Genes explain only about a quarter of how long people live
It is easy to credit long-lived relatives for your own prospects, but twin studies suggest genetics accounts for only about 20 to 30 percent of the variation in human lifespan. The rest comes down to behaviour and environment, things that can change. The longest verified life so far belongs to Jeanne Calment, at 122 years.
Longevity and life expectancy are different ideas. Life expectancy is a statistical average: the number of years a person of a given age can expect to live, so life expectancy at birth equals the average age at death of everyone born in that year. Longevity refers to the especially long-lived members of a population. Among the factors that shape life expectancy are sex, genes, access to health care, hygiene, diet, exercise, lifestyle and even crime rates.
Around 2010, estimates put developed countries at 77 to 90 years and developing countries anywhere from 32 to 80; Canada stood at about 81 and Mozambique at about 41. Averages were climbing. Japan went from about 81.6 years in 2002 to 82.8 in 2010, and Spain from roughly 79.1 to 81.1 over the same period, while the United States rose more slowly, from 77.4 to about 78.2.
Verifying extreme ages is hard because birth records are often missing or wrong, and folklore is full of impossibly long lives. The Gerontology Research Group validates claims by modern standards. Its milestones include Eilif Philipsen, the first person whose 100th birthday could be confirmed, in 1782, and Geert Adriaans Boomgaard, first validated to reach 110, in 1898. Jeanne Calment, who lived from 1875 to 1997, set the documented human maximum of 122 years and 164 days. Jiroemon Kimura, at 116, is the oldest verified man.
Although more than 200 gene variants have been linked with longevity, together they explain only a small slice of its heritability. One intriguing clue comes from centenarians' blood cells, which show markedly higher activity of PARP, a DNA repair protein, than cells from people aged 20 to 70, and respond to oxidative damage like young cells. That supports the idea that ageing is driven partly by accumulated DNA damage. The dream is ancient: Herodotus wrote of a fountain of youth.
Source: Longevity
