What’s wrong with this picture? Stefon Diggs (14) scored a winning, last-second touchdown on Sunday because Marcus Williams (43) went for the hit, not the traditional tackle…

MINNEAPOLIS, Minn. — Minnesota Vikings wide-out Stefon Diggs may go on to do many more spectacular things during his career but, for now, his miraculous walk-off touchdown to win last January’s playoff game vs. the New Orleans Saints remains his claim to fame. But let’s widen the scope on this play and connect a few dots, for in so doing we link the signature moment last year’s playoffs to the league’s most pressing issue. Look at the picture that accompanies this essay (or watch the video of the play here) and examine with me what New Orleans Saints safety Marcus Williams was thinking as time ran out.

We should first take a moment to pity the man, a rookie whose coaches put him in a god-awful position — “on an island,” as they say, by himself defending half the field when the situation clearly called for the Mother of All Prevent Defenses. Even in this highly vulnerable position, however, all Williams needed to do was play center field, keep Mr. Diggs in front of him, eventually wrap him up and wait for help, or bring him down, ideally in the field of play (but even a shove out of bounds would have sufficed).

Instead, Williams did what most professional footballers tend to do in the 21st century: He went for the “spectacle hit”, head first.

Competitively, as we’ve seen, the results were disastrous. (Williams even managed too compound his misfortune, somewhat comically, by whiffing on Diggs entirely, then taking out his teammate — the only guy in a position to chase the wide receiver down.) What’s more, according to rules taking effect for the 2018 regular season, it would draw a 15-yard personal foul penalty. But if we step back, we see here yet another consequence of football’s troubling evolution on the defensive side of scrimmage. Despite a litany of league-wide initiatives to curb headfirst tackling — the result of mounting evidence linking repeated, football-related head trauma to brain injury (chronic traumatic encephalopathy, or CTE) — the NFL’s hit culture remains firmly in place. Even in a situation like Williams’, where old fashioned, rugby-style tackling was called for, the defender acted on the instinct that football today engenders.

NFL Football in the here and now is plenty good fun, the most popular and culturally dominant game in 21st century North America. Minnesota’s unlikely victory last Januaary (indeed, three of the four games that weekend) showcase exactly why this is so. NFL games can be spectacularly entertaining.

But it would be a stretch to consider the game of professional football “perfected”. In reality, any sport played at the elite level exists as a moving target, a work in evolutionary progress, because the salient factors affecting that evolution — rules, tactics, equipment, geography and fashion — also shift and evolve. All this transforms the way a game is played over the course of time, sometimes by design, sometimes organically without much guidance at all.

In 2018, we can add “culture” and “the legal process” to this list of salient change-agents. People took notice when former NFL player Ed Cunningham resigned from his position of ESPN football analyst — on account of the game’s growing concussion dilemma — but, in truth, we’ve become somewhat inured to stories like this because nearly every week brings some new, relevant development, be it evidence that concussions sustained in pee wee football can lead to adult brain trauma, or steps the Canadian Football League has taken to reduce the volume of dangerous hits.

The idea that former Patriots tight end and convicted murderer Aaron Hernandez might have committed his violent crimes while experiencing advanced-stage CTE adds to this potent mix the elements of irony and the macabre. Did you know that a class-action lawsuit, brought on behalf of current and former NCAA student-athletes, remains pending before Judge John Z. Lee of the United States District Court for the Northern District of Illinois? Me neither. Class actions have their own online portals these days, naturally. Visit this one and be prepared for the following greeting: “Welcome to the NCAA Student-Athlete Concussion Injury Litigation Website.”

Bit by bit, the forces of change would appear to be gathering over football, as they have intermittently but more or less continuously for more than a century. No game, it seems to me, has evolved so far, so quickly or so dangerously.

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Football’s robust evolutionary dynamics, when viewed in an historical context, have done more than change the game we know today. They’ve splintered a single game and set its various branches on separate, distinct paths around the world. In the early 19th century, the word football referred to a single sporting entity. Today it can be used to describe two forms of rugby (Union and League) in England, soccer the world over, Gaelic football in Ireland, Aussie Rules down under in Oz, and American football (what Brits and many Commonwealth types call “gridiron”) here in North America. Even Canadians have their own distinct brand of gridiron.

Time and geography tend to obscure this shared heritage, but Michael Munger’s excellent NYT column from early in 2017 reminds us how some athletic pursuits, once knit closely together and occupying the same exact cultural and geographic space, can diverge. Munger also suggests the sanguine extent to which one game can perhaps learn from its distant cousins.

Munger asserts that rugby, for all its brutality, doesn’t really have a concussion/CTE problem. Not like the NFL has. Why? He argues that helmets in particular (and excessive padding generally) have needlessly and ironically transformed American football into an ever more dangerous, head-first hitting game — the key argument being, athletes wearing helmets will attempt and ultimately adopt more dangerous tackling techniques (dangerous even to their own heads) than someone lacking a helmet would ever dare. By eschewing helmets, rugby has better avoided this particular evolutionary pitfall.

At first blush, Munger’s point would appear a bit squishy and anecdotal. But we see this sort of behavioral tick all the time, and it has a name.

“They call it the Peltzman effect, after the economist Sam Peltzman,” Munger explains. “The feeling of safety, it seems, induces us to be less careful. A famous illustration of the Peltzman effect is that the better sky diving gear becomes, the more chances sky divers take, keeping the fatality rate from sky diving roughly unchanged over time.”

[This hits home with me. I rode bikes sans helmet my entire childhood and never once went over the handlebars. As a generally risk-averse adult, trying to show my young children a good example, I strapped on a helmet and went over twice in the space of 18 months.]

Stepping back a bit, we also recognize that it’s the common history of rugby and American football that lends a new level of credence to Munger’s argument and observations. In another less associative context, this idea would carry less weight: It is one thing for the NHL to borrow some in-game strategy from, say, international soccer. But it is altogether more valid (and intriguing) to think that sister sports have the very real option of reaching back into their shared DNA in order to produce a more safe or otherwise more compelling state of play.

Because this much we know: There was a time when these two games were nearly identical. Like humans and chimps, they will always share a common ancestor. Munger has demonstrated for us how one sporting species so removed can still borrow, learn and perhaps benefit from another — if only the powers that be have the good sense to thoughtfully examine their own past.

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This blood-thick linkage between sports is hardly uncommon. If we pay attention, neither are the bonds and vestigial characteristics that remain (like a panda’s thumb) in spite of divergent evolutionary paths.

Most baseball fans recognize intellectually that cricket and its more school yard version, rounders, ultimately begat baseball. But as John Thorn makes clear in his wonderful book, “Baseball in the Garden of Eden,” modern fans would be amazed at just how similar cricket and baseball remained as recently as 1915. That’s when baseball’s powers that be recognized that fans went ape-shit for Babe Ruth’s long-ball displays. In reaction, the two major leagues quickly hardened the balls, created fences to hit them over, and so baseball was changed forever. Up to that point, a softer ball and mere “boundaries” forming outfield perimeters rewarded contact and placement over power and distance. Wee Willie Keeler was famous for “hitting ‘em where they ain’t”, but that’s what every batter did or tried to do throughout the 19th century and well into the 20th. This shouldn’t surprise us: Finding the space between fielders had for centuries been (and continues to be) the singular goal of any cricket batsman.

Some shared elements remain timeless and unbroken: Bring a Brit to a modern baseball game and the thing they appreciate first and foremost? Fielding. For a cricket fan, it still computes straightforwardly.

American football, too, is a fundamentally English game, though no sport has splintered away from the mother pursuit to such diverse effect. Geographic isolation and subtle changes in rules, tactics, equipment and fashion — over time — have accounted for the separate and distinct growth of these footballing offshoots, which will nevertheless share a common ancestor forever.

Is the concussion rate among otherwise comparable rugby and NFL septuagenarians relevant? Maybe it is. Munger is a former rugby player and when he compares his chosen sport to American football he accurately cites a far lower concussion rate today among elite rugby players, who don’t wear and have never worn protective headgear. Some ruggers do wear a small cap to protect their ears from being mangled in the scrum (many old school types still wrap their heads with tape, thereby pinning, securing and protecting their outer ears). Gridiron players in America wore helmets for the same reason as early as the 1890s. But helmets as a means of meaningful cranial protection never caught on or evolved in the rugby context.

As generally hard bastards, rugby players are notoriously dismissive of American football and its players, citing the candy-assed nature of today’s massively evolved headgear (and the proliferation of head-to-toe body padding, for that matter). But Munger’s nuanced argument moves well beyond this prejudice. The relative paucity of concussions in rugby speaks persuasively to the fact that its equipment and fashion choices — not just today but over the course of decades — have resulted in a safer game, cranially. His point is further buttressed when we take into account the distinct evolution of American football itself.

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Do yourself a favor, flip over to the NFL Network sometime and watch anew some extended NFL Films archives from the 1950s and ‘60s. All manner of things will jump out at you, but I’m confident you’ll be most struck by the extent to which tackling still resembled the waist-down tackling of rugby. And keep Marcus Williams in mind: There is remarkably little hurling of one’s body at ball carriers, head first or otherwise. It was a fundamentalist’s dream.

Leather helmets were introduced to American football in the 1920s, but this was mere window-dressing, a lingering attempt to shore up safety rules first introduced earlier in the century. More on that later, but honestly, what would a single layer of hardened leather really do to affect the way people tackled? Not much, vintage football footage reveals. The technology here didn’t truly affect the evolution of tackling until the 1970s. Prior to that, the best way to bring down a ball carrier (the way coaches taught tackling, for decades, up to and including my own pee wee football days) was to get your head out of the way, wrap the guy up from the waist down, and drive those legs. In the open field, one wrapped him up and held on for dear life.

Hardy Brown was a linebacker for the 49ers and Redskins in the 1950s, and he is the subject of one such NFL Film. Just 6’1” and 190 pounds, he perfected a sort of drop-shoulder body blow that every once in a while caught some crossing flanker off balance and set the guy flying. Brown was famous and somewhat feared for this outlying maneuver, which illustrates just how rare his approach was at the time. But even he ducked his head away from the runner, in the traditional rugby style, when administering his signature hits. Neither Brown nor anyone in the NFL dared deploy their noggins as part of the tackling process at this time. Helmet technology back then would not allow it. By that time helmets were made of hard plastic, but I’ve seen more sturdy headgear holding soft-serve ice cream at Portland Sea Dogs games.

It was self-preservation (salted with decades of traditional coaching methods) that obliged defenders to tackle in this traditional way — the way rugby players still tackle in the 21st century.

When helmet technology improved, starting in the 1970s, American football players got more and more reckless — as the Peltzman Effect would predict — and the game changed accordingly. Go watch something as recent as the first two Super Bowls, from 1967 and ’68. Then go watch any 21st century Super Bowl archive. What you will see is a completely different attitude toward tackling, the byproduct of 40 years’ evolution in the art of defending, which, in large part, evolved in concert with (and on account of) 40 years’ of improvement in helmet technology.

These dynamics spill over into officiating: Put helmets and pads on NBA players, let them play that way for a while, and eventually the game and its rules will change.

They spill over into technique: American football coaches all the way down to the pee wee level have adopted these changes in light of improved helmet technology. At all levels, the rugby-style tackling tradition still exists, but only side by side with a more dangerous, technology-enabled “hitting” tradition that fans, coaches and fellow players just happen to love.

As with baseball and home runs, fans and media have further influenced and reinforced this evolution of the tackling ethos. “Lighting a guy up”, or merely laying him out, is not judged solely for its efficacy in bring a man to ground. It’s the spectacle of these hits that is met with hoots of delight, even if those that might be followed by hushed tones of concern, fleeting chagrin, and polite applause as some casualty is subsequently wheeled off on a gurney.

For several decades, beginning in the 1970s, National Football League poobahs and programmers basked in this new strain of tackling. It made for undeniably great television. Players were (and remain) more or less dispensable and interchangeable. The fans loved it… Today, in light of concussion tallies and CTE diagnoses, in light of revelations re. the long-term effects of multiple head trauma (even in kids as young as 12), attitudes appear to be modifying once again. Indeed, the pendulum of change has swung back to a position football has not been obliged to occupy since 1906.

After years of public denial, today’s NFL is attempting to bolster that back swing. Kickoff returns have been strongly discouraged, if not eliminated (by moving kickoff points further up the field, resulting in touchback after touchback), as they were judged to be highly and needlessly conducive to high-speed collisions. Under a new ruling taking effect for the 2018 regular season, helmet-to-helmet tackles now draw maximum, 15-yard penalties; multiple infractions will get you thrown out, suspended and fined.

Folks like Dr. Munger (a professor of political science at Duke) suggest doing away with helmets altogether and it’s an interesting proposal. But football has evolved in other ways that contribute to the modern frequency and severity of concussions. We need to recognize and better understand them before we fixate on any single response, lest the game descend (further) into some perverse, barbaric, bread-and-circuses delivery system. This sort of nuanced exploration is necessary because I fear that if American football continues unchecked on its current evolutionary course, no high school in the country will play it in 20 years’ time. The liability, the insurance policy premiums for public school systems will simply become too high.

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Tackling technique isn’t the only fascinating antiquity served up by your typical late-night, half-in-the-bag, vintage NFL Films festival. You will notice that players are uniformly smaller, more wiry and whiter. The first two factors surely contribute to the fact that few in 1958 worried about an epidemic of concussions. The players weren’t big or fast enough to hurt each other in the same way, to the same degree, at the same speed, with the same troubling frequency they can and do today. Tackling techniques had yet to change by 1958.

But there’s something else going on here, in terms of velocity: Old-time football players were clearly engaged in something they considered a marathon, not a sprint.

By the early 1960s, the game had specialized to a point where nobody played both offense and defense anymore (Chuck Bednarik was the last fellow to play both ways on a consistent basis; he retired in 1962). Even when old-time players started specializing in offense or defense, one is struck (in these vintage game films) by the lack of substitutions deployed from play to play. Clearly tactics regarding substitution have evolved over time, too. Today there are third-down specialists, run-stopping specialists, pass-rushing specialists, nickel backs, etc. As many as 20 separate defensive guys might participate in any one set of downs. Back in the day, it was largely 11 v. 11 for long, long stretches.

What is the connection between specialization and increased exposure to head injury?

Well, specialization places a smaller onus on player fitness. Today’s American football players are superb athletes in their own way, of course, but those who play both offense and defense will, by the end of game, naturally be more fatigued than someone who plays just one or the other. If he is playing on both sides of the ball, a more fatigued defender is perhaps more susceptible to pulling a hamstring. But he is less likely to expend the additional energy it takes to hurl one’s body at an opponent headfirst, when a simple rugby-style tackle will do.

NFL fan, media and team culture might remain strongly supportive of today’s all-out hitting culture. But if NFL teams started playing 22 guys only — 11 on defense, 11 on offense — the hits (and the concussions) would surely diminish. [Meanwhile, every 6’1″, 320-pound, run-stopping nose tackle would submit to obsolescence — or a diet.]

On account of fan and media bloodlust, we can agree that showmanship also plays a role in today’s NFL’s hit culture. Football players in the 1950s and ‘60s did not play to the cameras in this way, at all, because, while the sporting culture was more reserved and conservative (read: whiter), there were also comparatively few TV cameras. Most games weren’t televised at all, which meant way less preening and precious few TV timeouts (another serial source of stoppage that de-emphasizes the modern need for endurance).

This lack of commercial breaks also stands out. NFL Films are often highly edited game tapes, but still — one can see that play proceeded more or less uninterrupted. Go to a high school or small college football game — that’s what it was like. Naturally, this sort of uninterrupted play, combined with a lack of substitution, asked even more of players physically. This further limited their ability and willingness to administer potentially concussive hits. They still had to tackle the opponent. But as the game went on, they did so while conserving their energy as best they could.

This brings us back to the side-by-side evolution of football and its sporting cousins. Rugby is a 15-a-side game that has traditionally frowned on substitution. This has been true of a third cousin, Association Football (or soccer, for short). For decades, neither sport allowed substitutions, at all. That was essentially the way American football was played into the 1940s. Only recently have substitutions been introduced to rugby. Still, it’s not unusual for a team’s best dozen players to play the entire 80 minutes. Soccer at the international and professional levels today allows three substitutions per game (in both cases, once you’re off, you can’t come back on), meaning that 8 of 11 soccer players are expected to “go the full 90”.

Because of the way both games have evolved, modern soccer and modern rugby still require an element of energy conservation that simply does not exist in modern American football today, when maximum effort is given at all times, in short bursts, before coming off for a breather. In this way, ice hockey, where substitution has most markedly reduced energy conservation, is the better comp.

In this respect, American football into the 1950s operated a lot more like rugby and soccer. Players expended effort in the context of a long, physical, uninterrupted marathon broken up only by the end of quarters. There were big hits, surely, but the bigger ones happened early in the game when players were fresher (and when they administered those hits, they ducked their heads well out of the way — because helmets still afforded so little protection). As the game dragged on, any focus on “spectacle hitting” (however rare in comparison to modern football) was further and further replaced by an emphasis on simply bringing the guy down, thereby best conserving a defender’s energy.

It’s a simple point: As the game of American football changed, standards of fitness changed. Modern football players simply aren’t in the same kind of shape compared to guys in the 1950s. Manic/tactical substitution and the commercial broadcast of every game mean today’s players don’t require the same type of endurance. What’s more, today, a player’s value to his team (and in the larger marketplace) relies far less on endurance and far more on bulk, strength and speed.

Bulk, strength and speed. These are the qualities so obviously lacking when we (equipped with our modern sensibilities) watch game film from the 1950s and ‘60s. Not surprisingly, these are the qualities — along with mature helmet technology — that make running backs, wide receivers and quarterbacks so very vulnerable today.

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Some things cannot be walked back. Kick-offs returns might be effectively skirted or de-emphasized, but television is never going away, for example, and it’s hard to imagine NFL teams, with their expansive rosters and taxi squads, limiting substitutions to an extent that will allow fatigue to positively affect the frequency and severity of headfirst tackles.

Taking helmets away, however, is a different matter. That rule change costs nothing and, were it implemented, American football tackling would change very quickly indeed. It would revert almost overnight to something closer to rugby, Munger argues. What’s more, it would make the game more human, as players would be recognizable not just by name and number but by their faces — a marketing optimization that NBA, Major League Baseball and international soccer have enjoyed and exploited for some time.

And yet it’s quite impossible to accurately forecast what such a change — what any change in the rules, equipment, geography, fashion, and legal reality — might mean 5, 10, 15 years from now. NFL brass and their attendant kinesthesiologists can study these issues all they want, and journalists can further weigh in, as I’ve done here. But there are no guarantees in this realm. While changing something like helmet use might well have one desired affect, in the short term, there is equal risk that rules and tactics will adapt/evolve in ways that prove even more dangerous for participants — precisely because they’re not wearing helmets.

It’s also instructive to understand that American football has been here before. At the turn of the 19th century, the game’s dangers provoked an arguably more widespread anxiety and heated public outcry. After all, participation wasn’t just concussing players with dire long-term consequences; it was killing them straightaway. In 1905, at least 18 people died on the field, playing football. According to the Washington Post, some 45 football players died between 1900 and October 1905, “many from internal injuries, broken necks, concussions or broken backs.”

Then-President Theodore Roosevelt, a noted fan of football and rigorous manly pursuits of all kinds, was inevitably drawn into this fray. Early in 1905, he used his bully pulpit to call for reform and ultimately summoned to the White House coaching luminaries from three big-time football factories of the day: Harvard, Yale and Princeton. Nothing came of that skull session but later that year, in November, when Union College halfback Harold Moore died on the field (of cerebral hemorrhage, after being kicked in the head while trying to tackle a New York University opponent), a tipping point was reached. Columbia, Duke and Northwestern all suspended their football programs summarily and Roosevelt called his patrician Big Three buddies back to 1600 Pennsylvania Avenue.

This meeting did have an effect. Several important new rules were introduced for the 1906 season. One followed Munger’s formula, borrowing something back from rugby (at that time, not so distant a cousin) by allowing teams to cede possession, at any time, by punting the ball downfield — instead of simply running the ball into the line four times, absorbing that 25 percent more punishment, and turning the ball over downs.

Another stopped and reset the game when a player went to ground with the ball. This mitigated the mayhem inherent to pig-piling and incessant ball-prying (in rugby, there remains no stoppage; ball carriers must instead relinquish the ball once tackled to the ground).

Implementation of the forward pass is another fairly direct outgrowth of the 1906 anti-violence reform effort. Not until 1913 did anyone figure out how to actually win games using this novel tactic (Notre Dame made its reputation turning that trick), but the mere threat of forward passing changed the game immediately. It spread defenses and drew men away from the line of scrimmage, where most of the mangling, mauling and maiming had been perpetrated.

On-field fatalities all but disappeared in wake of these changes. It took 70 further years of evolution to bring us Jack Tatum and Daryl Stingley. That was 1978, the height of Pittsburgh center Mike Webster’s Hall of Fame career. Today he is dead, a victim of CTE — one of hundreds and hundreds. One imagines that Munger isn’t the only rugby fan who looks across the ages at its sister sport and says to himself, “Dearie me. That’s not cricket. Not at all. ”