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Race of humans cannot start with one man and one women?

  1. Oct 30, 2005 #1
    Can someone please explain the reason as to why a race of humans cannot start with one man and one women? This silly idea keeps popping up with creation people and I can't see that this is even what the Bible holds true. But I'd like to hear as to why this can't be true from a biological point of view. I have vague recollections of genetic problems which would make this far from being a viable race. Thanks.

    Pete
     
  2. jcsd
  3. Oct 30, 2005 #2

    Moonbear

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    No reason it couldn't happen at a hypothetical level; you'd have a founder effect (lack of genetic variation that can leave the species with difficulty adapting to changes in the environment), but if the environment was stable enough as mutations occurred and variation developed, it's possible. But that's not the contradiction between evolution and creationism. The issue is where the first modern humans (Homo sapiens sapiens) came from. In creationism, they posit that these first humans were created by a god, completely de novo, exactly as they currently appear, within 7 days of the creation of the entire universe (some creationists don't hold as strictly to this time-frame, but still believe that all species were created by god at the same time, exactly as they are now, with no change over time). In evolutionary theory, they came to exist through a progression of changes from ancestral species until they were sufficiently different from the ancestral species to be designated a new species, and it happened much more recently than 7 days after the start of the universe. Evolutionary theory also doesn't require that there were only two first humans in this gradual progression from one species to another, so much of the variation in traits already present in the prior species could be retained in humans, with of course the exception of those traits that distinguish modern humans from their ancestors.
     
  4. Oct 30, 2005 #3
    so basically, can we prove that creationism is not accurate because we can look at ancient skulls from human beings and see that they did change instead of having the same form since creation?
     
  5. Oct 30, 2005 #4

    Moonbear

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    That, along with stratification of fossils in different geological layers, is part of the evidence that refutes creationism in favor of evolution.
     
  6. Oct 30, 2005 #5
    Minimum population required for racial founding

    A biological race can indeed be founded by only one male and one female:
    groups.yahoo.com/group/e-l/messages/13925?threaded=1&viscount=7&m=e

     
  7. Oct 30, 2005 #6

    Moonbear

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    hitssquad, that first link can only be accessed by members, apparently.

    I think pmb_phy meant species, and used race in the common usage of "human race," not in the sense of biological subspecies, but your second link does help illustrate in a real example that the founder effect does not mean humans can't survive. It also helps counter the young-Earth creationist argument by showing that with such a founder effect, even after 500-1000 years, individuals in a population still have nearly identical DNA, so a few thousand years is not enough time for the amount of variation currently observed in the human population as a whole to have developed.
     
  8. Oct 30, 2005 #7
    I personally do not adhere to what others use the term "creationism" to mean. To me it means that God created the universe and he created man and the mechanism that he used to do so is described by evolution.

    Pete
     
  9. Oct 31, 2005 #8
    I would have thought the minimum and maximum population required to found a race would be 1. Say you define a race as different to another race on the basis it has property X. The first male or female to have property X passes this property on to some of its progeny, who in turn pass it on to some of theirs, etc, etc. If the mutation in question is what differentiates the race from that from which it evolved, then the source of that mutation will always be the founder of that race, no?
     
  10. Oct 31, 2005 #9

    Moonbear

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    First, let's be clear here and not confuse terms. In biology, race and species are different terms. I believe we are really talking about species, so let's use that term.

    Second, it isn't that simple. It would take more than a single mutation to create a new species. New species evolve through an accumulation of new traits over time, and are determined to be a species at a population level, not at an individual level. If it is only one individual, it is not a species but a mutant. In hitssquad's example, a new species has not evolved in that tribe due to the founder effect, they are still very definitely human. The example serves to show that the founder effect is not lethal at a population level, not that it necessarily leads to a new species evolving.
     
  11. Oct 31, 2005 #10

    Phobos

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    There is certainly a broad spectrum of beliefs about it and your description seems to fit what is sometimes called "theistic evolution". Technically, the term "creationism" could include that, but usually "creationism" refers to an explanation that does not include so-called "macro" evolution (i.e., creationists may agree that species can vary up to a point, but not have larger changes).

    Current Intelligent Design advocates are playing a little game by trying to appeal to the broadest range possible...inclusive of both young-earth, man-from-clay creationists all the way across the spectrum to theistic evolutionists.
     
  12. Nov 1, 2005 #11
    one reason is that it doesnt give a genetical variation, everyone would almost be genetical identical
     
  13. Nov 1, 2005 #12
    True, but that's not the question. The question is how many animals are required to start a species, not how many are needed before you call it a species. As I said earlier, if a species is defined by having a property X, then the first animal with property X who has progeny some of whom receive property X and so on and so forth has essentially started a new species, irrespective of whether or not that animal is ever counted among them.

    My point was that just having one or two animals with property X does not spell doom for that species, since those animals will mate and have progeny with animals of their (parent) species which do not have property X. Once enough animals have property X and this property effects those animals' fitness, then yes - you can now say "new species". However, the species has still been started with one animal with property X, be it one mutation or a set of mutations, some of which were inherited (I believe this answers your other point).
     
  14. Nov 1, 2005 #13

    daniel_i_l

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    We all are almost genetical identical - more than 98% I think. I read on Nova that we share about 90% with fruitflys.
     
  15. Nov 1, 2005 #14

    Phobos

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    Not sure it's so clear cut. What you are describing sounds like the potential start of a speciation event, but you may not get actual speciation unless that subgroup becomes isolated from the parent population and continues to diversify. If the Property X'ers are still breeding with the parent population, then it's still essentially one species (one gene pool), albeit with a more diverse genetic range.

    So, if you were able to identify a clear speciation event, you might not be able to tell how many originals there were because those individuals were mixed in the parent population.
     
  16. Nov 1, 2005 #15
    Yes, but then the species would not emerge and so not be the subject of the question: "could it have emerged from one/two animals?" Only cases where a new species does emerge are relevant.

    Well, that's kind of what I was arguing against (although I defeated myself in that argument in my head later), since I was saying that there will be a first animal that has the property X that would later define it as part of that species.

    Of course, the argument was incorrect. Say property X consists of mutation A and mutation B. Adam has mutation A, Eve has mutation B, they beget children, several of which have both mutations and so property X.

    This disproves my "maximum of one" argument from before, but my "minimum of one" still holds (I think).
     
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