The Vedic period (or Vedic age) (c. 1500 – c. 500 BCE) was the period in Indian history during which the Vedas, the oldest scriptures of Hinduism, were composed. During the early part of the Vedic period, the Indo-Aryans settled into northern India, bringing with them their specific religious traditions. The associated culture (sometimes referred to as Vedic civilisation) was initially a tribal, pastoral society centred in the northwestern parts of the Indian subcontinent; it spread after 1200 BCE to the Ganges Plain, as it was shaped by increasing settled agriculture, a hierarchy of four social classes, and the emergence of monarchical, state-level polities. Scholars consider Vedic civilisation to have been a composite of the Indo-Aryan and Harappan cultures.