It’s funny to hear children talk ____ about age. “He’s a nice guy,” one will say, “but he’s old.” “Oh, how old is he?” “I don’t know. Forty, I guess. Your age.” In the year 1200, forty may have been old, but it isn’t any longer. For well-understood reasons, life ____ has increased significantly in the last century. People are eating healthier, smoking less, and ____ understand the ____ of exercise. ____ to advances ____ medicine and public health, doctors ____ a better job treating life-____ illnesses. They are ____ ____ their ____ ____ ____ chronic diseases like cancer and heart disease. The result is mind-____. In 1900, an American could ____ a life ____ of 48 years, whereas in 2000, the average ____ span has ____ ____ 75! Naturally, this leads us to ____, “What is the limit? How old is old?” According to ____ believed to be ____, a man in Japan lived to the age ____ 120. Scientists agree that the answer ____ in these three factors: genetics, environment, and lifestyle. It may not be easy, but people can change their environments and their lifestyles. However, for a long time, most experts felt that ____ could be done about the first, genetics. Now, with recent ____ ____, there’s reason to ____ ____ that is true. For example, Helen Blau of Stanford University was able to ____ the genetic ____-up of muscle cells. These ____ cells could then be ____ into muscle mass, where they would produce human growth hormone. (Human growth hormone, a synthetic version of the hormone produced by the pituitary ____, has been shown to ____ the effects of aging.) Skeptics say that it’s silly to want to ____ more and more years to one’s life. What matters, they ____, is the quality of that life. ____ yourself, they say, and let the end come when it ____. ____ ____, we now have reason to ____ ____ Ponce de Leon’s “Fountain of Youth” is more than just a ____. We seem to be closer than ever to ____ our previous conceptions of the average human life ____

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