Despite its relative isolation, the Koya area has been the object of numerous population movements, including those of the Koyas themselves, who are probably migrants from the north. Today increasing numbers of Hindu castes from the south have been moving in and displacing the Koyas, their movement into the area facilitated by the construction of a bridge over the Godavari at Bhadrachallam in the 1970s. Historically, the Koyas were subjects of Zamindars (landlords) holding royal grants from various outside rulers, but apart from taxation and corvée, the Zamindars had relatively little authority and were able to exercise control only over the plains villages, and even there only sporadically. British rule over the area came about as a result of their exploitation of the coal deposits at Singareni and from their attempts to make the Godavari River commercially navigable year-round. Christian influence dates from the 1860s, when missionaries were brought in during the construction of an irrigation canal at Dummagudem. Many Koyas in the area around Dummagudem were converted to Christianity and there is still a sizable population of Christian Koyas in the villages near Dummagudem. Many of the Koyas living in the most accessible villages are now indistinguishable from Hindu castes. Much of their land has been appropriated by non-Koyas and many of their villages now have mixed populations of Koyas, Christian Koyas, and Hindus. Acculturation has been a longterm process, and many aspects of Koya ritual and mythology are now informed by Hindu ideas and practices. Since independence, the Indian government has increased its influence over the Koyas, and its various programs and institutions have brought them more and more into the orbit of Indian culture. Koyas have from time to time attempted to free themselves from foreign domination, and have mounted Numerous rebellions, most of which succeeded only for brief periods. The most recent rebellion occurred in the 1950s, when the majority of Koyas supported the Andhra Communist Party and joined in the violence that marked the relations Between Congress and Communist parties in Andhra at that time. Koyas continue to be resentful of outside encroachment and are especially unhappy about land alienation, restrictions on the use of reserve forests, restrictions on the distillation of drinking alcohol, the unjust protection of rapacious moneylenders, and revenue assessments.