The oldest officially recognized human was a French woman named Jean Calment. She met the artist Vincent Van Gogh when she was nine years old, describing him as grungy-looking. Calment was born in 1875 and died at the age of 122 in 1997. Although claims have been made for people who lived for as long as 150 years, those claims have never been verified, and Calment remains the longest-lived person whose age was verified. Very few people live past 100, and the average age at death for Americans is 72 for men and about 78 for women. This contrasts with certain other living things that live far longer. One example of this is certain trees, some of which are still alive after 5,000 years. The secret of tree longevity is that these trees have the ability to replace all the essential parts that wear out. Some types of jellyfish are immortal for the same reason--they are able to replace the worn-out parts and start anew as if they were reborn. Some animals also show extended lifespans. Just recently, a type of shark was found to be nearly 500 years old and still going strong. In the case of the shark, the aging secret was a slower time to maturity. The way the human body works is that youth remains while you are fertile and able to reproduce, but once you get past that age, usually in the mid-30s, the systems in the body that maintain youth diminish and signs of aging begin to appear.
The extent of longevity for anyone does involve a certain amount of genetic differences. In essence, those who live to 100 or older are a type of genetic freak in that they show upgraded cellular repair mechanisms especially in relation to DNA, the compound involved in cellular health and replication. Unless you have these genetic mutations, your chances of living to over 100 are slim to none, no matter how healthy you are or how clean a life you live. On the other hand, if you have genes for longevity (which are inherited from your mother) and you squander these beneficial genes through such bad habits as smoking, becoming obese, eating poorly and so on, you will increase your risk of mortality despite having good aging genes.
Years ago, a scientist named Leonard Hayflick theorized that cells can replicate a total of about 50 times. After that, the cells enter a state of senescence, where they don't replicate anymore, but they do crowd out normal cells and also promote the release of inflammatory substances in the body that are associated with the primary killer diseases, cardiovascular disease, and cancer. But while Hayflick believed that cells can only replicate themselves about 50 times, which is now called the Hayflick limit, exactly what determined that limit remained elusive. One thing that was known, however, was that tumor or cancer cells can . . .