From National Geographic:
How long can humans conceivably live? In most developed countries, life expectancy has grown steadily to an average of 75 years. But scientists are exploring ways to extend lifespan to lengths that seem inconceivable now—perhaps 120 years and beyond. Ideally, future centenarians who avail themselves to life-prolonging advances won’t suffer the familiar frailties of old age. The goal is for them to retain their youthful vitality, rather than add extra years of decline. Several studies show lifespans can be stretched far beyond normal limits. In one example, Cynthia Kenyon, a professor at the University of California in San Francisco, has doubled the lifespans of simple roundworms from two weeks to a month by altering the function of a single gene, known as daf-2. Even near death, these mutated worms look better than normal worms half their age. Their bodies are smooth and plump, and they wriggle along like much younger worms.