The 30-odd residents of the tiny town of Darwin, Calif., prefer to keep themselves to themselves, as evidenced by the “No services ahead” sign they’ve erected to discourage visitors. We can only marvel, then, at their candor when faced with Nick Brandestini’s camera in “Darwin,” a droll and dusty portrait of a place where privacy is prized and boundaries respected.

Nestled amid the placid, arid landscapes of Death Valley, its only neighbors a top-secret military base and the infamous Barker Ranch, the town manages its own water supply and buries its own dead. In its silver-mining heyday, Darwin thrived on a reputation for debauchery and lawlessness, but today’s townsfolk (the film was shot in 2009 and 2010) are an altogether quieter, more thoughtful bunch.

“There are a lot of things we just don’t talk about,” says Monty Brannigan, a former miner, but Mr. Brandestini knows how to listen without visual trickery or manipulative musical cues. Teasing out tales of shady pasts and estranged children, he exposes ever-deeper layers, connecting relationship and genealogy dots gradually and without fanfare. In the background Michael Brook’s melancholy score honors a survivalist spirit that draws comfort from inhospitable surroundings.

Whether stockpiling for disaster or just relishing the here and now, Darwin’s aging residents — including an anarchist, a rock artist, a few pagans and a charming lady described on screen as “Bon Vivant” — get by mostly on disability and unemployment checks. The town’s lone job belongs to its ornery postmaster, Susan.