Outsmart Your Genes, Be Young Forever

As medicine vanquishes more and more enemies once thought unconquerable, the victories highlight its impotence against the ultimate foe: growing old. No matter how many people approach the apparent maximum life span of about 120 years, Methuselah's feat still seems as out of reach as parting a sea. Yet in "Longevity, Senescence and the Genome," (932 pages. University of Chicago Press. $49.94.) to be published this winter, Caleb Finch of the University of Southern California reaches a conclusion both scary and hopeful. Not only are there few limitations on life span, he writes, but "many mechanisms of senescence should be reversible" by turning selected genes off or on.

A central enigma in biology is whether growing old is the result of random environmental factors or an immutable genetic clock. Finch, covering everything from the aging of elephant teeth to how starving extends life span, believes that there is indeed a genetic clock--but that its timing can be dramatically affected by lifestyle and medical technology. The keys to aging are probably related to the genes that regulate how long it takes an individual to grow and sexually mature. But DNA is not omnipotent. Although queen honeybees and sterile female worker bees have identical DNA, queens often live 50 times longer. One difference: queens-to-be eat special food during development.

Proper diet and exercise slow aging in people, too. But Finch also raises the possibility of regenerating "damaged molecules, cells, or organs" to turn back the clock. Soon, we may even understand how to activate "youth" genes and dampen "age" genes responsible for such signs of decrepitude as a depressed immune system. Then, the question will be, will we want to?