"What did he do?"
"He took some cells from a fetus and raised them in a petri dish. This was back in 1961—it's difficult now to conjure up the memory of how primitive the thinking was back then. In those days, aging was viewed as a straightforward matter of biological destiny. You got old because your body wore out, like a machine whose parts disintegrated under wear and tear. Your skin wrinkled, your hair fell out, your brain shrank, your arteries clogged. There was nothing you could do. A human was born, lived a certain number of years and died, and that was more or less all there was to it. Of course, you could cheat around the margins — depending upon whether you were an abstemious librarian or a Left Bank poet drowning in absinthe — but basically your life span was prescribed. One hundred years at the outside. It was the dictates of Nature. Now, of course, we know that all that is hogwash."
"So I've just heard."
"Well, you heard right. Believe me, the advances in life extension over the next fifty years are going to make your head spin. Future generations will look back at our pathetic span of eighty years and shake their heads in wonderment. Did you ever tour the chateaux of the Loire? When the guide points to those little beds five feet long and those tiny suits of armor, you're astonished that people could ever be so small. They'll regard our lifetimes like that. Remember your amazement upon learning that Alexander the Great died at age thirty-three? Future generations will feel that way when they discover that Einstein died at seventy-six."
He fixed Jude with a hard stare.
"And it began with Hayflick. You see, he tackled aging head on. He asked the pertinent question — why does aging happen? Does it happen because the individual cells give out, eventually incapacitating the whole human organism? Or does it happen because of an age-related deterioration in some part of the organism that shuts down the cells? When does an army lose a decisive battle? When so many soldiers are cut down that it can no longer mount an effective force in the field, or when a superior officer perceives a rout and gives the order to surrender? My metaphor, incidentally, not his.
"In any case, Hayflick designed a simple experiment — that is, simple in hindsight, like all great experiments. He put the cells in the petri dish to see how long they would live, left to their own devices. They didn't have to do anything — they didn't have to perform work on behalf of the nonexistent human. All they had to do was what cells do naturally, divide and multiply. Which they did. About fifty times. And then they died. He repeated the procedure with cells from a seventy-year-old person. They divided, but only about twenty or thirty times before they, too, died."
"So the answer is that the soldiers die?"
"Don't get hung up on the metaphor," said McNichol brusquely. "Real life is more complicated. Real life is not either/or. In real life, thousands of soldiers die and the general gives up."
McNichol stood up and began gesturing as he talked.
"The point is that the cells from the seventy-year-old were themselves older than the ones from the fetus. The point is that Hayflick had established that there is a natural limit to the life of a cell, that from the time it's a newborn, it divides fifty times and then turns senescent."
"If there's a natural limit, then there's no hope of overcoming aging."
"On the contrary, it means that there is hope. In biology, things don't just happen by themselves for no reason. In nature, nothing is so natural that it can't be undone by man. If there's a limit, that's because something is imposing a limit. Something is making it happen."
He was getting more and more excited.
"Don't you see? There's a clock, a clock inside the cells that tells them when their time is up. And if there's a clock there, it means we can find it and go in and tinker with it and eventually even learn how to reset it. We can make it last longer. Which is what we are doing."
"Where?"
"In laboratories all around the world. Scientists are discovering single genes that postpone senescence in simple organisms. There is only one tree of evolution, so the same gene sequences exist in us. Some of the most important work has been done on a one-celled protozoan that lives in ponds. It provided the key to the clock."
"What's the clock?"
"Telomeres."
"Telomeres?"
"Strips of DNA that cap the end of our chromosomes. As you know, chromosomes are long strands of DNA that contain the cell's genetic instructions. At the end of each one is a telomere. It's been compared to the little plastic tip at the end of a shoelace that keeps it from unraveling. And that seems to be pretty much its job here. Each time the cell divides, it loses a little bit more of its telomeres, so that the strand keeps getting shorter as the cell gets older. When the cell reaches its Hayflick limit of fifty divisions, the telomere is down to a nub. That's the point at which the cell switches over into old age and declines. That's the beginning of cell death.
"So the age of cells has nothing to do with chronological time, as we experience it. Which makes sense when you think of it — time is an artificial human construct to begin with. The age of cells is related to how much work they do, to how many times they have to divide. That is why the skin of someone who has spent his life tanning in the sun is so much more wrinkled than someone who stayed in the shade; the skin cells of the tanning fanatic have to keep reproducing in order to replace those destroyed by ultraviolet rays. They have to work harder — their telomeres are shorter."
"Fascinating," said Jude. "But for whatever reason, the cell still ultimately has to die."
"Ah, but does it? Or rather, does it have to die at such an abysmally early age?" McNichol drew his words out dramatically. "You see, living cells are extremely efficient. They are magnificent creations — they consume food, expel waste, perform work, and have a strong membrane for protection. A perfectly balanced world within a microcosm. So perfect that there is no reason to think they are cursed with a built-in limit to their longevity.
"That much we know from looking at cancer cells. Cancer cells replicate themselves endlessly, generation after generation, so much so that experiments to count the number of divisions virtually never end. There are cancer cells in laboratories that live on in petri dish after petri dish for decades. They are, for all intents and purposes, immortal."
"How do they do it?"
"How indeed? The secret lies in an enzyme called telomerase. It works like a little repair kit. Every time a bit of telomere is lost through cell division, it comes along and replaces it so that the strand never gets shorter. The shoelace never gets frayed, if you will, because it gets a new plastic tip. Telomerase is present in cancerous cells. It's also there in egg and sperm cells because, of course, these cells have to remain young — they're passed on to the offspring. But the enzyme is not in your run-of-the-mill normal cells even though normal cells could make it. They have a gene to make it, but the gene is switched off."
"So if the cells only had the enzyme, they'd live longer? That's the theory?"
"It's not theory. It is demonstrable fact. Scientists at the University of Texas Southwestern Medical Center have injected the core of the enzyme-producing gene into human cells. Incidentally, they were able to get the gene by studying our little pond protozoan, which happens to produce huge amounts of telomerase. After they injected it, the telomeres regained their youthful length and the cells kept on dividing happily way beyond their life span. The cells have been rejuvenated."
"So they've discovered the fountain of youth — Ponce de Léon?"
"No, aging is much more complicated. For one thing, not all cells follow the same rules — brain cells and heart cells, for example. But it's certainly an important start. It's confirmation of the fact that the human body, like all living organisms, has a remarkable capacity for self-repair. It turns out we are not machines after all."