Homo heuristicus makes inferences in uncertain environments using simple heuristics that ignore information (Gigerenzer and Brighton, 2009). Traditionally, heuristics are seen as second-best solutions which reduce effort at the expense of accuracy, and lead to systematic errors. The prevailing assumption is that, to understand the ability of humans and other animals to cope with uncertainty, one should investigate cognitive models that optimize. We introduced the term Homo heuristicus to highlight several reasons why this assumption can be misleading, and argue that heuristics play a critical role in explaining the ability of organisms to make accurate inferences from limited observations of an uncertain and potentially changing environment. In this chapter we use examples to sketch the theoretical basis for this assertion, and examine the progress made in the development of Homo heuristicus as a model of human decision-making.