The dinner table erupts in Stephen Karam’s ‘The Humans’

Gathering a family around the dinner table for a big meal that is bound to run amok is one of the great conceits of modern theater (see Chekhov, O’Neill, Tracy Letts, and the list goes on). And of course the more dysfunctional that family is, the better.

“The Humans,” the delirious tragicomedy by Stephen Karam that is now receiving a sensational world premiere by American Theater Company (with a different production at New York’s Roundabout Theatre Company already slated for fall 2015), takes this premise to the outer limits. But here’s the irony: The more the various forms of dysfunction are revealed, the more believable Karam’s play becomes.

It’s a very clever trick, but a sleight-of-hand gift that should not be surprising to those who saw the playwright’s zany earlier work, “Sons of the Prophet” (a finalist for the 2012 Pulitzer Prize), which also was staged by ATC. Karam has a special flair for making the absurd realities of contemporary life at once wildly laughable and heartbreakingly true. He knows that if you can’t laugh at the human condition you might as well just hang yourself. And the excellent director PJ Paparelli, and his uniformly exceptional cast, are primed for the crazy ride of it all.

The Thanksgiving dinner that brings together three generations of the Irish Catholic Blake family unfolds in one of those New York apartments with an air-shaft view and an awkward layout that suggests the city’s surreal housing situation. (This apartment is in Chinatown, and designer David Ferguson nails it, with help from Patrick Bley’s sound and Brian Hoehne’s lighting.)

Sharing this weird duplex are Brigid (Kelly O’Sullivan), a 20-something musician with urban pretensions who mostly works as a bartender, and her boyfriend, Richard (Lance Baker), in his late 30s, who is working on a masters in social work. Their furniture has yet to be delivered, so dinner is served on paper plates atop two card tables.

Brigid’s working class parents — her clearly anxiety-filled dad, Erik (Keith Kupferer), and her mom, Deirdre (Hanna Dworkin), who clings desperately to her faith — have driven up from their home in Pennsylvania, and they’ve brought Erik’s mom, “Momo” (Jean Moran), who is suffering from dementia but has one great, surprising burst of joy. Joining them is their other daughter, Aimee (the ever-astonishing Sadieh Rifai), a lawyer, who we learn was in the World Trade Center on the morning of the Sept. 11 terrorist attacks, and more recently has broken up with her girlfriend, been fired from her job and is facing serious surgery for ulcerative colitis.

“Shouldn’t it cost less to be alive?” asks Dad, who slowly reveals both his personal and financial problems. But money is only the tip of the iceberg here. And it’s Richard, the “outsider” in this massive family pileup, who captures the essence of the play when he observes that while humans often have nightmares about monsters, the really scary stories for monsters have to do with humans.

And yes, people are the problem. But, as Karam affirms, they also are the solution, for despite the chaos, trauma and pain generated within a family, there is a blood connection that is all but impossible to destroy. And this connection is playfully but poignantly embodied in the Blakes’ “smashing the peppermint pig” tradition, as each person at the table makes a wish and hammers apart a candy pig that ultimately will be shared by all.

A great deal more occurs during the course of this Thanksgiving dinner that encompasses the full spectrum of life. And the wonder of it all is that Karam easily stuffs it all into just 95 minutes, supplying an ending worthy of Samuel Beckett to boot.