Life extension refers to an increase in maximum or average lifespan, especially in humans, by slowing down or reversing the processes of aging. Average lifespan is determined by vulnerability to accidents and age-related afflictions such as cancer or cardiovascular disease. Extension of average lifespan can be achieved by good diet, exercise and avoidance of hazards such as smoking. Maximum lifespan is determined by the rate of aging for a species inherent in its genes and probably by certain environmental factors. Currently, the only widely recognized method of extending maximum lifespan is calorie restriction. Theoretically, extension of maximum lifespan could be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues.
Researchers of life extension are known as biogerontologists. They seek to understand the nature of aging and they develop treatments to reverse aging processes or to at least slow them down, for the improvement of health and the maintenance of youthful vigor at every stage of life. (Biomedical gerontologists are distinguished from biogerontologists in that the latter may take a purely academic interest in the biological mechanisms of aging, without seeking a "cure".) Those who take advantage of life extension findings and seek to apply them upon themselves are called "life extensionists" or "longevists". The primary life extension strategy currently is to apply available anti-aging methods in the hope of living long enough to benefit from a complete cure to aging once it is developed. Raymond Kurzweil, a somewhat controversial futurist and transhumanist, believes that the rapidly advancing state of biogenetic and general medical technology could make this possible by approximately 2020.
Many biomedical gerontologists and life extensionists believe that future breakthroughs in tissue rejuvenation with stem cells, organs replacement (with artificial organs or xenotransplantations) and molecular repair will eliminate all aging and disease as well as allow for complete rejuvenation to a youthful condition. Whether such breakthroughs can occur within the next few decades is impossible to predict. Many life extensionists arrange to be cryonically preserved upon legal death so that they can await the time when future medicine can eliminate disease, rejuvenate them to a lasting youthful condition and repair damage caused by the cryonics process.
Whether the maximum human lifespan should be extended is the subject of much ethical debate amongst politicians and scientists. But the life extension movement, which began in the early 1980s, continues to grow rapidly in popularity and momentum among scientists and the general public.
Aging is an accumulation of damage to macromolecules, cells, tissues and organs. The maximum life span known for humans may be in excess of 120 years, whereas the maximum lifespan of a mouse, commonly used as a model in research on aging, is about four years. Genetic differences between humans and mice that may account for these different aging rates include efficiency of DNA repair, types and quantities of antioxidant enzymes, and different rates of free radical production.
Some supplements have been shown to be of benefit against some aging-related disease conditions, or have extended average lifespan in animals, though none have been proven to do so in humans. Calorie restriction and supplementation with the minerals selenium, chromium and zinc have been shown to extend maximum lifespan in mice. Metformin may also extend life span in mice, and in the first experiments with fish, resveratrol looks promising. (Resveratrol is presently (2006) being tested in mice.)
Dr. Denham Harman spent years experimenting with antioxidants, and was able to establish only that they can extend mean lifespan; he was unable to demonstrate an effect on maximum lifespan. Non-antioxidant nutrients (such as selenium, chromium and zinc) are more effective and have extended maximum lifespan. In response to what they saw as unscrupulous profiteering by those engaged in the selling of supplements and the practice of anti-aging medicine, a group of prominent biogerontologists began a "war" on anti-aging medicine in general and the A4M in particular. Jay Olshansky, Leonard Hayflick, and Bruce Carnes wrote a position paper against anti-aging medicine.
Politics relevant to the substances of life extension pertain mostly to communications and availability. In the United States, the claims which can be made on food and drug product labels are strictly regulated. Meanwhile, freedom of speech guaranteed by the First Amendment currently only protects the right of third-party publishers to print books, newsletters, websites, etc. on every aspect of these substances, including opinions, speculations, etc. Many manufacturers and suppliers also provide publications, but because they are also marketing the substances, they are subject to the monitoring and enforcement efforts of the Federal Trade Commission (FTC) which has jurisdiction over false claims made by marketers in public media. What constitutes the difference between truthful and false claims is hotly debated and is a central controversy in this arena.
Despite the results on yeast, fruit flies and nematodes, criticisms have been raised that the results of calorie restriction experiments on laboratory rats are not generalizable because years of inbreeding have made these animals different from those found in the wild. Even if it is conceded that the rat work may be generalizable to some extent, some argue that the results are applicable only to short-lived species that have evolved to respond to feast and famine with alterations in longevity. Proving that the results are generalizable in a way that encourages hope of extended life for human beings is difficult, because experiments with long-lived species necessarily take a very long time to perform.
Scientists have varying theories on why calorie restriction experiments would increase the life spans of the test animals. These include the habitat, the genetic line of the test subjects, and the nutritional content of the animal's diets, and the frequencies of feeding. Some critics observe that the test animals are not exposed to the same stresses that humans are in everyday life in modern environments, which may give humans a greater need for the calories.
The evidence for use of growth hormone is mixed. An early study suggested that supplementation of mice with growth hormone increased average life expectancy. Additional animal experiments have suggested that growth hormone may generally act to shorten maximum lifespan; knockout mice lacking the receptor for growth hormone live especially long.
Likewise, the Sir2 class of genes is conjectured to be involved in the calorie restriction mechanism; yeast genetically engineered to overexpress Sir2 live longer.
Large availability of insulin generally leads to shorter lifespan. Mice genetically engineered to lack an insulin receptor in fat tissue live longer. Mice with an overexpression of the Klotho gene, which limits insulin sensitivity, also show an extended lifespan.
Recently (2008), in an experience presented in a program of Portuguese television (RTP - ABciência - elixir da imortalidade), it was demonstrated, for the first time, that it is possible to immortalize yeast cells thanks to the effect of a vegetable extract. The plant biomolecules protect the cells in fatal conditions of oxidative and thermal stresses. This vegetable extract is seven times more powerful than resveratrol in the extension of the yeast chronological lifespan.
Recently, the US Department of Defense has initiated a program to regrow human body parts on mice, which could be removed and attached to the amputee.
Moral controversy surrounding stem cell research and human cloning continues to cloud the issue.
Similarly, therapeutic cloning is a way to generate cells, body parts, or in theory even whole bodies (generally referred to as reproductive cloning) genetically identical to a prospective patient. The controversies over cloning are similar to those over embryonic stem cell research, except general public opinion in most countries stands in even greater opposition to reproductive cloning. However, some proponents of therapeutic cloning argue that production of a never-conscious cloned soma might be the most successful and compassionate form of therapeutic cloning.
For those in cryonics, future medicine will not only be able to cure all disease and rejuvenate everyone to a youthful condition, but it will be able to repair any damage that is caused by the cryopreservation process. Molecular repair technology (nanotechnology and nanomedicine) is expected to be able to achieve these results. But to be safe, and to minimize damage, efforts have been made to eliminate all freezing damage through vitrification and to minimize ischemic damage through rapid cooling and cardio-pulmonary support immediately following pronouncement of death.
Cryonics is not freezing of humans or animals. Ice is very damaging to body tissues, so all cryonics organizations use cryoprotectants to prevent ice formation, i.e., anti-freeze substances that can reduce or prevent ice formation. Formerly cryonics organizations used glycerol as their cryoprotectant, which resulted in about 80% ice elimination (vitrification) and about 20% freezing. Cryonicists believed that damage that was being caused by disease, by aging and by the freezing would someday be repaired by nanotechnology. With vitrification the burden on future technology has been greatly reduced. With cells and tissues mainly preserved by cooling, future technology should be able to repair damage resulting if the cooling process is not too delayed.
Since the 1990s vitrification solutions have been developed that have virtually eliminated ice formation (reduced to less than 0.2%). In fact, it was announced in July 2005 that one such solution had been used to vitrify rabbit kidney at −135°C, and was later transplanted into a rabbit with full viability.
Stoppage of heartbeat and breathing, the usual criteria for legal death, do not correspond to the death of cells and tissues of the body. The cells and tissues are still very much alive when death is pronounced. Even at room temperature cells and tissues take hours to die, and days to decompose. Although neurological damage is the usual consequence of cessation of heartbeat for more than 4-6 minutes, the irreversible neurodegenerative processes do not manifest for hours.
Rapid cooling and cardio-pulmonary support applied immediately after pronouncement of death can preserve cells and tissues for long-term preservation at cryogenic temperatures. People, especially children, have survived up to an hour without heartbeat after having fallen into ice water. Full recovery has been reached for up to 45 minutes. Cryonics "standby teams" wait by the bedside of cryonics patients to apply cooling and cardio-pulmonary support as soon as possible after declaration of death. Cryonicists do not believe that legal death is real death (irreversible destruction of the anatomical basis of mind) any more than conventional medicine now accepts that cessation of heartbeat is "real death", when the heart can be restarted with a defibrillator.
Almost from the beginning the Society for Cryobiology has attacked cryonics as being "fraud" and "quackery" and has banned cryonicists from being members of the Society. There are cryonicists who are members, but they are necessarily discreet about their affiliations. Most of the members of the Society have also made it clear that they have non-scientific grounds for their hostility, including the usual anti-life extension arguments as well as aesthetic arguments.
As a result of a media circus surrounding following a 2003 Sports Illustrated article claiming that Alcor had mishandled the body of baseball super-star Ted Williams, a bill was passed in 2004 by the Arizona House of Representatives to place cryonics and cryonics procedures under the regulation of the state funeral board. In its original form, the law would have prevented Alcor's use of the Uniform Anatomical Gift Act. The bill was withdrawn while under consideration in the Arizona Senate. Although the Cryonics Institute (CI) was not responsible for Ted Williams, the media attention resulted in CI being placed under a "Cease and Desist" order by the State of Michigan for six months. Finally the Michigan government decided to regulate CI as a cemetery.
There are many people who have negative feelings about cryonics in general, and Alcor in particular. The Ted Williams affair has become a focus of such people. In many cases, cryonics was less an issue than the perception that the final wishes of Williams had not been respected and that Williams had not been treated with dignity.
In March, of 2006, Technology Review announced that it had chosen a panel of judges for the Challenge. On July 11, 2006, Technology Review published the results of the SENS Challenge. In the end, no one won the $20,000 prize. The judges felt that no submission met the criterion of the challenge and disproved SENS, although they unanimously agreed that one submission, by Preston Estep and his colleagues, was the most eloquent. In publishing the results, Technology Review also announced that it would make a $10,000 payment to Estep et al. in recognition of what the publication called their "careful scholarship." Although Estep et al. voiced their disapproval in a subsequent article, reiterating that they did agree with the goal of human life extension but considered that de Grey's approach was clearly pseudoscientific and that the panel of judges were mistaken in not admitting this (a position which Dr. de Grey characterised as “protest at the Challenge judges' failure to see SENS their way”). Estep et al. donated the entirety of the $10,000 to the American Federation for Aging Research.
Mind uploading is the transfer of the human mind/consciousness to a more durable material vessel (stereotypically but not necessarily a silicon computer). The concept is based on materialism, the philosophy of mind that argues that the human spirit is entirely composed of a very complex system of physical and chemical interactions. However, it is not understood how consciousness exists, and thus no existing scientific understanding for "reading" the "contents" of a human mind. With computer power increasing exponentially, and technology in the pipeline to keep up the trend, futurist Ray Kurzweil predicts that computer hardware will be powerful enough to run a functional model of the human mind by the 2020s. Several developing technologies hypothetically allow the complete mapping of human brains on a similar timescale. Uploading the human mind to a computer, if possible, would potentially greatly extend human lifespan due to the ability to construct highly durable computer hardware and the potential to copy or transfer the mind to multiple computers.
However, a key objection, if science were able to read and transfer the mind's contents, and a model of a human mind was then actually moved to a computer, would the personal identity of that human be retained? And what would be the status of personal identity after duplication?
A possible solution to the first objection is to interface biological humans brains with computer parts, and the gradual replacement of biological components with mechanical ones — functionally no different to the biological renewal of synapses. The philosophical Ship of Theseus enigma still remains with this solution.
The difficulty in seeing mind uploading as a solution is along the same lines of mind cloning and transporter duality paradox. The situation is contemplated where the mind is uploaded, yet the original mind remains. In this case, the person will still be themselves, and the clone will be alien to them, and vice versa. The biological mind would view itself as the original, but would die. The computer mind would view itself as original yet artificial. If the clone is a separate individual, then the consciousness of the original would still die. Even in the case where there is never a clone (killing the original upon mind uploading, or the gradual replacement of biological components) while the distinction would be less apparent, it would still be applicable in some regards.
Although the desire to extend life can be traced as far back as the Epic of Gilgamesh, it was the 1982 bestselling book Life Extension: A Practical Scientific Approach (ISBN 0-446-51229-X) by Durk Pearson and Sandy Shaw that popularized the phrase. In that book the authors detailed six major causes of aging, and presented dietary supplementation strategies for slowing down five of those. They also emphasized improving the quality of life, presenting methods of using the same dietary supplements that extend life to enhance sex (sex drive and sexual performance), cognitive function (intelligence, concentration, memory, mental stamina, etc.), stress management, sleep (quality of sleep, sleep reduction, and fast recovery from jet lag), athletic performance, body building, sports medicine, etc. The authors' two-pronged approach (showing how to live long and live well) makes their book a virtual nutritional toolbox, and this may account for why the book was so successful at kickstarting the life extension movement. Many other authors have followed this general strategy, promoting the quality of life applications of nutrients and drugs to attract readers to the subject of life extension.
The 1980 book The Life Extension Revolution (ISBN 0-688-03580-9) by Saul Kent did not sell so well. But Mr. Kent appeared on the Merv Griffin Show with Pearson and Shaw, and was able to use the flood of letters to create the nutraceutical firm called the Life Extension Foundation, which is non-profit. The Life Extension Foundation has grown to produce a magazine which has a large circulation. The group has a track record which includes promoting the benefits of many health supplements such as S-adenosyl methionine and melatonin many years before the medical field accepted the benefits of those substances.
Money generated by the Life Extension Foundation allowed Saul Kent to finance the Alcor Life Extension Foundation, the largest cryonics organization. The cryonics movement had been launched in 1962 by Robert Ettinger's book, The Prospect of Immortality. In the 1960s, Saul Kent had been a co-founder of the Cryonics Society of New York. Alcor gained national prominence when the baseball star Ted Williams was cryonically preserved by Alcor in 2002 and a family dispute arose as to whether Ted had really wanted to be cryopreserved.
In 1983, Dr. Roy Walford, a life-extensionist gerontologist published a popular book called Maximum Lifespan. Later, Dr. Walford and his student Dr. Richard Weindruch summarized years of their research into the ability of calorie restriction to extend the lifespan of rodents in their 1988 scholarly work The Retardation of Aging and Disease by Dietary Restriction (ISBN 0-398-05496-7). It had been known since the work of Clive McCay in the 1930s that calorie restriction can extend the maximum lifespan of rodents. But it was the work of Walford and Weindruch that gave detailed scientific grounding to that knowledge. Walford's personal interest in life extension motivated his scientific work and he practiced calorie restriction himself. Dr. Walford died at the age of 80 from complications caused by amyotrophic lateral sclerosis, a disease not firmly related to aging with causes still not understood.
For years the Food and Drug Administration (FDA) was in contention with the Life Extension Foundation, including through seizure of merchandise and court action. The FDA did not regard aging as a disease or life extension as a valid treatment category. In 1991 Saul Kent and Bill Faloon, the principals of the Foundation were jailed and told by the FDA that they would become the target of criminal indictments that would "destroy their lives forever and were advised to plead guilty of crimes against the state. Against legal advice, Kent and Faloon fought the FDA in court and filed countercharges concerning their mistreatment. In 1995 the FDA informed Kent and Faloon that, in exchange for a guilty plea, they would not have to go to prison and could continue doing business on a more limited basis. Instead of pleading guilty, Kent and Faloon filed a new battery of legal motions, escalated their counterattack against the FDA and began extensive preparations for their trial. In November 1995, the FDA dropped all charges except the charge of "obstruction of justice" against Saul Kent. In February 1996, this charge was also dropped.
In 1992 the American Academy of Anti-Aging Medicine (A4M) was formed to create an anti-aging medical specialty distinct from geriatrics, and to hold conferences for physicians interested in this field.
An important development in the life extension movement was the creation of the Usenet group, sci.life-extension. Brian M. Delaney created sci.life-extension in 1993, and the forum made possible, among other things, the creation of the CR Society.
A recent development in life extension has been the work of biogerontologist Aubrey de Grey of Cambridge University. Dr. de Grey proposes that damage to macromolecules, cells, tissues and organs can be repaired by advanced biotechnology.
The concept of actuarial escape velocity, invented by futurist and author Ray Kurzweil, posits that developments in life extension technology will reach a point at which the technology keeps pace with or even outpaces the rate at which humans age. This represents a kind of gateway to immortality.
Life extension is also associated with the potential problem of overpopulation. Leon Kass (chairman of the US President's Council on Bioethics from 2001 to 2005) has exemplified the anti-life extension view. He states his hostility to life extension with the words:
Some life extensionists perceive a lack of respect for individual choice in these words. This view would characterize Kass and others as seeking to use government power to ensure that no one's life is extended regardless of their wishes:
In retort to Leon Kass's stance, transhumanist philosopher Nick Bostrom published an article titled "The Fable of the Dragon-Tyrant", in which death is metaphorically personified as a monstrous dragon who demands horrific human sacrifices upon a mountain. A debate rages in the kingdom in the valley below between those who believe the dragon is a fact of life because he has existed for longer than any one can remember despite innumerable attempts to kill him, and those who believe the dragon is merely flesh and blood and that the kingdom has advanced to the point where a concerted effort may be mounted against him. In the end, the dragon-tyrant is killed by a ballistic missile launched from the valley, but not before a billion people die unnecessarily due to the initial fatalism and consequent inaction.