WE’RE ALL ALIKE under the skin. And the factors that unite us are among the most complicated systems ever evolved. Airing over six parts between now and June 2, “Human: The World Within” (9 p.m. and 10 p.m., PBS, TV-PG, check local listings) asks us to take stock of the things that literally make us tick.

“Human” begins, naturally with “Birth.” This hour examines both the biology of human reproduction and the remarkable breakthroughs in medical science over the past half-century that have contributed to new understanding of human fertility.

Part 2, “Pulse,” looks at the spectacular human heart; “Fuel” (May 12) examines food and digestion; “Defend” (May 19) looks at how the body fends off disease; “Sense” (May 26) explores perception; and “React” (June 2) maps the human nervous system, arguably the most complex network in the universe.

Don’t expect a dry biology seminar. “Human” takes many side trips, perhaps too many. In “Birth” it introduces new research in the science of human attraction by interviewing a pair of European tango instructors who explain how they met and began their delicate dance. In the words of Don Corleone, “Is this necessary?” Probably not. Unless it’s in pursuit of expanding a documentary into a six-part marathon.

• Speaking of the long run, the new Netflix true-crime slog “Sons of Sam” unspools four hourlong episodes exploring the notion that David Berkowitz, the infamous serial killer arrested in 1977, did not act alone, and that he was part of a satanic cult.

That theory was the brainchild of a journalist named Maury Terry, who dedicated much of his career to a diligent (some might say obsessive) examination of Berkowitz and his supposed ties.

There is a great deal of footage linked to the Son of Sam case, and it has shown up in many previous documentaries. They feature New Yorkers with thick accents, disco-era hairstyles and ’70s outfits expressing fears that their lives might never return to normal. I’ve seen these clips so many times they’ve come to resemble home movies.

This too-familiar footage all but crowds Terry out of the first hour. We learn that he was working as an editor at IBM’s in-house magazine at the time when New York City’s tabloids were using .44 caliber paranoia to sell papers. We’re told by close friends and relatives that he was a curious and thorough guy, but neither his day job nor his training gave him any particular expertise.

Are Terry and his theories worth four hours of our time? Except as an excuse to wallow in all of this grim footage?

• Not content to be an afternoon series in prime time, “Kids Say the Darndest Things” (8 p.m., CBS, TV-PG), hosted by Tiffany Haddish, visits the set of “The Price Is Right” and its host, Drew Carey.

It’s interesting to note that Carey’s eponymous sitcom was the only successful series on ABC way back in 1999 when it turned over hours of prime time to “Who Wants to Be a Millionaire.” Network television has never been the same.

Other highlights

• The Cubs host the Dodgers in MLB action (7:30 p.m., ESPN).

• A car accident fills the wards on “Chicago Med” (8 p.m., NBC, TV-14).

• An agent struggles to prevent the beginning of a new world war in the 2020 time-bending thriller “Tenet” (9 p.m., HBO).

• A mysterious caller needs help on “Chicago Fire” (9 p.m., NBC, TV-14).

• An expectant mother’s murder shocks the squad on “Chicago P.D.” (10 p.m., NBC, TV-14).

• Gary’s dad recalls his war experiences on “A Million Little Things” (10 p.m., ABC, TV-14).

Cult choice

A bully’s (Paul Meurisse) wife and mistress (Vera Clouzot, Simone Signoret) conspire to murder him in the 1955 French language thriller “Diabolique” (5:45 p.m., TCM, TV-MA).

Series notes

“The Masked Singer” (8 p.m., Fox, TV-PG) ... Erica needs a distraction on “The Goldbergs” (8 p.m., ABC, TV-PG) ... A shooting shocks Chinatown on “Kung Fu” (8 p.m., CW, TV-PG) ... Tom apologizes on “Home Economics” (8:30 p.m., ABC, TV-PG).

A hostage crisis on “SEAL Team” (9 p.m., CBS, TV-14) ... “Game of Talents” (9 p.m., Fox, TV-PG) ... On two helpings of “The Conners” (ABC, r, TV-PG): Chuck’s choice (9 p.m.); Darlene deflates (9:30 p.m.) ... Birthday wishes on “Nancy Drew” (9 p.m., CW, TV-14) ... Hondo’s regrets on “S.W.A.T.” (10 p.m., CBS, TV-14).

Late night

Jimmy Fallon welcomes Channing Tatum, Josh Duhamel and Joyelle Nicole Johnson on “The Tonight Show” (11:35 p.m., NBC) ... Sen. Amy Klobuchar, Robin Thede and Ryan Hurd with Maren Morris visit “Late Night With Seth Meyers” (12:35 a.m., NBC).

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