Human beings, like other species, enter the world with a wide range of innate capacities. These initial abilities are not acquired through learning or experience, as such processes develop later, but are rooted in genetic inheritance and the biological growth of the body and brain. Guided by self-organizing developmental mechanisms, these inborn tendencies shape perception, behaviour, and cognition from the earliest stages of life. The study of these inherited patterns and predispositions forms the foundation of evolutionary psychology, which is introduced in this work. Although evolutionary psychology is not strictly a subfield of complexity science, it shares many themes with broader studies of complex systems. Unlike many animals, human infants are born in an immature state and continue significant biological and cognitive development well after birth. This extended period of development can obscure the presence of early abilities, yet genetic continuity across species suggests that many human capacities are present in potential form from birth. This perspective challenges the notion that individuals begin life as a blank slate. Instead, humans are equipped with underlying assumptions about their environment and natural tendencies to interpret information and respond in specific ways. This encyclopaedia provides students of sociology and psychology with a coherent conceptual framework and methodological insight into the essential principles shaping human behaviour and social development.