“Science of Dogs” (8 p.m., National Geographic Channel): Are canines the product of our

“Science of Dogs” (8 p.m., National Geographic Channel): Are canines the product of our cut-and-paste whims? Is man’s best friend a man-made creation? That’s how it appears in “Science of Dogs,” which charts the human quest to shape a perfect pet — and more.

This “Explorer” edition points out that the dog is more varied in size and behavior than any other species on Earth (even though, genetically, dogs are 99.8 percent alike). And much of the variation is thanks to science’s evolutionary manipulation to create breeds that suit human needs.

Today there are 400 breeds (and counting), according to the film — “each one designed by us, for us.” And 80 percent of those breeds didn’t exist 150 years ago. It’s history’s longest-running experiment in eugenics — the quest for perfection in a species. Exhibit A: the dogo argentino, a fearless, aggressive dog bred in the early 1900s to combat wild boars (which in Texas alone destroy more than $50 million in crops annually) — and yet, off the job, becomes a gentle house pet. The creature we now know as the dog started out as a wolf, then was pulled from the wild to give companionship to early humans.

Gradually it became domesticated. Then, many thousands of years later, the Industrial Revolution sparked an unprecedented focus on material design and physical perfection, with dogs a beneficiary as they became a status symbol of the new middle class. The customized canine was suddenly the rage. It still is. And as “Science of Dogs” explains, it began in the wag of a tail.

“NASCAR in Primetime” (9 p.m., ABC): Strap yourself in for a behind-the-scenes, behind-the-wheel look at the preparation, logistics and rivalries that drive NASCAR. “NASCAR in Primetime” is a five-part ABC News series that examines a multibillion-dollar empire built on marketing, speed and the American dream.

Given access to NASCAR’s nuts-and-bolts, ABC News spent six months following drivers (including Tony Stewart and Jimmie Johnson) as well as fans and officials to document what happened both on and off the track.

“House of Payne” (9 p.m., TBS): On the latest episode of “Tyler Perry’s House of Payne,” a newly divorced CJ finds that everyone in his life wants to hook him up with a date and think they have the perfect woman for him.

Meanwhile, growing tensions between Angel and Calvin lead everyone to believe they have feelings for one another.