From Chapter VIII
THAT'S LIFE:
WHY YOU AND YOUR iPOD MUST DIE

Seth Cook is the oldest living American with a particularly rare genetic disorder. He's lost all his hair. His skin is covered in wrinkles. His arteries are hardened. His joints hurt from arthritis. He takes an aspirin and a blood thinner every day.

He is twelve years old.

Seth has Hutchinson-Gilford progeria syndrome, often just called progeria. Progeria is very rare—thought to occur in just 1 of every 4 to 8 million births. It's also very unfair; the word comes from the Greek for prematurely old, and that's the difficult fate in store for people born with it. Children who have progeria age at up to ten times the speed of people without it. By the time a baby who has progeria is about a year and a half old, his or her skin starts to wrinkle and their hair starts to fall out. Cardiovascular problems, like hardening of the arteries, and degenerative diseases, like arthritis, soon follow. Most people who have progeria die in their teens of a heart attack or a stroke; nobody is known to have lived past thirty.

Hutchinson-Gilford progeria isn't the only disease that causes accelerated aging—it's just the most heartbreaking, because it's the fastest, and it starts at birth. Another aging disorder, Werner syndrome, does'’t manifest itself until someone carrying the mutation that causes it reaches puberty; it's sometimes called adult-onset progeria. After puberty, rapid aging sets in, and people who have Werner syndrome usually die of age- related disease by their early fifties. Werner syndrome, although more common than Hutchinson-Gilford progeria, is still very rare, affecting just one in a million.

Because these rapid-aging diseases are so uncommon, they haven't been the focus of much research (and they're called orphan diseases for that reason). But that's starting to change, as scientists have realized that they hold clues about the normal aging process. In April 2003, researchers announced that they had isolated the genetic mutation that causes progeria. The mutation occurs in a gene that is responsible for the production of a protein called lamin A. Normally, lamin A provides structural support for the nuclear membrane, the package that houses your genes at the core of every cell. Lamin A is like the rods that hold up a tent—the nuclear membrane is organized around it and supported by it. In people who have progeria, lamin A is defective and cells deteriorate much more rapidly.

In 2006, a different team of researchers established a link between lamin A deterioration and normal human aging. Tom Misteli and Paola Scaffidi, researchers at the National Institutes of Health, reported in Science that the cells of normal elderly people show the same kinds of defects that are found in the cells of people who have progeria. That's very significant—it's the first confirmation that the accelerated aging that characterizes progeria is related to normal human aging on a genetic level.

The implications are far-reaching. More or less since Darwin described adaptation, natural selection, and evolution, scientists have been debating where aging fits into the picture. Is it just wear and tear, the way your favorite shirt picks up little stains and rips and marks over the years, eventually fraying and wearing out? Or is it the product of evolution? In other words, is aging accidental or intentional?

Progeria and the other accelerated-aging diseases suggest that aging is preprogrammed, that it's part of the design. Think about it—if a single genetic error can trigger accelerated aging in a baby or an adolescent, then aging can't only be caused by a lifetime of wear and tear. The very existence of the progeria gene demonstrates that there could be genetic controls for aging. That, of course, raises a question you've no doubt come to expect. Are we programmed to die?

Leonard Hayflick is one of the fathers of modern aging research. During the 1960s he discovered that (with one special exception) cells only divide a fixed number of times before they up and quit. This limit on cellular reproduction is appropriately called the Hayflick limit; in humans the limit is around fifty-two to sixty.

The Hayflick limit is related to the loss of a genetic buffer at the end of chromosomes called telomeres. Every time a cell reproduces it loses a little bit of DNA. In order to prevent that information loss from making a difference, your chromosomes have what amounts to extra information at their tips; those bits of information are telomeres.

Imagine you have a manuscript and need to make fifty copies but Kinko's has just thrown you a curveball. Instead of charging you money, they're just going to take one page off the end of your manuscript after every copy. That's a problem—your manuscript is two hundred pages long; if you give them a page after every copy, the last copy is only going to have one hundred fifty pages and whoever gets it is going to miss a quarter of the story. So, being a highly evolved organism with a gift for clever solutions, you add fifty blank pages to the end of your manuscript and present Kinko's with a two-hundred-fifty-page manuscript. Now, all fifty copies will have the complete story; you won’t lose a page of precious information until you decide to make copy fifty-one. Telomeres are like blank pages; as cells reproduce, telomeres are shortened, and the truly valuable DNA is protected. But once a cell replicates between fifty and sixty times, the telomeres are essentially gone and the good stuff is in jeopardy.

Now, why would we evolve a limit against cellular reproduction?

In a word? Cancer.

The foregoing is excerpted from Survival of the Sickest by Sharon Moalem. All rights reserved. No part of this book may be used or reproduced without written permission from HarperCollins Publishers, 10 East 53rd Street, New York, NY 10022

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