The earliest anatomically modern human remains found in South Asia date from approximately 30,000 years ago. Nearly contemporaneous Mesolithic rock art sites have been found in many parts of the Indian subcontinent, including at the Bhimbetka rock shelters in Madhya Pradesh. Around 7000 BCE, the first known Neolithic settlements appeared on the subcontinent in Mehrgarh and other sites in western Pakistan. These gradually developed into the Indus Valley Civilisation, the first urban culture in South Asia; it flourished during 2500–1900 BCE in Pakistan and western India. Centred around cities such as Mohenjo-daro, Harappa, Dholavira, and Kalibangan, and relying on varied forms of subsistence, the civilisation engaged robustly in crafts production and wide-ranging trade.
During the period 2000–500 BCE, in terms of culture, many regions of the subcontinent transitioned from the Chalcolithic to the Iron Age. The Vedas, the oldest scriptures of Hinduism, were composed during this period, and historians have analysed these to posit a Vedic culture in the Punjab region and the upper Gangetic Plain. Most historians also consider this period to have encompassed several waves of Indo-Aryan migration into the subcontinent from the north-west. The caste system, which created a hierarchy of priests, warriors, and free peasants, but which excluded indigenous peoples by labeling their occupations impure, arose during this period. On the Deccan Plateau, archaeological evidence from this period suggests the existence of a chiefdom stage of political organisation. In southern India, a progression to sedentary life is indicated by the large number of megalithic monuments dating from this period, as well as by nearby traces of agriculture, irrigation tanks, and craft traditions.
In the late Vedic period, around the 5th century BCE, the small chiefdoms of the Ganges Plain and the north-western regions had consolidated into 16 major