Gatha (Zoroaster) in the context of "Avesta"

This is a list of languages arranged by age of the oldest existing text recording a complete sentence in the language. It does not include undeciphered writing systems, though there are various claims without wide acceptance, which, if substantiated, would push backward the first attestation of certain languages. It also does not include inscriptions consisting of isolated words or names from a language. In most cases, some form of the language had already been spoken (and even written) considerably earlier than the dates of the earliest extant samples provided here.

A written record may encode a stage of a language corresponding to an earlier time, either as a result of oral tradition, or because the earliest source is a copy of an older manuscript that was lost. An oral tradition of epic poetry may typically bridge a few centuries, and in rare cases, over a millennium. An extreme case is the Vedic Sanskrit of the Rigveda: the earliest parts of this text date to c. 1500 BC, while the oldest known manuscripts date to c. 1040 AD.Similarly the oldest Avestan texts, the Gathas, are believed to have been composed before 1000 BC, but the oldest Avestan manuscripts date from the 13th century AD.

Zarathushtra Spitama, more commonly known as Zoroaster or Zarathustra, was an Iranian religious reformer who challenged the tenets of the contemporary Ancient Iranian religion, becoming the spiritual founder of Zoroastrianism. In the oldest Zoroastrian scriptures, the Gathas, which he is traditionally believed to have authored, he is described as a preacher and a poet-prophet. Some have claimed, with much scholarly controversy, to find his influence in Heraclitus, Plato, Pythagoras, and, perhaps less controversially, in the Abrahamic religions, including Judaism, Christianity, and Islam, particularly through concepts of cosmic dualism and personal morality.

He spoke an Eastern Iranian language, named Avestan by scholars after the corpus of Zoroastrian religious texts written in that language. Based on this, it is tentative to place his homeland somewhere in the eastern regions of Greater Iran (perhaps in modern-day Afghanistan or Tajikistan), but his exact birthplace is uncertain. His life is traditionally dated to sometime around the 7th and 6th centuries BC; though most scholars, using linguistic and socio-cultural evidence, suggest a dating to somewhere in the second millennium BC.

Proto-Indo-Iranian, also called Proto-Indo-Iranic or Proto-Aryan, is the reconstructed proto-language of the Indo-Iranian branch of Indo-European. Its speakers, the hypothetical Proto-Indo-Iranians, are assumed to have lived in the late 3rd millennium BC, and are often connected with the Sintashta culture of the Eurasian Steppe and the early Andronovo archaeological horizon.

Proto-Indo-Iranian was a satem language, likely removed less than a millennium from its ancestor, the late Proto-Indo-European language, and in turn removed less than a millennium from its descendants: Vedic Sanskrit (of the Rigveda) and Old Avestan (of the Gathas).