PIE verbs (6) -- no use pretending they're simple

From: Piotr Gasiorowski
Message: 7308
Date: 2001-05-13

VI. Verbs: Tense, person, number; ‘primary’ and ‘secondary’ endings
PIE has only two tenses, present and preterite (past). Oddly enough, it is the present tense that is overtly signalled by obligatory morphological markers. Since a regular present/preterite contrast is clearly evidenced for the durative aspect only, it is likely that ‘past-tense’ verbs were originally used without particular time reference, and did not acquire a distinctively preterite meaning until the development of specially marked ‘present continuous’ forms.
Sets of endings contrasting the present with the preterite exist for all the three persons singular and the third person plural:
Athematic stems (*gWHen-/*gWHn- ‘strike’)
     Preterite   Present
1sg. *gWHén-m    *gWHén-m-i
2sg. *gWHén-s    *gWHén-s-i
3sg. *gWHén-t    *gWHén-t-i
3pl. *gWHn-ént   *gWHn-ént-i
Thematic stems (*bHer-e- ‘carry’)
     Preterite   Present
1sg. *bHér-o-m   *bHér-o: (see below)
2sg. *bHér-e-s   *bHér-e-s-i
3sg. *bHér-e-t   *bHér-e-t-i
3pl. *bHér-o-nt  *bHér-o-nt-i
The morphologically simpler preterite endings are called ‘secondary’, while the present endings (usually involving the present-tense marker *-i) are called ‘primary’. These traditional terms are rather confusing, and I’m in favour of avoiding them.
The remaining endings (the first and second persons plural and the dual endings of all three persons) can be reconstructed only approximately. In their early history they were probably prone to dialectal variation and analogical restructuring:
1pl. *-me-s(-i), *-mo-s or *-me-N(-i), preterite *-me(-N)
     (the thematic vowel was *-o- before this ending)
2pl. *-te, *te-s or *te-N
1du. *-we-N(-i) or *-we-s, preterite *-we(-N)
2du. *-to-N or *to-s
3du. *-to-N or *te-s (?), preterite *-ta-h2-N (> *ta:N)
(N = m or n)
One puzzling feature of the system sketched above is the ending *-o: of thematic presents instead of expected *-o-mi. Various analyses have been offered to account for this curious asymmetry; the explanation I find most convincing, though not unproblematic, is that *-o: reflects PIE *-o-h2, an ending related to that of the perfect (our fellow list member Miguel Carrasquer Vidal has a very different personal theory about its origin). Many scholars argue that the *-si, *-ti and *-nti endings of thematic verbs were analogically modelled on those of the athematic conjugation, and that the original endings were like those found in the IE perfect and the so-called hi-conjugation in Hittite, yielding patterns more or less like this:
1sg. *bHér-o-h2
   (perhaps analogical, instead of *bHer-a-h2)
2sg. *bHér-e-th2a
3sg. *bHér-e
1pl. *bHér-o-me-
2pl. *bHér-e-te-
3pl. *bHér-o-nt-i (preterite *bHer-e:r)
Apparently a number of athematic verbs (e.g. those with characteristic o-grade presents, like *k^onk- ‘hang’) were conjugated in a similar way:
1sg. *k^ónk-h2a
2sg. *k^ónk-th2a
3sg. *k^ónk-e
1pl. *k^nk-mé-
2pl. *k^nk-té-
3pl. *k^nk-é:r or (present) *k^nk-ént-i
It is hard to tell to what extent or by what means tense was signalled in this conjugation. If *-i was employed as the present-tense tense marker, we should expects presents like 1sg. *k^ónk-h2a-i or 3sg. *k^ónk-e-i. It is also possible that preterite endings were levelled out very early, so that, say, the preterite *bHér-e-s contrasted with a present like *bHér-e-th2a no matter if the latter was additionally marked with *-i or not.
If there is any substance to these highly speculative reconstructions, the IE ‘perfect’ may turn out to be just one of several formations belonging to a distinct conjugation type. As regards non-perfect verbs, analogical changes obliterated these patterns almost completely at an early date in most branches of IE. What can be said at present is that IE studies are at crossroads in this respect: the classic reconstruction seems to be unsatisfactory, and there is little consensus as to what should replace it.