During the Early Vedic period (c. 1500 - 1100 BCE) Indo-Aryan tribes were pastoralists in north-west India. After 1100 BCE, with the introduction of iron, the Indo-Aryan tribes moved into the western Ganges Plain, adapting an agrarian lifestyle. Rudimentary state-forms appeared, of which the Kuru-tribe and realm was the most influential. It was a tribal union, which developed into the first recorded state-level society in South Asia around 1000 BCE. It decisively changed their religious heritage of the early Vedic period, collecting their ritual hymns into the Veda-collections, and developing new rituals which gained their position in Indian civilization as the orthodox srauta rituals, which contributed to the so-called "classical synthesis" or "Hindu synthesis".