Devanagari -A script without a language?

Summary of Responses Received
At the outset let me thank all members who have responded to
my above post.The under-noted questions form the crux of the issue.
1)Can there be a fully developed phonetic script,without a backing
language?
2)For a phonetic script to develop, a language spoken for a
significantly long period is a condition precedent.
Some respondents suggested Brahmi as the source of the
Devanagari script.The above two questions,however remains unanswered.
After due application of mind,I have arrived at the
following possibilities.
Possibility 1:
Some scholars consider Brahmi as a possible source of the
Devanagari script Asokan insciptions circa 300 BC were reported to be
in Brahmi script.But no evidence is available to indicate that Brahmi
was a spoken language at all(except the Tamil dialect Brahmi spoken
in Baluchistan).Asokan inscriptions are in a script that appears to
have centuries of development behind it .It is highly improbable that
Brahmi could have been a source of such highly developed script.Some
scholars suggested Indus script.However this possibility has been
ruled out by some linguists as Indus script was pictorial in nature.
I attempted to solve this problem on the following
lines. I examined all the possibilities and my findings are:
1)Possibility: The script could have been borrowed from any IE
language.
Findings: Ruled out as no basic similarity is evidenced,
Even the construction of vowels and consonants are unquestionably
different.The number of vowels and consonants do not agree,after
allowing a margin of, say, five for possible additions
2)P :The script could have been borrowed from an established language
spoken in the geographical area where Indic languages were spoken.
F: The only other language family with established
presence in India, is the Dravidian family of languages. The lead
language of the family, Tamil has a history of atleast 2000 years and
evidence of having been spoken widely in major parts of Indian sub-
continent .The dialects of Tamil spoken across India upto
Baluchisthan ,are
Kolami,Parji,Naiki,Gondi,Ku,Kuri,Konda,Malda,Oroan,Gadna,Khurukh,
Brahmi of Baluchistan.As Tamil literary works dating circa 500 BC are
available , the `speech' should have been pretty old. Tamil has a
perfect script which could not have been borrowed, considering its
history of independent development and the geographical insulation
of its command area.In the Tamil grammar treatise 'Tholkappiam'
c 500BC,clear reference is available about a script
called 'Vattaezhuthu'. Considering these factors, Tamil appears to be
the source of the ` Devanagari script'.
I sat down to confirm the position, Here is my
comparative analyis,taking Hindi script as a representative for the
purpose.
Vowels:Tamil has 12 vowels . Hindi has 13. Certain Tamil
vowels are absent in Hindi.Additional vowels in Hindi are `ru'
and `am'.It may be observed that the additional vowels in Hindi are
not pure vowels but a combination of vowel and consonant sounds.As
such it could have been additions, necessitated by certain sounds
prevalent in Sanskrit but not prevalent in Tamil.
Consonants: Tamil has 18 consonants whereas Hindi has more
than 30 in number.It may be observed that the additional consonants
in Hindi are nothing but sound variants of the 18 consonants of Tamil
only.For example, the consonant `k' of Tamil has additional 4
variants namely `kha','ga',and'gha'in Hindi.Similarly `cha' of Tamil
has three additional variants `chha' 'ja' and'jha'.These script
letters seem to have been carved out of the original Tamil letters by
slight alterations .Such alterations are quite easy as the basic
skeletal framework is already provided by Tamil .The illustration
provided in the annexure to this e-mail (as a .jpg attachment) would
help you understand my point better.
Based on the foregoing findings I propose that the
script used by the Indic branch of the Indo-European family of
languages is basically provided by Tamil.As this is an investigative
exercise I have not limited my search in the defined linguistic
territories.I have also not considered the various language
families ,as we know them, as water-tight compartments. I am of the
view that imposing such kind of restrictions on a fact finding
process will not help finding out the correct position or the
possibilities that can be thought of .
The findings answer the above two questions
completely.I may add that in matters of this kind 100% proof is not
possible as no one knows what constitutes 100% proof.As long as the
proof available is beyond reasonable doubt ,it should be deemed to be
acceptable .

A.S.Sundar,