Zoroaster, also known as Zarathustra, or as Zarathushtra Spitama, was the founder of Zoroastrianism. Though he was a native speaker of Old Avestan and lived in the eastern part of the Iranian Plateau, his birthplace is uncertain. Most of his life is known through the Zoroastrian texts. Modern scholars of Zoroastrianism generally place Zarathushtra as having lived in north-east Iran some time between 1400 and 1200 BCE. Avestan, the language spoken by Zoroaster and used for composing the Yasna Haptanghaiti and the Gathas, on archaeological and linguistic grounds, is dated to have been spoken probably in the first half of the 2nd millennium BCE.