The quest for eternal life looms large in human imagination -- from Egyptian burial tombs and mummification to Ponce de Leon's search for the Fountain of Youth to today's breakthroughs in genetic engineering and medicine.
As technology and science advance, some believe we're getting closer to living significantly longer -- even eternally. But are we still tilting at windmills in trying to hold off the inevitable, with technology offering little more than new-fangled snake oil?
Here are some of the more recent, and unique, efforts to stop the aging clock.
Calorie-Restrictive Diets -- People who practice caloric restriction, or CR, believe they can slow down the aging process by significantly cutting calories from their diets.
CR is based on animal research that shows rodents and other animals on a low-calorie, high-nutrient diet live about 30 percent longer than regular rats.
The CR regime is comparable to not pushing your car too hard -- the less fuel you burn, the less wear and tear on your body. Many who practice CR say they feel better and more energetic on the diet.
"I have more energy than I ever dreamed would be possible to have at any time in my life," says Paul McGlothin, a 57-year-old who has been practicing CR since 1994.
Dr. Roy Walford, a scientist at the University of California, Los Angeles, pioneered the study of CR in the late 1980s. His daughter, who co-authored "The Longevity Diet," is 50 years old and has been on the diet for over 15 years.
Lisa Walford stands at just under 5 feet tall and weighs 80 pounds -- about 15 pounds less than an average woman her height. She stresses caloric restriction is not the same as anorexia -- she eats throughout the day, but consumes only about 1,300 calories in foods like nuts, fruits and vegetables, and she is an avid practitioner of yoga.
Dr. David Katz, a nutritionist from Yale University, says the jury is still out on how healthy caloric restriction is for humans.
"The verdict is not in in terms of longevity, and the reason for that is that it will take 120 years to see if people can live 120 years on this diet," Katz said. "Short term, it improves cardiac risk factors and it has the prospect of extending life."
The diet does have certain side effects for most people, including being cold from lack of body fat, a reduced sex drive and loss of bone mass, which can lead to osteoporosis and breakage.
Plus, there are not many of us who can maintain the rigors of eating far less food. "It's unrealistic for a public that we can't even talk into moderation, let alone severe calorie restriction," Katz said.
Cryonic Suspension -- Cryonic suspension puts your body on ice until medical science advances enough to cure the ailments of aging. In theory, you'll be frozen, stored, thawed, repaired and revived, ready to get back to the business of living.
Admittedly, cyronics is a "speculative life support technology," says the Alcor Life Extension Foundation, one of five companies in the country that offers the service.
In the cryonics process, a dead body is slowly cooled to a chilly -166°F using liquid nitrogen. Cryro-protectants are then pumped through the body, which is immersed head first in a stainless-steel vat of liquid nitrogen and stored at -320°F.
There are a few options if you're thinking about chilling out in the afterlife. The American Cryonics Society in Cupertino, Calif., which opened in 1969, is the oldest cyronics facility. The Cryonics Institute, in Clinton Township, Mich., touts itself as the cheapest ("the most affordable prices available anywhere," the group crows on its Web site) at $28,000 for a full-body freeze.
And Alcor, located in Scottsdale, Ariz., is home to the most famous "patient" -- baseball legend Ted Williams, whose head and body are frozen in separate vats, as Sports Illustrated revealed in 2003. Alcor's prices are steep -- about $80,000 to preserve just the head, and $150,000 for the whole body.
Mainstream biologists and cryobiologists shudder at the concept of cryonic suspension. "What they are pursuing is not science, and they are banned from membership in our bylaws," John Bischof, a professor of mechanical engineering at the University of Minnesota and an official of the Society for Cryobiology, told the Chicago Tribune recently.
Nanotechnology and Robotics -- The future is upon us, according to inventor and futurist Ray Kurzweil. His most recent book, "The Singularity Is Near: When Humans Transcend Biology," envisions a future where humans and technology merge, making us super-intelligent half-machines with the ability to live almost forever.
It sounds like science fiction, but Kurzweil, an MIT graduate, argues that the "singularity" -- when technology will advance beyond our ability to comprehend it -- will happen around 2045.
As part of the "singularity," nanotechnology will have evolved such that tiny robots operating on a molecular level will swim through our bloodstream, repairing our damaged organs and cleaning up diseases.
Also during the "singularity," artificial intelligence will become so advanced we won't know whether we are interacting with a computer or another person. We may also have the ability to transcend our bodies, or "hardware," altogether, according to Kurzweil, and live forever as non-biological entities -- essentially living virtually as "software."
Not everyone is thrilled about living forever in a "Blade Runner"-like future. In his 2003 book "Enough: Staying Human in an Engineered Age," environmentalist Bill McKibben says that too much tinkering with technology makes us less and less human.
"Immortality may give us a world in which there is less meaning in life rather than more," McKibben told the San Francisco Chronicle recently.
But just in case you are looking forward to Kurzweil's vision of eternal life, you don't have to wait until 2045 and hope the singularity occurs. Kurweil and Terry Grossman, M.D., the author of "The Baby Boomers' Guide to Living Forever," have started a company called Ray & Terry's Longevity Products, selling a host of nutritional supplements.
For just $33.95, you can begin your quest for a longer life with their premier product, the Supreme Chocolate Meal Replacement System, a low-calorie, high-nutrient shake mix. And if you're really serious about living longer, you can buy a dozen containers of the shake mix and save 25 percent.