it's hard to imagine what kind of crackpot thinking survives freshman year.

    Indeed pseudoscience involves mixing ideas from religion and politics and then selling them off as something the purports to be based in science.

    You've never been to museum of natural history?

    The proof is in the fossil record. What more do you need?

    No, natural selection is observed as one of the important causes of genetic variation in population.

    No, natural selection can be observed in fossils.

    It's the other way around. Evolution explains the fossil record. That's your stumbling block.

    Other way around. Religion has some serious explaining to do. Where did the fossils come from? Of course to even get there you have to at least be equipped with the level of science known in the era between Galileo and Darwin. Pick a date, and start there. Trace the historical development of human knowledge leading to the Industrial Age, which huge construction projects (dams, canals, deep foundations) less to widespread excavations and discovery of so many fossils that new sciences - like geology and paleontology - were born. Of course that would involve covering some actual science which may be hard for you if you're so poisoned by belief in myth that you can't handle the truth.

    Crack any first year text in biology and come back and explain what niche-filling means and this kind of nonsense just withers.

    There would be no such thing as recessive genes if this logic was remotely plausible. Of course it's just pseudoscience. Crack the book and let's hash out what the actual science teaches, and all of this styrofoam evaporates.

    Your doubts are rooted in superstition, not science.

    Niche filling under selective pressure proves your entire logic invalid.

    At the nano scale there are some finite set of state changes that occur which might be modeled as Markov processes. To some extent these might be reversible, but to try to extrapolate this to the macro scale is absurd. If anything it demonstrates drift, not a re-centering as you think. What you see is what you get. Evolution is highly organic, not subject to the whims of religious ideation.

    When pigs fly.
  22. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Many animals that made fossils died very long ago, and there are "gaps" in the fossil records, but the land creature that became the whale, still an air breather,* did that evolution relatively recently and there were many of them, so that transformation fossil record has no gaps. I. e. we have fossil examples of every small transformation.

    For example fossils with the hind legs growing shorter and less complex and other changes. Finally the residue of the hind legs is smaller still and still clearly a leg, but it is total inside the body and attached to what was the "pelvic bone." Then it is just one small somewhat elongated bone detracted from the rest of the skeleton. I think some modern whales still have a small totally useless calcified lump "floating" in their tail area body that many ancestors earlier was the hind leg the land animal the whale evolved from walked on.

    I'm too lazy to search again to re-post some of these photographs of these fossils, and it is pointless to do so as some are too closed minded to learn, even if looking at the obvious proof of "macro-evolution" via tens of thousands of "micro- evolution" steps. Also Sciforum's limit of only three photos would made "gaps" permitting ignorance to persist.

    * Whales still breathing air is another example of evolution "trapped" by prior history as I stated in post 23. There is no advantage and considerable cost for a large "air breather" to keep his lungs and add some rudimentary tissue that can take oxygen from the water and after ~10,000 generations becomes slightly like gills.**
    ** If you are a small air breather that is often eaten by carnivores that also spends a lot of time in the water, there is evolutionary selection advantage to being able to remain hours on a lake bottom without motion. Thus, frogs can absorb some oxygen from the water via their skin, but not enough to swim under water without occasionally coming to the surface for a "gulp of air." I doubt whales get significant O2 thru their skin. It seems to have been more advantageous to have thick layer of fat / blubber to be able to swim thru floating ice fields etc. I'm sure the land animal the whale evolved from did not have a mass of blubber to lug around, but blubber would leave not fossil record.
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  23. Grumpy Curmudgeon of Lucidity Valued Senior Member

    Actually, many mammals have a subcutaneous layer of fat, including humans. They would only have to modify that over time.

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