Indefinite lifespan or, indefinite life extension, is a term used in the life extension movement to refer to the longevity of humans, and other life-forms, under conditions in which aging can be effectively and completely prevented and treated. Such individuals would still be susceptible to accidental or intentional death by trauma or infectious diseases, but not death from aging. Their lifespans would be "indefinite," because protection from the effects of aging on health does not guarantee survival. Some life extensionists consider the term "indefinite lifespan" technically more correct than "immortality" which, especially in religious contexts, implies an inability to die.
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Life expectancy increases slightly every year as treatment strategies and technologies improve. At present, more than one year of research is required for each additional year of expected life. Actuarial escape velocity occurs when this ratio reverses, so that life expectancy increases faster than one year per one year of research, as long as that rate of advance is sustainable.[1][2][3]
The concept was first publicly proposed by David Gobel, founder of the Methuselah Foundation. The idea has been championed by biogerontologist Aubrey de Grey[4] and futurist Ray Kurzweil.[5] These two claim that by putting further pressure on science and medicine to focus research on increasing limits of aging, rather than continuing along at its current pace, more lives will be saved in the future, even if the benefit is not immediately apparent.[1]
The terms "immortality" and "eternal youth" are often used as synonyms for "indefinite lifespan", but they carry connotations from their other contexts which science has deemed to be impossible. That is, immortal means "incapable of dying". Eternal implies guaranteed existence for eternity, and in this context is also implausible because of entropy. Even if cures were found for all the degenerative diseases, and effective treatments were developed for all the processes of aging, so that bodies could be maintained as easily as cars can be repaired, people would still be killed in accidents, slain in wars, choosing to die, etc. The term indefinite lifespan represents this more achievable state of affairs, because it merely implies freedom from death by age or infirmity. The use of the term is also sometimes favored for reasons of linguistic aesthetics, in the same way that the term birth control is preferred to "birth prevention" or "birth elimination" which both imply, as does 'immortality', that the choice is one-time only and has permanent consequences, whereas the point of 'indefinite lifespans', like the point of 'birth control', is to gain the opportunity to lead one's life in a more conscious and deliberate manner.
This question is twofold. On the one hand it can be interpreted to mean, "Will a cure (or program of effective treatments) for aging ever be developed?" while on the other hand it could mean "Will the effective treatment of aging become available soon enough for those alive today to take advantage of it?" The answer to the first question is conditional on medical advancement: if medical science continues to advance in the fields of biogerontology and bioengineering, then some people hope the answer is "yes, that it will happen eventually, excepting if some event or series of events were to prevent the further advance of biological science" (see Risks to civilization, humans and planet Earth and the Doomsday Clock). Many scientists researching this area at the moment do not agree. They see a problem in not just individual diseases but in failure of repair mechanisms alluded to above in the discussion of thermodynamic considerations.
While science is constantly advancing and technology is becoming ever more sophisticated, the human body and mind are finitely complex and have not changed significantly in one hundred thousand years, and the aging process has not, in that time, become any more damaging (which, in short, is why we live three times as long on average in the twenty-first century as we did ten thousand years before).
The answer to the second question depends on two factors: the first being how fast medical science advances, and the second being how well each person takes care of himself (such as utilizing the best available life extension technology or not, and generally eating and behaving in a healthful and non-degrading way), both of which may affect whether or not a given person is still alive when the cure (or set of treatments) becomes available. This strategy is captured in the subtitle "Live Long Enough to Live Forever" of the popular life extension book Fantastic Voyage, by Ray Kurzweil and Terry Grossman, M.D.
The second factor to the second question hinges on the first factor - no amount of healthy living will enable somebody alive today to reach the point of indefinite lifespan if medical science is curtailed significantly, or if aging turns out to be massively more complex than currently believed. However, if biomedical gerontology continues to improve, if somatic genetic engineering becomes safe and effective (and is not banned by opponents) within the relatively near future, it may be conceivable for some of those now alive to attain indefinite lifespans.
According to biogerontologist Marios Kyriazis, indefinite lifespans will become possible (even inevitable) because of inherent properties of natural laws governing human evolution.[6] Kyriazis believes that[7] as humanity is enhanced by technology, human evolution by natural selection will become redundant, and humans will continue to evolve through an indefinitely-long process of self-development. This process will necessitate the elimination of death due to aging.[8]
Calorie restriction has been presented as a piece of the puzzle of reaching actuarial escape velocity.[2][3][5] Other proposed techniques include genetic engineering, telomere extension, organ regeneration, nanotechnology, and even mind uploading.[9]
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