Final answer:
Robert Carneiro's theory attributes a key role to environmental circumscription in the formation of early states, with limited arable lands leading to competition and the development of centralized political structures in early coastal Peru.
Step-by-step explanation:
Robert Carneiro's theory of state formation, particularly in relation to the early coastal states in Peru, gave a key role to environmental circumscription. Carneiro's theory suggests that in areas where arable land is limited by environmental features such as mountains or deserts, the competition for scarce resources can lead to warfare and ultimately the development of centralized political structures or states. The early civilizations of coastal Peru, such as the ones at Caral, faced such limitations, which may have prompted the rise of complex societies and state formation.