MMA, or mixed martial arts, is exactly what it sounds like: a Molotov cocktail of fighting skills combining the strikes of traditional boxing and muay Thai kick-boxing with the grappling of Brazilian jiu-jitsu and wrestling (Olympic-style, not the off-the-top-rope, gold spandex–wearing kind). A well-rounded MMA fighter can attack you standing up, with feet, fists, knees, elbows, shins and shoulders. He can force you to the ground and tie up your arms and legs with painful joint locks that threaten to pull meat from the bone like a chicken wing until you tap out—the MMA equivalent of crying uncle. Or he can wrap his arms around your neck and choke you unconscious by cutting off the blood supply to your brain.

When MMA fights were first staged in North America 16 years ago, the then-senator John McCain likened them to human cockfights and tried to have them banned. Now MMA is the fastest-growing sport on the planet, rivalling soccer, NASCAR and NFL football for our Jumbo­tron-loving, slo-mo-replay-addicted, foam finger–waving attention. Even Hollywood has taken notice: George Clooney, Keanu Reeves and Mandy Moore are fans; and last year David Mamet released a movie called Redbelt, which was set in the world of MMA. The billion-dollar Ultimate Fighting Championship, the NHL of MMA, has, for better or worse, made the sport what it is today: a cultural juggernaut. And nowhere in North America is MMA more popular than in Toronto.

On nights when the UFC is on pay-per-view (about once a month), Toronto sports bars are packed with patrons wearing UFC or Affliction (a smaller competitor) or Tapout (an MMA clothing line) T-shirts. The Fight Network, a Toronto-based digital channel that was created to give fans a round-the-clock UFC fix, has more than five million subscribers across Canada. The annual Mixed Martial Arts Expo attracts thousands to the International Centre to meet such UFC stars as Matt Serra, Dan Henderson and Carlos Newton, the first Canadian to win a UFC championship. And the UFC’s Web site gets more visits from Toronto per capita than from any other city in the world.

And this despite the fact that MMA fighting is illegal in Ontario. Critics often decry the sport as a prime example of the coarsening of society, but it has tapped into our fighting spirit in a way not seen since George Chuvalo went 15 rounds with Muhammad Ali at Maple Leaf Gardens in 1966. MMA is the last arena where might makes right, and many of us are drawn to its lack of ambiguity. The urge to fight is a survival mechanism hard-wired to our DNA since caveman days yet out of place in modern society. Fighting, we’re taught, is bad. Disputes are not to be settled with fists and knees and elbows, but with lawyers and arbitrators and negotiators. Nobody tells their son to fight like a man anymore; even hockey fights are under threat of extinction. Yet, like it or not, when faced with conflict, our first impulse is still to fight. To deny it is simply unnatural.

Mixed martial arts has been around in some form since the ancient Olympic Games, where the most popular sport was pankration, a savage, anything-goes style of wrestling in which some competitors chose death over surrender. In the 19th century, bare-knuckle boxing was the most popular combat sport. In the late ’60s, Bruce Lee became the first modern mixed martial artist when he combined traditional kung fu with elements of boxing, French savate (kick-boxing), judo and tae kwon do to create his “style of no style.”

The sport we now call MMA was ushered in by Royce Gracie, a gracious and diminu­tive Brazilian who took on all comers—kick-boxing champions, karate experts, kung fu masters. He used a synthesis of Japanese jiu-jitsu and judo (a style now known as Brazilian, or Gracie, jiu-jitsu) to control and smother his larger, stronger opponents, forcing them to submit via joint locks and choke holds while he hardly broke a sweat. He won three of the first four UFC events, although his relatively blood­less encounters were an anomaly in a sport billed as no-holds-barred. (There were only two rules: no eye gouging and no biting.) The early UFC fights promised victory by “knockout, surrender, doctor’s inter­vention or death.” In fact, there has only ever been one death resulting from a sanctioned MMA event, two in non-sanctioned events in Europe, though UFC fights rarely ended without the canvas looking like a Jackson Pollock painting. The violence led to the sport being banned in 36 states by the mid-’90s, and pay-per-view distributors stopped carrying events, putting the UFC on life-support.

Then, in 2001, casino owners Lorenzo and Frank Fertitta, billionaire brothers with connections to the Nevada State Athletic Commission, bought the flailing organization for $2 million. They put Dana White, an obnoxious ex-boxercise instructor and a high school buddy, in charge, and he immediately made changes. Weight classes were imposed, along with timed rounds. More rules were added, for a total of 31, including no hair pulling, groin shots or kicking a downed opponent in the head. Fights became more competitive, more entertaining and more palatable to non-fans. States began to sanction bouts, notably Nevada and New Jersey (home to Las Vegas and Atlantic City, where betting and brawling have always been popular), and pay-per-view companies scrambled back on board. “Suddenly we were being treated like superstars,” says Carlos Newton, the 32-year-old UFC veteran. “We started making money, and people recognized us on the street.”

Dramatically improving the sport’s mainstream profile was the launch of the UFC-produced Ultimate Fighter on Spike TV in 2005. The Big Brother meets Bloodsport reality series demystified MMA to outsiders and made celebrities out of its combative house guests. It was an instant smash, often beating out the NBA, NFL and major-league baseball games in the ratings. (Season nine begins this month.)