Proto-Chukotko-Kamchatkan is the hypothetical common ancestor of the Chukotko-Kamchatkan languages. It is purported to have broken up into the Northern (Chukotian) and Southern (Itelmen) branches around B.C.E. 2000, when western reindeer herders moved into the Chukotko-Kamchatkans' homeland and its inland people adopted the new lifestyle.
A reconstructed version of the language is presented by Michael Fortescue in his Comparative Dictionary of Chukotko-Kamchatkan (2005).
According to Fortescue, Proto-Chukotko-Kamchatkan had the following phonemes, expressed in IPA symbols.
*/c/ is a true voiceless palatal stop (not the affricate č). Note that Proto-Chukotko-Kamchatkan had only voiceless stops, no voiced stops (such as /b d g/). However, there is a series of voiced fricatives, */v ð ɣ ʁ/. These have no voiceless counterparts (such as /f θ x/).
*/v/ is a voiced labiodental fricative (like v in English). */ɣ/ is a voiced velar fricative (like the g in Dutch ogen, modern Greek gamma, Persian qāf, etc.). */ʁ/ is a voiced uvular fricative (like r in French).
The entire */t ð n l r/ series is alveolar — i.e. */t ð n/ are not dentals.
It is generally accepted that Proto-Chukotko-Kamchatkan had an eleven-case system for nouns, but Dibella Wdzenczny has hypothesised that these evolved from only six cases in Pre-Proto-Chukotko-Kamchatkan. Below is the reconstructed case system of Proto-Chukotko-Kamchatkan.
1Note that the (mostly inanimate) nouns of the first declension only marked plurality in the absolutive case.
The protolanguage is thought to have been a nominative-accusative language, with the current Chukotko-Kamchatkan ergative aspects coming later in the (Northern) Chukotian branch, possibly through contact with nearby Eskimo-Aleut-speaking peoples. This would explain why Itelmen, spoken further south than any Eskimo-Aleut speaking peoples visited, lacks ergative structures. Some linguists, however, maintain that Proto-Chukotko-Kamchatkan began as an ergative language and lost that feature over time.