Final answer:
The fear of darkness contributing to the survival of human ancestors is most relevant to the evolutionary perspective of psychology, which examines how genetic behaviors evolve to increase survival and reproductive success.
Step-by-step explanation:
Understanding why the fear of darkness may have contributed to the survival of our human ancestors is primarily related to the evolutionary perspective. This perspective is concerned with how behavioral traits such as a fear response to the dark could have been advantageous for survival and thus were naturally selected over generations. The tendency to be cautious or fearful of darkness would likely reduce the chances of encounters with nocturnal predators and other risks, supporting the survival and reproduction of those with such instincts.
The field of study that focuses on genes and their expression in the context of behavior is evolutionary psychology. Evolutionary psychology suggests that much of human behavior is the output of psychological adaptations that evolved to solve recurrent problems in human ancestral environments. This perspective fits the context of the initial question by aligning with the concept that some behaviors, such as fear of the dark, may be deeply ingrained in our genetic makeup because they were once beneficial for our ancestors.