Social conflict and the development of technologies can produce changes within a society by altering social dynamics and promoting new cultural models, and spurring or enabling generative action. These social shifts may accompany ideological shifts and other types of cultural change. For example, the U.S. feminist movement involved new practices that produced a shift in gender relations, altering both gender and economic structures. Environmental conditions may also enter as factors. For example, after tropical forests returned at the end of the last ice age, plants suitable for domestication were available, leading to the invention of agriculture, which in turn brought about many cultural innovations and shifts in social dynamics.