Civilization first emerged in the Indus River Valley of India in the third millennium B.C.E. The large cities of this Harappan civilization were carefully planned, with straight streets and sewers; buildings were of kiln-dried brick. Harappan cities were largely abandoned by 1800 B.C.E. for unknown reasons.

A few centuries later, the Aryans, speakers of an early form of the Indo-European language Sanskrit, rose to prominence in north India, marking the beginning of the Vedic Age. Aryan warrior tribes fought using chariots and bronze swords and spears, gradually expanding into the Ganges River Valley. The first stages of the Indian caste system date to this period, when warriors and priests were ranked above merchants, artisans, and farmers. The Vedas document the religious ideas farmers. The Vedas document the religious ideas of this age, such as the importance of sacrifice and the notions of karma and rebirth.

Beginning around 500 B.C.E. three of India’s major religions emerged. Mahavira, the founder of the Jain religion, taught his followers to live ascetic lives, avoid harming any living thing, and renounce evil thoughts and actions. The founder of Buddhism, Siddhartha Gautama, or the Buddha, similarly taught his followers a path to liberation that involved freeing themselves from desires, avoiding violence, and gaining insight. Hinduism developed in response to the popularity of Jainism and Buddhism. Hindu traditions validated sacrifice and caste and developed devotional practice, giving individuals a more personal relationship with the gods they worshipped.

From contact with the Persians and Greeks in the sixth century B.C.E. and fourth century B.C.E., respectively, new political techniques, ideas, and art styles and the use of money entered the Indian repertoire. Shortly after the arrival of the Greeks, much of north India was politically unified by the Mauryan Empire under Chandragupta. His grandson Ashoka converted to Buddhism, promoted its spread inside and outside of India.

After the decline of the Mauryan Empire, India was politically fragmented for several centuries. Indian cultural identity remained strong, however, because of shared literature and religious ideas. In the northwest, new monadic groups, the Shakas and the Kushans, emerged. Cultural interchange was facilitated through trade both overland and by sea.