The Indian subcontinent was home to the urban Indus Valley Civilization of the 3rd millennium BCE — one of the world’s earliest civilizations. It is known from archaeological evidence that a highly sophisticated urbanized culture—the Indus civilization—dominated the northwestern part of the subcontinent from about 2600 to 2000 BCE. From that period on, India functioned as a virtually self-contained political and cultural arena, which gave rise to a distinctive tradition that was associated primarily with Hinduism, the roots of which can largely be traced to the Indus civilization. Other religions, notably Buddhism and Jainism, originated in India—though their presence there is now quite small—and throughout the centuries residents of the subcontinent developed a rich intellectual life in such fields as mathematics, astronomy, architecture, literature, music, and the fine arts. India remains one of the most ethnically diverse countries in the world. Apart from its many religions and sects, India is home to innumerable castes and tribes, as well as to more than a dozen major and hundreds of minor linguistic groups from several language families unrelated to one another. Religious minorities, including Muslims, Christians, Sikhs, Buddhists, and Jains, still account for a significant proportion of the population; collectively, their numbers exceed the populations of all countries except China.