The Old Iranian languages known from texts are Old and Young Avestan and Old Persian. Comparative study of these three languages permits the reconstruction of proto-Iranian as a branch of the Indo-Iranian languages, an eastern branch of the Indo-European languages that may have been spoken in the area south and south-east of the Aral sea in the third millennium , splitting into Iranian and Indo-Aryan some time before 2000 . Geographical names contained in the Young Avesta confirm this location and also show that, by the time of the Achaemenids, the Avestan speakers had moved farther south as far as the Helmand valley in modern south Afghanistan (Skjærvø 1995: 163-66). See also section 1.4.