 The Iranians dominated the modern day plateau, while the Indo-Aryans ultimately headed towards the Indian subcontinent.The Avesta is believed to have been composed possibly as early as 1800 BC and written in ancient Ariana (Aryana), the earliest name of Afghanistan which indicates an early link with today's Iranian tribes to the west, or adjacent regions in Central Asia or northeastern Iran in the 6th century BC.Due to the similarity between early Avestan and Sanskrit (and other related early Indo-European languages such as Latin and Ancient Greek), it is believed that the split between the old Persians and Indo-Aryan tribes had taken place at least by 1000 BC.