Dravidian origins

[Bjarte Kaldhol]

Dear listmembers,

Since I wanted to know something about the Dravidian languages without
going so far as to read a grammar of Tamil, I sat down to read Zvelebil's
article in Encyclopaedia Britannica (Vol. 22, 15th edition). In the third
paragraph, he states: "Nothing definite is known about the origin of the
Dravidian family."
        Well, let us see what this professed ignorance leads to:

1. There are vague indigenous traditions about an ancient migration from
the south.
2. According to some scholars, Dravidian languages are indigenous to India.
3. A hypothesis has been gaining ground that posits a movement of Dravidian
speakers from the northwest to the south and east of the peninsula, a
movement originating possibly from Central Asia. (This hypothesis is not
substantiated, and Zvelebil later confesses that "nothing definite is known
about the ancient domain of the Dravidian parent speech".)
4. Another theory connects the Dravidian speakers with the peoples of the
Indus Valley civilization.
5. The circumstances of the advent of Dravidian speakers in India are
shrouded in mystery. (An "advent" is now taken for granted.)
6. It is possible that a Dravidian-speaking people that can be described as
dolichocephalic Mediterraneans mixed with brachycephalic Armenoids and
established themselves in northwest India during the 4th millennium BC.
Along their route, they may have possibly come into an intimate, prolonged
contact with Ural-Altaic speakers, thus explaining the striking affinities
between the Dravidian and Ural-Altaic language groups. (No such affinities
are mentioned.)
7. It is possible that Proto-Brahui was the first language to split off
from Proto-Dravidian, probably during the immigration movement into India
some time in the 4th millennium BC...

Now, if nothing definite is known about the origin of the Dravidian family,
or about the ancient domain of the Dravidian parent speech, why speculate
about an immigration movement? And why must this immigration have happened
in the fourth millennium BC?

One sentence (p. 698) is completely unintelligible to me: "Several scholars
have demonstrated that pre-Indo-Aryan and pre-Dravidian bilingualism in
India provided conditions for the far-reaching influence of Dravidian on
the Indo-Aryan tongues..." What pre-IA and pre-Dravidian languages were
involved here? (No other languages are mentioned.) The conclusion is also
enigmatic: "Thus a form of Proto-Dravidian... must have been extensive in
north India before the advent of the Aryans."

Perhaps somebody on this list with some insight into the matter would care
to explain what is meant by pre-(not proto-)Indo-Aryan and pre-Dravidian
bilingualism?

Best wishes,
Bjarte Kaldhol