Roughly 8.6 per cent of India's population is made up of "Scheduled Tribes" (STs), traditional tribal communities. Whilst most members of these tribes have adopted variants of Hinduism, Islam, or Christianity, a considerable number still adhere to their traditional tribal religions, with varying degrees of syncretism. Numbers According to the 2011 census of India, about 7.9 million out of 1,210 million people did not adhere to any of the subcontinent's main religious communities of Hinduism, Islam, Christianity, Sikhism, Buddhism, or Jainism. The census listed atheists, Zoroastrians, Jews, and various specified and unspecified tribal religions separately under the header "Other Religions and Persuasions". Of these religious census groupings, the most numerous are Sarna (4.9 million respondents), Gondi (1 million), Sari Dharma (506,000), Donyi-Poloism (331,000); Sanamahi (222,000) and Khasi (139,000), with all other religions numbering less than 100,000 respondents, including 18,000 for "tribal religion", 5,600 for "nature religion", and 4,100 "animists". Customs The tribal people observe their festivals, which have no direct conflict with any religion, and they conduct marriage among them according to their tribal custom. They have their own way of life to maintain all privileges in matters connected with marriage and succession, according to their customary tribal faith. In keeping with the nature of Indian religion generally, these particular religions often involve traditions of ancestor worship or worship of spirits of natural features. Tribal beliefs persist as folk religion even among those converted to a major religion. The largest and best-known tribal religion of India is that of the Santhal of Jharkhand, West Bengal, Odisha, and neighbouring regions. The Santals and other Indian tribes practice, profess and propagate their own traditional tribal religions since time immemorial. They have their own Gods and Goddesses and separate places of worship which is completely different from other Indo-Aryan religions. The Gods and Goddesses of the Santals and other tribals do not belong to Hindu pantheon or any other Indo-Aryan pantheon. "Saridharam" is the only religion of the Santal tribe. And the Sarna religion is the religion of the Munda and Oraon tribe of India. The Santals and Munda belong to the Austric language family. Tribal communities like the Gond, Bhil, Oraon and Mina belong to the Dravidian language family. Tribal communities like the Bhutia, Lepcha and tribes living in the North-Eastern states belong to the Sino-Tibetan / Tibeto-Burmese language family. People belonging to the Indo-Aryan language family came to the Indian sub-continent