Longevity

The word longevity is sometimes used as a synonym for "life expectancy" in demography. However, this is not the most popular or accepted definition. For the general public as well as writers, the word generally connotes 'long life', especially when it concerns someone or something lasting longer than expected (an 'ancient tree', for example).

Reflections on longevity have usually gone beyond acknowledging the basic shortness of human life and have included thinking about methods to extend life. Longevity has been a topic not only for the scientific community but also for writers of travel, science fiction and utopian novels. There are many difficulties in authenticating the longest human lifespan ever, due to inaccurate birth statistics; though fiction, legend, and mythology have proposed or claimed vastly longer lifespans in the past or future and longevity myths frequently allege them to exist in the present.

A life annuity is a form of longevity insurance.

History

A remarkable statement mentioned by Diogenes Laertius (c. 250) is the earliest (or at least one of the earliest) references about plausible centenarian longevity given by a scientist, the astronomer Hipparchus of Nicea (c.185—c.120 B.C.), who, according to the doxographer, assured that the philosopher Democritus of Abdera (c.470/460—c.370/360 B.C.) lived 109 years. All other accounts given by the ancients about the age of Democritus appear to, without giving any specific age, agree on the fact that the philosopher lived over 100 years. This is a possibility that turns out to be likely, given the fact that many ancient Greek philosophers are thought to have lived over the age of 90 (e.g., Xenophanes of Colophon, c.570/565—c.475/470 B.C., Pyrrho of Ellis, c.360—c.270 B.C., Eratosthenes of Cirene c.285—c.190 B.C., etc.) and because of the difference that the case of Democritus evidences from the case of, for example, Epimenides of Crete (VII, VI centuries B.C.), who is said to have lived 154, 157 or 290 years, as has been said about countless elders even during the last centuries as well as in the present time. These cases are not verifiable by modern means.

Present life expectancies around the world

Various factors contribute to an individual's longevity. Significant factors in life expectancy include gender, genetics, access to health care, hygiene, diet and nutrition, exercise, lifestyle, and crime rates. Below is a list of life expectancies in different types of countries:

• First World: . . . 77-83 years (e.g. Canada: 80.1 years, 2005 est)
• Third World:. . . 35-60 years (e.g. Mozambique: 40.3 years, 2005 est)

Population longevities can be seen as increasing due to increases in life expectancies around the world:

• Spain:. . . . . 81.02 years in 2002, 82.31 years in 2005
• Australia: . . 80 years in 2002, 80.39 years in 2005
• Italy:. . . . . . 79.25 years in 2002, 79.68 years in 2005
• France: . . . .79.05 years in 2002, 79.60 years in 2005
• Germany: . . 77.78 years in 2002, 78.65 years in 2005
• UK: . . . . . . 77.99 years in 2002, 78.4 years in 2005
• USA: . . . . . 77.4 years in 2002, 77.7 years in 2005

Exceptions: Populations from developing world with high life expectancy

Some populations have reputation of producing unusual number of individuals with exceptionally high ages, for example:

• Okinawans,
• people from the Hunza valley of Pakistan, the Burusho also called the Hunza,
• the inhabitants from the high mountain valley of Vilcabamba Ecuador, in South America,
• inhabitants of some regions in the Caucasus mountains.

Long lived individuals

The current validated longevity records can be found in the list of supercentenarians. Notable individuals include:

• Jeanne Calment (1875-1997, 122 years and 164 days) — the oldest person in history whose age has been verified by modern documentation. This defines the human lifespan, which is set by the oldest documented individual who ever lived.
• Shigechiyo Izumi (1865-1986, 120 years 237 days, disputed) — the oldest male ever recognized by the Guinness Book of World Records; this is widely questioned by scholars, who believe that conflation of dates has occurred and this has compromised the authenticity of Izumi's age.
• Christian Mortensen (1882-1998, 115 years 252 days) — the oldest male widely accepted by scholars.

Longevity myths

Longevity myths are cultural narratives that speak of exceptional, improbable or impossible longevity, with or without eternal youth. They include the Fountain of Youth myth, the "village elder" narrative, the story of Shangri-La, the Nationalist tale, etc.

The legendary Fountain of Youth is based upon a fantasy of living a very long time by taking potions, or finding some other secret that results in longevity combined with a youthful healthiness.

The "village elder" narrative is often based upon a pre-literate societal respect for aging, patriarchy, etc., which leads to a venerating age exaggeration of the oldest male (or sometimes female) in the village.

The Shangri-La myth is the idea that a certain remote mountain area may contain an entire village of long-lived (or eternally lived) people (such as Vilcabamba or Abkhazia).

The "Nationalist longevity myth" is an age exaggeration story motivated by nationalist pride (such as Stalin proclaiming special longevity in Soviet Georgia, because he was born in that country.)

Future

The mainstream view on the future of longevity, such as the US Census Bureau, is that life expectancy in the United States will be in the mid 80s by 2050 (up from 77.85 in 2006) and will top out eventually in the low 90s, barring major scientific advances that can change the rate of human aging itself, as opposed to merely treating the effects of aging as is done today. The Census Bureau also predicted that the United States would have 5.3 million people aged over 100 in 2100. The United Nations has also made projections far out into the future, up to 2300, where it projects that in 2300 life expectancies in most developed countries will be between 100 and 106 years, and still rising, though more and more slowly than before. However, these projections also show that life expectancies in poor countries will still be less than in rich countries in 2300, in some cases by as much as 20 years, and the UN itself mentioned that gaps in life expectancy so far in the future will likely not exist, especially since the exchange of technology between rich and poor countries and the industrialization and development of poor countries will cause their life expectancies to fully converge with those of rich countries long before that point, similarly to how life expectancies between rich and poor countries have already been converging over the last 60 years as better medicine, technology, and living conditions became accessible to many people in poor countries. The UN has warned that these projections are uncertain, and caution that any change or advancement in medical technology could invalidate their projections.

Recent increases in the rates of lifestyle diseases, such as obesity, diabetes, hypertension, and heart disease, may however drastically slow or reverse this trend toward increasing life expectancy in the developed world.

Oeppen and Vaupel have observed that since 1840 record life expectancy has risen linearly for men and women, albeit more slowly for men. For women the increase has been almost three months per year. In light of steady increase, without any sign of limitation, the suggestion that life expectancy will top out must be treated with caution. Oeppen and Vaupel observe that experts who assert that "life expectancy is approaching a ceiling ... have repeatedly been proven wrong." It is thought that life expectancy for women has increased more dramatically due to the considerable advances in medicine related to childbirth.

Some argue that molecular nanotechnology will greatly extend human lifespans. If the rate of increase of lifespan can be raised with these technologies to a level of not three months per year, but twelve months per year, we will have achieved effective immortality. This is the goal of radical life extension.

Non-human biological longevity

Living:

• Methuselah — 4,800-year-old bristlecone pine in the White Mountains of California, the oldest currently living organism known.
• Cheeta — a 76-year-old chimpanzee, the oldest chimpanzee known.

Dead:

• A bristlecone pine nicknamed "Prometheus", felled in the Great Basin National Park in Nevada in 1964, found to be about 4900 years old, is the longest-lived single organism known.
• A quahog clam (Arctica islandica), dredged from off the coast of Iceland in 2007, was found to be from 400 to 410 years old, the oldest animal documented. Other clams of the species have been recorded as living up to 374 years.
• Tu'i Malila, a radiated tortoise presented to the Tongan royal family by Captain Cook, lived for over 185 years. It is the oldest documented reptile. Adwaitya, an Aldabra Giant Tortoise, may have lived for up to 250 years.
• A Bowhead Whale killed in a hunt was found to be approximately 211 years old (possibly up to 245 years old), the longest lived mammal known.
• Lamellibrachia luymesi, a deep-sea cold-seep tubeworm, is estimated to reach ages of over 250 years based on a model of its growth rates.
• Hanako (Koi Fish) was the longest-lived vertebrate ever recorded at 215 years.