Re: Nostrils: a definition

David L Burkhead (r3dlb1@dax.cc.uakron.edu)
23 Jul 1995 21:52:16 GMT

In article <467300194wnr@desco.demon.co.uk> Elaine@desco.demon.co.uk writes:
[ 8< ]
>
> This trajectory also involves an awkward detour- the air has to go up,
>and over the top, and down. I believe I quoted this as one of the
>"scars"of evolution, an unwanted consequence of the aquatic phase.
>

"Awkward?" There's nothing awkward about it. The viscosity of
air is low enough that it really doesn't care whether the path is
straight or curved--not at the Reynolds numbers of human air passages
and breathing.

> If I were a follower
>of SMT (savannah-mosaic theory) I would say boo-sucks to Elaine Morgan.
>That curve is the consequence of bipedalism, and would be there whatever
>the cause of bipedlaism might be. It is the same kind of development as
>the course of the vagina - straight in quadrupeds, awkwardly curved in
>the only biped.

This is a straw man. I haven't heard _anyone_ suggest that the
direction of airflow through the nasal passages is a result of
bipedalism per, se. Instead, the directions, and changes of
direction, are the result of putting a nose not too dissimilar from
those on our closest primate relatives on a face that does not have a
protruding snout.

The nose serves a function--filtering air intake primarily. This
will act to prevent the nose from shrinking beyond a certain size,
since it becoming too small to perform its functions well enough would
be selected against. A look at the range of human nose sizes reveals
that the possible sizes is pretty large. Also, individuals have
survived the loss of the nose entirely, but the question isn't whether
some individuals could survive, but whether in groups they would be
selected against.

>
>EM would reply:Up to a point. But if it was due only to bipedalism the
>top end of the respiratory canal would travel up from the lungs, and
>turn through say 90% to face outwards - i.e. parallel to the surface of
>the earth, as it is in most primates when their torsos are erect. (That
>applies to
>platyrrhines as well as catarrhines.) .They don't feel the need to go
>further and make a positive downturn (let's call it

Do other primate noses serve filtering functions? If so, then
size will likely be dictated by that requirement, not what turns the
airflow takes.

>dorsally-directed) and cover the whole thing with a lid, buttressed
>with cartilage, and flanked by fleshy and
>muscular nostrils flaps. The worst that can happen to them is that in
>a very severe rainstorm some rain might get in and make them
>sneeze.If they dived into water from a few hundred feet up as proboscis
>monkeys do they would need a bit more protection. And the proboscis has
>got it.

Oh, this just gets better and better. Now our putative ancestors
were cliff divers?

In a very short time (evolutionarily speaking) these aquatic apes
went from tree dwelling, to wading, to swimming, to cliff diving, to
savannah dwelling--all of these apparently requiring a different set
of adaptations--and each of these first three are required to
"explain" the so-called "aquatic adaptations." We need deep wading to
"explain" bipedalism (even though there have been _no_ cases of wading
leading to bipedalism). We need swimming to "explain" hairlessness
and direction of body hair growth (although the actual patterns found
don't match those of water flow during swimming). And now we need
cliff diving to "explain" the nostrils!

David L. Burkhea
r3dlb1@dax.cc.uakron.edu
d.burkhead@genie.geis.com

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