Two years ago, at the Summer Olympics in Rio, Wayde van Niekerk ran the 400 meters in 43.03 seconds. Before the South African sprinter could catch his breath, the announcers had already cast his record-setting run as an unbelievable feat of human performance. “I can’t believe it!” howled one. “He has obliterated Michael Johnson’s world record!” Over at NBC, a second announcer goaded, “Guess what, Michael Johnson? The world record has been destroyed!” Later that day, an equally enthusiastic release from the Olympic committee reupped the flowery verbiage with the headline, “Van Nierkerk Smashes World Record.”

But here’s the thing: Van Niekerk’s time was just 0.15 seconds quicker than Michael Johnson’s. That’s a literal blink of an eye. (Actually, it’s probably less: A single blink ranges from .1 to .4 seconds.) So, even though van Niekerk’s margin of victory was too short for most people to even lubricate their corneas, it was sufficiently impressive to “obliterate,” “destroy,” and “smash” the 17-year-old record that came before it.

This is where athletic performance stands today: Each new achievement is shockingly impressive because it’s become so rare for anybody to run faster, jump higher, or throw farther than his or her predecessors. And when they do, it’s usually by an infinitesimal margin.

Consider this: During the first 50 years of the 20th century, the 400-meter record was broken nearly once every four years, for a net gain of two seconds. In the most recent 50 years, the record was broken only three times — once every 17 years — and the total gain amounted to a mere 0.83 seconds. Last year, van Niekerk broke Michael Johnson’s 17-year-old record in the 300 meters; his time was 30.82 seconds, a mere .04 seconds faster than Johnson’s. You couldn’t even squeeze half a blink of an eye into that much time.

Those are just the records that have been broken. At least a dozen track-and-field events — including the 3,000- and 1,500-meter runs — haven’t seen a single new record in more than two decades. Not one! The long-jump record has gone untouched for 27 years; the shot-put record for 28 years. Both discus and hammer-throw records were established more than 30 years ago.

New records have become so rare that academics have begun to seriously consider whether humans have plateaued physically. “Nobody believes that you’re going to see huge improvements anymore,” says Anders Ericsson, PhD, author of Peak: Secrets from the New Science of Expertise. “It’s not like you’re going to reduce the 100-meter dash by two seconds or something like that.”

Geoffroy Berthelot, PhD, a senior research director at the École Polytechnique, outside Paris, concurs. Last year, he published a series of scatter plots that illustrated the best track-and-field performances by year. Some of the graphs stretch back to 1890, and within each sport, the resulting wave of dots increase steadily over decades, implying consistent gains in sprint times and shot-put distances. But shortly before the turn of this century, all the graphs level off, creating what looks like the outline of a volcano that blew its top. That’s the plateau: a visual representation of our stagnating strength and speed. And it holds for both men and women, despite the fact that men have had, on average, a 30-year head start in Olympic competition.

“I don’t think we can expect much change anymore,” says Berthelot. “It’s not a very positive point of view, but that’s what it is.”

For all of modern history, humans have been growing taller and living longer. But shortly before the athletic records began to taper, so too did our size and longevity.

Could he be wrong? If the past century has taught us anything, it’s that when it comes to feats of athletic prowess, we don’t know what we don’t know until we know it. To understand where human performance might go next, it helps to understand what brought us here in the first place: the unique, unexpected confluence of factors — genetic, financial, geographical, and technological — that combined to create a decades-long string of athletic achievements that would have seemed like science fiction to previous generations. The fact is that world records have always seemed impossible to break. And yet, somehow, we’ve continued to do it. Who says that has to stop?

The human body consists of 7,000 trillion trillion atoms, which comprise 206 bones, 640 muscles, and some 100,000 miles of blood vessels that support a more or less set number of arms and legs, fingers and toes, kidneys and lungs. These make it a “finite organism,” wrote Berthelot last year, constrained by “functional boundaries at every level of organization.”

For most of history, human achievement was tested by pushing this configuration to its limits. And given how little we knew about training, nutrition, and sports psychology, there was a lot of room for improvement. People got bigger and stronger, training regimens became more effective, and with each generation of athletes, people discovered new reserves of strength for jumping, running, and throwing things.

They also discovered a significant new motivation for getting better. Namely: money.

It wasn’t until about the middle of the 20th century that professional athletics began in earnest, Berthelot says. With serious cash on the line, a once-recreational pursuit became a legitimate opportunity for a financial security. “There was a dramatic turning point after World War II,” he says. “The fact that you use money to motivate is a strategy for increasing performance at the world scale.”

Over the years, the prize pool has grown. In his book The Sports Gene: Inside the Science of Extraordinary Athletic Performance, David Epstein explains that by 1975, professional athletes in major American sports like football, baseball, and basketball received salaries about five times as big as the median American man’s. Today, salaries in those sports stand between 40 and 100 times the median salary.

Track-and-field athletes don’t earn as much as NBA players, but for the poor countries that churn out the fastest runners, the cash prizes are still potentially life-changing. A major marathon victory could net a six-figure reward, while the per-capita income in Kenya and Ethiopia, which together hold every one of the 50 fastest marathon times, is $1,508 and $762, respectively.

Right on the heels of professional athletics came a second trend that appears to have added a momentous push toward our current athletic peak: We became incredibly good at identifying the specific body types that perform best within each sport.

Before the rise of big cash payouts, the ideal athlete was thought to possess a body that was “well-rounded, or average,” writes Epstein. “Not too tall or too small, neither too skinny nor too bulky, but rather a just-right Goldilocks-porridge version of a man. (And it was only men.)” That body type essentially held for all sports, which is why for a long time, say, professional baseball players, runners, and swimmers all looked about the same.

Through the development of vaccines, improvements in medicine, and a better understanding of hygiene and nutrition, we’ve maxed out the potential of the 20,000 to 25,000 protein-coding genes contained within each of our cells.

In decades past, however, average Joe athletes have been ousted by those whose bodies appear custom-built to vanquish opponents and shatter records. Runners came to have longer legs and lightweight appendages, while swimmers grew supersized torsos and arms that unfurled like eagle wings. Recent decades have given us both beefier football lineman and taller NBA players. Data collected by researchers at the University of South Australia indicate that in 1946, there were zero seven-foot-tall pro basketball players. Today, recruiters actively seek these giants, and by combining NBA measurements with the Centers for Disease Control and Prevention’s height data, Epstein determined that for all seven-foot-tall men ages 24 to 40, 17 percent are currently playing professional basketball. “Find six honest seven-footers, and one will be in the NBA,” he writes.

We’ve also discovered which specific populations tend to fare best. For certain sports, we’ve become so good at identifying talent that we know exactly where to look for the next champion. For sprinters, it’s Jamaica, which claims 30 of the 50 fastest 100-meter finishes in history. The other 20 are held by the United States, which recruits from a population that’s more than 100 times bigger.

Left to right: Bob Feerick, the player with the best stats in the NBA in 1946. Gheorghe Mureșan, the tallest player in NBA history (Focus on Sport/Getty). Yohan Blake, the fastest Jamaican sprinter (Cameron Spencer/Getty).

As these handsomely paid superathletes clobbered and reclobbered the old records, even physically imperfect performers benefitted from their string of achievements. Unlike dogs and horses, humans have the ability hold previous performances in our minds as we race, and this can be a powerful motivator. “Humans can take advantage of their ability to compete against history,” says Alex Hutchinson, author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. “A horse can only compete against whoever happens to be there that day.” No wonder the Kentucky Derby record is 45 years old.

And yet today, human beings seem destined to go the way of the thoroughbred. Last year, the aforementioned French researcher Geoffroy Berthelot and a group of his colleagues published a paper titled, “Are We Reaching the Limits of Homo sapiens?In it, they argue that, through the development of vaccines, improvements in medicine, and a better understanding of hygiene and nutrition, we’ve maxed out the potential of the 20,000 to 25,000 protein-coding genes contained within each of our cells.

Along with the decline in world records, Berthelot and his cohorts pointed to two other characteristics that seem to be stalling: height and lifespan. For all of modern history, humans have been growing taller and living longer. But shortly before the athletic records began to taper, so too did our size and longevity.

In the United States, the average lifespan has actually decreased for the past two years. The average height in high-income Western countries peaked about three decades ago, as evidenced by a 2016 review from UK researchers. The United States experienced this most dramatically: Once the tallest in the world, Americans are today shorter than their European contemporaries. The Dutch, on average, stand five inches taller.

The financial rewards remain, of course, but the natural optimization of the body and sorting of body types appears to have concluded. “The tall athletes are no longer getting taller compared with the rest of humanity at the rate they were two decades ago, nor the small smaller,” writes Epstein. “And the march of constantly shattered world records is slowing right along with it.”

Perhaps it’s no coincidence that our current plateau roughly corresponds with the widespread use of anabolic steroids, hormones, and other performance-enhancing drugs (PEDs). Athletics have always been about relentless improvement, and as the march toward godlike strength slowed, people began looking for preterhuman means toward achieving better performance.

Doping’s impact on sports was made clear when cyclist Lance Armstrong was stripped of seven Tour de France titles, and then again when a covert Russian doping conspiracy in Sochi called the entirety of Olympic history into question. Barry Bonds’ all-time home-run record of 762 was allegedly achieved with the help of a drug cocktail. (He confessed only to the unwitting use of steroids.) And a series of Cold War–era records set by East German athletes are widely considered to be artificially enhanced. (“That’s drugs, pure and simple,” says Hutchinson.)

But PED use is still pervasive. Recent research from the World Anti-Doping Agency finds that banned performance enhancers are “remarkably widespread among elite athletes.” Wang Junxia, an admitted participant in state-sponsored Chinese doping, held the women’s 10,000-meter running record for more than two decades. When her time was finally defeated in 2016, the new champ, Almaz Ayana, was also accused of doping. The drug problem is so severe that last year, the European governing body of track and field petitioned to erase all world records set before 2005.

Still, it’s hard to imagine they’re currently doing much more than helping us keep up. Official crackdowns and ire from fans makes major boosters like steroids and human growth hormone harder to get away with. Whatever major improvement drugs can provide to world records have likely already happened.

That leaves technology as perhaps the last major force propelling today’s best performances. Lighter bikes and shoes, smoother running tracks, and clothing that keeps athletes cool have conspired to shed seconds and centimeters off the world records since the middle of the 20th century.

Today’s Tour de France bicycles are 30 to 50 percent lighter than they were in the 1970s, thanks to advancements in carbon fiber. Clap skates, which rely on a hinge to keep the blade on the ice as the skater lunges forward, propelled speedskaters to set five new world records in the 1998 Olympics. Four years later, at the Olympic Games in Salt Lake City, clap skates helped break eight more world records. In the 2008 Olympic Games, for instance, swimmers began donning new polyurethane swimsuits developed through a partnership between Speedo and NASA. Of the 25 world records broken that year, 23 were done in the new suits. The suits have since been banned, but those records remain.

The sporting world’s focus on technology to drive performance gains explains why Berthelot calls our current period “the era of augmented humans.” Each new sweat-wicking, weight-dropping, traction-improving breakthrough makes us appear to be better athletes without doing anything to truly make us stronger or faster. “We’ve moved beyond our physiological bodies,” he says. “World records have become reliant on the technology.”

“I’m pretty skeptical of claims that we’ve reached some limit of performance, simply because historically, the vast majority of improvements have been unforeseen. That’s probably the main the source of fundamental improvement: new people being intrinsically better than anybody who came before.”

Tech can be powerful source for incremental gains, but ultimately it can’t unshackle humans from the constraints of physics. Nike made this clear last year when it orchestrated a multimillion-dollar attempt to run a marathon in under two hours. As Hutchinson details in Endure, the company spent nearly two years laying the groundwork that it hoped would bring success. The athletes were three top East African distance runners, two of whom had already come within five minutes of the two-hour barrier.

The technological advantages were a new shoe said to provide 4 percent better running economy and clothing designed to minimize drag. The nutritional edge came from personalized carbohydrate blends formulated to push the most sugar into each athlete’s blood. For precise pacing, the company arranged for an electric car to drive around a track, followed by a team of accomplished athletes who took turns running ahead to create a low-pressure air pocket for the would-be record setters to run within. The event was so heavily manipulated that the official time wouldn’t have been formally recognized. It was simply a test of human potential.

In the end, not even perfect conditions paired with perfect specimens could break through the limitations of the human body. The fastest runner came in 25 seconds short of the goal.

Ours is a culture obsessed with self-improvement, taught to believe that we are unbound by the limitations of the people who came before us. At some point during childhood, maybe frequently, you were probably told that you could do anything — anything! — that you put your mind to. Then you found your role models, many of whom were likely top-performing athletes, and their accomplishments served as a constant reassurance that, yes, any barrier can be broken.

But some barriers can’t be broken, not even by the best representatives of our species. We are all constrained by the limitations of the bone and muscle that support our fleshy exteriors, along with the soft neural tissue that drives the whole machine. A two-hour marathon is probably within the grasp of human potential, but a 90-minute marathon isn’t. Neither is a four-meter high jump or a seven-second 100-meter sprint. Some achievement simply won’t be attained — not in your lifetime, not ever.

If our current plateau seems hard to acknowledge, perhaps it’s because stagnation implies mortality. A species that isn’t getting stronger is fading, and the same is true of each individual.

But Hutchinson, for his part, doesn’t think the peak should concern you. Not yet, anyway. “I’m pretty skeptical of claims that we’ve reached some limit of performance, simply because historically, the vast majority of improvements have been unforeseen,” he says. “That’s probably the main the source of fundamental improvement: new people being intrinsically better than anybody who came before.”

World records are always set by outliers — the Serenas, Usains, Vonns, and Lebrons of the world. Currently living human Michael Phelps has more than twice as many Olympic gold medals as anybody else in history. He could represent peak athlete, or he could just be somebody else’s titan to topple. Without a crystal ball, it’s impossible to know. For the most part, we’ve already corralled the strongest among us into their ideal competitions, and we’ve motivated them with money, fame, and fierce competition. From here, in traditional sports at least, world records will go to those with best technology, the strongest genetic advantage, and the grit to dedicate an entire life to crushing their predecessors by a fraction of a blink.