Longevity

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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.

The word 'longevity' is sometimes used as a synonym for "life expectancy" in demography. However, this is not the most popular or accepted definition.[1] 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).

Contents

[edit] History

There are many organizations dedicated to exploring the causes behind aging, ways to prevent aging, and ways to reverse aging. Despite the fact that it is human nature not to wish to surrender to old age and death, a few organizations are against antiaging, because they believe it sacrifices the best interests of the new generation, that it is unnatural, or unethical. Others are dedicated towards it, seeing it as a form of transhumanism and the pursuit of immortality. Even among those who do not wish for eternal life, longevity may be desired to experience more of life, or to provide a greater contribution to humanity.

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 account given by the ancients about the age of Democritus, appears to, without giving any specific age, agree in the fact that the philosopher lived over 100 years. This is a possibility that turns out to be likely given, not only by 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.), but also because of the difference that the case of Democritus evidences from the case of, for example, Epimenides of Crete (VII, VI centuries B.C.) of whom it is said to have lived 154, 157 or 290 years, like it has been said about countless elders even during the last centuries, as well as in present time. These cases are most likely (or at least in most cases) exaggerations, if not deliberate frauds.

[edit] 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:[2]

Population longevities can be seen as increasing due to increases in life expectancies around the world:[3][2][citation needed]

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.

[edit] Exceptions: Populations from developing world with high life expectancy

In the Anti-Aging Plan, it is reported that besides the Okinawans, people from the mountains of India (the Hunzas, the inhabitants from the high mountain valley of Villcabamba in South America and inhabitants in South Georgia have achieved extremely great life spans.[4] [5] [6]

[edit] Religion

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Further information: Longevity myths

The Bible contains many accounts of long-lived humans, the oldest being Methuselah living to be 969 years old (Genesis 5:27). Today some maintain that the unusually high longevity of Biblical patriarchs are the result of an error in translation: lunar cycles were mistaken for the solar ones, and that the actual ages being described would have been 12.4 times less (a lunar cycle being 29.5 days). This makes Methuselah's age only 78. This rationalization, however, seems doubtful too since patriarchs such as Mahalalel (Genesis 5:15) and Enoch (Genesis 5:21) were said to have become fathers after 65 "years". If the lunar cycle claim were accepted this would translate to an age of about 5 years and 3 months.

One claim of Christian scholars[who?] is that the life span of humans has changed; that originally man was to have everlasting life, but due to man's sin, God progressively shortened man's life in the "four falls of mankind" — first to less than 1000 years, then to under 500, 200, and eventually 120 years. After those long living people died around the time of the Biblical Flood, God decided that humans would not be permitted to live more than 120 years (Genesis 6:3) However, since later biblical figures (and more recent people) such as Sarah lived for longer than that, 120 years should be considered the "usual" upper limit to man's lifespan. Some individuals can live slightly longer than that.

Another theory proposed by a self-described “rational faith apologist”[who?] is based on the fact that some longevity specialists propose that aging occurs primarily due to telomere shortening during cell replication. Each time a cell replicates itself telomeres lose length until finally, replication cannot occur and the cells die. The theory postulates that prior to the flood there existed a thick cloud cover as described in Genesis. This cover protected DNA from UV and other radiation and their subsequent destructive mutation. Post flood with the cloud cover removed, UV rays and radiation could have caused both DNA and cellular destruction; specifically the type that cause telomere shortening or accelerated telomere shortening. As this mutation was passed on, shorter life spans would result for presumably both human and animals.

It has been hypothesized[who?] that there is a trade-off between cancerous tumor suppression and tissue repair capacity, and that by lengthening telomeres we might slow aging and in exchange increase vulnerability to cancer (Weinstein and Ciszek, 2002). Experimentation with telomeres on worms has yielded increased worm life spans by about 20% (Joeng et al., 2004). Even if further study shows that telomeres specifically are not tied to aging, the concept that some sort of DNA damage can cause genetically accelerated aging cannot be abandoned, thus providing a rational explanation for longevity and a subsequent reduction of longevity post-flood.

Many cultures like the Sumerians and Indus Valley also document groups of people who have lived for hundreds of years.

Furthermore, starting with reformers John Calvin and Martin Luther, an alternative explanation has arisen: 120 years would not refer to man's lifespan but to the amount of time left before the flood.

A more commonly accepted explanation[who?] is that such stories are longevity myths; age exaggeration tends to be greater in "mythical" periods in many cultures; the early emperors of Japan or China often ruled for more than a century, according to tradition. With the advent of modern accountable record-keeping, age claims fell to realistic levels. Even later in the Bible King David died at 70 years; other kings in their 30s, 40s, and 50s.

[edit] 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.[citation needed]

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 (see Science:1029, 2002) 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.

[edit] Non-human biological longevity

Main article: List of long-living organisms

Living:

Dead:

[edit] See also

[edit] Scientific books on longevity

  • Leonid A. Gavrilov & Natalia S. Gavrilova (1991), The Biology of Life Span: A Quantitative Approach. New York: Harwood Academic Publisher, ISBN
  • John Robbins' Healthy at 100 garners evidence from many scientific sources to account for the extraordinary longevity of Abkhasians in the Caucasus, Vilcabambans in the Andes, Hunzas in Central Asia, and Okinawans.
  • Beyond The 120-Year Diet, by Roy L. Walford, M.D.
  • Forever Young: A Cultural History of Longevity from Antiquity to the Present Door Lucian Boia,2004 ISBN 1861891547

[edit] References

  1. ^ longevity: Definition and Much More from Answers.com
  2. ^ a b CIA World Fact Book
  3. ^ CIA World Fact Book 2002
  4. ^ "The Anti-Aging Plan: Strategies and Recipes for Extending Your Healthy Years" by Roy Walford (page 27)
  5. ^ [The Okinawaprogram: Learn the secrets to healthy longevity by Willcox, Willcox and Suzuki (page 3)]
  6. ^ Long lived populations: Extreme old age. J Am Geriatr Soc 30:485-87
  7. ^ Carl Hall, "Staying Alive", San Francisco Chronicle, 23 August 1998
  8. ^ Bangor University: 400 year old Clam Found(retrieved 29 October 2007) BBC News: Ming the clam is 'oldest animal' (retrieved 29 October 2007)
  9. ^ Rozell (2001) "Bowhead Whales May Be the World's Oldest Mammals", Alaska Science Forum, Article 1529 (retrieved 29 October 2007)

[edit] External links

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See also Gerontology · Ageing