What I am offering is a critical overview of ideas about depression, some new, some old, which fall under the discipline of 'evolutionary psychology'(EP). Do most types of depression represent an adaptation - an evolved mechanism which has improved our survival and reproductive value in our ancestral environment? Has depression been selected? Could it still be useful to us today? This book makes a contribution to the field while communicating the issues to a wider audience than EP currently receives and deserves. There are important implications for how we should prevent or treat an increasingly common condition, and how we might view the condition in a more constructive way. - Paul Keedwell, in the Preface.