The central idea is the central, unifying element of the story, which ties together all of the other elements of fiction used by the author to tell the story. The central idea can be best described as the dominant impression or the universal, generic truth found in the story. Therefore that is why that is the central idea
The paragraph specifically talks about how the body responds to stress.It does not give information on the caveman,neither does it give information on how modern and ancient stresses differ.
