The Vedic period, or the Vedic age (c. 1500 – c. 500 BCE), is the period in the late Bronze Age and early Iron Age of the history of India when the Vedic literature, including the Vedas (c. 1500–900 BCE), was composed in the northern Indian subcontinent, between the end of the urban Indus Valley Civilisation and a second urbanisation, which began in the central Indo-Gangetic Plain c. 600 BCE. The Vedas are liturgical texts which formed the basis of the influential Brahmanical ideology, which developed in the Kuru Kingdom, a tribal union of several Indo-Aryan tribes. The Vedas contain details of life during this period that have been interpreted to be historical and constitute the primary sources for understanding the period. These documents, alongside the corresponding archaeological record, allow for the evolution of the Indo-Aryan and Vedic culture to be traced and inferred. The Vedas were composed and orally transmitted with precision by speakers of an Old Indo-Aryan language who had migrated into the northwestern regions of the Indian subcontinent early in this period. The Vedic society was patriarchal and patrilineal. Early Indo-Aryans were a Late Bronze Age society centred in the Punjab, organised into tribes rather than kingdoms, and primarily sustained by a pastoral way of life. Around c. 1200–1000 BCE the Aryan culture spread eastward to the fertile western Ganges Plain. Iron tools were adopted, which allowed for the clearing of forests and the adoption of a more settled, agricultural way of life. The second half of the Vedic period was characterised by the emergence of towns, kingdoms, and a complex social differentiation distinctive to India, and the Kuru Kingdom’s codification of orthodox sacrificial ritual. During this time, the central Ganges Plain was dominated by a related but non-Vedic Indo-Aryan culture, of Greater Magadha. The end of the Vedic period witnessed the rise of true cities and large states (called mahajanapadas) as well as śramaṇa movements (including Jainism and Buddhism) which challenged the Vedic orthodoxy.