1In an ancient Aztec cultural practice, priests would choose a man to represent one of their gods, Tezcatlipoca. The man would be worshiped as a god for a year, but at a preordained date, the priests would sacrifice him, sometimes cannibalizing his body. Each year the priests turned from the sacrifice to select a new “god,” repeating the cycle of reverence and destruction.

2I wonder what the Aztecs would make of the view in front of me. I am in a sports bar with my family, eating after a walk around town. The other patrons’ eyes mostly rest, enthralled, on the many football games televised before them.

3One can’t avoid watching the flatscreens that hang off every wall, or the brutal athleticism they capture. Throughout each play, the players’ heads can be seen as shells traveling at a certain vector, pinballing with others, sometimes whipping to sudden impacts with the ground. Force equals mass times acceleration. Masses hit each other with high velocities, creating sudden and twisting accelerations, and the forces proportionally rise. No human rule trumps physics.

4The high-definition flatscreen TVs show it all, but don’t provide a deeper, more physiological look. Inside a football helmet is a skull, and inside each skull is a free-floating brain. Inside the brain are billions of neurons, chattering with each other in a code we scarcely understand, wired to each other with long and slender projections called axons. An internal scaffolding structure holds each axon in place. The axons crisscross the brain, side to side, forwards and backwards, up and down.

5As force is applied to the brain, a shockwave ripples through. If large enough, the shock tears the axons and can result in catastrophic injury. Smaller forces stun the neurons, their electrical firing decreases, and symptoms of concussion occur. The player may go limp, or stumble and appear unfocused. He is usually amnestic of the event. If the force is milder, none of these symptoms may manifest, but the changes are still felt in the long and slender axons. Their supporting scaffolds, on a human scale akin to bridges from San Francisco to Taipei and Perth to Cape Town, experience an earthquake.

6Over and over, every head blow stresses the scaffolding. A protein called tau normally stabilizes the scaffolds, but the tau proteins become dysfunctional, pathologic, then malignant. The tau binds together, twists in on itself, assembles into sharp aggregates that poke holes in the fragile cell wall and kill the neuron. A neuron goes silent, its axonal bridge crumbles. As the brain digests the dead neuron, it leaves behind the twisted skeleton of the tau aggregate, a “tangle.”

7Other than the injuries that are so obvious they leave the player unconscious, impaired, or dead, we do not know exactly how harmful low-velocity impacts are. We see the ice above the water—in the form of a stunned and staggering player—but we’re starting to realize how deep the risk extends. Emerging data shows low-force head blows produce tau pathologies. Over time the minor head injuries combine and the tau can turn malignant. When enough cells die, symptoms begin. It is now known as chronic traumatic encephalopathy (CTE). It was “dementia pugilistica” when I was in med school, falsely implying a restriction to boxers, as in the later Rocky movies. Before that it was called “punch drunk.” Just as “shell-shock” came before “Post-Traumatic Stress Disorder,” these are different names for the same problem. It leaves victims with cognitive and emotional derangements, prone to odd behaviors, suicide, and dementia. There is no treatment. In the parlance of the announcers, you can’t unring the bell.

8Knowing all this, I can hardly watch the game, but I can’t stop myself from watching either. The plays on the bar’s screens are a thrilling combination of grace, toughness, and skill, and the sport is easily seen as a metaphor for all that is great in humans. But within this escapism it’s easy to forget that football is only a game, albeit one with real-world sacrifices and consequences.

9Consider the case of Owen Thomas, a University of Pennsylvania football player who committed suicide, and whose parents afterward came forward to expose the truth behind the tragedy. Thomas’s brain carried an amount of skeleton tangles that would be expected in mild dementia. His impact burden was small, and he may never have even suffered a concussion, yet at only 21 years of age, his brain showed tangles, which have become the signature injury from repetitive head traumas. Tangles are a signature for which football carries a pen full of ink.

10From junior-high football and even earlier, boys are told to hit hard. Even though they may never suffer a concussion, they do suffer head blow after head blow. It seems no one is safe, and the level of risk is unknown. Mr. Thomas did not have unique neuropathology; there are other deceased players who have displayed similar symptoms: Chris Henry, John Glenn Grimsley, and Justin Strzelczyk, to name just a few. There are likely to be many more still unrecognized and, judging from the bizarre behavior of others still living, more to come. As of now, the youngest case was an 18-year-old player. It seems the more football players’ brains come under neuropathologists’ microscopes, the more pathology they display.

11Perhaps it is wrong to directly compare football to a dead religion that sacrificed young men and ate them. But it is easy to do partially because the Aztecs were honest: one year as an enslaved god, then death. We don’t have the data, so we can’t offer a timeline, or a reasonable cap on concussions, or guess at the probabilities of a player losing his mind in the next year, three years, or three decades.

12Why not?

13There is something sacrosanct about the game itself. It celebrates our ideals of battle and victory. It touches the divine, and not in just the inhuman abilities and sizes of the players. The numbers of fans bear this out. They not only find entertainment; they invest their passions in it. Many fans, in all outward appearances, worship the players, and treat the teams as a personal, religious, and tribal brand. Better than discussions with in-laws over Thanksgiving dinner, where all these aphasic dogmas compete, in the matter of football, one clearly wins. Religion, ethnicity, and team are even explicitly linked in some colleges: Go Irish!^*

14A touch of the divine may explain why Mr. Thomas’s death and neuropathology have been met with words of no consequence, no change, and certainly no moratorium. Currently the NFL takes “no position” on low-velocity head impacts—impacts that, though they do not cause concussions, can cause CTE. Proposals so far have been designed around a single desire: Do not upset the boat. “Better helmets” are a laughable solution, as if any helmet could eliminate the full inertial force of a charging offensive lineman. Who knows, it might be paradoxically more sensible to have worse helmets, so the players routinely feel the impact’s force as nature intended, and consequently modulate their play. Sensors to measure helmet force and accelerations are the best start in a good-faith effort to collect data, but without medical outcomes, the numbers have no context. One NFL study will compare 120 retired players with 60 players with no game time. The study’s design is telling: a “placebo” group with nearly the same exposure, chosen to deliver negative results.

“Better helmets” are a laughable solution.

15There is a “head, neck, and spine committee” that tries to keep things as safe as possible, akin to making a playground safe without getting rid of the hungry Grizzly bears. There is a new, moderately sensible policy about visible concussions: When symptoms surface in a player, that player cannot get on the field for one day, and the player must be examined and cleared by a neurologist before suiting up again.

16How like theology it all is. With no effects on low-impact injuries, these words, studies, and positions allow fans to feel better about their revered amusement. The thousands of coaches, vendors, journalists, and merchandisers turn to their next tasks. Among all those who don’t wear the helmets, there is a serious moral hazard.

17In my business, medicine, if a product caused a brain disease or death, then we would immediately work to define the risk. We would get the numbers, quantifying how many individuals are harmed compared to how many are exposed or treated. We would quantitatively define any resulting neurological damage and deficits, and try to define safe behavioral thresholds. Finally, we would perform a calculation: Do the risks of the product or behavior in question outweigh its benefits? Medicine is hardly perfect in this regard, and in the places it fails to quantify risk, faith-based reasoning reigns: witness herbal supplements.

18But risk can be downplayed, especially if the culture doesn’t want to hear it. Adherents assign infinite benefit to something seen as divine. In relation, any evil can be permitted. Outright denial is the chief danger and most common tactic in the face of anything that might disrupt wishful thinking. A perceived immunity to risk is rarely an actual immunity to risk.

19It is temporal distance from the human-sacrificing Aztecs that allows us to find their practice abhorrent, an example of a culture worshiping death and false celebrity. They were unable to elevate their culture out of Stone-Age technologies, unable to address their problems. Because they could not improve themselves with new medicines and new technologies, or put an end to their puny internecine wars, their empire came to an end. Yet they found their behavior reasonable. They were invested in their religion and culture, and found themselves as normal as we find ourselves.

20We also declare ourselves different and more civilized than those today who watch dogs fight to the death, and those who in the ancient world watched gladiator death matches. We like to imagine there is a comfortable margin. After all, most of us watch these events via divine technology, each of us a modern Zeus, removed from visceral immediacy in the Olympus of our living rooms. But our view is suspect. The TV’s divine eye feeds an unchanged, insatiable, human lust for blood sport, death, and celebrity. When considering the victims, Owen Thomas and others like him, it is difficult to distinguish between their game and those we pretend to be so different.

21What is the good? And where does it lie? I do not know. I am not a moral philosopher. Nor am I a fan, nor one whose salary depends upon not understanding football’s risks. I am a neurologist. Perhaps I place too great a value on brains, not enough on selling cars and beer, and not enough on divine amusements.

22Other societies display barbarism, which is supported by seemingly sacrosanct cultural inertias. People fight cocks, kill albinos, or mutilate genitals. You can usually find internal efforts to stop these abominations. The efforts seem a far fringe and minority view. This isn’t, however, such a far fringe view for football. The American Academy of Pediatrics’ guideline on concussions has this to say, “When in doubt, sit it out.” Most see the wisdom when applied to concussed individuals. Current data introduces doubt into the perceived safety of multiple low-velocity impacts. It is reasonable to apply the same guideline to football in general, from junior high to college and beyond.

23I don’t anticipate action, even to sit out developing brains until we know more. Nor do I predict a ban on tackles, a weight limit, or an upper limit of traumatic exposure. What does it say about a society without support for a moratorium or limitations on this game? The silence is unflattering, as millions turn to their TVs.

^*A reference to the Fighting Irish, the football team of the Catholic University of Notre Dame. [Editor’s note]