Attachment theory not only illuminates developmental issues and clinical phenomena, such as the formation of attachment ties, separation anxiety and loss, from new perspectives, but has also generated a research program that has confirmed fundamental premises of the theory and enriched and expanded the theory with new empirical findings. This essay is organized in four parts, the third and the fourth being to be published in the next issue (24/2007). In the first part the authors lay out the basic structure of attachment Theory compared with other motivational systems. In the second part they propose a multi-motivational model of human nature to propose a basic taxonomy of human motivation in an evolutionary perspective. In order to develop a comprehensive view of human motivation, the essay answers to two key questions: 1) What are the new characteristics of our species that make us unique? 2) How do these emerging properties modify the basic motivational systems that unite us to other mammals and primates?