The Aryan invaders who conquered India created a new society. Early Indian religious writings taught the principles of Hinduism, India's major religion. Hinduism includes the concept of an eternal spirit, reincarnation, and the obligation to perform the duties of one's social group. A thousand years later, Siddhartha Gautama founded Buddhism, which later spread from India to East Asia and Southeast Asia. Gautama taught that people can free themselves from suffering by eliminating desire and following rules of behavior. Both Hinduism and Buddhism had a profound influence on literature, arts, and architecture in Asia. Asoka, a Mauryan ruler in northern India, helped spread Buddhism. For a time the Guptas united India, and during that period scholars made numerous advances, including the development of algebra, the numbers 1 through 9, and the concept of zero.