Final answer:
Sociobiology is the theory that explains gender differences and behaviors through the lens of evolutionary processes and the need to reproduce. It attributes different survival and reproductive strategies to men and women based on historical gender roles.
Step-by-step explanation:
The theory that focuses primarily on our biological need to reproduce to explain gender differences and behaviors is known as sociobiology. This field posits that evolutionary processes have influenced human behavior, with men and women evolving different strategies for survival and reproduction based on their roles in early human societies. Sociobiologists argue that men evolved to be more aggressive and to compete for opportunities to mate, while women evolved to be nurturing and more focused on child-rearing and securing long-term relationships for support and protection.