Sociological, economic and evolutionary paradigms of human agency have often seen social agents either as the rational controllers of their fate or as marionettes on the strings of historical, functional or adaptive necessity. They found it therefore difficult to account for the variability, intentionality and creativity of human behaviour and for its frequently redundant or harmful results. This paper argues that human agency is a product of evolution, but that genetic variation and inheritance can only provide a limited explanation of its complex nature. The primary evolutionary problem which human agents face while they are alive is not to adapt to stable environments, but to respond flexibly and creatively to a contingent, uncertain world. Variation and selection therefore take two connected but distinct forms, one external, genetic, and inherited across generations, the other internal and cognitive, and operating during the lifetime of individuals. An examination of this lived part of evolution provides a better understanding of key properties of agency.