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[evol-psych] Re: Neanderthals not human ancestors

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  • H. M. Hubey
    ... Well, let s see our options. Logic is not sufficient. Nobody wants to use probability theory or even learn it. Fuzzy logic is apparently for computer
    Message 1 of 12 , Mar 31, 2000
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      "C. Loring Brace" wrote:
      >
      > > >
      > > > All categories are arbitrary. "Speciation" is an arbitrary point on a
      > > > continuum of increasing reproductive isolation, and the mechanisms that
      > > > promote reproductive isolation are many and varied.
      > >
      > > No I cannot agree with this statement. That is like claiming a woman
      > > can be almost pregnant. Either there is fertility or there is not.
      > > This is definitely one of those discontinous functions which has
      > > great implications for evolution.
      >
      > And yet in the case of Rana pipiens, the Canadian specimens cannot breed
      > with the Florida ones, but there is a complete transect from Canada to
      > Florida where adjacent groups are perfectly fertile with each other.

      Well, let's see our options.

      Logic is not sufficient. Nobody wants to use probability theory or
      even learn it. Fuzzy logic is apparently for computer scientists.

      So we can spend the next 500 years discussing these problems in
      English or another natural language and get as far as the
      Medieval philosophers did.


      --
      M. Hubey, Computer Science
      /\/\/\/\...I love humanity. It's people I can't stand.../\/\/\/\/\/\/\
      hubeyh@... =-=-=-= http://www.csam.montclair.edu/~hubey
    • Peter Frost
      From: C. Loring Brace ... On this point, I can only quote what Tyrrell and Chamberlain found in their study of Krapina Neanderthal dental
      Message 2 of 12 , Apr 3, 2000
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        From: C. Loring Brace <clbrace@...>

        > Oh that latter simply is not true. Late European Neanderthal dental
        > traits and dental metrics are indistinguishable from early 'modern'
        > European dental traits and metrics but quite different from the traits and
        > metrics of any other people in the world.


        On this point, I can only quote what Tyrrell and Chamberlain found in their
        study of Krapina Neanderthal dental traits:

        "All of the modern human populations are included within a global cluster
        that is well separated from the Krapina Neanderthals. The average distance
        between the Neanderthals and modern humans is substantially greater than the
        mean pairwise distance between modern human populations. These findings
        agree with earlier morphometric studies and mtDNA analysis in demonstrating
        the distinctiveness of Neanderthals. There is no evidence for Neanderthals
        being closer to modern Europeans than to any other modern human population."

        Tyrrell, A.J. and A.T. Chamberlain. 1998. Non-metric trait evidence for
        modern human affinities and the distinctiveness of Neanderthals. Journal of
        Human Evolution 34:549-554.

        The Krapina Neanderthals date back to the last interglacial and would
        therefore fall into the "late Neanderthal" category. Moreover, the dental
        traits in question are dental crown variants, which are normally considered
        to be evolutionarily conservative and of low selective value. If modern
        Europeans are indeed the descendents of Neanderthals, it's hard to see how
        such traits could undergo such rapid change over a relatively short span of
        evolutionary time.

        We've discussed this point before and I think your position was that dental
        metrics can evolve rather quickly. That argument may be true for metrics
        (which have a higher selective value) but I don't see how it could hold true
        for crown variants (which are close to selective neutrality). Perhaps I'm
        missing something here.

        Of course, anything is possible if one makes enough assumptions. Perhaps
        the Krapina Neanderthals were somehow atypical. Perhaps there was an
        unusual combination of genetic drift, founder effects, exceptionally strong
        selective pressures, etc. subsequent to them. As I see it, and perhaps I'm
        wrong, the most parsimonious explanation seems to be population replacement.

        -------------------------------------------------------------------
        Dr. Peter Frost

        Groupe d'études Inuit et circumpolaires
        Pavillon De Koninck
        Université Laval
        Sainte-Foy (Québec)
        G1K 7P4 CANADA
        L'homme qui veut faire l'ange finit par faire la bête.
        Tel. (418) 683-1740

        Website: http://www.globetrotter.net/gt/usagers/pfrost
      • C. Loring Brace
        ... When that paper came out, I was afraid that just the kind of misinterpretation that is represented here would be the result. I shall try to give some
        Message 3 of 12 , Apr 3, 2000
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          On Mon, 3 Apr 2000, Peter Frost wrote:

          > From: C. Loring Brace <clbrace@...>
          >
          > > Oh that latter simply is not true. Late European Neanderthal dental
          > > traits and dental metrics are indistinguishable from early 'modern'
          > > European dental traits and metrics but quite different from the traits and
          > > metrics of any other people in the world.
          >
          >
          > On this point, I can only quote what Tyrrell and Chamberlain found in their
          > study of Krapina Neanderthal dental traits:
          >
          > "All of the modern human populations are included within a global cluster
          > that is well separated from the Krapina Neanderthals. The average distance
          > between the Neanderthals and modern humans is substantially greater than the
          > mean pairwise distance between modern human populations. These findings
          > agree with earlier morphometric studies and mtDNA analysis in demonstrating
          > the distinctiveness of Neanderthals. There is no evidence for Neanderthals
          > being closer to modern Europeans than to any other modern human population."
          >
          > Tyrrell, A.J. and A.T. Chamberlain. 1998. Non-metric trait evidence for
          > modern human affinities and the distinctiveness of Neanderthals. Journal of
          > Human Evolution 34:549-554.

          When that paper came out, I was afraid that just the kind of
          misinterpretation that is represented here would be the result. I shall
          try to give some perspective on a point-by-point basis.


          >
          > The Krapina Neanderthals date back to the last interglacial and would
          > therefore fall into the "late Neanderthal" category.

          Both ESR and Uranium Series dates put Krapina at 130,000. That is early
          Neanderthals and not Late Neanderthals. The latter are those that date to
          40,000 years ago or less, i.e. Vindija, Hortus and Saint-Cesaire


          Moreover, the dental
          > traits in question are dental crown variants, which are normally considered
          > to be evolutionarily conservative and of low selective value. If modern
          > Europeans are indeed the descendents of Neanderthals, it's hard to see how
          > such traits could undergo such rapid change over a relatively short span of
          > evolutionary time.
          >

          The crown attributes of the Krapina dentition are scarcely different from
          those of the erectus Material from Zhoukoudian in China. If anything, the
          shovel and the tuberculum dentale of the incisors is even more extreme in
          Krapina. Those traits, however, have adaptive value and decrease in
          parallel (but genetically separated from) decreases in crown dimensions.
          The reduction in the hypoconulid is related to a reduction in crown size
          in the lower molars and is part of the change from a Y to a + pattern.
          Again, as the selective pressure maintaining tooth size relaxes, both the
          crown size and that aspect of crown complexity decrease. The same thing
          is true for the hypocone in the upper molars



          > We've discussed this point before and I think your position was that dental
          > metrics can evolve rather quickly. That argument may be true for metrics
          > (which have a higher selective value) but I don't see how it could hold true
          > for crown variants (which are close to selective neutrality). Perhaps I'm
          > missing something here.
          >

          As I explained above, you certainly are missing something here. Now, the
          next point is that the crown pattern on the real Late Neanderthals -- for
          example the largest collection of teeth at Hortus -- is absolutely
          intermediate between Krapina and living Europeans. So is tooth size. In
          addition, the earliest Upper Paleolithi, such as Predmost, has a crown
          pattern complexity and dental dimensions that are exactly the same as that
          of the Late Neanderthals. The shovel is still there although not so
          extreme, and the tuberculum dentale has disappeared leaving only
          denticulate processes on the lingual surface of the central incisors. The
          hypocone is missing on some of the upper third molars, and the lower third
          molars have a +5 or even a +4 pattern. I got the data on the Hortus
          material myself, and discovered that they were duplicated in the
          Aurignacian at Grimaldi, again from my own measurements.


          > Of course, anything is possible if one makes enough assumptions. Perhaps
          > the Krapina Neanderthals were somehow atypical.

          Krapina is anything but atypical. It represents the general human
          condition in the northern reaches of human habitation at the end of the
          Middle Pleistocene, but if you put the rest of the picture in for 60,000
          years, 50,000 years, 40,000 years, 30,000 years, 20,000 years and 10,000
          years ago, then the graded change from Krapina to living European tooth
          morphology and size is a smooth unbroken trajectory.


          Perhaps there was an
          > unusual combination of genetic drift, founder effects, exceptionally strong
          > selective pressures, etc. subsequent to them.

          No, there was no unusual combination of anything and certianly not of
          exceptionally strong selective pressures.

          As I see it, and perhaps I'm
          > wrong, the most parsimonious explanation seems to be population replacement.
          >

          In order to support population replacement, one would at least have to
          demonstrate the existence of a replacing population as a first step. And
          there simply is no evidence for the existence of such.

          C. L. Brace
        • Peter Frost
          From: C. Loring Brace ... Fine. According to the Out-of-Africa model, any Neanderthals later than 40,000 BP would have co-existed with
          Message 4 of 12 , Apr 4, 2000
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            From: C. Loring Brace <clbrace@...>

            > Both ESR and Uranium Series dates put Krapina at 130,000. That is early
            > Neanderthals and not Late Neanderthals. The latter are those that date to
            > 40,000 years ago or less, i.e. Vindija, Hortus and Saint-Cesaire


            Fine. According to the Out-of-Africa model, any Neanderthals later than
            40,000 BP would have co-existed with modern humans (the entry of modern
            humans into Europe is usually pegged at around 45,000-50,000 BP). This
            raises the possibility of gene flow from modern humans. Even if a smooth
            unbroken trajectory towards European values could be demonstrated prior to
            the 50,000 BP time horizon, one could not rule out admixture from the
            Skhul-Qafzeh humans in the Middle East.

            Why, then, do you exclude gene flow as a possible explanation?


            > The crown attributes of the Krapina dentition are scarcely different from
            > those of the erectus Material from Zhoukoudian in China. If anything, the
            > shovel and the tuberculum dentale of the incisors is even more extreme in
            > Krapina. Those traits, however, have adaptive value and decrease in
            > parallel (but genetically separated from) decreases in crown dimensions.


            If crown patterns are as sensitive to natural selection as you suggest, why
            did they change so radically in Europe but not in Africa? Modern
            sub-Saharan Africans still have crown patterns that are found in Krapina
            Neanderthals but not in modern Europeans. This is one reason why crown
            patterns are considered to be evolutionarily conservative: they tend to
            disappear only as a result of founder effects, population bottlenecks, or
            outright population replacement, and not because of natural selection. For
            this reason, sub-Saharan Africans retain crown patterns that are prevalent
            in the dentitions of many extinct hominids, from australopithecines through
            archaic Homo sapiens, as well as extinct and extant non-human primates.

            Reference:

            Irish, J.D. 1998. Ancestral dental traits in recent Sub-Saharan Africans and
            the origins of modern humans. Journal of Human Evolution 34: 81-98.

            -------------------------------------------------------------------
            Dr. Peter Frost

            Groupe d'études Inuit et circumpolaires
            Pavillon De Koninck
            Université Laval
            Sainte-Foy (Québec)
            G1K 7P4 CANADA
            L'homme qui veut faire l'ange finit par faire la bête.
            Tel. (418) 683-1740

            Website: http://www.globetrotter.net/gt/usagers/pfrost
          • C. Loring Brace
            ... There are no modern humans in Europe between 45,000 and 50,000 years ago. In fact, there is no evidence that there are any modern humans outside of
            Message 5 of 12 , Apr 4, 2000
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              On Tue, 4 Apr 2000, Peter Frost wrote:

              > From: C. Loring Brace <clbrace@...>
              >
              > > Both ESR and Uranium Series dates put Krapina at 130,000. That is early
              > > Neanderthals and not Late Neanderthals. The latter are those that date to
              > > 40,000 years ago or less, i.e. Vindija, Hortus and Saint-Cesaire
              >
              >
              > Fine. According to the Out-of-Africa model, any Neanderthals later than
              > 40,000 BP would have co-existed with modern humans (the entry of modern
              > humans into Europe is usually pegged at around 45,000-50,000 BP).

              There are no "modern humans" in Europe between 45,000 and 50,000 years
              ago. In fact, there is no evidence that there are any "modern humans"
              outside of Europe at that date.


              This
              > raises the possibility of gene flow from modern humans. Even if a smooth
              > unbroken trajectory towards European values could be demonstrated prior to
              > the 50,000 BP time horizon, one could not rule out admixture from the
              > Skhul-Qafzeh humans in the Middle East.
              >
              Skhul and Qafza are not the same thing. Qafza, in fact, has larger teeth
              than the classic Neanderthals of Europe.


              > Why, then, do you exclude gene flow as a possible explanation?
              >
              >
              I doubt the possibility of gene flow when there simply are no known
              "modern" populations from which genes could flow.


              > > The crown attributes of the Krapina dentition are scarcely different from
              > > those of the erectus Material from Zhoukoudian in China. If anything, the
              > > shovel and the tuberculum dentale of the incisors is even more extreme in
              > > Krapina. Those traits, however, have adaptive value and decrease in
              > > parallel (but genetically separated from) decreases in crown dimensions.
              >
              >
              > If crown patterns are as sensitive to natural selection as you suggest, why
              > did they change so radically in Europe but not in Africa? Modern
              > sub-Saharan Africans still have crown patterns that are found in Krapina
              > Neanderthals but not in modern Europeans.

              Now that again is simply not true. Krapina has the largest shovels found
              in the entire hominid record, fossil and living, and shovel-shaped
              incisors are largely absent from sub-Saharan Africa. The tuberculum
              dentale is also larger at Krapina than in any other past or present
              population, and it is missing entirely in sub-Saharan Africa. Carabelli's
              cusp is present in European Neanderthals including Krapina and is found in
              higher frequencies in living Europeans than in any other populations. The
              change from Krapin to living Europeans is in the frequency of the hypocone
              on the upper third molar and the hypoconulid on the lower third (along
              with a plus pattern). That is something that is a part of tooth size
              reduction. African teeth have reduced less from their Pleistocene
              ancestral size than is the case with European teeth, so the molars have a
              higher frequency of hypocones and hypoconulids. It is only in that sense
              that they resemble Krapina. One of the striking things I noticed is that
              the change in size from adjacent tooth to adjacent tooth in the European
              Neanderthals has the same pattern in living Europeans that it does in
              European Neanderthals (including Krapina), but that pattern is markedly
              different from the African pattern where molars are proportionately larger
              when compared with incisors than is true for Europe. The modern West
              African pattern is strikingly similar to that at Qafza, but then I was
              able to show that the craniofacial pattern of Qafza is more like that of
              living West Africans than that of anybody else. I did this by testing the
              battery of craniofacial measurements by Fisher's discriminant function to
              see what probability existed for the occurrence of given specimens in the
              samples with which they were compared. I published this in "Cro-Magnon
              and Qafzeh -- Vive la difference. Dental Anthropology Newsletter
              10(3):2-9 (1996).


              This is one reason why crown
              > patterns are considered to be evolutionarily conservative: they tend to
              > disappear only as a result of founder effects, population bottlenecks, or
              > outright population replacement, and not because of natural selection. For
              > this reason, sub-Saharan Africans retain crown patterns that are prevalent
              > in the dentitions of many extinct hominids, from australopithecines through
              > archaic Homo sapiens, as well as extinct and extant non-human primates.
              >
              Again, this is simply not true. Dental patterns change with the overall
              change in dental dimensions, and the change is gradual and in situ and it
              has nothing to do with founder effects, population bottlenecks, or
              population replacement. The late Hyacinthe Brabant in Belgium produced a
              lovely picture of dental change in situ in western Europe from the Upper
              Paleolithic to living Europeans in a series of papers in the Bulletin du
              Groupement International pour la Recherche Scientifique en Stomatologie.
              I refer you only to his Observations sur l'evolution de la denture
              permanente humaine en Europe Occidentale 7:11-84 written with Teiwsselmann
              in 1964.



              > Reference:
              >
              > Irish, J.D. 1998. Ancestral dental traits in recent Sub-Saharan Africans and
              > the origins of modern humans. Journal of Human Evolution 34: 81-98.
              >
              As Joel is the first to admit, he made no effort to look at prehistoric
              Europeans, and he made no effort to look at the impact of the different
              time depth that the adoption of food-preparation and cooking practices had
              on the groups in question.

              C. L. Brace
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