Evidence for human habitation in Karnataka exists until at least the 2nd millennium BCE, and it is postulated to have had contact with the Indus Valley civilisation. The existence of artifacts (such as Roman coins) shows Karnataka was involved in trade as early as the 1st century CE. In the 4th century BCE the land was ruled by the Mauryans and Jainism was very popular. After the Mauryas, parts of Karnataka were variously ruled by dynasties either ethnically Kannadiga or outside. The Kadambas, Chalukyas, Rashtrakutas and Hoysalas were some of the many major Kannada kingdoms and dynasties ruling the region. The Vijayanagara Empire was founded by Kannadiga chieftains and they were great patrons of Kannada art and literature.