WHEN Harriet died in 2006, she was about 175 years old. Of course, Harriet was not a human. She was a Galapagos tortoise, and she lived at a zoo in Australia. Compared with us, Harriet had a very long life. But in comparison with other living things, her life span was not extraordinary. Consider some examples.
The freshwater pearl mussel, say researchers in Finland, may live for 200 years.
The burrowing clam (ocean quahog) often lives beyond 100 years and has even been reported to live more than 400 years.
Various trees, such as the bristlecone pine, the giant sequoia, and some species of cypress and spruce, live for thousands of years.
Yet humans, who are generally considered to be at the apex of terrestrial life, do well to live for 80 or 90 years—despite our sometimes extraordinary efforts to extend life!
What do you think—is eight decades or so the best we can hope for? Or is there the possibility that we can live much longer? Many people hope that science and medical technology hold the key.
Science has contributed much to the fields of health and medical technology. “Fewer people [in the United States] die from infectious diseases or the complications of childbirth,” says Scientific American magazine. “Infant mortality is down by 75 percent since 1960.” But science has met with limited success in extending adult longevity. “Even after decades of research, aging largely remains a mystery,” says another edition of Scientific American. However, “evidence suggests that aging may occur when genetic programs for development go awry.” The article continues: “If aging is primarily a genetic process, conceivably it could one day be preventable.”
In their search for the underlying causes of aging, including age-related diseases, some scientists are exploring recent developments in a field of genetics called epigenetics. What is epigenetics?
Living cells contain genetic information, which is needed for the production of new cells. Much of this information is found in the genome, a term that refers to all the DNA in a cell. In recent times, however, scientists have delved deeper into another array of mechanisms within the cell—the epigenome, a word that can mean “above the genome.” Epigenetics is the study of this amazing group of mechanisms and their chemical reactions.
The molecules that make up the epigenome look nothing like DNA. Whereas DNA resembles a twisted ladder, or double helix, the epigenome is essentially a system of chemical marks, or tags, that attach to DNA. What is the role of the epigenome? Like a conductor directing an orchestra, the epigenome directs the way genetic information in the DNA is expressed. The molecular tags turn sets of genes on or off in response to both the needs of the cell and environmental factors, such as diet, stress, and toxins. Recent discoveries involving the epigenome have caused a revolution in the biological sciences, one that links epigenetics with specific diseases and even aging.
“[Epigenetics is] implicated in diseases from schizophrenia to rheumatoid arthritis, and from cancer to chronic pain,” says epigenetics researcher Nessa Carey. And it “definitely has a role to play in ageing.” Thus, research into epigenetics may lead to effective therapies for improving health, fighting disease—including cancer—and therefore extending life. At present, however, no major breakthroughs are on the horizon. “We’re still stuck with our old routine [for combating ageing],” says Carey, “lots of vegetables” and “plenty of exercise.”
Why, though, do humans go to so much trouble to extend life? Why do we want to live indefinitely? The British newspaper The Times asked: “Why this universal human obsession with cheating death, whether through immortality, resurrection, afterlife or reincarnation?” The answer, as we shall now see, sheds light on the real underlying cause of aging.