Stephen Jay Gould presents the story of the revision of interpretation of the Burgess Shale in the format of a five act play. What is he getting at, what is he implying by this? The format of 5 acts is familiar from Shakespeare, and is grounded in the concepts of unity in Aristotle's Poetics. Scholars have analyzed the five act structure, notably Gustav Freytag who described a "pyramidal" structure, with Act 3 at the apex. Here is what to expect from the various acts:
Act 1 -- Exposition. We meet the dramatis personae, and time and place are established. We learn about the antecedents of the story. Attention is directed toward the germ of conflict and dramatic tensions.
Act 2 -- Complications. The course of action becomes more complicated, the "tying of knots" takes place. Interests clash, intrigues are spawned, events accelerate in a definite direction. Tension mounts, and momentum builds up.
Act 3 -- The Climax of Action. The development of conflict reaches its high point, the Hero stands at the crossroads, leading to victory or defeat, crashing or soaring.
Act 4 -- Falling Action. Reversals. The consequences of Act 3 play out, momentum slows, and tension is heightened by false hopes/fears. If it's a tragedy, it looks like the Hero can be saved. If not, then it looks like all may be lost.
Act 5 -- Catastrophe. The conflict is resolved, whether through a catastrophe, the downfall of the hero, or through his victory and transfiguration.
Act 1 -- 107. The stage is set, we meet Whittington and understand the antecedents in terms of the "shoe-horn" of Walcott. Attention is drawn to the problem with Marrella and Yohoia.
Act 2 -- 124. Things grow complicated by the clearly defined "weirdness" of Opabinia, and now Whittington can't hold back and pretend it's just another fossil.
Act 3 -- 136. Whittington assembles his team, and we meet Briggs and Conway Morris. The "Climax" of the action hinges on Conway Morris's strong personality, and his series of "weird wonders" notably Hallucigenia. The point is clearly made.
Act 4 -- 164. The "reversals" portrayed include Naraoia -- sometimes you don't need the shoehorn! It's just a very strange trilobite after all. Aysheaia is clearly a sort of "velvet worm" or Onychophoran. Nowadays this act might have to be significantly longer.
Act 5 -- 172. In real life in science, it is rare to have either a career-ruining "catastrophe" or a Nobel mediated "transfiguration." So Gould uses this act as an epilogue, bringing the topic up to date (circa 1987).
In a way this is a tour de force because the film is only about seven minutes long, but nearly any well-told story will have the structure described by Freytag:
Act 1 Scene in dorm, walk across campus, interview with prof
Act 2 Entanglement -- the screening room scene
Act 3 Climax of action -- Lucas is typing, imagining
Act 4 "False direction" with Marian in dorm, getting closer
Act 5 Mom arrives (i.e. this is a "tragedy"), "Hi Kids!"
It is an interesting exercise to take any film or novel and "cut it up" this way. Understanding the structure of a well told story is essential to writing one.