I watched that movie today. It was out of an odd interest. Even though I am no longer of the faith, I am interested in what people believe, why they believe it, and how these stories were conceived.
The Deluge is not a purely judaeo-christian story. As I gathered on the wikipedia page dedicated to this topic, it is a story older than the neolithic revolution. Moses "merely" retold it in a fashion fitting his other works. There are numerous theories from serious scientists trying to match the event to actual floods. When I watched this movie, I hit a completely different angle: what if "serious" scientists were handling the matter too literally?
People have a habit of telling elaborate stories to explain quite simple, sometimes even totally banal stuff. The oldest known version of Romeo and Juliet, Pyramos and Thisbe, retold in Ovid’s Metamorphoses, was used to explain why a tree bore red berries: because the blood of the lovers from feuding families was spilled at the roots of the tree. The tree sucked up the blood, and its white berries turned red.
Of course, the story of Noah’s Arc is deeply embedded in the world view of the abrahamitic religions. Noah is, in many of our understandings, the forefather of all humans. Him and his family are the sole human survivors of aforementioned deluge. What if the deluge was a different, currently unknown catastrophe, that acted as a genetic bottleneck event? What if the only plausible explanation to preliterate humans was a flood that wiped out all but a few hundred of our progenitors? And for dramaturgical reasons, they just reduced the number of survivors.
Humans do have an exceptionally low genetic variety. There are species on earth with less, but they don’ tell stories of floods covering the earth for a year or more. The catastrophy must have been long enough ago for us to develop a natural feeling of disgust toward mating with the people we grew up with – most of us. We feel naturally compelled to seek mates outside of our homes. The need to explain this phenomenon, and a common human memory, probably gave rise to the story of the deluge, across multiple cultures of humanity. As I’ve said: multiple cultures. Not all cultures.