Attachment theory is based in part on biological considerations concerned with the selective forces that probably acted in our environment of evolutionary adaptedness. This functional approach poses questions seldom addressed by developmentalists – for instance why are humans so constructed that particular childhood experiences have particular outcomes? Today much behaviour is directed towards goals other than the maximisation of inclusive fitness. This fact poses a number of questions about the relations between biological and cultural desiderata and the methods for assessing attachment. Finally, the relations of biological and cultural desiderata to the individual desideratum of psychological well-being are considered.