Proto-Chukotko-Kamchatkan language

Proto-Chukotko-Kamchatkan is the reconstructed common ancestor of the Chukotko-Kamchatkan languages. It is purported to have broken up into the Northern and Southern branches around 2000 BCE, when western reindeer herders moved into the Chukotko-Kamchatkans' homeland and its inland people adopted the new lifestyle.
A reconstruction is presented by Michael Fortescue in his Comparative Dictionary of Chukotko-Kamchatkan.

Phonology

According to Fortescue, Proto-Chukotko-Kamchatkan had the following phonemes, expressed in IPA symbols.

Consonants

is a true voiceless palatal stop. Note that Proto-Chukotko-Kamchatkan had only voiceless stops, no voiced stops. However, there is a series of voiced fricatives,. These have no voiceless counterparts.
is a voiced labiodental fricative. is a voiced velar fricative. is a voiced uvular fricative.
The entire series is alveolar — i.e. are not dentals.

Grammar

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.

Case	Declension 1	Declension 2	Declension 1 ₁	Declension 2
absolutive
dative
locative
instrumental
comitative		-		-
associative		-		-
referential
ablative
vialis
allative
attributive

₁Note that the 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 Chukotian branch, possibly through contact with nearby Eskimo–Aleut-speaking peoples. This would explain why Itelmen, spoken further south than any Eskimo–Aleut speakers visited, lacks ergative structures. Some linguists, however, maintain that Proto-Chukotko-Kamchatkan began as an ergative language and lost that feature over time.