>the existence of Kallam system supports the tipological
> reliability of IE vocalic system: /e, a, o/.
There is no problem at all with a system /e, a, o/. Such systems are fairly
common. What is unusual is the apparent PIE system /e/. Yes, there are
other vowels as syllabic allophones of /r, l, m, n, y, w, h1, h2, h3/ and
there is the apophonic /o/, and there are a few roots which seem to have an
irreducible /a/, but the only real vowel appears to be /e/. A one vowel
system with /a/ or /&/ woudl be more believable, so some people have
suggested that we shoudl reconstruct **/a/, which > */e/ as **h2e > *a.
There has been much discussion of this, even on this list, so I won't repeat
it here.
Peter