In a world populated by billions, 51 men share a common bond. They all climbed into a boxing ring to fight Muhammad Ali for money.
Most of them were defeated by the man known as "The Greatest." A select few knew the feeling of having their hand raised in victory.
On Saturday, six of those 51 fighters were at the MGM Grand Garden to pay tribute to their former foe, who was feted at a gala to raise money and promote awareness for the Cleveland Clinic Lou Ruvo Center for Brain Health.
While heavyweights George Foreman, Ken Norton, Leon Spinks, Earnie Shavers, George Chuvalo and Chuck Wepner share the bond of having fought Ali, they have diverse memories of the 70-year-old former three-time champion, who was diagnosed with Parkinson's disease in 1984.
"The one thing fighting Ali taught me is never assume anything -- in boxing or in life," said Foreman, Ali's opponent in the famed "Rumble in the Jungle" in 1974 in Zaire. "When we were getting ready to fight in Africa, I thought everything was lined up in place. I was going to knock (Ali) out in one or two rounds so as not to hurt him.
"But instead, it was him knocking me out. It's a lesson I never forgot."
Spinks and Norton are part of an even more exclusive club. They're two of five men to defeat Ali in the ring, the others being Joe Frazier, Larry Holmes and Trevor Berbick.
"It was an honor to fight him," said Spinks, now 58 and living in Las Vegas, where he won a 15-round split decision from Ali in 1978 at the Hilton to capture the WBC and WBA heavyweight titles. "He was someone I always looked up to growing up. He believed in the same thing I did -- civil rights for everyone. He didn't care about black or white. He treated people the way they would want to be treated, and that's something I've tried to live my life by.
"But beating him was very special. It was a big thing in my life."
Norton, who like Frazier fought Ali three times and beat him in their first meeting in 1973 in San Diego, said he always respected his adversary.
"Ali could take a heck of a punch," Norton said. "He had great hand speed and a good mind. He could set you up for that next punch."
Norton, 68, said he knew Ali would try to psyche him out, but he refused to let him.
"He tried to get inside your head," Norton said. "He talked and talked. But I never listened."
For Shavers, who fought Ali in 1977 at Madison Square Garden in New York and went the 15-round distance before losing a unanimous decision, it was a battle of emotions he couldn't win.
"Ali was the nicest guy in the world," said Shavers, 66. "When I fought Ali, I had mixed feelings. I wanted to win. But there was a small part of me that didn't want to beat him. That's how much respect I had for Ali."
Chuvalo, a Canadian of Croatian heritage, fought Ali in 1966 in Toronto and again in 1972 in Vancouver. He went the distance in both defeats, something of which Chuvalo is proud.
"I always thought I could beat him, and I think he respected me for giving my best," said Chuvalo, 74. "We had two very tough fights, and we became good friends."
Chuvalo recalled a funny incident from the 1966 bout at Maple Leaf Gardens.
"We're in the center of the ring, and the referee is giving us the final instructions," Chuvalo said. "I look at Ali, and he's got his (protective) cup way above his trunks. It's a red cup, and I'm thinking to myself, 'Holy mackerel, how am I going to hit him in the body?' It reminded me of that Bugs Bunny cartoon when he was boxing Elmer Fudd and Bugs Bunny had his trunks up to his ears and the ref said, 'No hitting below the belt.' I felt like Elmer Fudd when I fought Ali."
Chuvalo did the best he could. He attacked Ali's kidneys over the 15 rounds, and Ali had to go to a hospital after the fight because of blood in his urine.
"He was such a competitor," Chuvalo said. "But I feel very connected to Ali. You try and kill each other in the ring. Then when it's over, you hug and you become friends."
Wepner, 72, didn't know it at the time, but his fight against Ali in 1975 in Richfield, Ohio, would make him famous beyond his wildest dreams.
Wepner was a journeyman who everyone figured had no shot at defeating Ali. But after taking a savage beating for 15 rounds, Wepner's courage was the inspiration for the "Rocky" film series.
"I'll always remember just getting in the ring with him," Wepner said. "I'm walking from my dressing room to the ring, and when Ali got into the ring, it really hit me -- I'm about to fight the most famous person in the world."
Wepner said Ali was gracious to him before and after their fight.
"I love the guy," Wepner said. "He's become a good friend of mine. That's why it hurts me to see him the way he is. He was such a free spirit.
"I remember seeing him five years ago, and he pulls me close to him and says, 'Chuck, I'm a prisoner in my own body.' It just breaks my heart seeing him the way he is."
Shavers, who lives in Las Vegas, said he might have been blessed for not having beaten Ali.
"Look at all the guys who beat him," he said. "Joe (Frazier) is dead. (Leon) Spinks has health problems. Same with Kenny Norton. Me? I've got my health. I'm in good shape. So I'm glad he won.
"But it hurts me to see (Ali) the way he is now. He's helped so many people, myself included."
Foreman, 63, said even with Ali struggling with Parkinson's, he remains beautiful -- inside and out.
"I'm a little jealous of him," Foreman said. "Even with everything he's been through, he's still tall, handsome and beautiful. I'm proud to call him my friend."
Contact reporter Steve Carp at email@example.com or 702-387-2913. Follow him on Twitter: @stevecarprj.