Americans born in 1900 had a life expectancy of just 47 years. Those born at the start of the 21st century will have a good chance to see the start of the 22nd.
CBS News' Mike Wallace reports that cutting-edge research points to people living a more active and longer life in the future.
Mary Bowermaster refuses to let time slow her down.
At 82, she is a world-class track and field athlete, competing at the National Senior Games, the Olympics for the over-50 set.
She works hard to keep fit. She runs two miles every day, in the months before a meet.
A latecomer to competitive sports, Bowermaster was 63 and recovering from breast cancer when she first hit the track.
"After I had my mastectomy, this opened up a whole new world to me. The window just opened up," Bowermaster says.
Today, she is a phenomenon, breaking senior records. But researchers who study aging say that what's exceptional in 1999 may well be the norm in the new millennium.
Baby boomers will push the average life span another 20 years, living into their 90s and beyond.
"In 50 or 100 years, I would be disappointed if we could not extend [the] human life span by 30 to 50 years," says Dr. Woodring Wright of the University of Texas Southwestern Medical Center.
Scientists already have some clues to the mystery of extending life. Exercise helps but genes also play a crucial role. Five of Bowermaster's siblings lived into their 70s and 80s. Her grandmother lived to be 94.
Mice may help answer the question of how people age. Dr. Richard Miller of the University of Michigan is manipulating mouse genes and finding surprising results.
"The small mouse has a mutation in the dwarf gene, and that mutation is going to make it live 30 to 40 percent longer than its brothers and sisters like the large normal-[size] one," Miller says.
Is it their size or a change in the hormones they produce? That's what Miller is investigating.
"By learning how the genes work, we can learn enough about aging itself to be able to manipulate it and to slow it down in some way," Miller says.
Adding years to life is one thing, but Wright and Dr. Jerry Shay, also of the University of Texas Southwestern Medical Center, want to make sure they are healthy years.
As humans age, their cells do not reproduce the same way as their cells did when they were younger; that may contribute to the body's inability to repair damage as it grows old.
But what if you could immortalize cells? Human heart cells grown in the lab could make old hearts young again. Cellular rejuvenation may be a way to keep old age at bay.
"It's not inconceivable that one could take something equivalent to a vitamin pill that would help keep our cells functioning at their optimum level," Shay says.
Extending the life span of cells could help lengthen people's lives.
"Rather than just curing the diseases that occur because we get old, we'll be able to change the clock," he says.
"We'll be able to change the counting mechanism, so we'll be able to stay younger much longer," Shay adds.
Science probably won't solve the complex puzzle of aging in Bowermaster's lifetime, but she's got a prediction at least for herself.
Bowermaster laughs and says maybe she'll live to be 100. She adds, "I'd love to if I'm still like I am now. I'd love to."
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