Tuesday, June 14, 2011

As Promised

Here is the first installment of my noble attempts to educate you sufficient to refute common arguments against the theory of evolution by natural selection. Remember (Ammon) that my purpose here is not to convince skeptics that current evolutionary theory is the final word, I merely wish to correct common misconceptions about evolution. In this way, as you continue to think about the validity of these theories you won't be encumbered by a false understanding of what the theory actually states.

Oh, and I won't cover all 10 of the previosly stated misconceptions in this post for the sake of time. I'll do 5 now and 5 later.

1 - "Evolution is just a theory" - The implication here is that evolution hasn't been proven, that it's just an unsubstantiated guess. People who say this are most likely to be people who don't know what Darwin actually theorized and are too lazy to look into it so they just dismiss it out of hand. They're like agnostics; they prefer to remain ignorant. But let's analyze the actual statement. While it's true that evolution is a theory, the use of the word "JUST" reveals a fundamental inability to comprehend what a scientific theory is. Well, first of all a simple definition of evolution is "a change in allele (ie - some variant of a gene) frequency over time" and is thus an undisputed fact. The informal usage of the word "theory" is very different than the scientific use of the term. In science, a theory is a collection of proposals to explain some observed phenomena. The proposals are supported and substantiated by alot of evidence over time. Often, some will claim that evolution is not a scientific law. Well, it's not a chain of progression. Scientific theories don't graduate to the status of law given a sufficient amount of evidence. Theories remain theories. These theories continue to accumulate evidence in support of them, or new evidence arises which causes the community to tweak the theory a bit. The theory of evolution by natural selection continues to be supported by all available evidence across all fields of biology (genetics, embryology, anatomy, microbiology, paleontology, behavioral science, molecular biology, etc.)

2 - There are no transitional fossils - A transitional fossil would be one that represents an intermediate between two species. Thus, it would have certain features representative of species A and others that are representative of species B. Well, first of all this is just false. Secondly, the fossil is record is imperfect and always will be given that the conditions for fossilization to occur are very stringent and the occurrence of fossil formation is the rare exception to the rule. However, we do have transitional fossils found in different strata of the earth documenting dramatic progressive changes in features of ancient animals. This, of course, all supports the idea of descent with modification.

3 - If we all evolved from apes, why are there still apes running around? - Well the first problem with this is that the asker doesn't understand that the theory of evolution doesn't claim that we evolved from modern apes. Modern apes and humans share a common ancestor that no longer exists. An ancestral species doesn't have to give rise to just one descendant. There can be parallel evolution where different species evolve differently (based on the available gene alleles and environmental conditions) from the common ancestor. This is apparently what happened. But either way, just because a new lineage begins to split off doesn't mean that an ancestral species HAS to go extinct. So even if we descended from modern apes, that doesn't mean modern apes would have to go extinct in order for us to exist.

The explanation for this one is a bit more subtle and I fear I'm having trouble explaining it but inside this statement is a fundamental misunderstanding about the theory of evolution so don't ever be foolish enought to say that evolution can't be true because there are still apes on the earth. On a personal note, if you've ever spent time really staring at an ape in the zoo you can't honestly tell me that there isn't something "more" there. Looking, really looking, into the eyes of an ape is worlds different that looking at a bird or even an elephant or giraffe. There's a closer relationship there, there's alot more commonality and it is very evident. It's quite an experience.

4 - Natural selection always leads to greater complexity (organisms are always "getting better") - Simply false. Selection is blind to anything except whether or not an organism can reproduce. In nature, good enough is good enough.

5 - Evolution promotes the survival of species - Evolution can take place at the level of a gene and what promotes the survival of a particular gene doesn't always lead to great reproductive fitness for a population. For example there are parasitic DNA elements that can spread through a population but cause disease. Hemophilia is caused by such a DNA element and this certainly doesn't promote survival. Varying mutation rates can affect survival as well. A mutation rate that is too high can be very detrimental to a species because nature doesn't have time to weed out the "bad" mutations before they spread too widely. For example, HIV exists on a very narrow error threshold. HIV mutates so rapidly that it is precariously close to destroying itself because many of the mutations create unviable virus.

17 comments:

  1. Interesting. I look forward to further installments.

    ReplyDelete
  2. Glad you finally posted. I haven't read it yet, but I will tonight... on my iPad :)

    See, you write this stuff... and I make it exciting to read.

    :)

    ReplyDelete
  3. OK, kinda boring stuff here :)

    Now explain how two Asexual organisms randomly evolved into sexual organisms (both a male and a female), near the same location on earth, @ the same time so that they could conveniently fool around and eventually mate, creating a new anisogamous species.

    Or rather, what would the statistical probability be of this actually happening based on the randomness of the theory of evolution:)

    ReplyDelete
  4. Ammon you are aware that there are organisms that can reproduce on their own or with a mate right?

    ReplyDelete
  5. I'm not talking about what we have now. I am talking about how or why an asexual organism, in the first place, would develop something that is fundamentally "wrong" according to the ideas laid out by evolution.

    ReplyDelete
  6. There is nothing fundamentally wrong with sexual vs asexual reproduction in terms of the theory of evolution. In fact, sexual reproduction presents certain advantages in terms of genetic variation that would make it a viable mutation in terms of survivability. Maybe I'm just not understanding what you are trying to argue.

    ReplyDelete
  7. Oh, and it does matter what he have now, as it shows the the possible bridge step in the evolutionary process where an organism has the ability to do both. That means it is plausible that other organisms had both, but over time the population lost the ability to reproduce asexually.

    ReplyDelete
  8. I echo Kyle's comments. I tried to post these exact ideas earlier today but had trouble with my computer at work.

    ReplyDelete
  9. I think that you guys are missing my point. I will let others, professionals who are working on Evolution full time, say it better.

    In his book “Evolution: The Triumph of an Idea,” Carl Zimmer concedes:

    “Sex is not only unnecessary, but it ought to be a recipe for evolutionary disaster. For one thing, it is an inefficient way to reproduce…And sex carries other costs as well…By all rights, any group of animals that evolves sexual reproduction should be promptly outcompeted by nonsexual ones. And yet sex reigns… Why is sex a success, despite all its disadvantages?”

    In his book, “The Masterpiece of Nature: The Evolution of Genetics and Sexuality”, Graham Bell described the dilemma in the following manner:

    “Sex is the queen of problems in evolutionary biology. Perhaps no other natural phenomenon has aroused so much interest; certainly none has sowed as much confusion. The insights of Darwin and Mendel, which have illuminated so many mysteries, have so far failed to shed more than a dim and wavering light on the central mystery of sexuality, emphasizing its obscurity by its very isolation.”

    There are currently 4 main theories on "why" and "How" an organism that can reproduce itself, would evolve into an organism that cannot. Not only that, but it only passes on half of it's genome, not all of it.

    What they concede is that it really dosn't make sense based on the "survival of the fittest" idea. it is opposite of it. What makes even less sense is that the VAST MAJORITY of species use sex in some fashion or another to reproduce.

    That is what I am talking about. Not that sex exists. that is pretty much a given.

    And pointing out that fungus plants can do both is kind of dumb. we are NOT even close to mushrooms.

    ReplyDelete
  10. Oh, and of the 4 main theories, I have read that in recent years basically only one is holding any water at all. And that is very sketchy.

    From most articles I have read, almost all professionals working in the field concede that it doesn't make sense. They can't explain it. And they are daily toward proving laws of evolution.

    ReplyDelete
  11. **I am posting this for Troy**

    who apparently cannot figure out how to work a computer. I'm not sure I trust the opinion of a "scientist" who cannot even post to his own blog :)

    "I disagree Ammon. True, sexual reproduction as efficient as asexual reproduction but you're
    misrepresenting scientific consensus. You're using only a single quote from a huge hardback book on evolution from Carl Zimmer. The last line of your quote is 'why is sex a success despite all its disadvantages?' Well, he probably goes on in that book to answer that question. I've read a good part of that book and Carl Zimmer is no skeptic of evolution. Science does have explanations for the success of sexual reproduction and Carl Zimmer himself wrote an article in Science (one of the two most widely read and most respectable scientific journals) in 2009 explaining just this issue.

    I'm not quite sure which websites and studies you are finding but everything that I look at is discussing studies that demonstrate a reason why organisms would want to evolve to reproduce sexually. For instance, I just read a summary of a study from the University of Iowa on freshwater snails. The sexually reproducing variety of this snail accumulates fewer harmful DNA mutations than their asexually reproducting counterpart.

    Further studies from Indiana over the course of 20 years have demonstrated that sexual reproduction offers clear advantages in a parasite-rich environment.

    An entire 8-page, peer-reviewed article titled "Advantages of sexual reproduction" was published in the journal Develompental Genetics.

    So while it's true that science doesn't FULLY understand the evolution of sex it certainly DOES see alot of the reasons it makes sense. Don't despair because science can't fully explain something. After all, how can you know when you FULLY understand something. I think that is impossible.

    The Graham Bell quote that you share was from 1982 and, while informative, 29 years is a long long time in science. We know far more now than we did then.

    The end point is this - while there are costs to the process of sexual reproduction, there are benefits as
    well which can readily be explained. The fact that sexual reproduction dominates in the animal kingdom makes it clear that nature selected for this type of reproduction. And may I, just as an aside, express my gratitude for that as a man. Continuing on then, sexually reproduction certainly isn't suitable for all forms of life or we wouldn't find so many examples of asexual reproduction in our world still. But it has
    served to give an advantage to higher organisms.

    "I think that a misconception that is being relayed in this whole discussion though is that evolution always results in the perfect way of doing things. That's not the case and so it shouldn't surprise that evolution has resulted in sexual reproduction for certain species despite some of the negatives. It's a cost-benefit
    thing and clearly the benefits outweigh the costs.

    Ammon, what are the "4 main theories" that you mention and where did you find them?"

    ReplyDelete
  12. I am glad that you noted I was quoting from a respected expert. But you failed to notice the second quote that was given much more recently. Nice oversight.

    The four hypothesis are:
    1. The Lottery Principal
    2. The Tangled Bank Hypothesis
    3. The Red Queen Hypothesis
    4. The DNA Repair Hypothesis

    I have read about all of these from multiple sources. Most for their respective theories.

    NONE of them really explain what would "motivate" evolution to do the following:

    A chance occurrence that brings about an interdependent process of, first, splitting the genetic information into equal halves, and, second, recombining it through sexual reproduction.

    Not only is an intricate to produce a sperm or egg cell in the first place by meiosis, but another equally intricate mechanism is required to rejoin the "split" genetic information during fertilization in order to produce the zygote, which will become the embryo, which will become the fetus, which eventually will become the newborn.

    The "chance" that evolution would drift toward this type of "development" really doesn't make sense in my mind based on my current understanding of the theory of evolution. This appears to me to be evidence of intelligent design. Especially when the cards really don't add up. Do we understand the benefits of sexual reproduction today? of course. But what would motivate something "billions" of years ago to drift toward something that is so much riskier!

    Balogna.

    ReplyDelete
  13. Bologna motivates the best things in the worst of creatures. Have you ever seen the lengths to which a hostile pit-bull will go to get a slice of that stuff?

    Take your hand clean off :)

    ReplyDelete
  14. Ammon, I am confused as to why you think evolution needs to be motivated. From my understanding of what Troy is arguing, that is one of the fundamental misunderstandings of current evolutionary theory.
    Bio-molecular changes occur, some beneficial, some not, and a process of selection occurs in the population depending on the environment that may weed out, not affect, or spread the levels of the mutation in the population. It doesn't have to develop simultaneously, and it doesn't have to be motivated, it just has to happen.

    Oh, and I was referring to some invertebrate species having the ability to reproduce sexually/asexually, not to fungi.

    ReplyDelete
  15. True, the origin requires no motivation. In fact, natural selection is blind. Remember good enough is good enough. However, once established, a mutation or novel function must have a benefit in order for nature to continue to select in favor of it and I think I will pull my hair out if I have to repeat again the benefits of sexual reproduction. I think we're not at odds over that issue.

    Another misconception that you're demonstrating Ammon is that evolution always selects for the most efficient and least risky process. This is untrue. The benefits need simply to outweigh the risks. You are probably unaware of the process by which T cells develop in our thymus. It is a hiiiiiiiiighly inefficient process if you just look at the process alone. 95% of all developing T cells are killed in the thymus because they are not suitable. In fact, many of them are produced in a fashion that would cause them to react with our own tissues (this is called autoimmunity). These ones, among many others, need to be killed and not allowed into our circulation. Is it an efficient process to expend so much energy and resources to make so many cells when 95% of them will be killed before they are fully developed? The obvious answer is no. So why do we do it this way? It's because random rearrangement of the pivotal T cell receptor genes is necessary to generate a T cell repertoire with enough diversity to confront pathogenic threats that we do not even know we will be encountering. The trade off is that random gene rearrangement also creates a whooooole lot of T cells that are potentially harmful to us. Very, very inefficient but the benefit makes the energy expenditure worthwhile.

    Sexual reproduction; very inefficient but the benefits outweigh the downside. It's not really that complicated.

    ReplyDelete
  16. Oh, and in your last post Ammon why did you put the word billions in quotation marks towards the end of your comment? Are you hinting that you don't believe life on earth developed billions of years ago? Because that's another discussion we can have :)

    ReplyDelete
  17. You guys are wierd

    I LOVE MY IPAD! and I can't wait for it to evolve :)

    ReplyDelete