Another way of arriving at ablaut

I read somewhere that the latest trend is to assume that phonetic
changes spread from an initial limited phonetic context to ever more
diverse contexts, until the change runs out of new contexts, by which
time the rule is said to have applied generally.

So what would be a limited context in which PIE ablaut could
have "born"? We should be looking for a set of changes that would be
common in phonetics.

Here's two (one, depending on one's temperament):

u > w
u > u
u > &w > ew
u > ow

i > y
i > i
i > &y > ey
i > oy

Now these two sets of rules give us exactly what we would expect from
the assumed ablaut vowel /A/ in the traditionally assumed contexts
-Aw- and -Ay-. Let's speculate that by chance (more likely by the
varying stress patterns) the results of these changes came to
distinguish various grammatical forms. If the language
had /r./, /l./, /m./ and/or /n./ it would be tempting to extend the
vowel pattern (the nascent ablaut) to the epenthetic vowel that might
occur before these liquids and nasals. Once there, the vawe might
continue to other phonetic contexts.

Basque has ur "water" but no trace of *wer- (pace Miguel's *(w)ur-).
I think that is a pointer that this loanword from wherever was
originally *ur, as in Basque, and that it was borrowed into PIE as
such, which then manhandled it according to its ablaut rules. Thus,
no PIE *wer-, but PIE *ur-.


Torsten