In Proto-Germanic, free accent was retained long enough for Verner's Law to be dependent on it, but later, stress was shifted to the first syllable of the word.
[3] This quality persisted in Vedic Sanskrit and Ancient Greek, as in the declension of the nouns descended from PIE *pṓds 'foot, step': or in the conjugation of athematic verbs (compare Sanskrit root present first-person sg.
However, Greek is almost completely worthless for reconstructing the PIE accent in verbs, because (other than in a few cases) it is consistently positioned as close to the start as the rules allow.
For the reconstruction of the Proto-Balto-Slavic accent, the most important evidence comes from Lithuanian, from Latvian (traditionally Lithuanian is thought as more relevant, but that role is being increasingly being taken over by Latvian[4]), and from some Slavic languages, especially Western South Slavic languages and their archaic dialects.
Accentual alternations in inflectional paradigms (both verbal and nominal) are also retained in Balto-Slavic.
These facts are often interpreted as being the result of the interplay between individual morphemes, each of which belonged, unpredictably, to one of several accentual classes in PIE.
Traditionally the PIE accent has been reconstructed in a straightforward way, by the comparison of Vedic, Ancient Greek and Germanic; e.g. PIE *ph₂tḗr 'father' from Sanskrit pitā́, Ancient Greek πατήρ, Gothic fadar.
In 1973 (an early version of the hypothesis was presented in 1962),[6] the Moscow accentological school, headed by linguists Vladimir Dybo and Sergei Nikolaev, reconstructed the PIE accentual system as a system of two tones or valences: + (dominant) and − (recessive).
[7][8][9] Proto-Indo-European would thus not have, as is usually reconstructed, a system of free accent such as is found in Vedic, but instead every morpheme would be inherently dominant or recessive, and the position of the accent would be later determined in various ways in the various daughter languages (depending on the combinations of (+) and (−) morphemes), so that Vedic would certainly not be the most archaic language.
Many correspondences among IE languages, as well as certain phenomena in individual daughters dependent on PIE tones, should corroborate this interpretation.