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Re: Human Language. (long post)
Michael McBroom (bodhi@earthlink.net)
Tue, 07 Jan 1997 15:22:31 -0800
John A. Halloran wrote:
> What are the oldest skeletons that show evolution away from the primate vocal
> tract pattern?
There is evidence to suggest that the hominid vocal tract began to
deviate from the standard plan with the species H. habilis. This puts
the beginnings of language back some 2+ MY.
> >> The principal question is for what reason have other species developed a vocal
> >> tract that permits or enhances long-distance vocalizations. This can throw
> >> light on the evolution in the human vocal tract.
>
> >Oh really. Your principal question is germane to the issue only if we
> >assume that the human vocal tract evolved due to selectional pressures
> >that favored long-distance communication. There is clear evidence that
> >it did not. When's the last time you've tried to carry on a
> >conversation by shouting to somebody down the street? Pretty hard to
> >do, huh? The hard consonants don't travel, and even the ones that do,
> >don't travel that far. What you're left with are open vowels and vowels
> >that are "colored" by the nasals and the retroflex [r]. One of the
> >principle advantage we possess as users of a full-blown system of
> >language is the ability to communicate rapidly with each other. You
> >just can't do this sort of thing at a distance.
>
> Long-distance communication need not involve forming words involving
> consonants. The long-distance vocalizations of other species serve a valuable
> communicative function without requiring the enunciations that you describe.
Without the use of consonants, language would be virtually useless.
Consonants are critical for spoken symbolic communication. Consonants
are *stable* sounds because they occur at fixed points in the anatomy.
They are the "hooks" we hang the vowels on. Vowels, by their very
nature, are not stable. They are fluid, they change. There is no clear
demarkation from one vowel sound to the next, thus vowels are poor
carriers of information by themselves.
If we were to have evolved with a vocal tract optimized for
long-distance communication, chances are that it would more closely
resemble that of the howler monkey, an animal that does not have a
descended larynx, yet is able to communicate over long distances quite
effectively.
> >> This does not mean that improved vowel production was not
> >> important to nonlinguistic vocalizations, however. But you have not dealt
> >> with the issue that descent of the larynx also aids in producing deeper,
> >> lower-pitched vocalizations.
>
> >I have stated repeatedly that non-linguistic vocalizations were not what
> >our vocal tract has been selected for. I have also stated that the
> >descent of the larynx was for different reasons than the specific
> >production of lower-pitched vocalizations. In other words, I reject
> >your claims on the basis that there is no evidence to suggest that the
> >human vocal tract evolved for the uses you indicate.
>
> If it is true that
>
> 1. low-pitched sounds travel longer distances than high-pitched sounds; and
>
> 2. a larynx lower in the throat enables creation of lower-pitched
> vocalizations,
>
> then there is a clear alternative to the theory that the human larynx
> descended for linguistic reasons.
But yours is not a reasonable alternative because there are more
reasonable explanations. Your alternative stretches credibility. It is
non-parsimonious. This is why:
You keep harping on this business about low pitch. But you have
apparently overlooked the fact that pitch is relative among humans. The
human female voice is generally an octave higher in pitch than a male's,
yet she has a descended larynx. Further, the pitch of male voices can
vary over a wide range -- three octaves or more, from bass to tenor,
although the range in pitch between various male speakers during normal
speech would probably not encompass more than 1.5 octaves. Even so,
such a range of pitch does not argue particularly well for a descended
larynx, does it? Furthermore, the differences in pitch here are not
great enough to substantially increase or decrease their carrying
range. Your average male voice is probably somewhere around 100 Hz
(approx. the 2nd "A" below middle "C" on the piano), with the lower
limit being around 50 Hz, or so. Now, while it is true that lower
pitched tones will travel farther than high pitched tones, you never get
something for nothing. It requires proportionally more energy to
generate the long wavelengths of these low tones, and quite a bit of it,
to produce the same perceived volume. I used to play professionally in
bands for a number of years, and I can tell you this much: in order to
achieve a balance in perceived volume between highs and lows, a much
greater amount of power is required for the speakers that generate the
lows. You might only need to feed 50 watts to the tweeters, while the
bass cabinets would easily soak up 250 watts. So, if our vocal
apparatus was truly adapted to hooting and howling in deep baritones
over long distances, we should expect to find a very efficient vocal
system that has been optimized to produce low tones with great energy.
We simply don't have it.
The amount by which the descended larynx affects the distance at which
sounds can be perceived, as opposed to a non-descended larynx, is
negligible. At least one species of primates, howler monkeys, is able
to communicate at distances much greater than humans. Yet howler
monkeys do not have a descended larynx. Greater energy is needed to
produce the long wavelengths that travel these great distances, yet
there is no evidence in either the larynx or the respiratory system to
indicate optimization for this.
Give it up.
Michael McBroom
CSUF Linguistics
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