This paper considers the interface between the concepts of attachment and intersubjectivity in light of accumulated research on infant development Both Tomasello (1999) and Hobson (2002) have argued persuasively that the flexible human capability for sharing mental states with others reframes and revolutionizes our older more highly channeled primate biological heritage In contrast to this emphasis on discontinuity from primate to human evolution, attachment theorists have stressed the continuities between human attachment and attachment in other primates The implications of new work on infant intersubjectivity for refraining aspects of attachment theory are first explored Then it is argued that attachmtnt research also has much to offer in understanding the development of joint altention and the sharing of mental states under conditions of increased emotional arousal These potential contributions of attachment research for understanding the development of intersubjectivity are discussed in light of the author's longitudinal work demonstrating that borderline and dissociative symptoms in young adulthood are associated with deviance in the early intersubjective dialogue between mother and infant The idea that emerges from these converging bodies of work is that fostering more collaborative forms of communication may lie at the heart of evolutionary change developmental change and changes resulting from psychodynamic psychotherapy.