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Author | Topic: How do you define the Theory of Evolution? | |||||||||||||||||||||||||||||||||||||||
Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: "How do you define the Theory of Evolution?". The theory that attempts to explain how species have and continue to change over time.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
CRR writes: Looking at domestic dogs we can see how new varieties have been produced over time within the existing species. The species has changed but there has not been a new species. Yes, the species has changed, and the theory of evolution explains why that happened. The theory deals with changes within a single species and it also deals with cases where populations split into two new populations that don't interbreed.
Your definition is quite consistent with Young Earth Creationism which theorizes that many modern species have been produced by speciation within the created kinds. Actually your definition doesn't even claim that much change. Perhaps I'm more of an evolutionist than you are. You would have to define "created kinds" in order for that statement to make sense.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: The Theory of Evolution is the theory that all the living forms in the world have arisen from a single source which itself arose naturally from an inorganic form. That is not the definition that scientists use. No theory of evolution I have seen requires abiogenesis. As to universal common descent, it is a finding that has come out of the theory, but isn't a requirement of the theory. If you want to use your own private definition for the theory of evolution then that is your prerogative. However, it seems to be a bit silly to beat on a strawman.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: Including or excluding abiogenesis is always a point of contention. Again I am following the example of more than one evolutionist. Who?
What good is a theory of origin of species that doesn't explain the origin of the first species? It is good for explaining how species changed after the emergence of the first life. If you reject every theory that does not explain the ultimate origin of the thing it studies then you will have to throw out most of science. The Germ Theory of Disease does not explain where the first germs came from. Do you reject that?
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
CRR writes: Yes species IS hard to define and there are many "species" (and genera) today than can exchange genetic material. If I remember correctly Darwin doubted species as a valid taxonomic unit and thought of a species as a well defined variety. One problem of using "species" in the definition is that you then need to clearly define "species", especially where the meaning can vary. If evolution is true, then species should be hard to define. There should be a fuzzy line between populations during incipient speciation. There should be a continuum of morphological changes between generations as a species changes over time. The very fact that species are hard to define is strong evidence in favor of evolution.
That depends on your definition of species. There could be geographical, behavioral, or ecological reasons for maintaining separate varieties even though they could still interbreed. This happens with cichlids where several varieties (species?) can live in the same lake but will interbreed if put in an aquarium. You are looking at this completely backwards. What matters is what is going on in the genomes of those populations. It doesn't matter if two species can interbreed. What matters is do they interbreed, and to what extent. What matters is if their genomes are diverging. Species are defined by the effect of genome divergence. For cichlids, what matters is if they DO interbreed in the wild, and if they do so in great enough numbers so that the genomes of the two populations do not diverge.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
CRR writes: Yes. After all the thread is "How do you define the Theory of Evolution?"So, how do you define the theory of evolution? Why even bother asking others what the theory of evolution is when you will just use your own personal definition and attack that personal definition, otherwise known as a strawman.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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ringo writes: I would define the Theory of Evolution as, "the explanation of how evolution works." Those explanations can also change depending on the context, as is true for all theories. Expecting a one paragraph definition of the theory to cover all possible contexts is a Fool's Errand because biology is a big, complicated, and divergent field. What may apply for eukaryotes may not apply for prokaryotes, with such things as horizontal genetic transfer and sexual reproduction causing different effects. How we define species will differ as it applies to asexual, sexual, living, or fossil species. Context is everything.
Third, note that there is no mention of how many original ancestors, nor any need to mention it. The explanation works whether there is one or forty. To use an analogy, gravity as an explanation for the orbit of planets works whether there are 8 planets or just 1.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: (Although I understand Lamark's theory of evolution is making a bit of a comeback with epigenetics) It isn't. Almost all epigenetic markers are removed during gamete production, so most epigenetic markers are not passed on. Of the ones that are passed on they only make small changes and only last a generation or two. Epigenetics is incapable of explaining the differences seen between species, and is also incapable of explaining long term evolutionary changes.
Of course Darwin's theory has been modified since it was first proposed and some would say that there are today several theories of evolution all derived from Darwin's theory. There is still just one theory of evolution.
Darwin took a whole book to discuss his theory and ague his case but many people (e.g. Kerkut, Coyne, Gould, Weintraub) have given definitions of one paragraph or less. Those paragraphs are still incapable of describing the entire breadth of the theory.
So when I proposed this topic I asked for your definition of the Theory of Evolution. And that is a set up. You want to force people to propose a short definition that will necessarily be inadequate in explaining the entire breadth of the theory. You will then point to this inadequacy as a problem for the entire theory, but the only problem is in your expectation that a theory as broad as the theory of evolution can be boiled down to one sentence or one paragraph.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: As a working definition for discussion purposes I would be prepared to accept the one Jerry Coyne gives in his book "Why Evolution is True" There isn't a single sentence in existence that covers all of evolution. We are using the theory of evolution which is a complex and broad theory that can't be condensed down into one sentence or one paragraph. For example, molecular biologists and population geneticists would argue that the mechanism producing the most change in the genome is neutral drift, not natural selection. That's just one criticism of many. What you really need to ask yourself is why you think such a complex and broad theory should be oversimplified.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: How much space do you need? Two paragraphs? Three? You need the entire compilation of peer reviewed work done over the last 150 years on evolution.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7
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CRR writes: So he wrote a whole book about why evolution is true and never defined the theory of evolution? The entire book is a part of the definition.
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Taq Member Posts: 9973 Joined: Member Rating: 5.7 |
CRR writes: Looks like a definition to me. And yet you will twist yourself into logical pretzels in order to not understand it. Edited by Taq, : No reason given.
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