Re: diving hominids?


"Rich Travsky" <traRvEsky@xxxxxxxxxxxxxxx> wrote in message
news:46ED6FD0.3F1F7F24@xxxxxxxxxxxxxxxxxx
Cj wrote:

If there's much debate about homo swimming in water perhaps some
physiology
is worth considering. For example the diving reflex is well established
in
humans. When the face is immersed in water the heart rate drops
(bradycardia) and peripheral blood circulation is clamped down to
increase
blood levels in the thorax. In most humans the facial immersion reduces
heart rates by about 20%. Quite interestingly this depression of heart
rate
is gradually increased when one does a significant amount of diving and
starts to look a bit more like the diving reflex of seals. I suspect
most
mammals exhibit a diving reflex to some degree but in man it is markedly
enhanced with repetitive stimulation (diving). The reflex suggests that
humans developed some responses to immersion in water early in their
evolution.

Here is a tiger with diving reflexes:

http://www.youtube.com/watch?v=RvgsrT8Z924
SAN FRANCISCO, USA: Odin, the white Bengal Tiger, in his enclosure in San
Francisco. British keeper Lee Munro has been training Odin, who is the top
new attraction at Six Flags Discovery Kingdom in San Francisco, since he
was just 6. The park is one of the only places in the world where people
can see a tiger diving for food.

I doubt that "repetitive stimulation" plays any role. Millions of humans
do not
dive.

The extent to which 'conditioning' leads to human diving to
resemble that of seals is trivial. In true divers such as seals
and whales most oxygen is carried in the muscles in specialized
myoglobin molecules. This substance is unknown in humans.
As a result true divers *expel* the air from the lungs so as
not to attempt a dive while, in effect, hanging onto a couple
of large air-filled sacs. Needless to say this behaviour is
also unknown in humans. There is no reason to suppose
that dive training in other species would not lead to similar
enhancements of diving ability. Perhaps dogs, which in some
breeds are excellent but not 'true' divers, would be an ideal
experimental animal to check this out.

Rick Wagler


.

Relevant Pages

  • Human = beaver diving response (Re: diving hominids?
    ... When the face is immersed in water the heart rate drops ... humans as opposed to other primates etc.). ... In the diving response of trained humans, bradycardia is ...
    (sci.anthropology.paleo)
  • Re: Ealine Morgan
    ... The only diving humans do is trolling for sharks: ... underwater footage of macaques diving and swimming underwater, ... This is bed rock AAT ie humans, ... Marc continually asserts that chimps ...
    (sci.anthropology.paleo)
  • dry apers claim wildebeest can dive 50 m (Re: Look humans really are aquatic!
    ... >> birds seems to be devoid of any specialist mammals. ... They'll just keep on diving thank you very ... Humans who do dive to 50 meters do so at ... > ameliorated and savannah supplanted deserts in the region. ...
    (sci.anthropology.paleo)
  • Re: 2 sentences, 3 blunders (Re: Shellfish Allergies Re: Grass or sand apes
    ... > 1) The most common allergies in humans are hay fever, IOW, allergy to the ... > typical of diving mammals. ... Clearly he's unaware of diving bradycardia & ...
    (sci.anthropology.paleo)
  • Re: skinny runners
    ... I don't see why they should outrun anything: ... carrying water could perhaps outrun a few herbivores, ... Bramble and Lieberman in a recent paper in Nature propose that early Homo ... why they did not take into account swimming and diving - locomotion styles ...
    (sci.anthropology.paleo)