Re: Human language (long)

John A. Halloran (
10 Jan 1997 01:08:03 -0700

In article <> Phillip Bigelow <> writes:
>> I was talking about the larynx descending in the vocal tract for its value in
>> producing calls that would help members of a hunting pack to locate each
>> other.

>The problem with this idea is that in extant animals that hunt in packs
>(canids, for instance), they possess a *non*-"descended" larynx.
>There is really no need for a "descended" larynx for long-range
>oral communication. In fact, the plesiomorphic condition of
>the carnivoran larynx makes it *advantageous* for increased
>volume with an associated higher pitch. In humans, the relaxed
>laryngeal structure has made it possible to produce
>a wider range of pitches (including intermediate pitches that many
>other animals cannot reproduce), but it also incurred a cost
>(slightly less volume, when compared to carnivorans that obligatively
>communicate long distances (such as canids)).

Thanks for jumping in here. Canids seem to achieve a high volume with
explosive barks and long howls. What special adaptations do their vocal
tracts have to produce this volume? Michael has brought up the primate
example of the howler monkey, which had to evolve an enlarged, hollow hyoid to
act as a resonating chamber for its long-distance calls. Would it have been
possible for primates to evolve the vocal apparatus that canids possess? It
is a fact that canid vocalizing is part and parcel of their lifestyle, a
lifestyle that primates evolving into hominids began to adopt.

>> The main factor in language as in speech or talking is the brain, not
>> the vocal tract.

>I don't follow. Are you claiming that the enlarged hominid brain
>evolved prior to the re-arrangement of the laryngeal/pharyngeal
>structure? If so, what evidence do you know of that supports this
>order of development?

I think that the vocal tract preadapted itself to language for nonlinguistic
reasons. I also think that the brain preadapted itself to language for
nonlinguistic reasons, for which I am quite willing to adopt the
missile-throwing theories of William H. Calvin. I would then point to the
trend over the last 10,000 years which has involved expansion of the temporal
lobes of the brain at the expense of the parietal lobes. Language
comprehension is located in the temporal lobes. This trend is called

"The best documented but least well understood case of recent
evolution has been the increasing brachycephalization of the species."
Frederick S. Hulse, The Human Species (New York, 1963), p. 400.

"Brachycephaly means broad-headedness, and a person is said to be
brachycephalic if his head is 82 percent as wide as it is long.
He is dolichocephalic or long-headed if the proportion is 77
percent or less. The ratio between the length and breadth of the
head is called the cephalic index. Most Palaeolithic individuals
were dolichocephalic, but a great majority of living human beings
are not." ibid, p. 336.

"One of the most baffling and precipitous phyletic trends in
Homo Sapiens has been the appreciable shortening and moderate
widening of the head." Edward E. Hunt, Jr. "The Continuing
Evolution of Modern Man," Cold Spring Harbor Symposia on
Quantitative Biology, 24 (1959): 250.

A study of which cerebral lobes are involved is C.U. Ariens Kappers, "On
Some Correlations Between Skull and Brain," Philosophical Transactions of the
Royal Society of London, ser. B, vol. 221, pp. 391-429.

Ariens Kappers reports on studies of the brains of dolichocephalic and
brachycephalic individuals from Europe, Africa, and Australia. What he finds
is that the temporal lobe is much shallower in dolichocephalic skulled
individuals and the parietal lobe has less depth in brachycephalic skulled
individuals. The temporal lobe is important for acoustic tasks and verbal
comprehension. The parietal lobe is important for spatial mapping.

The most recent reference I know of on the subject of brachycephalization is
an article by N. Kondova and S. Cholakov, "Brachycephalization in Bulgaria",
Homo 45/1 (1994), pp. 63-73. They reference a 1989 study by Fw Roesing and
Ilse Schwidetzky, the great master of statistical European physical
anthropology, on "Causative factors of brachycephalization process". Their
summary says, "It is selection that is considered to be the main factor in the
process of brachycephalization in Central Europe during the period between the
8th and the 18th centuries. "By ascribing the shift to a more broad-headed
skull to selection, they are ruling out dietary factors, and saying that a
broad-headed skull provides a heritable survival/reproductive advantage.

These then are the only evolutionary brain changes that I would attribute
directly to selection as a result of spoken language.


John Halloran