The Sixth Extinction - Production

Production

Frank Spotnitz said of the episode's origins, "We've destroyed all the stuff about Mulder's father, the project, and the Syndicate. All the things that had sustained us for six years were suddenly gone. We had no crutches. From that point on, every time we sat down to write a mythology show, we knew it was going to be a completely different challenge." Chris Carter saw the episode as a transitional episode, stating "I felt that, with "The Sixth Extinction", I was just playing a supporting role and that the episode, essentially the middle episode of a three-episode arc, was just a transitional episode to get us to 'Amor Fati', which was really less about the mythology and more about Mulder's choices in life."

David Duchovny and Gillian Anderson both had other commitments as the season began, resulting in the producers delaying filming for this episode. It ended up being filmed third in the season, after the episodes "Hungry" and "The Goldberg Variation". Carter wrote the episode at the same time as Duchovny was working on the next episode, "The Sixth Extinction II: Amor Fati". Kim Manners said preparations were confusing since it wasn't known at the time how the storyline would unfold. Spotnitz said of the end result, "For me, it was a lot like a fifties monster movie with Scully out on the beach with this guy going nuts with a machete, the bug attacks, and the sea of blood. Yeah, it was supposed to be serious business but, overall, I thought it was shaping up as a pretty entertaining hour."

The producers had to move the filming of the beach sequences from the previous episodes due to changes in the tides at that time of year. Similar to the previous episode, the spaceship was computer-generated. The sequence where the locals are boiled by the ocean water was accomplished using underwater filming of stuntmen under various degrees of make up. Fifty thousand dead crickets were rented from a local entomologist for the scene where Scully's tent was attacked by bugs. The live insects were portrayed by blowing popcorn and packing foam at Anderson with fans and editing it into insects in post production.

A large portion of the episode was based on the ancient astronaut theory, which proposes that intelligent extraterrestrial beings have visited Earth in antiquity or prehistory and made contact with humans. Frank Spotnitz later remarked that he was astounded at how little negative fan mail the show received, despite the fact that the "Biogenesis"/"The Sixth Extinction"/"Amor Fati" story arc heavily hinted that aliens were the originators of the notion of God and religion. He credited the manner in which the show handled this delicate subject, saying, "Often in the past, we've done stuff where I was sure we would get angry letters. But we rarely do. And the reason is because of the way we handle things. In 'Amor Fati' we treated the religious side with respect." The ancient astronaut themes were later revisited in the two season nine episodes "Provenance" and "Providence."