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Re: [AAT] Basicranial flexion

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  • Rob Dudman
    Hello again, Marc...... ... Anyone who posts with a reference to less basicranial flexion in H.e/e. IIRC, you are one of those correspondents. ... Is this a
    Message 1 of 10 , Apr 30, 2006
      Hello again, Marc......
      >
      > What "correspondents" you mean?
      >
      Anyone who posts with a reference to 'less basicranial flexion' in
      H.e/e. IIRC, you are one of those correspondents.
      >
      > I usu.don't read your posts further than 1 or 2 sentences, but for
      > once I should "answer" here?
      >
      :-)

      Is this a question? If it is, then I suppose the answer is probably
      'yes, you should answer if you use 'less basicranial flexion' in relation
      to H.e/e'.
      >
      > I read the paper years ago, there was nothing that contradicted my
      > view, I'm not going to reread it.
      >
      Does this mean that like Ross and Henneberg, you accept that
      'Archaic Homo sapiens, Homo erectus, and Australopithecus
      africanus do not differ significantly from Modern Homo sapiens in
      their degree of basicranial flexion'?
      >
      > That R+H find no "significant"(=?) difference between different
      > Hs & fossil Homo & apiths depends on their measuring methods
      >
      Is this a criticism? To say that their findings depended on their
      measuring methods is almost tautological. Are you suggesting that
      they would have come closer to your view if they'd used different
      measuring methods? I did note the ambiguity inherent in the relative
      term 'significant', but in this case it's fairly safe to assume that they
      use it in its statistical meaning.
      >
      > http://www.anthro.ucdavis.edu/faculty/mchenry/phylo.htm Table 3
      > scores for BCF: P+G 0, afar.1, aethiop.2, afric.3, robusts 6,
      > habilis (fossil?) 5, rudolf.(fossil?) 3, ergaster 4, Hs 4.
      >
      Ergaster 4 & H.s 4.....I don't have a clue as to what these numbers
      represent, but I can certainly see that they are the same. My query
      was about the use of the phrase 'less basicranial flexion' in relation to
      H.e/e. If you don't refer to H.e/e as having 'less basicranial flexion',
      then these two 4s are not going to be a problem for you....OTOH,
      if you do use 'less basicranial flexion', then these two 4s do not
      support your position and they do support the conclusion made by
      Ross and Henneberg.
      >
      > Note the partial contradiction with Laitman.......
      >
      > 1) the basicranium is rel."flat" or nonflexed ... found to exist
      > consistently
      > in all the mammals we studied except for older humans. 2) ...found to be
      > markedly arched, or flexed ... found only in humans after the first year
      > of
      > life......
      >
      I wonder what is meant here by 'older humans' - modern humans
      getting on in years, or 'early Homo'? I see that (2) refers to 'humans
      after the first year of life' so maybe they're referring to elderly people
      rather than to early Homo. Either way, it's what comes next that
      bears on our present issue....
      >
      > ....It is among spms of He that we begin to find the first instances of
      > BCF, away from the the nonflexed pattern of the extant apes & apiths."
      > Here "apiths"=afarensis? cf.
      >
      There seems to be some difference with respect to A.africanus,
      but what Laitman says about H.e/e is consistent with Ross and
      Henneberg.
      >
      > Laitman tries to explain the difference he found between older Hs &
      > all the other spms by laryngeal descent......
      >
      Hang on.....in the passage above Laitman talks of H.e being the
      first to show a different pattern to extant apes and A'piths, but then
      he only tries to explain the difference in older H.s? What would be
      the point in only doing that? Is this a typo?
      >
      > - BCF: I guess correlated with present upright posture (wading
      > & later walking) in older Hs,
      >
      What are 'older' Hs as you use the term here? Laitman and R & H
      find a consistent pattern back to H.e/e and here you only go back
      to 'older Hs'. It would seem that if wading is the (partial) cause for
      the BCF found in archaic Homo sapiens, then the argument equally
      applies to H.e/e.
      >
      > ..................to redirect the eyes into the walking direction, IOW,
      > our present (less pronograde) locomotion is very recent, see also
      > (below): "Modern humans have more ventrally deflected orbits
      > than all other primates."
      >
      Ok.
      >
      > IOW, IMO there were 3 evol.changes that suggest that Hs is
      > generally more orthograde than our predecessors: - more BCF,
      >
      Ross and Henneberg say that H.e 'do not significantly differ' in
      BCF from H.s and you say 'more' BCF in H.s than in H.e/e....
      AFAICS, R & H do not support your view and Laitman is in
      agreement with them (Ergaster 4 & H.s 4).

      My thanks for the time you took to respond to my question.

      ---Rob.


      ----- Original Message -----
      From: "Marc Verhaegen" <marc.verhaegen@...>
      To: <AAT@yahoogroups.com>
      Sent: Sunday, April 30, 2006 9:43 PM
      Subject: Re: [AAT] Basicranial flexion
    • Mario Petrinovich
      ... Yes. And they do have shock absorbing S-shaped necks (just like we have S-shaped backbone), and absorbing air sacks. But still, the impact is huge, and I
      Message 2 of 10 , May 1, 2006
        Rob Dudman:
        > Bok, Mario.......

        : ))) Bok, Rob...

        > > What about basicranial flexion in plunge diving byrds?
        > > Anybody has any info? Backbone could push bones of skull.
        > > Although
        > > they dive bill first, not top of head first, like we do. And
        > > they do
        > > have very flexible, apsorbing necks. But maybe the push of
        > > backbone had some inpact on bones of skull of those birds.
        > >
        > Thanks for your response. At a guess I'd suggest that the over-
        > all
        > shape made by pointed beak, long slender neck and no shoulders,
        > breaks the water in much the same way as a spear-point and so
        > reduces the impact to a minimum. ---Rob.

        Yes. And they do have shock absorbing S-shaped necks (just
        like we have S-shaped backbone), and absorbing air sacks. But
        still, the impact is huge, and I guess they do need an off-center
        attachment point between backbone and skull. This attachment point
        could have some peculiarities. Although, the difference between
        weight of a bird and an ape also is huge, so it could be that
        peculiarities are greater in ape.
        Anyway, this is valid idea.
        Now, imagine this. We were the only animal in the position
        to have that shift (because we were the only heavy animal that
        plunge dives). This shift is responsible for our increased
        vocabularity (if this is the right expression). And we were in the
        right position (whole day floating in the sea), where we had the
        need for increased vocabularity. Next thing you know, we excange a
        lot of information between us, : ). -- Mario
      • strangetruther
        ... over- ... When birds dive like this, and gannets must be the supreme example, the idea is to get the neck as straight as possible so the stresses are taken
        Message 3 of 10 , May 14, 2006
          --- In AAT@yahoogroups.com, "Mario Petrinovich"
          <mario.petrinovic1@...> wrote:
          >
          > Rob Dudman:
          > > Bok, Mario.......
          >
          > : ))) Bok, Rob...
          >
          > > > What about basicranial flexion in plunge diving byrds?
          > > > Anybody has any info? Backbone could push bones of skull.
          > > > Although
          > > > they dive bill first, not top of head first, like we do. And
          > > > they do
          > > > have very flexible, apsorbing necks. But maybe the push of
          > > > backbone had some inpact on bones of skull of those birds.
          > > >
          > > Thanks for your response. At a guess I'd suggest that the
          over-
          > > all
          > > shape made by pointed beak, long slender neck and no shoulders,
          > > breaks the water in much the same way as a spear-point and so
          > > reduces the impact to a minimum. ---Rob.
          >
          > Yes. And they do have shock absorbing S-shaped necks (just
          > like we have S-shaped backbone), and absorbing air sacks. But
          > still, the impact is huge, and I guess they do need an off-center
          > attachment point between backbone and skull. This attachment point
          > could have some peculiarities. Although, the difference between
          > weight of a bird and an ape also is huge, so it could be that
          > peculiarities are greater in ape.
          > Anyway, this is valid idea.
          > Now, imagine this. We were the only animal in the position
          > to have that shift (because we were the only heavy animal that
          > plunge dives). This shift is responsible for our increased
          > vocabularity (if this is the right expression). And we were in the
          > right position (whole day floating in the sea), where we had the
          > need for increased vocabularity. Next thing you know, we excange a
          > lot of information between us, : ). -- Mario
          >

          When birds dive like this, and gannets must be the supreme example,
          the idea is to get the neck as straight as possible so the stresses
          are taken by lognitudinal pressure straight down the cervical
          column, rather than asking the muscles to do it, which would require
          very fast changes as the load was suddenly experienced. There would
          be little cushioning benefit since anything the head could cope with
          the rest of the body could. It's not like cushioning in the leg
          joints to protect the higher sections from shocks the foot has to
          endure.

          I doubt if an S-shape in any part of the backbone in humans was
          caused by evolutionary pressure by headfirst diving; on the rare
          occasions when they did plunge in, they'd probably go in bum-first.

          Cordially, and "Hello list",


          Strangetruther
        • Marc Verhaegen
          ... Most of the time, yes, I think you re right: see sea gypsies etc. ... Welcome, Strangetruther. --Marc
          Message 4 of 10 , May 21, 2006
            > > > > What about basicranial flexion in plunge diving byrds?
            > > > > Anybody has any info? Backbone could push bones of skull.
            > > > > Although
            > > > > they dive bill first, not top of head first, like we do. And
            > > > > they do
            > > > > have very flexible, apsorbing necks. But maybe the push of
            > > > > backbone had some inpact on bones of skull of those birds.

            > > > Thanks for your response. At a guess I'd suggest that the
            > over-
            > > > all
            > > > shape made by pointed beak, long slender neck and no shoulders,
            > > > breaks the water in much the same way as a spear-point and so
            > > > reduces the impact to a minimum. ---Rob.

            > > Yes. And they do have shock absorbing S-shaped necks (just
            > > like we have S-shaped backbone), and absorbing air sacks. But
            > > still, the impact is huge, and I guess they do need an off-center
            > > attachment point between backbone and skull. This attachment point
            > > could have some peculiarities. Although, the difference between
            > > weight of a bird and an ape also is huge, so it could be that
            > > peculiarities are greater in ape.
            > > Anyway, this is valid idea.
            > > Now, imagine this. We were the only animal in the position
            > > to have that shift (because we were the only heavy animal that
            > > plunge dives). This shift is responsible for our increased
            > > vocabularity (if this is the right expression). And we were in the
            > > right position (whole day floating in the sea), where we had the
            > > need for increased vocabularity. Next thing you know, we excange a
            > > lot of information between us, : ). -- Mario

            > When birds dive like this, and gannets must be the supreme example,
            > the idea is to get the neck as straight as possible so the stresses
            > are taken by lognitudinal pressure straight down the cervical
            > column, rather than asking the muscles to do it, which would require
            > very fast changes as the load was suddenly experienced. There would
            > be little cushioning benefit since anything the head could cope with
            > the rest of the body could. It's not like cushioning in the leg
            > joints to protect the higher sections from shocks the foot has to
            > endure.
            > I doubt if an S-shape in any part of the backbone in humans was
            > caused by evolutionary pressure by headfirst diving; on the rare
            > occasions when they did plunge in, they'd probably go in bum-first.

            Most of the time, yes, I think you're right: see sea gypsies etc.

            > Cordially, and "Hello list",

            Welcome, Strangetruther.

            --Marc
          • Marc Verhaegen
            Basicranial flexion in the evolution of Homo: new analyses of an old model M Bastir, A Rosas, C Stringer, JM de la Cuétara, R Kruszynski, CF Ross & MJ Ravosa
            Message 5 of 10 , Feb 3, 2009
              Basicranial flexion in the evolution of Homo: new analyses of an old model

              M Bastir, A Rosas, C Stringer, JM de la Cuétara, R Kruszynski, CF Ross & MJ
              Ravosa 2009 AAPA abstracts

              Understanding variation in the basicranium is of central importance to
              paleoanthropology because of its fundamental structural role in skull
              development and evolution. At the beginning of the 20th century it was
              suggested that encephalisation plays a role in producing flexion between
              midline basicranial elements. It has been proposed that basicranial flexion
              is also influenced by the size or shape of the face. This hypothesis was
              further refined during the 1950s by the Swiss anatomist Biegert, who
              suggested that brain size and facial size act as antagonists on basicranial
              flexion. Biegert¹s model is particularly relevant for understanding aspects
              of Neanderthal skull evolution because one important and unresolved problem
              is that these large-brained hominins have slightly less flexed basicrania
              than equally large-brained modern humans. We addressed this hypothesis by
              applying geometric morphometrics to a large comparative dataset of
              radiographic and/or CT images of adult non-human primates, hominin fossils
              and humans (29 species, 142 individuals). Multiple, multivariate regression
              and thin plate splines analyses suggest that basicranial evolution is highly
              significantly influenced by both brain size and face size. Our data show
              that in addition to brain size, the prime factor of basicranial evolution in
              Homo, facial size importantly influences basicranial morphology and
              orientation. These interactions can explain why, despite their similar brain
              sizes, Neanderthals as well as some Mid-Pleistocene humans have less flexed
              cranial bases than modern humans. To gain a detailed understanding of the
              multifactorial inputs into basicranial flexion, future studies should also
              focus on the underlying factors of facial size evolution.

              _____

              Biegert : CC & facial size act as antagonists on BCF?
              - large CC = high BCF
              - large face = small BCF

              Hn have slightly less BCF < Hs.

              IMO this problem is not so difficult:
              - BCF in Hs = when standing/walking vertically, our face is oriented less
              upward, more downward, to where we're going,
              - less BCF in Hn = when swimming horizontally, their face was directed less
              downward than it had been in Hs, more upward, to where they were swimming.

              The flat skull, the heavy supra-orbital torus (protecting the more
              anteriorly placed eyes), the slightly more dorsal foramen magnum in archaic
              Homo (He>Hn) are all adaptations to looking forward in more pronograde He-Hn
              (swimming, vs.orthogradely walking Hs).
              In He-Hn the eyes are placed +-before the brain skull (therefore a heavy
              torus is needed), in Hs +-under the brain skull (no torus any more: our eyes
              are proteced by the brain skull).

              --Marc
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