The celebrity genealogy series “Who Do You Think You Are?” (7 p.m., NBC) returns with a glance at a few of the gnarled branches in Martin Sheen’s family tree.

The star of “The West Wing,” ”Apocalypse Now” and “Badlands” is Irish on his mother’s side; his father’s people hail from Spain. A trip to both countries reveals uncles who were politically involved and arrested for their activities. His maternal uncle was imprisoned as an IRA radical during the Irish Civil War in the early 1920s and became infamous for burning down the prison that held him. His father’s brother, an alleged Spanish Communist, was given a life sentence under the military dictatorship of Francisco Franco.

Sheen is intrigued by this, given that he’s been arrested dozens of times for his own political activism. He admits the futility of his political passions and has no delusions that he is changing the world, or even changing minds. He sees activism as something central to his identity. “I cannot not do it,” he asserts.

I guess Sheen has every right to find his uncles’ activities interesting in light of his own. On the other hand, is he excavating stories from the past merely to hold a mirror to his own image? Is he cherry-picking his own family history?

What about his hundreds of other ancestors? Were they similarly rebellious? Would he be disappointed to find he came from farmers or shoemakers?

I guess I’m a little unconvinced by this genealogy-as- destiny business. I hold with the Shakespeare line from “Julius Caesar,” quoted famously by Edward R. Murrow: “The fault, dear Brutus, is not in our stars, but in ourselves.” I’m similarly convinced that our virtues do not stem from our genes.

Over the course of the season, the show will feature the backgrounds of Marisa Tomei, Blair Underwood, Reba McEntire, Rob Lowe, Helen Hunt, Rita Wilson, Edie Falco, Rashida Jones, Jerome Bettis, Jason Sudeikis and Paula Deen.

• Leaky vessels and bar room brawls abound on “Bering Sea Gold” (9 p.m., Discovery). Last week’s debut of this enjoyably ridiculous series was the highest-rated series launch in Discovery Channel history.

Tonight’s other highlights

• A drowning man is saved, but not his memory on “A Gifted Man” (7 p.m., CBS).

• Torrid tempers in Hotlanta on “Kitchen Nightmares” (7 p.m., Fox).

• Ray Suarez hosts a “Need To Know” (7:30 p.m., PBS) look at the employment picture.

• Organ harvesters strike on “Grimm” (8 p.m., NBC).

• Astrid meets her Alternate on “Fringe” (8 p.m., Fox).

• A look at politics and policy on “The War Room With Jennifer Granholm” (8 p.m., Current). The network was misidentified in an earlier column.

• A cause seems lost on “On Freddie Roach” (8:30 p.m., HBO).

• A gunman accosts Danny and his family on “Blue Bloods” (9 p.m., CBS).

• Portland police get a fashion makeover on “Portlandia” (9 p.m., IFC).