Though we live longer and healthier lives than our grandparents, 100 is more or less the outer limit because, catastrophic disease aside, we just plain wear out. But 60 Minutes correspondent Morley Safer talked to one scientist who says that's old-fashioned thinking, that sometime in the next 20 to 30 years or so we'll be able to recondition ourselves for the first steps towards immortality.
We begin our journey to the outer limits with a gentle trip down the River Cam, floating by that center of British learning, Cambridge University. Our guide and helmsman: Dr. Aubrey de Grey. He ponders while he punts.
"When I was a student, I bought my own punt, a secondhand one for a few hundred pounds. And I used it in the summer to do what's called chauffeur punting," says de Grey. "People come along, tourists, and you tell them lies for money."
Today he's pondering his favorite premise: eternal youth.
While most scientists talk about increasing longevity by a few years, de Grey says he is talking about the "indefinite extension of longevity."
"Average life spans would be in the region of 1,000 years," he says. "Seriously."
De Grey and his wife Adelaide are fixtures around Cambridge. She's a researcher in genetics; he's an academic maverick. While still in his early 30s he published groundbreaking work in theoretical biology and earned an international reputation. His day job is managing a fruit fly database.
But the work that consumes him involves larger game – humans. And he does his best thinking in the same 17th century pub where Watson and Crick refreshed themselves while unlocking the mysteries of DNA. De Grey believes he has unlocked the mysteries of immortality.
"The aging process is really a buildup of side effects of being alive in the first place," he says.
De Grey has identified the biological processes he thinks are responsible for aging, including the mutations that cause cancer and the gradual buildup of useless, toxic junk.
What does this accumulation of junk within the cells lead to?
"It depends on the tissue. In the eye, there is a type of junk that accumulates in the back of the retina that eventually causes us to go blind. It's called age-related macular degeneration. In the arteries, you have a different type of cell which accumulates a different type of junk that eventually causes arteriosclerosis," he says.
But de Grey has gone way beyond describing the causes of degeneration. In a series of papers he has developed a theory he calls "Engineered Negligible Senescence". Simply put, it says science will soon enable us to grow old without aging.
De Grey says that not all of the conditions that cause our bodies to age can be avoided or prevented…yet. "But I do claim that we have a fighting chance of developing ways to prevent them within the next 25 years or so."
So humans will be just as spry at 500 as we were at 25?
"If you have difficultly imaging this, think about the situation with houses. With moderate maintenance they stay up, they stay intact, inhabitable more or less forever. It's just that we have to do a bit of maintenance to keep them going. And it's going to be the same with us," says de Grey.