radicals burn through delicate cell membranes, injuring proteins, lipids… even our DNA.”
“Well, shit. What’s the point of quitting smoking?”
“Oh no, the amount of radicals in cigarette smoke…” He realized I was joking and screwed his mouth sideways. “Antioxidants are naturally-occurring enzymes which minimize free radical damage. Think of them as the body’s toxic waste cleanup crew. Even so, the body still experiences a staggering amount of oxidant hits a day. Add it to other chemical damages, and each genome in each of your cells endures 30,000 damage events every day .”
“Each genome?”
“Right. So, if the average adult human body contains about 10 trillion cells, on a typical day your DNA could rack up about 300,000 trillion hits.”
I whistled. “But not everybody wears out at the same rate, does it?”
“No. Our genes also determine how quickly, and how well, we age.”
“I see what you mean about it being complicated.”
“Oh, we’re not nearly done.”
I was afraid of that.
“We haven’t taken into account the cumulative mistakes theory. When cells reproduce, divide, and replace themselves, it’s called cell doublings. Cell doublings are directly related to the longevity of the species. Look at this chart.”
He hit a button on his desk and scrolled through some holoimages. He finally punched up a little graph:
SPECIESLIFESPANCELL DIVISION CEILING
Mice3 years15 divisions
Chickens12 years25 divisions
Humans122 years50 divisions
Galapagos tortoise175 years110 divisions
“Gotta get me some turtle DNA.” Gavin didn’t laugh. “So cells only have so many divisions in them?”
“It’s called the Hayflick limit. On top of that, cell division involves literally hundreds of factors and changes… a lot that can go wrong. And does, incrementally. Eventually cells start dying, making mistakes, even on the genetic level. Since these accumulated mistakes make the body more vulnerable to age-related diseases, one almost always dies well before their cell division limit is reached.”
“So… we wear out, and we have built-in cell limits, and a biological clock that’s running down. Sounds like the deck’s stacked against us.”
“More than you know. Now, as to telomeres—”
“Christ. There’s more.”
“Oh yes. We spoke about the genetic component. Each chromosome ends in a series of protective units called a telomere. Think of them like the plastic tips at the end of shoe laces. These telomeres don’t contain genetic information, just an empty number of repeating subunits, which shorten after each division.”
“Each time the DNA reproduces, it’s one unit shorter?”
“These units may serve as counting markers, growing shorter in direct proportion to how near the cell comes to death. Contrarily, cancer cells replenish their telomeres after each division. That’s why cancer grows so wildly out of control.”
I shook my head. “So for a person to be immortal, he’d have to have,” I ticked off each item on a finger, “cells that never made mistakes, cells that reproduced infinitely, a body that repaired itself perfectly from free radicals and other assaults, a biological clock that never ran down, and telomeres that didn’t shorten.”
“And a host of other factors we haven’t even discussed.”
“And we haven’t even gotten around to the issue of actually growing younger .”
Gavin leaned back in satisfaction. “I think you can see why, even after twenty-five years of research, a cure for the Shift is still a long way off.”
“Okay, so let’s get back to Crandall. His team was working on all this stuff.”
Gavin, who’d been swept away by his own breathtaking command of science, tightened suddenly. “That’s right. Our best and brightest. Morris Crandall, Dr. Smythe, Dr. Hakuri, and Dr. Renquist.”
“What aspect were they working on, specifically?”
Gavin hesitated. “They believed, since the issues involved in youthing are
“Well, shit. What’s the point of quitting smoking?”
“Oh no, the amount of radicals in cigarette smoke…” He realized I was joking and screwed his mouth sideways. “Antioxidants are naturally-occurring enzymes which minimize free radical damage. Think of them as the body’s toxic waste cleanup crew. Even so, the body still experiences a staggering amount of oxidant hits a day. Add it to other chemical damages, and each genome in each of your cells endures 30,000 damage events every day .”
“Each genome?”
“Right. So, if the average adult human body contains about 10 trillion cells, on a typical day your DNA could rack up about 300,000 trillion hits.”
I whistled. “But not everybody wears out at the same rate, does it?”
“No. Our genes also determine how quickly, and how well, we age.”
“I see what you mean about it being complicated.”
“Oh, we’re not nearly done.”
I was afraid of that.
“We haven’t taken into account the cumulative mistakes theory. When cells reproduce, divide, and replace themselves, it’s called cell doublings. Cell doublings are directly related to the longevity of the species. Look at this chart.”
He hit a button on his desk and scrolled through some holoimages. He finally punched up a little graph:
SPECIESLIFESPANCELL DIVISION CEILING
Mice3 years15 divisions
Chickens12 years25 divisions
Humans122 years50 divisions
Galapagos tortoise175 years110 divisions
“Gotta get me some turtle DNA.” Gavin didn’t laugh. “So cells only have so many divisions in them?”
“It’s called the Hayflick limit. On top of that, cell division involves literally hundreds of factors and changes… a lot that can go wrong. And does, incrementally. Eventually cells start dying, making mistakes, even on the genetic level. Since these accumulated mistakes make the body more vulnerable to age-related diseases, one almost always dies well before their cell division limit is reached.”
“So… we wear out, and we have built-in cell limits, and a biological clock that’s running down. Sounds like the deck’s stacked against us.”
“More than you know. Now, as to telomeres—”
“Christ. There’s more.”
“Oh yes. We spoke about the genetic component. Each chromosome ends in a series of protective units called a telomere. Think of them like the plastic tips at the end of shoe laces. These telomeres don’t contain genetic information, just an empty number of repeating subunits, which shorten after each division.”
“Each time the DNA reproduces, it’s one unit shorter?”
“These units may serve as counting markers, growing shorter in direct proportion to how near the cell comes to death. Contrarily, cancer cells replenish their telomeres after each division. That’s why cancer grows so wildly out of control.”
I shook my head. “So for a person to be immortal, he’d have to have,” I ticked off each item on a finger, “cells that never made mistakes, cells that reproduced infinitely, a body that repaired itself perfectly from free radicals and other assaults, a biological clock that never ran down, and telomeres that didn’t shorten.”
“And a host of other factors we haven’t even discussed.”
“And we haven’t even gotten around to the issue of actually growing younger .”
Gavin leaned back in satisfaction. “I think you can see why, even after twenty-five years of research, a cure for the Shift is still a long way off.”
“Okay, so let’s get back to Crandall. His team was working on all this stuff.”
Gavin, who’d been swept away by his own breathtaking command of science, tightened suddenly. “That’s right. Our best and brightest. Morris Crandall, Dr. Smythe, Dr. Hakuri, and Dr. Renquist.”
“What aspect were they working on, specifically?”
Gavin hesitated. “They believed, since the issues involved in youthing are
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