At its core, human behavioral ecology is a demographic science. Its central currency – fitness – is defined by demographic parameters, as are many outcomes of interest to behavioral ecologists. This chapter introduces the basic parameters that define the field of demography, emphasizing their utility both for testing hypotheses of interest to behavioral ecologists and for describing the ecological contexts that situate behaviors. The chapter is structured along the lines of many demography textbooks, describing fertility, mortality, and migration – the three key parameters used to understand population structure and change. We describe how these parameters relate to evolutionary fitness and how each may be used as predictors or outcomes in hypothesis testing in behavioral ecology. Given the importance of using demographic outcomes to test human behavioral ecological theory, the chapter concludes that human behavioral ecologists strongly benefit from familiarity with demographic methods, data sources, and literature. Familiarity with demography can also produce insights that contribute to novel, or more nuanced, theory.