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The '''[[maximum life span]]''' is a measure of the maximum number of years a member of a group can be expected to survive. Normally defined as the oldest documented age of a member, maximum life span is expected to increase as living conditions improve. For example, animals often live longer in captivity than in the wild.
'''Maximum life span''' is a measure of the maximum number of years a member of a group can be expected to survive. '''Maximum life span''' corresponds to the age at which the oldest known member of a [[species]] or experimental group has died. [[Mean life span]] ([[average lifespan]] or [[life expectancy]]) corresponds to the age at which half of a species or experimental group is still alive (measured from time of [[birth]]). In animal studies, '''maximum life span''' is typically taken to be the [[mean life span]] of the most long-lived 10%.

[[Bird]]s and [[squirrel]]s rarely live to their maximum life span, usually dying of [[accident]]s and [[disease]]. Grazing animals show wear-and-tear to their teeth to the point where they can no longer eat, and they die of [[starvation]]. Maximum life span is expected to increase as living conditions improve. For example, animals often live longer in captivity than in the wild. Only with technology have humans and the animals they protect been able to become elderly and live to ages close their maximum life span.

In [[ancient Rome]] [[average life span]] was 22 years, but by the mid−1800s the typical North American lived to be 40. Today, people in the most developed countries have an [[average life span]] of about 80. Reduction of infant mortality has accounted for most of the increased [[longevity]], but since the 1960s [[mortality rate]]s among those over 80 years has been decreasing by about 1.5% per year. Maximum life span for humans, however, has remained about 115−120 all through known history. The longest documented human lifespan has been for Frenchwoman [[Jean Calment]] who lived 122.3 years.

Curing specific diseases such as [[heart disease]] or [[cancer]] can do no more than extend [[mean life span]] with no effect on maximum life span. Curing cancer would add about 2 years to human life, whereas eliminating heart disease would add 3 or 4 years. [[Mean life span]] varies with susceptibility to disease, [[accident]], [[suicide]] and [[murder|homicide]] , whereas maximum life span is determined by "rate of aging". In aging research, maximum life span is regarded as a proxy for aging. Chemicals, [[calorie restriction]] with adequate nutrition, or other interventions which increase maximum life span are said to have slowed the [[Senescence|aging process]].

If human beings were free of [[disease]] and [[senescence]] the only causes of death would be [[accident]], [[suicide]] and [[murder|homicide]]. Under such conditions it is estimated that from a population of one billion, a 12-year-old would have a median life span of 1,200 years and a maximum life span of 25,000 years.


The maximum life span of each species is different. For [[mice|mouse]], the record is 4; for [[dog]]s, 29; for [[cat]]s, 34; for [[horse]]s, 62; for [[elephant]]s, 78; for [[human]]s, 122. The longest-lived [[vertebrate]]s have been variously described as [[tortoise]]s (175 years) and [[whale]]s (about 210 years). Although considered fiction for a time, recent research has indicated that [[blue whale]]s recently killed still had [[harpoon]]s in their bodies from the 1790's, which has indicated a maximum life span so far of 211 years.
The maximum life span of each species is different. For [[mice|mouse]], the record is 4; for [[dog]]s, 29; for [[cat]]s, 34; for [[horse]]s, 62; for [[elephant]]s, 78; for [[human]]s, 122. The longest-lived [[vertebrate]]s have been variously described as [[tortoise]]s (175 years) and [[whale]]s (about 210 years). Although considered fiction for a time, recent research has indicated that [[blue whale]]s recently killed still had [[harpoon]]s in their bodies from the 1790's, which has indicated a maximum life span so far of 211 years.


The differences in maximum life span for different species clearly indicates the role of [[genetics]] in determining maximum life span.
⚫
[[Plant]]s, of course, tend to come in [[annual]]s, [[biennial]]s, and [[perennial]]s. The longer-lived perennials, woody-stemmed plants such as trees and bushes, often live for hundreds and even thousands of years. The oldest-known tree is the [[bristlecone pine]], at 4700 years; it has been claimed that [[creosote bush]]es live for 11,000 years, but claims of this nature are based on estimates, rather than actual [[ring count]]s.

The maximum life span of most species has not been determined with very great accuracy because the data collection has been minimal and the number of species studied in captivity (or by monitoring in the wild) has been small. Evolution selects a greater maximum life span for species that are larger, can fly and have larger brains Of the approximately 30,000 genes in the human [[genome]], it is estimated that only 2% of these are different from those of a chimpanzee, which has half the estimated maximum life span of a human. The [[longevity]] difference could be due to as few as a hundred [[gene]]s or less. Identical [[twin]]s tend to die within 3 years of each other, whereas fraternal twins tend to die within 6 years. [[Senescence|Aging theories]] associated with [[DNA]] include programmed aging (or programmed aging-resistance) and theories that link aging with DNA damage/mutation or [[DNA repair]] capability.

[[Mammal]]s fed [[antioxidant]]s show up to a 30% increase in [[mean life span]], but no increase in maximum life span. Antioxidants are most valuable for animals that are cancer-prone, or subjected to [[radiation]] or [[chemical]] toxins. There are evidently homeostatic mechanisms in [[cell]]s that govern the amount of allowable anti-oxidant activity. Many [[Life extension|life-extensionists]] have dismissed the value of antioxidants simply because they have not been shown to increase maximum life span -- as if extending [[mean life span]] was not important.

⚫
[[Plant]]s tend to come in [[annual]]s, [[biennial]]s, and [[perennial]]s. The longer-lived perennials, woody-stemmed plants such as trees and bushes, often live for hundreds and even thousands of years. The oldest-known tree is the [[bristlecone pine]], at 4700 years; it has been claimed that [[creosote bush]]es live for 11,000 years, but claims of this nature are based on estimates, rather than actual [[ring count]]s.

==Increasing maximum life span==
Currently, the only method of increasing maximum life span that is recognized by [[Gerontology|biogerontologists]] is [[calorie restriction]] with adequate nutrition. [[Rat]]s, [[mouse|mice]] and [[hamster]]s experience maximum life span extension from a diet which contains 40−60% of the calories (but all of the required nutrients) which the animals consume when they can eat as much as they want. [[Mean life span]] is increased 65% and maximum life span is increased 50%, when calorie restriction is begun just before [[puberty]]. For [[fruit flies]] the life extending benefits of calorie restriction are gained immediately at any age upon beginning calorie restriction and ended immediately at any age upon resuming full feeding [SCIENCE; Mair,W; 301:1731-1733 (2003)].

Mammals fed [[anti-oxidant]]s show up to a 30% increase in [[mean life span]], but no increase in maximum life span. [[Antioxidants]] are most valuable for animals that are cancer-prone, or subjected to [[radiation]] or [[chemical]] toxins. There are evidently homeostatic mechanisms in cells that govern the amount of allowable antioxidant activity. Many [[Life extension|life-extensionists]] have dismissed the value of antioxidants simply because they have not been shown to increase maximum life span -- as if extending [[mean life span]] was not important.

Some biomedical [[Gerontology|gerontologists]] (the kind of gerontologists who search for ways to extend maximum life span) believe that [[biomedical]] [[molecular]] [[engineering]] can someday extend maximum lifespan and even bring about [[Rejuvenation (aging)|rejuvenation]].
Once such researcher is [[Aubrey de Grey]], who calls his project to reverse the damage we call '''''aging''''' '''[[Engineered negligible senescence|SENS]]''' ('''[[Engineered negligible senescence|Strategies for Engineered Negligible Senescence]]'''). Dr. de Grey has established the [[The Methuselah Mouse Prize]] to award money to researchers who can extend the maximum life span of mice.

==Research data concerning maximum life span==
* A comparison of the [[heart]] [[mitochondria]] in rats (4-year maximum life span) and [[pigeon]]s (35-year maximum life span) showed that pigeon [[mitochondria]] leak fewer [[radical (chemistry)|free-radicals]] than rat mitochondria, despite the fact that both animals have similar [[metabolic rate]] and [[cardiac]] output
::[MECHANISMS OF AGING AND DEVELOPMENT 98:95-111 (1997)]

* For [[mammal]]s there is a direct relationship between [[mitochondria]]l [[membrane]] saturation and maximum life span
::[JOURNAL OF LIPID RESEARCH 39:1989-1994 (1998)]

* Studies of the [[liver]] [[lipid]]s of [[mammal]]s and a [[bird]] ([[pigeon]]) show an inverse relationship between maximum life span and number of [[double bond]]s
::[JOURNAL OF GERONTOLOGY 55A(6):B286-B291 (2000)]

* Maximum life span correlates negatively with [[antioxidant]] [[enzyme]] levels and correlates positively with lower rate of [[radical (chemistry)|free-radicals]] production and higher rate of [[DNA repair]]
::[JOURNAL OF COMPARATIVE PHYSIOLOGY B 168:149-158 (1998)]

* Females express both more Mn−SOD and more glutathione peroxidase antioxidant [[enzyme]]s than males, and this has been suggested to be the reason females live longer than males in [[mammal]]ian species
::[FEBS LETTERS; Vina,J; 579(12):2541-2545 (2005)]

* The maximum life span of transgenic mice has been extended about 20% by overexpression of human [[catalase]] targeted to [[mitochondria]]
::[SCIENCE; Schriner,SE; 308:1909-1911 (2005)]

* A comparison of 7 non-[[primate]] [[mammal]]s (mouse, hamster, rat, guinea-pig, rabbit, pig and cow) showed that the rate of [[mitochondrial]] superoxide and hydrogen peroxide production in [[heart]] and [[kidney]] were inversely correlated with maximum life span
::[FREE RADICAL BIOLOGY & MEDICINE 15:621-627 (1993)]

* A study of 8 non-[[primate]] [[mammals]] showed a direct correlation between maximum life span and oxidative damage to mtDNA in heart & brain
::[THE FASEB JOURNAL; Barja,G; 14(2):312-318 (2000)</A>]

* A study of several species of mammals and a bird (pigeon) indicated a linear relationship between oxidative damage to protein and maximum life span
::[EXPERIMENTAL GERONTOLOGY 31(3):387-392 (1996)]

* There is a direct correlation between [[DNA repair]] and maximum life span for [[mammal]]ian species
::[MECHANISMS OF AGING AND DEVELOPMENT; Cortopassi, GA; 91:211-218 (1996)]

* [[Drosophila]] (fruit-flies) bred for 15&nbsp;generations by only using eggs that were laid toward the end of reproductive life achieved maximum life spans 30&#37; greater than that of controls
::[JOURNALS OF GERONTOLOGY 55A(11):B552-B559 (2000)]

* A mutation in the <B>age&minus;1</B> gene of the [[nematode]] [[worm]] [[Caenorhabditis elegans]] inceased [[mean life span]] 65&#37; and maximum life span 110&#37;
::[GENETICS 118:75-86 (1988)]

* Fat-specific [[Insulin]] [[Receptor]] [[Knock-Out]] (<B>FIRKO</B>) mice have reduced fat mass, normal calorie intake and an increased maximum life span of 18&#37;
::[SCIENCE; Bluher,M; 299:572-574 (2003)]

* The capacity of mammalian species to detoxify the [[carcinogenic]] chemical benzo(a)pyrene to a water-soluble form also correlates well with maximum life span
::[EXPERIMENTAL CELL RESEARCH 116:359-364 (1978)]


==See also==
==See also==
*[[Life expectancy]]
* [[Ageing]]
* [[American aging association|American Aging Association]]
⚫
*[[Life extension]]
*[[Longevity]]
* [[Aubrey de Grey]]
* [[Gerontology|Biogerontology]]
* [[Biological immortality]]
* [[Calorie restriction]]
* [[Engineered negligible senescence]]
* [[Life expectancy]]
⚫
* [[Life extension]]
* [[Longevity]]
* [[The Methuselah Mouse Prize]]
* [[Senescence]]


==External links==
* [http://www.benbest.com/lifeext/aging.html Mechanisms of Aging]
* [http://www.senescence.info/ senescence.info] Informational website on the biology of aging.
* [http://www.calorierestriction.org/ Calorie Restriction Society]
* [http://www.longevitymeme.org/ The Longevity Meme (Longevity Activism)]
* [http://www.gen.cam.ac.uk/sens/ Strategies for Engineered Negligible Senescence (SENS)]


[[category:gerontology]]
[[Category:Gerontology]]
[[Category:Aging]]

Revision as of 03:23, 6 January 2006

Maximum life span is a measure of the maximum number of years a member of a group can be expected to survive. Maximum life span corresponds to the age at which the oldest known member of a species or experimental group has died. Mean life span (average lifespan or life expectancy) corresponds to the age at which half of a species or experimental group is still alive (measured from time of birth). In animal studies, maximum life span is typically taken to be the mean life span of the most long-lived 10%.

Birds and squirrels rarely live to their maximum life span, usually dying of accidents and disease. Grazing animals show wear-and-tear to their teeth to the point where they can no longer eat, and they die of starvation. Maximum life span is expected to increase as living conditions improve. For example, animals often live longer in captivity than in the wild. Only with technology have humans and the animals they protect been able to become elderly and live to ages close their maximum life span.

In ancient Rome average life span was 22 years, but by the mid−1800s the typical North American lived to be 40. Today, people in the most developed countries have an average life span of about 80. Reduction of infant mortality has accounted for most of the increased longevity, but since the 1960s mortality rates among those over 80 years has been decreasing by about 1.5% per year. Maximum life span for humans, however, has remained about 115−120 all through known history. The longest documented human lifespan has been for Frenchwoman Jean Calment who lived 122.3 years.

Curing specific diseases such as heart disease or cancer can do no more than extend mean life span with no effect on maximum life span. Curing cancer would add about 2 years to human life, whereas eliminating heart disease would add 3 or 4 years. Mean life span varies with susceptibility to disease, accident, suicide and homicide , whereas maximum life span is determined by "rate of aging". In aging research, maximum life span is regarded as a proxy for aging. Chemicals, calorie restriction with adequate nutrition, or other interventions which increase maximum life span are said to have slowed the aging process.

If human beings were free of disease and senescence the only causes of death would be accident, suicide and homicide. Under such conditions it is estimated that from a population of one billion, a 12-year-old would have a median life span of 1,200 years and a maximum life span of 25,000 years.

The maximum life span of each species is different. For mouse, the record is 4; for dogs, 29; for cats, 34; for horses, 62; for elephants, 78; for humans, 122. The longest-lived vertebrates have been variously described as tortoises (175 years) and whales (about 210 years). Although considered fiction for a time, recent research has indicated that blue whales recently killed still had harpoons in their bodies from the 1790's, which has indicated a maximum life span so far of 211 years.

The differences in maximum life span for different species clearly indicates the role of genetics in determining maximum life span.

The maximum life span of most species has not been determined with very great accuracy because the data collection has been minimal and the number of species studied in captivity (or by monitoring in the wild) has been small. Evolution selects a greater maximum life span for species that are larger, can fly and have larger brains Of the approximately 30,000 genes in the human genome, it is estimated that only 2% of these are different from those of a chimpanzee, which has half the estimated maximum life span of a human. The longevity difference could be due to as few as a hundred genes or less. Identical twins tend to die within 3 years of each other, whereas fraternal twins tend to die within 6 years. Aging theories associated with DNA include programmed aging (or programmed aging-resistance) and theories that link aging with DNA damage/mutation or DNA repair capability.

Mammals fed antioxidants show up to a 30% increase in mean life span, but no increase in maximum life span. Antioxidants are most valuable for animals that are cancer-prone, or subjected to radiation or chemical toxins. There are evidently homeostatic mechanisms in cells that govern the amount of allowable anti-oxidant activity. Many life-extensionists have dismissed the value of antioxidants simply because they have not been shown to increase maximum life span -- as if extending mean life span was not important.

Plants tend to come in annuals, biennials, and perennials. The longer-lived perennials, woody-stemmed plants such as trees and bushes, often live for hundreds and even thousands of years. The oldest-known tree is the bristlecone pine, at 4700 years; it has been claimed that creosote bushes live for 11,000 years, but claims of this nature are based on estimates, rather than actual ring counts.

Increasing maximum life span

Currently, the only method of increasing maximum life span that is recognized by biogerontologists is calorie restriction with adequate nutrition. Rats, mice and hamsters experience maximum life span extension from a diet which contains 40−60% of the calories (but all of the required nutrients) which the animals consume when they can eat as much as they want. Mean life span is increased 65% and maximum life span is increased 50%, when calorie restriction is begun just before puberty. For fruit flies the life extending benefits of calorie restriction are gained immediately at any age upon beginning calorie restriction and ended immediately at any age upon resuming full feeding [SCIENCE; Mair,W; 301:1731-1733 (2003)].

Mammals fed anti-oxidants show up to a 30% increase in mean life span, but no increase in maximum life span. Antioxidants are most valuable for animals that are cancer-prone, or subjected to radiation or chemical toxins. There are evidently homeostatic mechanisms in cells that govern the amount of allowable antioxidant activity. Many life-extensionists have dismissed the value of antioxidants simply because they have not been shown to increase maximum life span -- as if extending mean life span was not important.

Some biomedical gerontologists (the kind of gerontologists who search for ways to extend maximum life span) believe that biomedical molecular engineering can someday extend maximum lifespan and even bring about rejuvenation. Once such researcher is Aubrey de Grey, who calls his project to reverse the damage we call aging SENS (Strategies for Engineered Negligible Senescence). Dr. de Grey has established the The Methuselah Mouse Prize to award money to researchers who can extend the maximum life span of mice.

Research data concerning maximum life span

[MECHANISMS OF AGING AND DEVELOPMENT 98:95-111 (1997)]
[JOURNAL OF LIPID RESEARCH 39:1989-1994 (1998)]
[JOURNAL OF GERONTOLOGY 55A(6):B286-B291 (2000)]
[JOURNAL OF COMPARATIVE PHYSIOLOGY B 168:149-158 (1998)]
  • Females express both more Mn−SOD and more glutathione peroxidase antioxidant enzymes than males, and this has been suggested to be the reason females live longer than males in mammalian species
[FEBS LETTERS; Vina,J; 579(12):2541-2545 (2005)]
  • The maximum life span of transgenic mice has been extended about 20% by overexpression of human catalase targeted to mitochondria
[SCIENCE; Schriner,SE; 308:1909-1911 (2005)]
  • A comparison of 7 non-primate mammals (mouse, hamster, rat, guinea-pig, rabbit, pig and cow) showed that the rate of mitochondrial superoxide and hydrogen peroxide production in heart and kidney were inversely correlated with maximum life span
[FREE RADICAL BIOLOGY & MEDICINE 15:621-627 (1993)]
  • A study of 8 non-primate mammals showed a direct correlation between maximum life span and oxidative damage to mtDNA in heart & brain
[THE FASEB JOURNAL; Barja,G; 14(2):312-318 (2000)</A>]
  • A study of several species of mammals and a bird (pigeon) indicated a linear relationship between oxidative damage to protein and maximum life span
[EXPERIMENTAL GERONTOLOGY 31(3):387-392 (1996)]
[MECHANISMS OF AGING AND DEVELOPMENT; Cortopassi, GA; 91:211-218 (1996)]
  • Drosophila (fruit-flies) bred for 15 generations by only using eggs that were laid toward the end of reproductive life achieved maximum life spans 30% greater than that of controls
[JOURNALS OF GERONTOLOGY 55A(11):B552-B559 (2000)]
[GENETICS 118:75-86 (1988)]
  • Fat-specific Insulin Receptor Knock-Out (FIRKO) mice have reduced fat mass, normal calorie intake and an increased maximum life span of 18%
[SCIENCE; Bluher,M; 299:572-574 (2003)]
  • The capacity of mammalian species to detoxify the carcinogenic chemical benzo(a)pyrene to a water-soluble form also correlates well with maximum life span
[EXPERIMENTAL CELL RESEARCH 116:359-364 (1978)]

See also

External links

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