A renewed interest from the late 1960s in "unorthodox" approaches to Marxism paved the way for an alternative to mainstream development and underdevelopment theories in the 1970s. Modernization theory was criticized for its evolutionary approach, while underdevelopment theory was rejected because it focused on trade relations. These theories were contrasted to a "scientific" method that took the mode of production as the determining concept. Although there were some divisions within this school of thought, the most influential thesis argued that Third World social formations were characterized by an articulation of modes of production.