Austronesian people form the majority of the modern population. They may have arrived in Indonesia around 2000 BCE and are thought to have originated in Taiwan.^[81] During this period, parts of Indonesia participated in the Maritime Jade Road, which existed for 3,000 years between 2000 BCE to 1000 CE.^[82] Dong Son culture spread to Indonesia bringing with it techniques of wet-field rice cultivation, ritual buffalo sacrifice, bronze casting, megalithic practises, and ikat weaving methods. Some of these practices remain in areas including the Batak areas of Sumatra, Toraja in Sulawesi, and several islands in Nusa Tenggara. Early Indonesians were animists who honoured the spirits of the dead believing their souls or life force could still help the living.

Ideal agricultural conditions, and the mastering of wet-field rice cultivation as early as the 8th century BCE,^[83] allowed villages, towns, and small kingdoms to flourish by the 1st century CE. These kingdoms (little more than collections of villages subservient to petty chieftains) evolved with their own ethnic and tribal religions. Java's hot and even temperature, abundant rain and volcanic soil, was perfect for wet rice cultivation. Such agriculture required a well-organized society, in contrast to the society based on dry-field rice, which is a much simpler form of cultivation that does not require an elaborate social structure to support it.