Once you have created all of your cannon fodder in a format which works for you (electronic, paper, index cards, etc.) it is time for you to think about how to expose it in your story. Will your story begin before, during or after the extinction level event? Is it central to the story or does the event just have a role to play? These aren’t minor questions and you alone can answer them. Do not ask for advice on this from friends, family or, most importantly, other writers. Answering of this question makes it _your_ story. Taking the answer provided by another makes it _their_ story even if you write it because it is where _they_ would start. Their answer generally comes with a why along with the where so your mind has already started down _their_ path. Listen to your characters. They will tell you where the story actually begins.
Screenwriters have infinitely more ways to incorporate the cannon fodder than a novelist. Before people start burning me in effigy let me provide a real life example you’ve probably already seen and can most likely view for free via your local public library. The original “Planet of the Apes.”
If you walked into the movie cold, having heard nothing about it before seeing it, this movie was a true mind shag . . . at the end. To get the full impact you really needed to see the movie when it was first released. It played on a lot of cultural fears which were both vocalized and kept private. Some chose to speak about them, others chose to worry in silence. Anyone who saw the movie, actually watching it, remembers this:
Taylor: They blew it up! God, damn you! Damn you all to hell!!!
During the final scene of the movie as the camera pans to show what is left of the Statue of Liberty sticking out of the sand. It was a simple special effect requiring some time to build the set, but when it showed for the first time many in the audience could be knocked over with a feather. With one line and a camera pan the fears of a nation were made manifest. There were 4 additional movies using apes to explore how man got the the point of wiping itself out covering human culture from the stone age to the nuclear.
This may not come as a shock, but I’m a huge fan of building to a thesis as the last line of a paragraph or document. I know. People rag at me all the time. That writing style also defeats the cheats many of your were taught when you were taught how to study. I remember sitting in class being told educational texts usually make the first sentence the most important. Honestly, how many of you looked at used text books and paid attention to the highlighting? Wasn’t it almost always the first sentence like the book came from the printer that way?
Why am I a huge fan of making it last much of the time and burying some in the middle? Because someone actually has to _read it_. How many of you bought a used text book and only read the highlighted stuff? See. Here’s a note I’m sure you found out. You did, at best, as good as the person who did the highlighting. You all assume it was an A student and not the one who flunked out didn’t you?