Phonological Development from PIE to Greek

Question

I found the following phonological development (from PIE to Greek) patterns very interesting.

*kw>t / __ {e, i}

(e.g., *penkwe- > πέντε)

*gw>d / __ e

(*gwelbhu- > δελψύς)

*gwh>th / __ e

(*gwhen- > θείνω)

What I’m curious is that the letter “i” can’t be applied to *gw and *gwh to make the consonants change into an alveolar or a dental just like *kw does. When “i” follows *gw and *gwh, the results are “bi” and “fi” respectively (which are labials like when *kw changes into p when followed by a consonant, as in *penkwtos- > πεμπτός), as in *gwih- > βίος and *hegwhi- > ὄφις.

I’m wondering if it is about voicing (vibration)? Don’t know if “i” can’t be applied to voiced consonants and make them change into an alveolar or a dental. If so, are there any other sound change patterns similar to these?

Edit: ὄφις, not ὄψις, thanks for the typo correction. Thanks for all the answers and comments!

Answer 1

I assume you mean ὄφις, not ὄψις. The process where kʷ etc become [kp] is reasonably well-attested in the languages of Africa as well as in Indo-European where the outcome would be [p] ([kp] is a typologically anomalous outcome limited mostly to a band of languages in Africa). The lingual outcome can be explained as an acoustically-driven modification of the shift forward of the primary place of articulation, triggered by a front vowel. Labialization as a secondary articulation is primarily identifiable by a significant lowering of a consonant's formants, whereas front vowels lead to palatalization which is identifiable from raised consonant formants.

A voicing-related asymmetry is predicted to be possible, because at the C-to-V transition with a voiceless consonant, there will be a brief voiceless period with turbulent airflow, which is lacking with voiced consonants. That transition then creates more of a fricative-like transition which is easily identifiable, and before a front vowel it is likely to have a more palatal identity, hence an ultimate outcome as a dental rather than a labial. So there are at least two perceptual factors: palatalization leading to a dental, and greater probability of dentalization of a voiceless consonant.

The final puzzle is why dentalization before [e] is the general rule and doesn't have voicing-relation complications. The greater frequency of occurrence of labio-velar plus [e] may well be a systemic factor that encourages maximum generality of the labio-velar to dental shift (examples like ὄφις are not plentiful). A perceptual basis for the asymmetry is not obvious.