Common Anatolian language
The first branch of Proto-Indo-European which drifted apart and began its independent existance in history was Anatolian. There language was born not in Anatolia itself; it appeared already as a dialect in the Common Indo-European area somewhere in Central Asia. In the 4th millennium BC Anatolian community started its migration through the continent. At these times Anatolians were nomadic tribes, and where they were going until they arrived in Asia Minor in the 3rd millennium, we do not know. But it's that "dark" period where the most srange features of Anatolian languages were born.

We can state for sure only several grammar traits of Common Anatolian. Four noun cases had flexions practically the same as in Proto-Indo-European. There were only 2 genders: common and neuter, and this is really unique, because it reflects the stage of the Proto-language when animate and unanimate things were the only distinction, no masculine and feminine opposition.

The verb system consisted of two moods (indicative and imperative), two tenses (present and preterite), two voices (active and medium). But verbal endings are very strange for they have few correspondences in Proto-Indo-European or other Indo-European languages. The -hn / -n ending of the 1st person preterite is not found anywhere else except Anatolian languages; the same can be said about -weni, -meni (1st person plural), -lu (1st person singular of imperative).

Common Anatolian is a highly archaic tongue, with lots of traits derived directly from the ergative (early) stage of Proto-Indo-European. And this was inherited by later Anatolian branches - Hittite, Luwian, Palaic.