Niko Tinbergen (1963) described four complementary questions to be asked of any animal’s behaviour in order to understand it. Two of the questions seek proximate explanations for behaviour: What are the material causes of behaviour? And how does the behaviour develop within the lifetime of an individual? These are questions of mechanism and ontogeny, and they are the primary focus of many psychologists and neuroscientists. While other chapters in this volume will explore at length the proximate causes of prospective cognition , we will direct our attention to the other two questions, which concern the ultimate, evolutionary causes of prospection: function and phylogeny.