Can random mutations increase fitness?

Discussion in 'Biology & Genetics' started by James R, Aug 14, 2004.

  1. James R Just this guy, you know? Staff Member

    It is a common argument of Creationists and others who know little of biology to claim that random mutations in a genome cannot produce an animal which is fitter than its ancestors. According to this argument, all mutations are harmful. So, I thought I'd post a simple analogy to show how this argument fails.

    Suppose, in some imaginary world, we have an animal whose complete genome is dictated by six "letters", which can each be either "H" or "T". You can think of this genome as being based on six coin tosses, if you like, where each coin can come up either heads (H) or tails (T).

    Imagine that in this particular environment, the "ideal" animal would have the following genome:


    Further, assume that for this animal, the more Hs there are in the genome, the better adapted the animal will be to its environment.

    For simplicity, we assume this animal reproduces without sex, so most of the time its offspring have exactly the same genome as the parent. However, occasionally, one-letter mutations can occur in the genome during reproduction. when this happens, the particular letter in the sequence which changes does so entirely at random (think of flipping a coin). So, for example, an animal with the genome:


    will produce offspring with an identical genome most of the time, but occasionally, it might produce something like:


    instead (where here the second last letter in the code has undergone a random change).

    So far, we have a system where there is no progression from less fit animals to more fit animals, because it is as likely that an animal with the genome THHTTH will produce offspring with genome TTHTTH (less fit) as it is that it will produce offspring with genome THHTHH (more fit).

    Now, put natural selection into the picture. Suppose our animal with genome


    has 7 offspring, with the following genomes:

    1. THHTTH
    2. TTHTTH
    3. THHTTH
    4. THHTTH
    5. THHTHH
    6. THHTTH
    7. THHTTH

    These offspring all compete with each other for limited resources such as food. Let's assume that there is enough food for only 4 out of 7 of these animals.

    Which ones, on average, get the food and survive to reproduce? Looking at the list, animals 1,3,4,6 and 7 all have the same genome, and so are equally well adapted to their surroundings. But animal 2 has a less well adapted genome, so it is less likely to be able to compete successfully with any of the other animals. And animal 5 has a "fitter" genome than any of the others, so it is a bit more likely to get the food.

    A reasonable outcome to expect would be that the following animals survive:

    1. THHTTH
    3. THHTTH
    5. THHTHH
    7. THHTTH

    Natural selection has eliminated animals 2,4 and 6.

    What happens in the next generation, when the surviving animals reproduce? Animals 1,3 and 7 have offspring in a similar pattern to their parent. But most of animal 5's offspring have the same genome as animal 5 itself. So, in the next generation, we might have, for example:

    15 animals with genome THHTTH
    5 animals with genome THHTHH
    8 animals with some other genome

    But now, most of the 5 animals with THHTHH genome will out-compete the animals with genome THHTTH, and probably some of the other 8 animals with the different genomes. In the generation after this one, or perhaps the one after that, we will most likely find that animals with genome THHTHH will outnumber animals with genome THHTTH (which the common ancestor of all these animals had).

    So, we are now at a situation where most of the animals in this population are better adapted to their environments than a few generations ago. How has the change come about? It is a 2 step process:

    1. Variation is produced randomly in the offspring.
    2. Natural selection culls those who are "less fit", leaving those who are better adapted to their environment.

    So, contrary to Creationist or "Intelligent Design" claims, progression in a species, or evolution of new species, does not require any intelligent planning. Random changes combined with natural selection are enough in themselves.

    Speaking of the evolution of new species from old, a new species can come about simply when the genome diverges far enough from the original so that creatures with the two different genomes can't interbreed any more. The example I have given is not a particularly good illustration of that, since I assumed asexual reproduction, but it is easy to see that if we introduced sex for this species, then after many generations it may well be the case that an animal with genome


    may not be able to breed successfully with an animal which has, for example:


    Any questions or comments?
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  3. 786 Searching for Truth Valued Senior Member

    My argument was not about being fit. My argument is abou distinctiveness of an animal. Well one could be fittest, but not a "distinct" animal. don't you think.

    If according to you, stuff happens to our genome. then why aren't be evolved in some other creature. I am saying why people are still Humans?
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  5. James R Just this guy, you know? Staff Member

    The usual definition of "species", as I said, is the members of a species can interbreed to produce viable offspring. In my example, it might be clear that animals with the following two genomes couldn't interbreed:


    However, it is equally clear that an animal with genome HHHTTT could evolve from one with genome TTTHHH via a sequence of steps over multiple generations. For example:

    1. TTTHHH
    2. TTTHHH
    3. TTTHHT
    4. TTHHHT
    5. THHHHT
    6. THHTHT
    7. HHHTHT
    8. HHHTTT

    While animal 2 might be able to breed with animal 3, perhaps animal 3 could not breed with animal 7. Hence, animals 3 and 7 would be considered separate species.

    Similarly, in our real world, each human being has a different genome from every other human being, but not sufficiently different not to allow them to interbreed with other human beings.

    While human beings cannot breed with chimpanzees today, that doesn't mean that humans cannot have shared a common ancestor with chimpanzees. In the example I've given here, animals 3 and 7 both have a common ancestor (animal 2), but they could not interbreed.
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  7. MacM Registered Senior Member

    This is actually the point. We are no longer apes. Your presentation always seems to assume some individual change which goes from from a pig to a pig with wings.

    That is not what happens. Follow the history of the evolution of horses. One of the best in terms of completeness of evidence. Horses once had 4 toes in from and three in back. OVER MILLIONS OF YEARS and numerous generations the number of toes began to dimenishs. today they only have hooves but the remanants (bones spurs) of multi-toed ancesters remain.

    Likewise our (humankind) appendacies once was much larger and was used to digest raw foods. But as we became civilized and began to cook and process foods it function was not reqired and now it remains as a small unused organ.

    It will in time vanish altogether.

    The parallel between humans and apes is indeed incrediable. I believe the DNA match is like 98%. But more important is the fact that the likely most restraint is an apes inability to speak. The fact are that there have been at least two amazing cases involved with apes.

    One some years ago when a research animal had been taught human sign language and knew and used over 1,000 signed words and communicated with lab technicians in composed sentances.

    The amazing part of this story was when the animal was retired and put in a zoo with other apes. Care takers were astounded when they discovered that this ape was teaching the other apes our sign language!!!

    So it is not that they don't understand language but that there envoirnment and needs for language are different. Placed in the lab envoirnment they learn and use our language. Except they have not developed the voice box since they haven't required one.

    The second case was just on national news this past week. Another trained ape that uses human sign language to communicate, had a tooth ache and not only communicated that to its handlers but actually used a pain level chart to describe the ailment.

    The point of this is to show that human kind is not unique other in that we have through evolution developed the appendages to make use of our intelligence. Other creatures have or can develope such intelligence but lack the ability to put such knowledge to use.
    Last edited: Aug 14, 2004
  8. 786 Searching for Truth Valued Senior Member

    I suggest you read the Inheritence law. It was discovered by Gregor Mendel. You are confusing inheritence with mutation.

    The science of Genetics that developed at the beginning of the 20th century proved that it was not acquired physical traits but only genes, that were transmitted to subsiquent generations. This discovery made it clear that a scenerio suggesting that acquired traits accumilated from generation to generation and generated different living species was implausible. In other words there were no inheritable variations for Darwin's proposed mechanism of Natural Selection to choose from.
  9. 786 Searching for Truth Valued Senior Member

    It is funny MacM that you talk of similarities.

    True that our DNA is very close to the DNA of Apes. But not as close as you thought it is.

    MANY evolutionist sources from time to time carry the claim that humans and apes share 98 percent of their genetic information and that this is proof of evolution. This evolutionist claim focuses particularly on chimpanzees, and says that this creature is the closest monkey to man, for which reason there is a kinship between the two. However, this is a false proof put forward by evolutionists who take advantage of the layman's lack of information on these subjects.

    98% similarity claim is misleading propaganda

    For a very long time, the evolutionist choir had been propagating the unsubstantiated thesis that there is very little genetic difference between humans and chimps. In every piece of evolutionist literature, you could read sentences like "we are 98 percent identical to chimps" or "there is only 1 percent of DNA that makes us human." Although no conclusive comparison between human and chimp genomes has been done, the Darwinist ideology led them to assume that there is very little difference between the two species.

    A study in October 2002 revealed that the evolutionist propaganda on this issue-like many others-is completely false. Humans and chimps are not "98% similar" as the evolutionist fairy tale went on. Genetic similarity turns out to be less than 95 %. In a news story reported by, entitled "Humans, chimps more different than thought," it reads:

    There are more differences between a chimpanzee and a human being than once believed, according to a new genetic study.

    Biologists have long held that the genes of chimps and humans are about 98.5 percent identical. But Roy Britten, a biologist at the California Institute of Technology, said in a study published this week that a new way of comparing the genes shows that the human and chimp genetic similarity is only about 95 percent.

    Britten based this on a computer program that compared 780,000 of the 3 billion base pairs in the human DNA helix with those of the chimp. He found more mismatches than earlier researchers had, and concluded that at least 3.9 percent of the DNA bases were different.

    This led him to conclude that there is a fundamental genetic difference between the species of about 5 percent.

    New Scientist, a leading science magazine and a strong supporter of Darwinism, reported the following on the same subject in an article titled "Human-chimp DNA difference trebled":

    We are more unique than previously thought, according to new comparisons of human and chimpanzee DNA. It has long been held that we share 98.5 per cent of our genetic material with our closest relatives. That now appears to be wrong. In fact, we share less than 95 per cent of our genetic material, a three-fold increase in the variation between us and chimps.

    Human DNA is also similar to that of a worm, mosquito, and Chicken!

    Moreover, the above-mentioned basic proteins are common vital molecules present, not just in chimpanzees, but also in very many completely different living creatures. The structure of the proteins in all these species is very similar to that of the proteins present in humans.

    For example, the genetic analyses published in New Scientist have revealed a 75% similarity between the DNA of nematode worms and man. This definitely does not mean that there is only a 25% difference between man and these worms!

    On the other hand, in another finding which also appeared in the media, it was stated that the comparisons carried out between the genes of fruit flies belonging to the Drosophila genus and human genes yielded a similarity of 60%.

    When living things other than man are studied, it appears that there is no molecular relationship such as that claimed by evolutionists. This fact shows that the concept of similarity is not evidence for evolution.
  10. MacM Registered Senior Member

    Your position is totally untenable and ludricrus. You now ant to assume some initial 98% finding that is really only 95% means total failure of the relationsip. The is nonsense. I would be more than content to accept the 95% figure.

    The point being the degree of correlation between DNA's the closure of relationships. You are also wrong to claim we have no relatinship to worms. that telationshipo however is much further removed from us in both time and evolutionary tracks.

    The point being we all did come from the basic conversion of inorganic material into organic material which evolved from there.

    You really shouldn't put so much faith in media claims either but actually go learn some science.
  11. ElectricFetus Sanity going, going, gone Valued Senior Member

    We can actually track genes though there evolution, each mutation individually and sort the order of animal relations.
    If you wish to try it your self: go to Pubmed web site, search fro a specific gene and compare the sequences of a variety of different species for that gene.
  12. James R Just this guy, you know? Staff Member


    No, I'm not. I specifically said before that I was using a model with asexual reproduction, in which the only changes to the genome come about via mutations.

    I hope you realise that genes code for physical traits, so that when certain genes are inherited, certain physical traits are also inherited. What has been shown is that learned traits are not passed on to offspring. It is important to distinguish these from genetic traits.

    Careful! Here you're blurring the distinction between learned traits and genetic traits. Genetic traits are "acquired" and accumulated from generation to generation, as I showed with my analogy above. You almost sound as if you're dileberately trying to blur the distinction to confuse people. Or maybe you don't really appreciate the distinction yourself. I hope this explanation helps you.

    Completely false. The inheritable variations are those carried by the genes.
  13. 786 Searching for Truth Valued Senior Member

    Yeah, but these "favorable variations" were occured by CHANCE. How many different living species are in this world? some million.

    You expect me to believe that all of these millions species were made by "favorable variations" which CHANCED to occur.

    First of all getting "favorabe variations" is a very hard thing by itself. Because almost 99% of Mutations are harmful not favorable. Then it gets even more impossible by stating it occurs by CHANCE.

    "But mutations are found to be of a random nature, so far as their utility is concerned. Accordingly, the great majority of mutations, certainly well over 99%, are harmful in some way, as is to be expected of the effects of accidental occurrences."—*H.J. Muller, "Radiation Damage to the Genetic Material," in American Scientist, January 1950, p. 35.

    "Natural Selection can do NOTHING until FAVORABLE variations CHANCE to occur."
    Charles Darwin The Origin of Species. 1.ed. p.177

    First of all, 1% of Mutations are favorable. But Even this 1% has to occur by CHANCE. So basically we have LESS THAN 1% of a CHANCE for a "favorable variation" to occur BY CHANCE.

    We are not only a product of CHANCE. BUT a product of IMPROBABLE CHANCE.

    The whole theory depends on CHANCES. BUt not ONLY CHANCE but a CHANCE of LESS THAN 1%

    Do you still not see the IMPROBABILITY for this process to occur?
    You expect me to believe in all of these CHANCES? What do you think is the CHANCE of that?
    Last edited: Aug 15, 2004
  14. MyosinII Registered Member

    Yes, but the likely hood of that is rare, chances are the mutation will be detrimental or have no effect.
  15. MyosinII Registered Member

    They don't want to admit there brains are unfit.
  16. 786 Searching for Truth Valued Senior Member

    Becoming "Fit" is different than becoming a whole new different specie.
  17. 786 Searching for Truth Valued Senior Member

    Yeah. But changes in DNA are more likely to harm the animal.

    "You'll recall we learned that almost always a change in an organism's DNA is detrimental to it; that is, it leads to a reduced capacity to survive. By way of analogy, random additions of sentences to the plays of Shakespeare are not likely to improve them! . . . The principle that DNA changes are harmful by virtue of reducing survival chances applies whether a change in DNA is caused by a mutation or by some foreign genes we deliberately add to it."

    Mahlon B. Hoagland, The Roots of Life: A Layman's Guide To Genes, Evolution, and the Ways of Cells, Houghton Mifflin Co., 1981, p. 145.

    The well-known mathematician Dr. Warren Weaver

    "Moreover, the mutant genes, in the vast majority of cases, and in all the species so far studied, lead to some kind of harmful effect. In extreme cases the harmful effect is death itself, or loss of the ability to produce offspring, or some other serious abnormality."
    Warren Weaver, "Genetic Effects of Atomic Radiation," Science, vol. 123, June 29, 1956, p. 1158

    "Many will be puzzled about the statement that practically all known mutant genes are harmful. For mutations are a necessary part of the process of evolution. How can a good effect-evolution to higher forms of life-result from mutations practically all of which are harmful?."
    Warren Weaver, "Genetic Effects of Atomic Radiation," Science, vol. 123, June 29, 1956, p. 1159

    Weaver's question is a very important one, and demands an answer from evolutionists: How can a good effect-evolution to higher forms of life-result from mutations practically all of which are harmful?
  18. James R Just this guy, you know? Staff Member


    Yes. Chance, combined with natural selection. See my first post.

    Most mutations are actually neutral, not harmful. I agree with you that favourable mutations are rare, but they do occur.

    This is from an article specifically discussing radiation damage, as it says. Mutations due to radiation damage may very well be 99% harmful, but that doesn't mean that in general 99% of mutations are harmful.

    It can eliminate the results of unfavourable variation.

    Improbable is very far from impossible.

    Bad analogy. In the case of Shakespeare you already have a pre-formed idea of what is good and what is not. The situation is nowhere near that black and white in the case of living things.

    Again, commenting on the effects of radiation.

    What follows this quote in the article? Please show me the following few paragraphs. You wouldn't be quoting selectively, I hope.

    Since it is relevant to this thread, I will also include a link here to Richard Dawkin's article regarding the addition of information to the genome by the process of evolution.
  19. James R Just this guy, you know? Staff Member


    Do you think we can have an argument free of appeals to authority? Let's just discuss the arguments I raised in my opening post. Do you see problems there? If so, what? Let's get away from quoting miscellaneous people. I can easily find as many pro-evolution quotes as you can find creationist quotes, but doing so doesn't really advance the argument.

    Let's discuss the actual issue, based on our own thoughts, ok?
  20. 786 Searching for Truth Valued Senior Member

    All Right. Basically what I am trying to say is that the whole theory rests on the word "CHANCE".
  21. 786 Searching for Truth Valued Senior Member

    Anyways, I am just curious. What would it take to disprove Evolution? I just want you view about this question.

    What thing if proven would shatter the Theory of Evolution?
    What would you want proven for you to reject the theory?
  22. James R Just this guy, you know? Staff Member

    Darwin's theory of evolution has 2 parts, not just one, as I said.

    1. Production of variation.
    2. Natural selection.

    Process 1 involves chance. Process 2 is what drives evolution in one direction or another.

    We did not evolve entirely by chance, like the roll of some dice. We evolved in a series of gradual steps over many generations, with slight random changes happening by chance at each stage. Detrimental changes were removed by natural selection, whilst beneficial changes were retained.
  23. 786 Searching for Truth Valued Senior Member

    Yes, gradual change is part of the theory. Which can be challenged by "Irreducible Complexity of Life".

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