Historical Linguistics: how is it that a language develops more than one regular verb conjugation?

Question

It seems intuitive to me that a language would have both regular and irregular verbs. But I have always wondered why it is that Spanish, for example, developed 3 regular conjugations ( -ar, -er, -ir). The quick answer is that these were inherited from Latin, but how did Latin come to have four conjugations?For that matter, why did Latin have 5 different regular noun declensions?

It's hard for me to imagine this being a natural course of evolution for a language. Multiple forms of irregularity strike me as something to be expected. But it seems almost an oxymoron to say we have multiple ways to do things "regularly" :)

Does this reflect a merging of different ancient indoeuropean languages? Or is there an explanation which parallels biological evolution, in terms of "mutations"? Or is this a question that's "out there" in the realm of pure speculation?

Answer 1

I think it's a phonological thing. Though maybe I just want it to be easy; I cannot deal with unexplained things too well :)

I would guess that there was once a single inflection system that worked the same with all verbs. But then, because verbs have different vowels or consonants in the stem, the sounds influenced each other and they were pronounced differently (same as inexpensive - imperfect - irregular). At some point, the old system would have been lost and the new, different inflections would have become the standard (although different for different groups of verbs).

Anyway, I'm only a noob linguist student and I really don't know. If you ever do find out, please let me know!