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Is *All* of evolution propelled by natural selection?

  1. Apr 7, 2013 #1
    I've always thought that evolution was this mysterious property of the universe and that natural selection was almost a separate theory. Now that I look more into it, i can almost always rationalize an answer as to why a property of life is the way it is by natural selection. For example, i always thought that it was strange that life had such a strong attraction for sex. But then if you think about it, that is the single most predominant characteristic that would be passed on. Our ancestors who didn't really care for sex didn't have the opportunity to pass on those passive sexual characteristics. Anyways, my question is this: are evolution and natural selection different subjects that happen to intertwine once in a while or is natural selection the way ALL of evolution takes place? If so, how was the first single cell evolved by natural selection? If not, how does the separate theory of evolution operate? Charges repelling and attracting each other in certain configurations? I hope i'm being clear. Thanks
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  3. Apr 7, 2013 #2


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    Biological evolution is simply alleles changing over time. How they change is what theory explains. NS is one theory of change and specifically it accounts for adaptive evolution. There are other theories of change like genetic drift, sexual selection, genetic hitchhiking, gene flow, etc. Theories in science explain the facts.

    Natural selection doesn't require something to be "alive" or made of cells to work on it. It requires that there be variation, heredity, more offspring than the environment can support (ie; limited resources) and that chance any offspring has to survive and reproduce is not equal (like your example above, people who weren't interested in sex didn't pass on their genes).

    Things decidedly not cells then, can evolve over time. Think of viruses for example, and why you need to get a new flu shot every year. Or the resistance HIV acquires to antiretrovirals.

    Prior to "cells" there would have been more primitive (phylogically speaking) and more primitive ones before that, until you have a population of replicators that certainly aren't cells by our standards (our standards aside though NS can still act upon replicators so long as they follow the above rules).

    Some good websites for you would be Wiki's page on evolution and Berkeley's Evolution 101
  4. Apr 7, 2013 #3


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    No, evolution is the more fundamental concept. Natural selection is only one mechanism that explains some evolutionary changes. As an example, sexual selection was proposed to be a mechanism that explains processes that natural selection appears not to. http://www.nature.com/scitable/knowledge/library/sexual-selection-13255240
    Last edited: Apr 7, 2013
  5. Apr 7, 2013 #4


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    Sometimes, evolution is driven by asteroids which drop in unexpectedly or volcanoes which pop their tops. (See dinosaurs, etc.)
    If evolution occurred only in a laboratory setting, you might argue that natural selection drives it, but since evolution occurs in nature, chance occurrences like unexpected asteroids or inconvenient ice ages have great influence.
  6. Apr 8, 2013 #5
    Well when i think of natural selection i just relate it to an animal not living to pass on its genes. I guess a better way to explain my question would be this: People ask what invisible force is guiding these molecules to connect together in such a way that they could start life. Is there some kind of attraction or is it all natural selection/disasters, sexual selection, genetic hitchhiking, gene flow, and genetic drift... AKA something that prevents a certain organism to pass on its DNA.
  7. Apr 8, 2013 #6
    Natural selection is the process where naturally occurring selective pressures cause certain inheritable traits to be favored because these traits lead to quantitatively more offspring, or qualitatively more fit offspring. Natural selection doesn't require bad traits to be weeded out through death (though that is a very important mechanism through which natural selection can work), it simply describes how desirable inheritable traits (more likely to produce fit offspring) will tend to be favored and thus begin to propagate in a population.

    Inanimate matter -> life is biogenesis. How this process occured on Earth (or even whether this happened on this planet or the Earth was "seeded") is not understood; currently there are no working "theories" to describe biogenesis, though there are some interesting ideas and hypothesis out there if you want to look into it.

    Biogenesis is not evolution, they literally have nothing to do with each other. Evolution has to do with reproducing organisms with inheritable traits that are, by definition already living, it has nothing to do with inanimate matter.

    I don't understand the question.
  8. Apr 8, 2013 #7


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    Precellular evolution is quite poorly understood. The "RNA world" is a hypothesis which comes in many variations. Carl Woese essay "On the evolution of cells" contains remarks on this hypothesis.

    For some free articles you can google "RNA world" and "PLoS". The PLoS journals are peer-reviewed, which doesn't mean the articles are correct, but at least they'll indicate what many consider "disciplined" speculation.
  9. Apr 8, 2013 #8


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    Remember that the mechanism "natural selection" requires a statistically significant presence of competing traits.
    It is within such a situation that one trait is "more adapted" to the given circumstances.

    For tiny populations, or extremely rare traits, coincidences may have significant relative impact on what happens to evolve, until it reaches the level of statistical significance (where natural selection kicks in)
  10. Apr 8, 2013 #9
    Nature selection is just nature killing off large populations in favor of the survivors
  11. Apr 8, 2013 #10
    Alright. So to sum it up, we don't know how the first single celled life was formed from inanimate matter yet? But after you get to that one single celled organism, evolution is basically different mutations... the ones that help survival are passed on, and the ones that don't aren't passed on? So from a single cell to a human is just mutations all the way down?
  12. Apr 8, 2013 #11


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    Very roughly - yes. But the "last common ancestor" refers not necessarily to a single cell, but could be a population of single cells (in fact it is more commonly assumed to be a population, since the default assumption in evolution is that it refers to the evolution of populations). Furthermore, the population of single cells that may have formed the last common ancestor could have been formed from a merger of several populations of cells that arose separately. The reason for this terminology is that the "last common ancestor" is a technical term for a population whose existence is inferred from the common genetic material shared by existing life forms.
  13. Apr 8, 2013 #12


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    I would like to emphasize that ther is no conceptual disagreement between my own, and atyys answers as they have been given, relative to the issue of natural selection as a mechanism for evolution.
  14. Apr 8, 2013 #13
    Random mutations all the way down!

    Of course, there are many types of "random mutations". Plus, the word "random" has a few qualifiers. "Random" and "chance" in evolution refer to the lack of correlation with respect to survivability. They do not infer that the odds of a certain mutation surviving can't be biased by "environmental" conditions.

    "Random" does not be "unconditional". Not all events are independent. Hence, "conditional probability" has to be considered. You can't always calculate the probability of a series of "random events" by multiplying the probabilities together. Usually, "conditional" probabilities are involved.

    There is a lot of research being done on "epigenetic" effects in evolution. There are some odd ways that "choice" modulates natural selection. As an example, look up "Baldwin effect."

    “The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary process that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific selection for general learning ability. Selected offspring would tend to have an increased capacity for learning new skills rather than being confined to genetically coded, relatively fixed abilities. In effect, it places emphasis on the fact that the sustained behavior of a species or group can shape the evolution of that species. The "Baldwin effect" is better understood in evo-devo (evolutionary developmental biology) literature as a scenario in which a character or trait change occurring in an organism as a result of its interaction with its environment becomes gradually assimilated into its developmental genetic or epigenetic repertoire (Simpson, 1953; Newman, 2002). “

    The field of evolution is quite complicated and wonderful even though every mutation is "random" in the mathematical sense of the term.
  15. Apr 9, 2013 #14
    This is a common misconception. Anything that results in an organism having more progeny than its peers (for practical reasons it is usually the number of "grandchildren") is natural selection. It could be floppy ears and a cute smile.

    First look at artificial selection. Farmers breed there animals to produce more desirable offspring. The insight of natural selection was that the same thing would happen naturally without a farmer. It seems pretty obvious in hindsight.
  16. Apr 9, 2013 #15
    Something has to die though, nature is cruel
  17. Apr 9, 2013 #16
    All that matters is reproductive success or lack thereof. A dead creature cannot reproduce, but there are many other reasons for failure to reproduce.

    From a simplistic point of view, if a creature does not mate then that creature is a reproductive failure no matter how long it lives or how successful it is otherwise. From a more modern point of view, all that matters is the survival of genes.

    As an example, modern human beings seldom die before sexual maturity. But reproductive success still varies greatly. Some individuals have many descendants, some have none. So evolution continues nevertheless.
  18. Apr 10, 2013 #17


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    Evolution within a species population is, quite simply, a shift in the gene frequencies within that population, over a "meaningful" period of time (short-term oscillations in gene frequencies that leads "nowhere" is typically, for convenience, excluded from the conception of evolution)
  19. Apr 10, 2013 #18
    There are other options that occasionally present themselves. It can slow down its reproduction. Or it can merge with some other organism. Or it can go dormant for a while.

    Usually, it dies. Very often in great pain. Slowly.
  20. Apr 12, 2013 #19
    I dont think you can blame it all on mutations. There is the nature vs nurture issue: both the genes and the environment influence behaviour. So the "force" that you asked about is anything that influences behaviour. Just look a at a human being to see what influences us: environment, genes, intelligence, emotions, etc.
  21. Dec 18, 2015 #20
  22. Dec 18, 2015 #21
    Generally it is accepted today that both mutation AND natural selection play a part in driving evolution.
    Frankly I have never heard before of the proposal that it has to be exclusively one or the other.
    Mutations in DNA are often of little consequence, and some mutations are harmful.
    Occasionally though a mutation can confer an advantage, (meaning the organism with the mutation has a better chance of surviving and propagating) - that's the natural selection bit.

    Darwin's original theory of evolution by means of natural selection made no mention of DNA or mutations since DNA was unknown at the time.
    Last edited: Dec 18, 2015
  23. Dec 18, 2015 #22


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    It is well known to those who study evolution, and often refered to as neutral drift: http://www.evolution.berkeley.edu/evosite/evo101/IIIE5bNeutraltheory.shtml[/URL]

    It is definitely accepted that both selection and drift play important roles in evolution. Quantifying exactly how much of a role each plays is a more difficult question that probably has different answers depending on the system you study. There can often be important interplay between drift and selection in determining which evolutionary paths are available to an organism. Here's something I've previously written on the topic copy-pasted from a previous PF discussion [URL]https://www.physicsforums.com/threads/human-evolution-bacteria-conjugation.841969/#post-5284454[/URL]:

    [quote]A few notes on long term evolution experiments (LTEE):

    1. Subsequent to the 2008 PNAS paper describing the Cit+ strain, the Lenski lab published a follow up paper identifying some of the actualizing mutations behind the Cit+ phenotype: [URL]http://www.nature.com/nature/journal/v489/n7417/full/nature11514.html[/URL]. We discussed the paper in the following PF thread: [URL]https://www.physicsforums.com/threads/long-term-evolution-experiment.638509/[/URL]

    2. In the 2008 PNAS paper, the authors note that all each of the 12 cultures in the LTEE had grown for long enough times such that each culture would sample all single point mutations possible in the genome. However, many evolutionary studies showed that [URL='https://en.wikipedia.org/wiki/Epistasis']epistasis[/URL] plays very important roles in evolution. The same point mutation can have different effects on an organism's phenotype depending on what other mutations are present. Thus, sampling every single point mutation cannot tell you the effect of every possible pair of single point mutations. Even though the experiment sampled all single point mutations, it has not sampled all combinations of mutations, so much of the evolutionary landscape still remains unexplored.

    3. In many cases, the evolution of beneficial traits require certain permissive mutations to precede acquisition of the actualizing mutations that confer the beneficial phenotype. In the absence of the permissive mutations, the actualizing mutations can be deleterious instead. This situation appears to be the case for the evolution of the Cit+ phenotype in the Lenski experiment, and this phenomenon has also been observed in the evolution of steroid receptors: [URL]http://www.ncbi.nlm.nih.gov/pubmed/17702911[/URL]

    4. In some cases, the permissive mutations confer an evolutionary benefit to the organism, so there exists an adaptive path toward the evolution of the beneficial trait (i.e. the fitness of the organism increases at all steps along the way). For example, this has been seen in the evolution of antibiotic resistance: [URL]http://www.sciencemag.org/content/312/5770/111.long[/URL] However, in the cases of the Cit+ and steroid receptor evolution, the permissive mutations seem to be neutral. Thus, evolution of these new phenotypes depended not only on natural selection, but also neutral drift. More broadly, given the pervasive roles of epistasis in evolution, neutral drift is likely continually opening and closing various potential adaptive paths towards new phenotypes, consistent with previous thoughts about the role of historical contingency on evolution. If true, this would suggest that evolution, to some extent, is fundamentally unpredictable.[/quote]

    At some point, I should probably write up an Insight article on this topic.
    Last edited by a moderator: May 7, 2017
  24. Dec 18, 2015 #23
    Evolution is a more general term, that things came to be in a gradual way. The theory of evolution was developed by Robert Chambers. It applied to planets as well as life. He wasn't a scientist and a lot of the details were wrong, but evolution was his idea. His book was Vestiges of the Natural History of Creation. It was a best seller and the essential idea was there. The author thought that stars, the earth, and living beings all evolved. He was right, but isn't remembered because the science was amateur. The author believed that insects could be created by electricity and other things. It was published anonymously, with great care to keep the author secret. He knew that his views would be denounced and wanted to avoid the fallout. He had his wife copy the entire book so that his handwriting wouldn't be recognized.

    Chambers inspired Darwin and Wallace to come up with the theory of natural selection, which applies to life only. That's what it was always called when I was in college. Many loosely call it "evolution."
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