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    #26
    Stuck in a Cul De Sac

    BrunoMaggiore wrote:
    Could not the tendency to become fatter (i.e. relatively) have been selected against, which wouldn't have required anyone ultimately running to fat?
    In principle, yes; in practice, why?

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      #27
      Stuck in a Cul De Sac

      Because it made you slower?

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        #28
        Stuck in a Cul De Sac

        Ginger Yellow wrote:
        I don't think he is assuming that at all. He's just counteracting the argument that mammals won out because they were objectively superior.
        Yeah, sure, but (a) straw man, innit, at least as far as debates within biology are concerned, and (b) if he uses phrases like "the dominant domain of the dinosaurs", he's to say the least of it inviting misunderstanding, if not actually falling prey to it.

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          #29
          Stuck in a Cul De Sac

          BrunoMaggiore wrote:
          Because it made you slower?
          Enough to outweigh your superior ability to survive the winter?

          Actually, the fact that there seems to be a high degree of heritable variation in obesity in modern populations suggests that this trait can't have been under strong selection pressure for very long, or else that variation would have been used up.

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            #30
            Stuck in a Cul De Sac

            Gould was not exactly a stranger to fighting straw men or inviting misunderstanding.

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              #31
              Stuck in a Cul De Sac

              Word.

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                #32
                Stuck in a Cul De Sac

                Wyatt Earp wrote:
                BrunoMaggiore wrote:
                Because it made you slower?
                Enough to outweigh your superior ability to survive the winter?
                (In Africa?) I would think you'd have to get quite a bit fatter to have a noticeably superior ability to survive winters, but not much fatter to become noticeably slower. The trait would seem more directly related to the latter outcome.

                Actually, the fact that there seems to be a high degree of heritable variation in obesity in modern populations suggests that this trait can't have been under strong selection pressure for very long, or that variation would have been used up.
                How long is very long?

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                  #33
                  Stuck in a Cul De Sac

                  BrunoMaggiore wrote:
                  Wyatt Earp wrote:
                  BrunoMaggiore wrote:
                  Because it made you slower?
                  Enough to outweigh your superior ability to survive the winter?
                  (In Africa?)
                  (Sigh) OK: lean times generally.

                  I would think you'd have to get quite a bit fatter to have a noticeably superior ability to survive winters, but not much fatter to become noticeably slower.
                  What are you basing that on? The fact is, we seem to be adapted to eat as much sugar and fat as we can get our hands on, suggesting that in the environment in which our ancestors evolved, diseases of plenty are unlikely to have been much of a problem.

                  How long is very long?
                  Depends on the strength of selection pressure. But "modern times" have existed for, at a generous estimate, 200 years, whereas anatomically modern humans have been around for (I think) around 50-100 thousand. Any selection pressure against fat deposition has to have been weak enough not to have used up the variation in that time, which is pretty weak.

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                    #34
                    Stuck in a Cul De Sac

                    It's interesting, by contrast, how humans have managed to seriously change the appearance of dogs and cats in just a couple of centuries, using selective breeding. (What is lesser known is that genetic make-up of dogs within breeds varies wildly, so that totally different breeds can have more in common that two dogs within the same breed. But that's another topic entirely.)
                    On this subject, Wyatt's point about the strength of selection pressure is very important. Artificial selection, particularly in crops/cattle/working animals creates huge selection pressures. The difference between maize soon after domestication by the Native Americans and modern varieties is staggering. Guns Germs and Steel has a fascinating table of seed sizes for many common crops and their closest wild relatives. See, for instance, teosinte vs maize:

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                      #35
                      Stuck in a Cul De Sac

                      Wyatt Earp wrote:
                      What are you basing that on? The fact is, we seem to be adapted to eat as much sugar and fat as we can get our hands on, suggesting that in the environment in which our ancestors evolved, diseases of plenty are unlikely to have been much of a problem.

                      Depends on the strength of selection pressure. But "modern times" have existed for, at a generous estimate, 200 years, whereas anatomically modern humans have been around for (I think) around 50-100 thousand. Any selection pressure against fat deposition has to have been weak enough not to have used up the variation in that time, which is pretty weak.
                      I'm sure you're right about all this; my questions were more the sort I might raise in class (as a dumb student, that is). What we've never had, then, is a built-in disposition not to be fat, since it didn't "come up" often enough when it would have been most useful, though it probably would eventually have done, if we'd needed to continue relying on speed and stamina to survive? Do I have that right at all?

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                        #36
                        Stuck in a Cul De Sac

                        Lamarck was delightfully bonkers Clive.
                        I also thought you seemed to be heading in towards going in a similar direction, thing about his ideas was they do kind of make sense in that there is a logic to it. Also his stuff about embryos going through all the stages of evolution as they grow, like from having gills to being like reptiles then other mammals then human, you've got to love the poetry of that.

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                          #37
                          Stuck in a Cul De Sac

                          To be fair, until we had a hereditary mechanism or systematic evidence to disprove his hypothesis, Lamarck's ideas weren't particularly crazy. Also, I wasn't aware that Lamarck was into ontogeny recapitulating phylogeny - that was Haeckel's bag, although Haeckel was a supporter of Lamarck.

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                            #38
                            Stuck in a Cul De Sac

                            Well quite that's why I said it makes a lot of sense in its way.

                            Haeckel invented the term for it but I think the concept was around for a bit before that. eg von Baer. I think the crucial difference was that it according to Von Baer it was the embryos of fish and birds etc that the human one's stages resembled whereas Haeckel said it was the adults'.

                            I worked out why I thought Lamarck said this in particular - it's because Chambers used both ideas. Sorry, Jean Baptiste.

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                              #39
                              Stuck in a Cul De Sac

                              I just googled and it's all complex. It's the difference between whether the embryos all follow one line and are just born at different stages (shorter gestation times!) or whether there's a line they all follow but each species branches of at a point and then develops more on its own. By the looks of it. Someone called Carpenter and someone called Lord are involved. I have run out of time to look as I am going to meet 1890 for lunch.

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                                #40
                                Stuck in a Cul De Sac

                                ... thing about his ideas was they do kind of make sense in that there is a logic to it.
                                Well, it's been pointed out, by Dawkins and Dennett among others, that it's not just that Lamarckism's empirically wrong, but that as a means of generating adaptations it can't possibly work, even in principle.

                                Or rather, it can't possibly work on its own. It's conceivable that some form of Lamarckian mechanism might co-exist with natural selection, though that doesn't seem to have happened anywhere on Earth*. But you need natural selection to be there first, at the very least, because any Lamarckian mechanism would have, itself, to be highly adapted in order to get off the ground. Lamarckian stuff can only go on, in principle, in systems that are already quite complex, and only natural selection can "bootstrap" you to the required level of complexity.

                                Thing is, with the way Darwinism happens to work on Earth, Lamarckism's flat impossible and that's that. There's no conceivable way that an acquired characteristic could work its way back into the genes. That would be like slicing a cake and thereby changing Delia's recipe for it.

                                (*Meme me no memes, GY. Warning you now.)

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                                  #41
                                  Stuck in a Cul De Sac

                                  Eh?

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                                    #42
                                    Stuck in a Cul De Sac

                                    I just don't want any knowledgeable person suggesting memes as a quasi-Lamarckian system of replicators, that's all. Ain't having it.

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                                      #43
                                      Stuck in a Cul De Sac

                                      You've dug yourself a trap there. How are memes quasi-Larmarckian? The whole point of them is as an analogue to natual selection in genes.

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                                        #44
                                        Stuck in a Cul De Sac

                                        Well, meme fans sometimes say that one key difference is that traits can be acquired then passed on, and I wanted to head that whole conversation off. But have achieved the exact opposite...

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