There's nothing at all extraordinary about this walk-off celebration in Miami, where the Marlins' Yadiel Rivera is chased down by his teammates, swatted with plastic bottles, thrown to the ground and repeatedly slugged.

There's nothing extraordinary because you're living in 2018. But to a person living in 1988? Hooboy. What's a Marlin? How did you make that video play on a phone? And what in heaven's name are they doing to that poor man?

This, after all, is what a walk-off celebration looked like in 1988:

That's not for some whatever victory by a last-place team in early July, but for arguably the most dramatic home run in major league history. It's an emotional but orderly series of high-fives and hugs and some pats on the head, all while the house organ keeps playing happily, and then there's a whisper in the ear from Tommy Lasorda, and then more hugs. There's a moment as Kirk Gibson crosses the plate, at 7:09 in the above clip, when Steve Sax seems to reach back to give Gibson a painful slug to the back -- and then, as though he has been trained by shock collar, his hand quivers and retreats. Because why would a teammate painfully slug another teammate in this happy, celebratory moment? How would that make sense? Who would even come up with such an idea?

Well ... the dominant form of walk-off celebration in professional baseball is now the collective beating up by the victors of their hero. How'd we get here? To answer that, we need to go back to the beginning, and we need to break it down into parts.

1. The very notion of the thing.

I've written before about the evolution of World Series dogpiles and discovered that the dogpile itself is relatively modern, developing more or less alongside the rise of television as the sport's primary broadcast medium. Before the games were on TV, the final out of the World Series would be recorded, and the players would run into the dugout to congratulate each other.

So it mostly is in that clip above, of Tommy Henrich hitting (in Game 1 of the 1949 series) the first walk-off home run in World Series history. Nobody left the dugout to greet Henrich. The three folks waiting for him are Yogi Berra, who was on deck; Bill Dickey, the first-base coach; and what looks to be the bat boy. Then they run into the dugout. There was no expectation of exceptional celebration, except presumably out of sight in the dugout or clubhouse or bar.

As with World Series dogpiles, though, the on-field walk-off celebrations came not long after television audiences grew, creating (arguably) the expectation that players would do their things in front of the big audience. In the 1956 Fall Classic, Jackie Robinson singled home the walk-off run, and a dozen Dodgers ran out onto the field, near the first-base line, to anoint him. By 1977, when Brooks Robinson hit a walk-off dinger in an April game, we can see more or less the shell of what was to come: Teammates circle home plate, wait for him to arrive, hug him and bop him a little, with the whole team on the field to touch the hero.

Peacefully.

2. The head.

An All-Star Game walk-off is a pale imitation of a real walk-off, but there's a crucial detail in this Stan Musial celebration (from 1955) that we don't see in the '49 clip: The focus on touching Musial's head.

Almost immediately upon the invention of a walk-off mob came the walk-off head rub, head pat, head squeeze, whatever form it takes -- hands on heads. Virtually every walk-off video we watched after this one involved hands on heads. These are mostly loving pats here, but if a human being reaches out to you and tries to touch your head, you are almost certainly going to flinch. There is no totally comfortable way to be grabbed by the head. So the hero flinches. He ducks. He deflects, or he scampers away. Here, as the result of a seemingly loving gesture, we see born the basic conflict that will later be acted out with ever-increasing tension: The walk-off hero trying to avoid his teammates, and his teammates trying to reach the walk-off hero. Its origin is in innocence, but it will grow into open warfare.

At this point, we're still many steps from reaching that stage, but there was one walk-off celebration that was decades ahead of the trend. It was in 1981, and Alan Ashby homered to end a game. His teammates give his head hard squeezes, as was the norm. Then, at about 0:38 in this clip, one teammate starts just wailing on him. On his head. The head is both very sensitive and very tempting, and it is a natural territory where both parties will find it in their interests to escalate.

3. The violence.

The overwhelming majority of walk-off highlights in major league history aren't available for highlight viewing. We watched close to 200 from the 1940s through the early 2010s to track the changes, but we can't say [X] was the first team to do something, only that it was the first team we observed doing something. Leaguewide trends tend to happen little by little and then all at once.

That said, I've become fairly convinced that the modern trend of beating up your teammates comes from Omar Vizquel, Jim Thome and the 1990s Cleveland Indians.

Here's 1995, with Omar Vizquel punching Jim Thome in the face:

Here's 1999, with Vizquel getting decked by Thome and then swarmed by punches and kicks:

Here, by contrast, is the typical walk-off celebration of the era, which has none of that abuse:

Those aren't nearly the only two clips of Vizquel and Thome beating each other (or their teammates) up, incidentally. When Thome hit a walk-off -- and, perhaps significantly, he hit more than anybody in major league history -- Vizquel would hop out in front of the mob, in a fighter's stance, to be the first person to take a shot at him. Thome, meanwhile, was a ferocious headlocker. Sometimes they'd tag-team another Clevelander: Thome puts the headlock on, and Vizquel jabs.

There are essentially no other available highlights of punching and kicking teammates in the 1990s. Just these guys. By the early 2000s, it had spread: Headlocks, near-riots, bats wielded threateningly. Here's a 22-year-old Adrian Beltre getting hit like a bongo drum in 2001:

It is no wonder he became so sensitive about teammates reaching for his skull.

4. The attempted escape.

Up to this point, there's still very little of the defensive maneuvers we expect from our 2018 walk-off heroes. There are glimpses of it, again in Cleveland: Thome would sometimes back away from the mob swinging or touch the plate and then pivot away from them, while Vizquel pre-empted the group tackle by sliding into the scrum. As a defensive maneuver, it ... didn't work:

But these clips have all been walk-off home runs, and there's a natural restriction on the home-run hitter's ability to run away: The hero must, by the rules of baseball, run directly into the mob for his run and victory to count. The batter would more often steer into the skid, making dramatic leaps into the mob. (And sometimes missing two years of baseball because of it. Note that in the famous Kendrys Morales celebration, some teammates continued to punch him for a few moments after his leg broke.)

To get real escape attempts, we need to expand the field. But until the early 2010s, the normal protocol for celebrations of non-homer walk-offs wasn't universal. Typically, the emptied dugout would first congregate around the runner who scored. The team would then go out to congratulate the player who got the hit, but it was a more dispersed wave of teammates, and much of the energy had been used up in the first burst at home plate:

Between 2010 and 2013, the evidence suggests, the rules got codified: Mob the batter. Mob the batter even if all the batter did was hit into an apparent double play that turned into a throwing error that turned into the run. Mob the batter. We're batter-mobbers. We mob batters around here.

If it is intimidating to see a mob of 20 large men waiting in a circle to hit you, imagine seeing a mob of 20 large men sprinting to hit you, a giant boulder of energy that could crush a pickup truck. So you run!

If you know a batter singled for a walk-off victory, and somebody asks you to guess where the celebration takes place, you might guess near first base, but in the 2010s, the safe bet is shallow center field. When your teammates are batter-mobbers, it's a natural instinct to look for open space.

5. Mob discovers tools.

Alas, as we all remember from that one time we went camping: If you see a mountain lion, the worst thing to do is run away. Running away makes you look like a cute, delicious deer. For the batter-mobbers, it creates an even thirstier urge to mob.

The past five years have been about escalating the attacks, in particular by bringing weapons: Water bottles, water jugs, buckets of gum, mascots, rosin bags or sometimes just a methodical pummeling of every single part of a collapsed man's body. Here's Yuli Gurriel getting a face full of what appears to be chalk, right there in his eyes totally unexpected -- great idea, good outcome.

I think this here might be the first totally modern, fully actualized, walk-off mob:

You've got the mob totally ignoring the runner who scored, leaping over the dugout rail to charge after the man who hit a sacrifice fly. You've got the batter, Wilmer Flores, backing away, then jogging away, until he's almost to shallow center field. You've got the weapons teammates carried with them -- sunflower seeds, towels -- along with punches, head swats, jersey tugging and a knee or two.

And about 25 seconds in, when Flores drops his helmet on the ground, you've got Eric Campbell, in uniform No. 29, thoughtfully kicking it out of the way so Flores doesn't step on it and twist an ankle. We are, after all, not actually trying to hurt anybody here.