請回答下列第21題至第25題 Humans are a fundamentally social species. They are unable to reproduce and 21 to reproductive age without a group. They lack natural 22 such as slashing canines, bodily armor, or fleetness of foot; they have an extended infancy 23 by years of further development before they reach reproductive maturity. Many of the evolved characteristics that have 24 humans to adapt to a wide range of physical environments, such as tool making and feeding on both animals and plants, and create dependence on collective knowledge and cooperative information sharing 25 individuals and between generations. Humans are, indeed, an obligately interdependent species.