Kinda curious about that one myself. Dog?
I think the mini-article on origin of grammatical gender in the sci.lang FAQ has some bearing on this question.
Originally (so it is thought), before gender came to exist in Proto-Indo-European, the main grammatical distinction was between animate nouns and inanimate nouns. The animate nouns developed into what we know as “masculine gender,” while the inanimate nouns developed into what we know as “neuter gender.” (The so-called feminine gender then developed as a spinoff of the neuter.)
Since animate nouns were considered dynamic, they got different endings for nominative and accusative. But inanimate nouns were static, so they didn’t get different endings. IIUC.
What happened in Proto-Indo-European of course doesn’t necessarily hold true for Dravidian. But there may have been some roughly analogous process at work in Dravidian also.
We should also note that case endings in Latin are made synthetically, while in Dravidian they are agglutinative.
Which is to say that each Latin case ending is a unique form combining case, number, and gender all in one, and can’t be analyzed into components. But in Dravidian, case is expressed by one suffix (which is the same for both masculine and feminine genders). Number is expressed by another suffix (which is the same for all three genders). Gender is implicit but not expressed.
Let me illustrate with some Tamil examples:
man:
âN* (nominative singular)
âNai (accusative singular)
âNkaL (nominative plural)
âNkaLai (accusative plural)
woman:
peN (nominative singular)
peNai (accusative singular)
peNkaL (nominative plural)
peNkaLai (accusative plural)
As you can see, the accusative suffix is -ai regardless of gender or number. The plural suffix is -kaL regardless of gender or case.
house:
vîTu (nominative singular)
vîTukaL (nominative plural)
The accusative suffix isn’t used with this neuter (inanimate) word. When it’s a direct object, it uses the same unmarked form that is also used for the nominative. I prefer to say “unmarked” because the nominative simply doesn’t take any agglutinative case ending.
*uppercase letters transliterate the retroflex consonants.