In the comedy Biosphere, Billy (Mark Duplass) and Ray (Sterling K. Brown) live in one of the titular domes. They’ve been here for years. Some sort of catastrophe took place outside, rendering them possibly the last people alive. Billy, we learn, had been the President in the before times. Ray was his top scientific advisor. Now it’s just the two of them, spending their days debating Super Mario Bros. video games and watching the Lethal Weapon movies.

The men survive by breeding and eating fish. When the last female fish dies, it appears that their food supply will run out, sealing their doom. An unexplained green light in the sky adds to the ominousness. Then a miraculous evolutionary event occurs that could save their lives, bringing an unexpected effect with it. I promise you are not ready for where the story goes after that. It gives new meaning to the term “bromance.”

Writing about Biosphere without giving away the central concept is difficult, but I must try. I did not know it in advance, so the very unpredictable places the film went were as amusing as they were surprising. The thing is, what transpires in this comedy might have been played for cheap shock value. Instead, director Mel Eslyn, who co-wrote the screenplay with Duplass, aims for a deeper, more thoughtful tone. She first wrings each new complication for a huge laugh, then uses it to deepen the dynamic between Billy and Ray.

If forced to pinpoint the theme with one word, the best choice is “evolution.” Sci-fi trappings aside, Biosphere is about how the relationship these old friends have changes and morphs throughout their predicament. They’re at odds sometimes, but then become closer in ways they couldn’t have imagined previously. We’re never told what happened outside, although there’s an implication that Billy caused it and Ray failed to prevent it. No formal explanation is necessary. We learn everything we need to know from observing what transpires between them.

The movie thrives on the excellent chemistry Duplass and Brown generate. Again, the instigating situation had the potential to be silly or stupid. Because the stars play it real, Biosphere takes on a thoughtful quality to match its hilarity. They ground the premise in identifiable emotion, even if there’s no way we can identify with the ordeal itself.

Visually, the movie grows a bit stale after a while, since everything takes place in a single cramped location. Eslyn also could have tightened the pace by cutting out a few of the short interludes that are used to convey the passage of time. Otherwise, Biosphere is an extremely funny picture that reveals a core of sweetness as it goes on.

out of four

Biopshere is unrated, but contains adult language and thematic/sexual material. The running time is 1 hour and 46 minutes.