During era of Joseph Stalin in the Soviet Union (1920s–1950s), research into prehistoric societies was encouraged, with some scholars arguing that pre-Christian society reflected a form of communitarianism that was damaged by Christianity's promotion of entrenched class divisions. In doing so, pre-Christian belief systems underwent a rehabilitation. Joseph Stalin himself was a supporter of the idea of Slavic Vedism, the shared Indo-European origins of Vedic and Slavic cultures. Boris Rybakov (1908–2001), former head of the Institute of Archaeology, provided the first academic studies about ancient Slavic religion. In the 1960s, the renewal of militant atheism under Nikita Khrushchev also presupposed a recovering of pre-Christian and pre-Islamic traditions.