Overview of personal identity from a philosophical perspective as conceived traditionally and disputed by Derek Parfit (Reasons and Persons; ‘personal identity is not required for the survival of the person’). An account of personal identity per philosophers Hume, Derrida, Deleuze, and Simondon. The evolutionary biological case for personal identity in humans. There is a large literature on the ability of members of many animal species (wasps for example) to distinguish specific individual others. I consider why and how personal identity might have evolved to bring adaptive fitness to humans, if the adaptation is still serving, and what forces might cause this to be different in the future.