Agile software development methods help software development teams respond to changing requirements. Fundamental to this ability to respond to change is the manner in which requirements are communicated and developed. The question of agile requirements development is considered through the lens of Complex Adaptive Systems theory, a theory used to explain agility in software development teams. A case study of the communication and development of requirements in a software development team is reported, where the three dimensions of CAS Theory described by Vidgen and Colleagues (Vidgen and Wang 2009) are adapted to describe requirements communication and development practices in greater detail. We find that this focus on requirements practices can further explain increases in a software team's agility.