Then he proved it again, winning the 100 meters in 9.81 seconds, securing his place as the greatest sprinter of all time and becoming the only man or woman to win the 100 three times and at consecutive Olympics.
His main rival, Justin Gatlin of the United States, the 2004 Olympic champion who later served a suspension for doping and was booed on Sunday, took the silver medal in 9.89 seconds. Andre de Grasse of Canada won the bronze in 9.91.
As Bolt ran down Gatlin in the final meters, he pounded his chest. He then blew kisses to the crowd and carried a toy Olympic mascot around the track, giving it away as a souvenir. Finally, he struck his signature pose, known as To Di World, cocking an elbow and pointing his fingers toward the sky, as if launching an arrow or a lightning bolt.
He is also favored to win a third straight gold medal at 200 meters and yet another as the most vital member of Jamaica’s 4x100-meter relay team.
Even an athlete as great as Bolt, though, can be upstaged on rare occasions. That happened Sunday when Wayde Van Niekerk of South Africa set a world record in winning the 400 meters in 43.03 seconds, shattering Michael Johnson’s 17-year old record of 43.18.
Running on the outside in lane 8, where he could not see his competitors, Niekerk astonishingly shaved more than four-tenths of a second from his previous career best of 43.48 and more than a second from his season’s fastest race before the Olympic final.
Fairly or unfairly, given the tainted state of track and field due to doping, that performance may bring as much skepticism as celebration.
For Bolt, Sunday’s victory carried both a sense of celebration and farewell. He will turn 30 next Sunday as the Rio Olympics end. He has said repeatedly that these will be his final Games.
He plans to retire next year after the world track and field championships in London, with one transcendent career goal remaining: to take his world record of 19.19 seconds at 200 meters below the 19-second barrier.
“This has got to be the most universal event other than the long jump,” David Wallechinsky, the president of the International Society of Olympic Historians, said of Bolt’s victory in the 100 on Sunday. “Everyone’s tried it at least once in their lives. To be the best in the Olympics three times in something that everyone has done at least once is incredible.” When Bolt crossed the line Sunday, it was not with the same astonishment as that night eight years ago at the Beijing Games, when he was new to the public and the 100 and he finished in 9.69 seconds, easing up and celebrating before the tape but still breaking his own world record. How fast he could have run that night, we will never know.
Nor did Sunday’s performance match the wonder of the 9.58 that Bolt ran a year later to set the current 100 record at the 2009 world track and field championships in Berlin. As with his victory at the 2012 London Games in 9.63 seconds, winning for Bolt is now more about career achievement and historical standing and dominance at the biggest moments than mere startling speed.
He stacks wins as if they were poker chips. Since he became an otherworldly figure with his performances in 2008, Bolt has won 69 of 74 races. His only truly important defeat came with his elimination on a false start in the 100 at the 2011 world track and field championships in Daegu, South Korea.
Bolt has raced little this season, and in recent years, he has become vulnerable to nagging injuries in his back that radiate down the muscles of his legs.
He withdrew on July 1, from the final of the 100 at the Jamaican Olympic trials with a slight tear in his left hamstring muscle. But Jamaica’s rules, unlike those of the United States, which require a top-three finish to qualify for the Summer Games, allowed Bolt to be entered in the Rio Games anyway.
Some American sprinters joked at the time that Bolt always seemed to sustain some injury before the Olympics or world championships. Sure, he would be ready for Rio.
“It’s a tradition,” Tyson Gay said.
But sprinting is a lot like boxing in the sense that they are individual and elemental sports, one man against another with his legs or his fists. Sleights, real or perceived, become dramatically exaggerated.
Bolt said he was disappointed by the tame, joking remarks of Gatlin and other Americans, adding: “I think they have not learned over the years that the more you talk, the more I will want to beat you. It’s one of those things but I’m looking forward to it, should be exciting and they will feel my full wrath as always.”
In the end, the buildup to Sunday’s final turned out to be more playful than antagonistic. Bolt held a news conference featuring samba dancers and a Norwegian journalist who broke into a worshipful rap song, saying he hoped that the Jamaican star would again prevail.
In Sunday’s final, Bolt reacted relatively slowly to the starting gun, as he often does, slower than every competitor but one. He is 6-feet-5 inches, and it can take his body some time to unfurl, like a flag. He also may have grown somewhat cautious after that false start at the 2011 world championships. Once, one false start was permitted. Now, an early lean or even a reaction to the gun in under a tenth of a second, brings automatic disqualification.
But Bolt wins races not in the first 50 meters, but in the second 50 meters. He is so tall, his legs so long, that he takes only 40 or 41 strides over 100 meters, where other sprinters might need 43 or 44 or even 46.
He also holds his top-end speed better than others. No sprinters speed up at the end of a 100-meter race as it appears they do. This is an optical illusion. The winner is not the person shifting into another gear but the one slowing down the slowest.
At the 2015 world track and field championships in Beijing, Gatlin had Bolt beat but leaned too early, wobbled with a kind of swimming motion, and Bolt caught him at the line, winning by a hundredth of a second.
Again on Sunday, Gatlin got a quicker start, but Bolt chased him down.
“His legacy depends on what he does with the rest of his life,” said Wallechinsky, the Olympic historian, said of Bolt. “The best is if he goes around, giving clinics, and travels the world like Muhammad Ali and becomes well known in Africa and Asia and is someone that everybody loves. Or he could just have a good time for the rest of his life.”