The Olympic motto is “Citius, Altius, Fortius,” or, in English, “Faster, higher, stronger.” And as sports science reporter David Epstein points out from the TED2014 stage, “Athletes have fulfilled that motto — and they’ve done so rapidly.”

Epstein investigates why it is that, year upon year, runners, swimmers, gymnasts, basketball players and so many others are able to push their sports to new levels. Epstein says that it comes down to three factors: changing technology, changing genes and changing mindsets.

Epstein, the author of the book The Sports Gene, starts by taking a look at runners. The winner of the 2012 Olympic marathon would have beat the winner of the marathon of the 1904 Olympic marathon by more than 1 hour and 20 minutes. Similarly, at last year’s World Championships, 100-meter-dasher Usain Bolt beat the world record set by Jesse Owens in 1936 by 14 feet. But much of the difference in these records comes down to technology. While Owens ran on cinders, and had to dig a hole with a trowel to use for the start of the race, Bolt and his contemporaries run on carpet specifically designed to help them go as fast as possible, and start races from well-engineered starting blocks. Take those technologies away, and Epstein says that Bolt and Owens would have been within a single stride of each other at the finish line. Similarly, while Sir Roger Bannister became the first man in the world to run the mile under four minutes in 1954, last year 1,314 runners did that. But running on cinders is 1.5 percent slower than running on a modern track. Account for that, and about half of those runners are no longer under the 4-minute mark.

Today’s athletes have faster skiis, more aerodynamic bikes, lighter shoes, high-performance swimsuits, and so much more. But it’s more than just the technology, says Epstein. Today’s athletes train at a much more intensive level than they once did. “Even college athletes are professionals in their training compared to Bannister, who trained for 45 minutes a day while ditching lectures on gynecology. “That guy was drinking rat poison and brandy because that’s what was considered a performance-enhancing drink,” says Epstein who, by the way, is one of the journalists who broke the news that Alex Rodriguez tested positive for steroid use.

But there’s still more to this story — the bodies of athletes have changed. In the 1920s, the average body type was considered the ideal for every sport. Both shot putters and high jumpers were medium height and medium build. “As financial incentives and fame and glory for elite athletes skyrocketed, it accelerated the artificial selection for specialized bodies,” says Epstein. “Athletes’ bodies became much more different from one another … The large got larger, the small got smaller, and the weird got weirder.” Some refer to this as the “Big Bang of Bodies.”

Today’s shot putter is much taller and about 130 pounds heavier than the high jumper. The average gymnast has gone from 5’3″ to 4’9″, while the average basketball player has gotten much taller. Epstein looks at the example of the NBA where, in 1993, players were made partners in the league. Nearly overnight, he says, the number of people in the league over the height of 7′ skyrocketed. “Today, if you know a man over 7′, there’s a 17 percent chance he’s in the NBA right now,” says Epstein.

Another example of a body particularly well-suited to a sport: Kenyan runners. Epstein points out that it isn’t all Kenyans who are amazing marathoners, but those from the Kalenjin tribe, which accounts for about 12 percent of the population. This tribe has “legs that are very long and very thin at the extremities.” Epstein explains that this leg shape is not only ideal for cooling purposes but, because the legs swing like pendulums while running, this shape is more energy efficient. While 17 American men in history have run a marathon in under 2:10, “32 Kalenjin men did that last October.”

And still, there is another entire set of factors at play: the psychological. Human beings are pushing themselves to take on greater physical feats than ever before, which requires a mental push too. “The brain acts as a limiter, preventing us from accessing all our resources to prevent us from hurting ourselves,” says Epstein. “The more we learn how that limiter functions, the more we can learn how to push it back.”

Epstein gives the example of Kilian Jornet Burgada, who recently did a vertical assent of 8,000 feet, going up and down in three hours. “Talented though he is, Kilian is not a physiological freak,” says Epstein. “Other athletes now will follow, as they did Sir Roger Banister.”

Because after all, the human body is uniquely suited to athletics. We have little body fur, sweat glands that keep us cool, joints that absorb shocks and amazing butt muscles that help us run upright, says Epstein. “Innovation in sports, the democratization of sport and the spread to new bodies and new populations have conspired to make athletes stronger, bolder and better than ever,” says Epstein.

Fascinated? Read a conversation on the future of sports between David Epstein, Chris Kluwe and Cynthia Bir »