Quote:
Originally Posted by Villages PL
The important thing to remember is that the above study was a "genome-wide association study of centenarians". Genes represent a potential for an outcome, not a certainty. Genes react and respond to the environment within the body and the environment outside the body. If there are genes associated with cancer, for example, they don't represent a certainty that a person will get cancer. Those genes have to be acted upon by the environment. The same applies to almost any disease where there is an association with certain genes. The same rule applies to longevity. Certain genes may be associated with longevity but it's only a potential for an outcome, not a certainty.
That's what twin studies illustrate. Let's say one twin lives to age 85 and the other lives to 100. They both have the same genes so the fact that one lived to age 100 indicates a potential. The other twin wasn't guaranteed the same outcome even though the genes were the same.
And the same rule applies to health. An example was given of twins at age 92. One enjoyed excellent health while the other was in poor health. The one in poor health was nearly blind, suffered incontenence, a broken hip and dememtia. Even though the genes were the same, the healthy twin indicates only a potential for health, not a certainty. If it was a certainty, both twins would have enjoyed the same good health.
If it's not your genes acting alone that determines health and longevity, what's left? It's lifestyle/environment. Genes are being turned on and off all the time, depending on the environment we live in and/or the environment we create for ourselves on a day-to-day basis.
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"exceptionally old individuals are carriers of
multiple genetic variants that influence their remarkable survival"
VARIANTS is the operative word, even with identical twins!