There are a few strong theories:
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First, genetics plays a big role. If your parents and grandparents lived to a ripe old age, your chances of living longer go up, too.
Secondly, we're all living longer. The average age in 1900 was only 46. Now it's nearly 80.
And third, watching your diet, not smoking, and moving every day also play a role in a lengthy life. So what are centenarians doing to hit the century mark?
SEE RELATED: Woman shares her secrets to long-lasting life after reaching 100th birthday
Ask Clarice Freeman, who is about to celebrate another big birthday next week when she turns 103.
She's packed a lot of life in that century-plus. Raised in Illinois, she went to college and taught before meeting her husband, the late minister Dr. Thomas Freeman. He became a legendary debate coach at Texas Southern University. After marrying, they moved from Virginia to segregated Texas in 1953.
"When I came to Houston, I felt like I stood still for about 25 years before Houston caught up," she said when asked what it was like moving to the Bayou City during the 1950s.
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She grew up in a largely white town near Chicago and says she remembers her grandmother.
"My grandmother, whom I got to know very well, was born a slave," she said.
After witnessing so many monumental changes in her long lifetime, she told ABC13 one of the most amazing events to her was the election of the nation's first Black president, Barack Obama.
"It did not surprise me, because Obama looked presidential," she admits.
Freeman has spent most of her life involved with the arts, raising three children, and four grandchildren. She said she continued to drive until she was nearly 100 years old, and wore heels even longer than that.
Then there was the motorcycle.
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"I was probably about 80 or 90 at the time," Freeman said. "It's like riding a bicycle. It just makes a lot of noise."
So what's her secret?
"I've taken very good care of myself," she goes on. "I watch what I eat. I do not have any bad habits, and I enjoy life."
Freeman said that is the real secret.
"There's so much living to do, so much living to do. That, and you must read, read, read," she said.
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