Why are people willing to fight for territories they have never seen? What are territories and why do they matter in international relations? This chapter seeks to address some of these questions by confronting several perspectives on the subject. In particular, the recent introduction of evolutionary theories in the field of international relations (IR) has provoked a debate on the role of hardwired cognitive mechanisms behind international dynamics. These theories appear to directly challenge some of the tenets of well-established research programs in IR, notably constructivism and its emphasis on social constructs. This chapter argues that while these evolutionary theories may redefine our conception of territories, their current shortcomings—regarding their transposition to the territories of complex political units such as modern states, among other things—undermine their argument and highlight the continued need for cultural interpretations of territories in IR. In order to do so, this chapter reviews the way various research programs in IR have conceptualized the territory into their theoretical framework, how evolutionary theories have progressively come to interact with IR theories—notably through the issue of war and territoriality—and how evolutionary theories and seemingly opposite propositions such as constructivism IR theories may offer conflicting yet complementary approaches to our understanding of territories in international relations.