Research specifically designed to test evolutionary hypotheses concerning mental disorders and human behavioural traits is still a new and as yet undeveloped area of enquiry. There are considerable problems involved in reconstructing the evolutionary history of the human mind/brain, for this history is unrecorded. As a result, theories about it are essentially deductive, being derived from such sources as behavioural observations of different species and anthropological observations of different cultures. However, analysis of behaviour in terms of its adaptive function can not only yield valuable insights, as we have seen, but also give rise to testable statements – such as that care-giving will be more consistently and reliably provided to offspring by their biological parents than by step-parents.