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  • only incridibly imbeciles deny H.erectus were shallow-divers

    From [email protected]@21:1/5 to All on Sun Apr 9 02:25:00 2023
    Sink or swim?
    Bone density as a mechanism for buoyancy control in early cetaceans
    Noel-Marie Gray cs 2007
    Anat Rec 290:638-653 doi 10.1002/ar.20533.

    Previous analyses have shown:
    secondarily aquatic tetrapods (incl. whales) exhibit osteological adaptations to life in water, as part of their complex buoyancy control systems.
    These structural specializations of bone span hyperostosis through osteoporosis.
    The past 15 yrs of paleontological effort has provided an unprecedented opportunity to examine the osteological transfm of whales:
    the transition to an obligate aquatic lifestyle over a 10-My period.
    Do whales manifest their osteological specialization in the same manner as extant semi- & fully aquatic mammals?
    We present a micro-structural analysis of bone in early & late archaic Cetacea, in a comparative sample of modern terrestrial, semi-aquatic & aquatic mammals.
    Bone histology was examined from the ribs of 10 fossilized individuals of 5 early cetacean families: Pakicetidae, Ambulocetidae, Protocetidae, Remintonocetidae, Basilosauridae.
    Comparisons were made with rib histology from 9 genera of extant mammals: Odocoileus (deer), Bos (cow), Equus (horse), Canis (dog), Lutra (river otter), Enhydra (sea otter), Choeropsis (pygmy hippo), Trichechus (sea cow), Delphinus (dolphin).
    Results:
    the transition from terrestrial, to semi- to bligate aquatic locomotion in Archaeocetes involved a radical shift in bone function, achieved by means of profound changes at the micro-structural level.
    Surprisingly, micro-structural change predates gross anatomical shift in archaeocetes ass.x swimming.
    Histological analysis shows:
    - high bone density is an aquatic specialization that provides static buoyancy control (ballast) for animals living in shallow water,
    - low bone density is ass.x dynamic buoyancy control for animals living in deep water:
    there was a shift from the typical terrestrial form, to osteopetrosis & pachyosteosclerosis, and then to osteoporosis in the 1st quarter of cetacean evol.history.

    _____

    IOW, only ridiculous kudu runners deny:
    H.erectus' osteopetrosis & pachyosteosclerosis (POS) indicates shallow-diving.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From [email protected]@21:1/5 to All on Sun Apr 9 03:54:16 2023
    Sorry for the title (becoming too old? too fast? too angry?):
    should be: "incredible" instead of "incridibly", of course...

    Op zondag 9 april 2023 om 11:25:02 UTC+2 schreef [email protected]:
    Sink or swim?
    Bone density as a mechanism for buoyancy control in early cetaceans Noel-Marie Gray cs 2007
    Anat Rec 290:638-653 doi 10.1002/ar.20533.

    Previous analyses have shown:
    secondarily aquatic tetrapods (incl. whales) exhibit osteological adaptations to life in water, as part of their complex buoyancy control systems.
    These structural specializations of bone span hyperostosis through osteoporosis.
    The past 15 yrs of paleontological effort has provided an unprecedented opportunity to examine the osteological transfm of whales:
    the transition to an obligate aquatic lifestyle over a 10-My period.
    Do whales manifest their osteological specialization in the same manner as extant semi- & fully aquatic mammals?
    We present a micro-structural analysis of bone in early & late archaic Cetacea, in a comparative sample of modern terrestrial, semi-aquatic & aquatic mammals.
    Bone histology was examined from the ribs of 10 fossilized individuals of 5 early cetacean families: Pakicetidae, Ambulocetidae, Protocetidae, Remintonocetidae, Basilosauridae.
    Comparisons were made with rib histology from 9 genera of extant mammals: Odocoileus (deer), Bos (cow), Equus (horse), Canis (dog), Lutra (river otter), Enhydra (sea otter), Choeropsis (pygmy hippo), Trichechus (sea cow), Delphinus (dolphin).
    Results:
    the transition from terrestrial, to semi- to bligate aquatic locomotion in Archaeocetes involved a radical shift in bone function, achieved by means of profound changes at the micro-structural level.
    Surprisingly, micro-structural change predates gross anatomical shift in archaeocetes ass.x swimming.
    Histological analysis shows:
    - high bone density is an aquatic specialization that provides static buoyancy control (ballast) for animals living in shallow water,
    - low bone density is ass.x dynamic buoyancy control for animals living in deep water:
    there was a shift from the typical terrestrial form, to osteopetrosis & pachyosteosclerosis, and then to osteoporosis in the 1st quarter of cetacean evol.history.

    _____

    IOW, only ridiculous kudu runners deny:
    H.erectus' osteopetrosis & pachyosteosclerosis (POS) indicates shallow-diving.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From JTEM is so reasonable@21:1/5 to [email protected] on Sun Apr 9 09:24:53 2023
    [email protected] wrote:

    Sorry for the title (becoming too old? too fast? too angry?):
    should be: "incredible" instead of "incridibly", of course...

    Apparently I was too old too fast in the 1990s...

    What was I going to say? Oh yes:

    i was going to start a thread but that seems impossible these
    days so I might as well just ask you about Denisovans.

    Supposedly Tibets "Adapted" to high altitude at least partly by
    acquiring some useful DNA for doing just that, and getting this
    DNA from the Denisovans.

    Why would the Denisovans have it? They seem nearly entirely
    associated with warmer climates -- southeast Asia and the
    pacific -- but then some odd group took to the mountains?

    So what I am speculating on here, more or less just tossing it
    out there, is what if the adaptations that allowed for exploiting
    low levels of oxygen was an emergent trait? You know, like they
    dove a lot, perhaps swam a lot and water not being a great spot
    for breathing, adapted to cope with low levels of oxygen?

    It's the kind of evolutionary quirk I'd look for, rather than Intelligent Design.

    The thing is, it's kind of necessary for them to acquire the
    adaptation so they could experience the selective pressure to
    acquire the adaption, in the mountains. Not so in the sea. They
    could dive without it, swim without it but not as well... so they
    could perform the act AND experience selective pressure to be
    better at performing it.

    But, high altitude cultures?





    -- --

    https://jtem.tumblr.com/post/714091698115035136

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    * Origin: fsxNet Usenet Gateway (21:1/5)