Certain scientists, futurists, and philosophers have theorized about the immortality of the human body, and advocate that human immortality is achievable in the first few decades of the 21st century, whereas other advocates believe that life extension is a more achievable goal in the short term, with immortality awaiting further research breakthroughs into an indefinite future. Aubrey de Grey, a researcher who has developed a series of biomedical rejuvenation strategies to reverse human aging (called SENS), believes that his proposed plan for ending aging may be implementable in two or three decades. The absence of aging would provide humans with biological immortality, but not invulnerability to death by physical trauma; although, mind uploading could solve that issue.
In religious contexts, immortality is often stated to be among the promises by God (or other deities) to human beings who show goodness or else follow divine law. What form an unending human life would take, or whether an immaterial soul exists and possesses immortality, has been a major point of focus of religion, as well as the subject of speculation, fantasy, and debate.
- Scientific 1.1
- Religious 1.2
- Alchemy 2
Physical immortality 3
Causes of death 3.1
- Aging 3.1.1
- Disease 3.1.2
- Trauma 3.1.3
- Environmental Change 3.1.4
Biological immortality 3.2
- Biologically immortal species 3.2.1
- Evolution of aging 3.2.2
Prospects for human biological immortality 3.3
- Life-extending substances 3.3.1
- Technological immortality 3.3.2
- Cryonics 3.3.3
- Mind-to-computer uploading 3.3.4
- Cybernetics 3.3.5
- Evolutionary immortality 3.3.6
- Causes of death 3.1
Religious views 4
- Ancient Greek religion 4.1
- Buddhism 4.2
- Christianity 4.3
- Hinduism 4.4
- Judaism 4.5
- Taoism 4.6
- Zoroastrianism 4.7
Ethics of immortality 5
- Undesirability of immortality 5.1
- Politics 6
- Symbols 7
- Fiction 8
- See also 9
- References 10
- Further reading 11
External links 12
- Religious and spiritual prospects for immortality 12.1
- In literature 12.2
Life extension technologies promise a path to complete rejuvenation. Cryonics holds out the hope that the dead can be revived in the future, following sufficient medical advancements. While, as shown with creatures such as hydra and planarian worms, it is indeed possible for a creature to be biologically immortal, it is not known if it is possible for humans.
Mind uploading is the transference of consciousness from a human brain to an alternative medium providing similar functionality. Assuming the process to be possible and repeatable, this would provide immortality to the computation of the original brain, as predicted by futurists such as Ray Kurzweil.
The belief in an afterlife is a fundamental tenet of most religions, including Hinduism, Buddhism, Sikhism, Christianity, Zoroastrianism, Islam, Judaism, and the Bahá'í Faith; however, the concept of an immortal soul is not. The "soul" itself has different meanings and is not used in the same way in different religions and different denominations of a religion. For example, various branches of Christianity have disagreeing views on the soul's immortality and its relation to the body.
Physical immortality is a state of life that allows a person to avoid death and maintain conscious thought. It can mean the unending existence of a person from a physical source other than organic life, such as a computer. Active pursuit of physical immortality can either be based on scientific trends, such as cryonics, digital immortality, breakthroughs in rejuvenation or predictions of an impending technological singularity, or because of a spiritual belief, such as those held by Rastafarians or Rebirthers.
Causes of death
metabolic processes, but which also, once they progress far enough, increasingly disrupt metabolism, resulting in pathology and death." The current causes of aging in humans are cell loss (without replacement), DNA damage, oncogenic nuclear mutations and epimutations, cell senescence, mitochondrial mutations, lysosomal aggregates, extracellular aggregates, random extracellular cross-linking, immune system decline, and endocrine changes. Eliminating aging would require finding a solution to each of these causes, a program de Grey calls engineered negligible senescence. There is also a huge body of knowledge indicating that change is characterized by the loss of molecular fidelity.
Disease is theoretically surmountable via
- Mary Shelley's The Mortal Immortal
- "Death and Immortality" Dictionary of the History of Ideas, etext at the University of Virginia Library
- "Immortality" Immortality – What Will Eternal Life Be Like?
- The Immortality of the Soul and the Resurrection of the Body Lecture by Heinrich J. Vogel
- An Essay on the Scriptural Doctrine of Immortality by James Challis
- Eternity: Christ’s Return, Chiliasm, Resurrection of the Dead, Judgment, Hell, Luther on Eternity, Heaven J.P. Meyer, The Northwestern Lutheran, August 22, 1954, Vol. 41, # 17 to April 14, 1957, Vol. 44, #8
- "How you Can Have Eternal Life" Jack Graham, PowerPoint Ministries, Christianity.com
- Got Eternal Life? Got Questions Ministries
- Immortality Taoist essay, personaltao.com
- The Trial to Conquer Death Ancient Scientific Yoga – The First Atom's Final Attempt
-  A review by Dr. Peter Fenwick of the book Human Immortality by Mohammad Samir Hossain
Religious and spiritual prospects for immortality
- Immortality entry in the Internet Encyclopedia of Philosophy
- Scientists are Close to Finding a Way to be Immortal
- Turritopsis nutricula:Palscience Meet The Only Immortal Species on Planet Earth
- The Methuselah Foundation Aubrey de Grey's non-profit organization dedicated to finding a cure for aging
- KurzweilAI.net Ray Kurzweil resource site
- BiologicalGerontology.com Chris Smelick's Biogerontology site
- Vitae Institute Chris Smelick's non-profit organization
- ELPIs Theory Marios Kyriazis' theory of human biological immortality
- Immortality Institute Scientific and sociological discussions, activism, research
- Endsjø, Dag Øistein (2008). “Immortal Bodies, Before Christ. Bodily Continuity in Ancient Greece and 1 Corinthians” in Journal for the Study of the New Testament 30 (2008):417-36.
- Bernstein C, Bernstein H. (1991) Aging, Sex, and DNA Repair. Academic Press, San Diego. ISBN 0120928604 ISBN 978-0120928606
- Gilberson, Lance, Zoology Lab Manual, 4th edition. Primis Custom Publishing. 1999.
- Clark, W.R. 1999. A Means to an End: The biological basis of aging and death. New York: Oxford University Press.  About telomeres and programmed cell death.
- Harrison's Principles of Internal Medicine, Ch. 69, Cancer cell biology and angiogenesis, Robert G. Fenton and Dan L. Longo, p. 454.
- Williams, G.C. 1957. Pleiotropy, natural selection and the evolution of senescence. Evolution, 11:398-411.  Paper in which Williams describes his theory of antagonistic pleiotropy.
- Kirkwood, T.B.L. 1977. Evolution of aging. Nature, 270: 301-304.  Origin of the disposable soma theory.
- Robert A. Freitas Jr., Microbivores: Artificial Mechanical Phagocytes using Digest and Discharge Protocol, self-published, 2001 
- Miconi T. Evolution and complexity: the double-edged sword. Artif Life. 2008 14(3:325-44
- Dag Øistein Endsjø. Greek Resurrection Beliefs and the Success of Christianity. New York: Palgrave Macmillan 2009; cf. Dag Øistein Endsjø “Immortal Bodies, Before Christ. Bodily Continuity in Ancient Greece and 1 Corinthians” in Journal for the Study of the New Testament 30 (2008):417-36.
- Dag Øistein Endsjø. Greek Resurrection Beliefs and the Success of Christianity. New York: Palgrave Macmillan 2009:47-104.
- Dag Øistein Endsjø. Greek Resurrection Beliefs and the Success of Christianity. New York: Palgrave Macmillan 2009:54-64; 100.
- Maharishi Mahesh Yogi on the Bhagavad-Gita, a New Translation and Commentary, Chapter 1-6. Penguin Books, 1969, pp 94-95 (v 15)
- "Even as we are conscious of the broad and very common biblical usage of the term "soul," we must be clear that scripture does not present even a rudimentarily developed theology of the soul. The creation narrative is clear that all life originates with God. Yet the Hebrew scripture offers no specific understanding of the origin of individual souls, of when and how they become attached to specific bodies, or of their potential existence, apart from the body, after death. The reason for this is that, as we noted at the beginning, the Hebrew Bible does not present a theory of the soul developed much beyond the simple concept of a force associated with respiration, hence, a life-force.", Avery-Peck, "Soul", in Neusner, et al. (eds.), "The Encyclopedia of Judaism", p. 1343 (2000)
- 2 Maccabees 7.11, 7.28.
- 1 Enoch 61.5, 61.2.
- 2 Baruch 50.2, 51.5
- Philip R. Davies. “Death, Resurrection and Life After Death in the Qumran Scrolls” in Alan J. Avery-Peck & Jacob Neusner (eds.) Judaism in Late Antiquity: Part Four: Death, Life-After-Death, Resurrection, and the World-To-Come in the Judaisms of Antiquity. Leiden 2000:209.
- Josephus Antiquities 18.16; Matthew 22.23; Mark 12.18; Luke 20.27; Acta 23.8.
- Acta 23.8.
- Josephus Jewish War 2.8.14; cf. Antiquities 8.14-15.
- Jubilees 23.31
- Maspero, Henri. Translated by Frank A. Kierman, Jr. Taoism and Chinese Religion (University of Massachusetts Press, 1981), p. 211.
- Robinet, Isabelle. Taoism: Growth of a Religion (Stanford: Stanford University Press, 1997 [original French 1992]), p. 3–4.
- Translated by Legge, James. The Texts of Taoism. 1962, Dover Press. NY.
- Hoshang, Dr. Bhadha. http://tenets.zoroastrianism.com/topi33.html
- Crown of Immortality
- Dyson's eternal intelligence
- Eternal youth
- Immortal DNA strand hypothesis
- Immortalist Society
- Internal alchemy
- List of people claimed to be immortal in myth and legend
- Methuselah Mouse Prize
- Molecular nanotechnology
- Negligible senescence
- Tipler's Omega Point
- Queen Mother of the West
- Rejuvenation (aging)
- Simulated reality
- Suspended animation
- Nikola Tesla
- Xian (Taoism)
There are numerous symbols representing immortality. The ankh is an Egyptian symbol of life that holds connotations of immortality when depicted in the hands of the gods and pharaohs, who were seen as having control over the journey of life. The Möbius strip in the shape of a trefoil knot is another symbol of immortality. Most symbolic representations of infinity or the life cycle are often used to represent immortality depending on the context they are placed in. Other examples include the Ouroboros, the Chinese fungus of longevity, the ten kanji, the phoenix, the peacock in Christianity, and the colors amaranth (in Western culture) and peach (in Chinese culture).
Although some scientists state that radical life extension, delaying and stopping aging are achievable, there are no international or national programs focused on stopping aging or on radical life extension. In 2012 in Russia, and then in the United States, Israel and the Netherlands, pro-immortality political parties were launched. They aimed to provide political support to anti-aging and radical life extension research and technologies and at the same time transition to the next step, radical life extension, life without aging, and finally, immortality and aim to make possible access to such technologies to most currently living people.
depicts immortality as "falling off the wheel of life" and is viewed as a curse as opposed to a blessing. Tuck Everlasting Likewise, the novel  Physical immortality has also been imagined as a form of eternal torment, as in
Undesirability of immortality
The Epic of Gilgamesh, one of the first literary works, is primarily a quest of a hero seeking to become immortal.
The possibility of clinical immortality raises a host of medical, philosophical, and religious issues and ethical questions. These include persistent vegetative states, the nature of personality over time, technology to mimic or copy the mind or its processes, social and economic disparities created by longevity, and survival of the heat death of the universe.
Ethics of immortality
Zoroastrians believe that on the fourth day after death, the human soul leaves the body and the body remains as an empty shell. Souls would go to either heaven or hell; these concepts of the afterlife in Zoroastrianism may have influenced Abrahamic religions. The word immortal is driven from the month "Amurdad", meaning "deathless" in Persian, in the Iranian calendar (near the end of July). The month of Amurdad or Ameretat is celebrated in Persian culture as ancient Persians believed the "Angel of Immortality" won over the "Angel of Death" in this month.
It is repeatedly stated in Lüshi Chunqiu that death is unavoidable. Henri Maspero noted that many scholarly works frame Taoism as a school of thought focused on the quest for immortality. Isabelle Robinet asserts that Taoism is better understood as a way of life than as a religion, and that its adherents do not approach or view Taoism the way non-Taoist historians have done. In the Tractate of Actions and their Retributions, a traditional teaching, spiritual immortality can be rewarded to people who do a certain amount of good deeds and live a simple, pure life. A list of good deeds and sins are tallied to determine whether or not a mortal is worthy. Spiritual immortality in this definition allows the soul to leave the earthly realms of afterlife and go to pure realms in the Taoist cosmology.
Rabbinic Judaism claims that the righteous dead will be resurrected in the Messianic age with the coming of the messiah. They will then be granted immortality in a perfect world. The wicked dead, on the other hand, will not be resurrected at all. This is not the only Jewish belief about the afterlife. The Tanakh is not specific about the afterlife, so there are wide differences in views and explanations among believers.
The views about immortality in Judaism is perhaps best exemplified by the various references to this in Second Temple Period. The concept of resurrection of the physical body is found in 2 Maccabees, according to which it will happen through recreation of the flesh. Resurrection of the dead also appears in detail in the extra-canonical books of Enoch, and in Apocalypse of Baruch. According to the British scholar in ancient Judaism Philip R. Davies, there is “little or no clear reference … either to immortality or to resurrection from the dead” in the Dead Sea scrolls texts. Both Josephus and the New Testament record that the Sadducees did not believe in an afterlife, but the sources vary on the beliefs of the Pharisees. The New Testament claims that the Pharisees believed in the resurrection, but does not specify whether this included the flesh or not. According to Josephus, who himself was a Pharisee, the Pharisees held that only the soul was immortal and the souls of good people will be reincarnated and “pass into other bodies,” while “the souls of the wicked will suffer eternal punishment.”  Jubilees seems to refer to the resurrection of the soul only, or to a more general idea of an immortal soul.
The Hebrew Bible speaks about Sheol (שאול), originally a synonym of the grave-the repository of the dead or the cessation of existence until the Resurrection. This doctrine of resurrection is mentioned explicitly only in Daniel 12:1–4 although it may be implied in several other texts. New theories arose concerning Sheol during the intertestamental literature.
The only Hebrew word traditionally translated "soul" (nephesh) in English language Bibles refers to a living, breathing conscious body, rather than to an immortal soul. In the New Testament, the Greek word traditionally translated "soul" (ψυχή) has substantially the same meaning as the Hebrew, without reference to an immortal soul. ‘Soul’ may refer to the whole person, the self: ‘three thousand souls’ were converted in Acts 2:41 (see Acts 3:23).
The traditional concept of an immaterial and immortal soul distinct from the body was not found in Judaism before the Babylonian Exile, but developed as a result of interaction with Persian and Hellenistic philosophies. Accordingly, the Hebrew word nephesh, although translated as "soul" in some older English Bibles, actually has a meaning closer to "living being". Nephesh was rendered in the Septuagint as ψυχή (psūchê), the Greek word for soul.
An Indian saint known as Vallalar claimed to have achieved immortality before disappearing forever from a locked room in 1874.
To Maharishi Mahesh Yogi, the verse means, "Once a man has become established in the understanding of the permanent reality of life, his mind rises above the influence of pleasure and pain. Such an unshakable man passes beyond the influence of death and in the permanent phase of life: he attains eternal life ... A man established in the understanding of the unlimited abundance of absolute existence is naturally free from existence of the relative order. This is what gives him the status of immortal life."
That man indeed whom these (contacts)
do not disturb, who is even-minded in
pleasure and pain, steadfast, he is fit
for immortality, O best of men.
Another view of immortality is traced to the Vedic tradition by the interpretation of Maharishi Mahesh Yogi:
There are explicit renderings in the Upanishads alluding to a physically immortal state brought about by purification, and sublimation of the 5 elements that make up the body. For example, in the Shvetashvatara Upanishad (Chapter 2, Verse 12), it is stated "When earth, water fire, air and akasa arise, that is to say, when the five attributes of the elements, mentioned in the books on yoga, become manifest then the yogi's body becomes purified by the fire of yoga and he is free from illness, old age and death." This phenomenon is possible when the soul reaches enlightenment while the body and mind are still intact, an extreme rarity, and can only be achieved upon the highest most dedication, meditation and consciousness.
Hindus believe in an immortal soul which is reincarnated after death. According to Hinduism, people repeat a process of life, death, and rebirth in a cycle called samsara. If they live their life well, their karma improves and their station in the next life will be higher, and conversely lower if they live their life poorly. After many life times of perfecting its karma, the soul is freed from the cycle and lives in perpetual bliss. There is no place of eternal torment in Hinduism, although if a soul consistently lives very evil lives, it could work its way down to the very bottom of the cycle.
his return. Part of this will be the resurrection of all the dead, who will 'awake', be embodied and participate in the renewal. Wright says John Polkinghorne, a physicist and a priest, has put it this way: 'God will download our software onto his hardware until the time he gives us new hardware to run the software again for ourselves.' That gets to two things nicely: that the period after death (the Intermediate state) is a period when we are in God's presence but not active in our own bodies, and also that the more important transformation will be when we are again embodied and administering Christ's kingdom." This kingdom will consist of Heaven and Earth "joined together in a new creation", he said.
Christian theology holds that Adam and Eve lost physical immortality for themselves and all their descendants in the Fall of Man, although this initial "imperishability of the bodily frame of man" was "a preternatural condition". Christians who profess the Nicene Creed believe that every dead person (whether they believed in Christ or not) will be resurrected from the dead at the Second Coming, and this belief is known as Universal resurrection.
The philosophical idea of an immortal soul was a belief first appearing with either Pherecydes or the Orphics, and most importantly advocated by Plato and his followers. This, however, never became the general norm in Hellenistic thought. As may be witnessed even into the Christian era, not least by the complaints of various philosophers over popular beliefs, many or perhaps most traditional Greeks maintained the conviction that certain individuals were resurrected from the dead and made physically immortal and that others could only look forward to an existence as disembodied and dead, though everlasting, souls. The parallel between these traditional beliefs and the later resurrection of Jesus was not lost on the early Christians, as Justin Martyr argued: "when we say ... Jesus Christ, our teacher, was crucified and died, and rose again, and ascended into heaven, we propose nothing different from what you believe regarding those whom you consider sons of Zeus." (1 Apol. 21).
Immortality in ancient Greek religion originally always included an eternal union of body and soul as can be seen in Homer, Hesiod, and various other ancient texts. The soul was considered to have an eternal existence in Hades, but without the body the soul was considered dead. Although almost everybody had nothing to look forward to but an eternal existence as a disembodied dead soul, a number of men and women were considered to have gained physical immortality and been brought to live forever in either Elysium, the Islands of the Blessed, heaven, the ocean or literally right under the ground. Among these were Amphiaraus, Ganymede, Ino, Iphigenia, Menelaus, Peleus, and a great part of those who fought in the Trojan and Theban wars. Some were considered to have died and been resurrected before they achieved physical immortality. Asclepius was killed by Zeus only to be resurrected and transformed into a major deity. In some versions of the Trojan War myth, Achilles, after being killed, was snatched from his funeral pyre by his divine mother Thetis, resurrected, and brought to an immortal existence in either Leuce, the Elysian plains, or the Islands of the Blessed. Memnon, who was killed by Achilles, seems to have a received a similar fate. Alcmene, Castor, Heracles, and Melicertes were also among the figures sometimes considered to have been resurrected to physical immortality. According to Herodotus' Histories, the 7th century BC sage Aristeas of Proconnesus was first found dead, after which his body disappeared from a locked room. Later he was found not only to have been resurrected but to have gained immortality.
Ancient Greek religion
As late as 1952, the editorial staff of the Syntopicon found in their compilation of the Great Books of the Western World, that "The philosophical issue concerning immortality cannot be separated from issues concerning the existence and nature of man's soul." Thus, the vast majority of speculation regarding immortality before the 21st century was regarding the nature of the afterlife.
Another approach, developed by biogerontologist Marios Kyriazis, holds that human biological immortality is an inevitable consequence of evolution. As the natural tendency is to create progressively more complex structures, there will be a time (Kyriazis claims this time is now), when evolution of a more complex human brain will be faster via a process of developmental singularity rather than through Darwinian evolution. In other words, the evolution of the human brain as we know it will cease and there will be no need for individuals to procreate and then die. Instead, a new type of development will take over, in the same individual who will have to live for many centuries in order for the development to take place. This intellectual development will be facilitated by technology such as synthetic biology, artificial intelligence and a technological singularity process.
Transforming a human into a brain implants or extracting a human processing unit and placing it in a robotic life-support system. Even replacing biological organs with robotic ones could increase life span (i.e., pace makers) and depending on the definition, many technological upgrades to the body, like genetic modifications or the addition of nanobots would qualify an individual as a cyborg. Some people believe that such modifications would make one impervious to aging and disease and theoretically immortal unless killed or destroyed.
Whatever the route to mind upload, persons in this state could then be considered essentially immortal, short of loss or traumatic destruction of the machines that maintained them.  One idea that has been advanced involves
aging is reversible. Modern cryonics procedures use a process called vitrification which creates a glass-like state rather than freezing as the body is brought to low temperatures. This process reduces the risk of ice crystals damaging the cell-structure, which would be especially detrimental to cell structures in the brain, as their minute adjustment evokes the individual's mind.
Technological immortality is the prospect for much longer life spans made possible by scientific advances in a variety of fields: nanotechnology, emergency room procedures, genetics, biological engineering, regenerative medicine, microbiology, and others. Contemporary life spans in the advanced industrial societies are already markedly longer than those of the past because of better nutrition, availability of health care, standard of living and bio-medical scientific advances. Technological immortality predicts further progress for the same reasons over the near term. An important aspect of current scientific thinking about immortality is that some combination of human cloning, cryonics or nanotechnology will play an essential role in extreme life extension. Robert Freitas, a nanorobotics theorist, suggests tiny medical nanorobots could be created to go through human bloodstreams, find dangerous things like cancer cells and bacteria, and destroy them. Freitas anticipates that gene-therapies and nanotechnology will eventually make the human body effectively self-sustainable and capable of living indefinitely in empty space, short of severe brain trauma. This supports the theory that we will be able to continually create biological or synthetic replacement parts to replace damaged or dying ones.
Embryonic stem cells express telomerase, which allows them to divide repeatedly and form the individual. In adults, telomerase is highly expressed in cells that need to divide regularly (e.g., in the immune system), whereas most somatic cells express it only at very low levels in a cell-cycle dependent manner.
In normal circumstances, without the presence of telomerase, if a cell divides repeatedly, at some point all the progeny will reach their Hayflick limit. With the presence of telomerase, each dividing cell can replace the lost bit of DNA, and any single cell can then divide unbounded. While this unbounded growth property has excited many researchers, caution is warranted in exploiting this property, as exactly this same unbounded growth is a crucial step in enabling cancerous growth. If an organism can replicate its body cells faster, then it would theoretically stop aging.
Some scientists believe that boosting the amount or proportion of in the body of telomerase, a naturally forming enzyme that helps maintain the protective caps at the ends of chromosomes, could prevent cells from dying and so may ultimately lead to extended, healthier lifespans. A team of researchers at the Spanish National Cancer Centre (Madrid) tested the hypothesis on mice. It was found that those mice which were genetically engineered to produce 10 times the normal levels of telomerase lived 50% longer than normal mice.
There are some known naturally occurring and artificially produced chemicals that may increase the lifetime or life-expectancy of a person or organism, such as resveratrol.
Prospects for human biological immortality
- Mutation accumulation is a theory formulated by Peter Medawar in 1952 to explain how evolution would select for aging. Essentially, aging is never selected against, as organisms have offspring before the mortal mutations surface in an individual.
- The disposable soma theory was proposed in 1977 by Thomas Kirkwood, which states that an individual body must allocate energy for metabolism, reproduction, and maintenance, and must compromise when there is food scarcity. Compromise in allocating energy to the repair function is what causes the body gradually to deteriorate with age, according to Kirkwood.
Modern theories on the evolution of aging include the following:
 This may be a tradeoff between selecting for cancer and selecting for aging. As the existence of biologically immortal species demonstrates, there is no
Evolution of aging
- Bacteria – Bacteria reproduce through binary fission. A parent bacterium splits itself into two identical daughter cells which eventually then split themselves in half. This process repeats, thus making the bacterium essentially immortal. A 2005 PLoS Biology paper suggests that after each division the daughter cells can be identified as the older and the younger, and the older is slightly smaller, weaker, and more likely to die than the younger.
- Turritopsis dohrnii, a jellyfish (phylum Cnidaria, class Hydrozoa, order Anthoathecata), after becoming a sexually mature adult, can transform itself back into a polyp using the cell conversion process of transdifferentiation. Turritopsis nutricula repeats this cycle, meaning that it may have an indefinite lifespan. Its immortal adaptation has allowed it to spread from its original habitat in the Caribbean to "all over the world".
- Hydra is a genus belonging to the phylum Cnidaria, the class Hydrozoa and the order Anthomedusae. They are simple fresh-water predatory animals possessing radial symmetry.
- Bristlecone pines are speculated to be potentially immortal; the oldest known living specimen is over 5,000 years old.
Life defined as biologically immortal is still susceptible to causes of death besides aging, including disease and trauma, as defined above. Notable immortal species include:
Biologically immortal species
Biologists have chosen the word immortal to designate cells that are not limited by the Hayflick limit, where cells no longer divide because of DNA damage or shortened telomeres. The first and still most widely used immortal cell line is HeLa, developed from cells taken from the malignant cervical tumor of Henrietta Lacks without her consent in 1951. Prior to the 1961 work of Leonard Hayflick and Paul Moorhead, there was the erroneous belief fostered by Alexis Carrel that all normal somatic cells are immortal. By preventing cells from reaching senescence one can achieve biological immortality; telomeres, a "cap" at the end of DNA, are thought to be the cause of cell aging. Every time a cell divides the telomere becomes a bit shorter; when it is finally worn down, the cell is unable to split and dies. Telomerase is an enzyme which rebuilds the telomeres in stem cells and cancer cells, allowing them to replicate an infinite number of times. No definitive work has yet demonstrated that telomerase can be used in human somatic cells to prevent healthy tissues from aging. On the other hand, scientists hope to be able to grow organs with the help of stem cells, allowing organ transplants without the risk of rejection, another step in extending human life expectancy. These technologies are the subject of ongoing research, and are not yet realized.
Biological immortality is an absence of aging, specifically the absence of a sustained increase in rate of mortality as a function of chronological age. A cell or organism that does not experience aging, or ceases to age at some point, is biologically immortal.
If there is no limitation on the degree of gradual mitigation of risk then it is possible that the cumulative probability of death over an infinite horizon is less than certainty, even when the risk of fatal trauma in any finite period is greater than zero. Mathematically, this is an aspect of achieving "actuarial escape velocity"
Organisms otherwise unaffected by these causes of death would still face the problem of obtaining sustenance (whether from currently available agricultural processes or from hypothetical future technological processes) in the face of changing availability of suitable resources as environmental conditions change. After avoiding aging, disease, and trauma, you could still starve to death.
Physical trauma would remain as a threat to perpetual physical life, as an otherwise immortal person would still be subject to unforeseen accidents or catastrophes. The speed and quality of paramedic response remains a determining factor in surviving severe trauma. A body that could automatically repair itself from severe trauma, such as speculated uses for nanotechnology, would mitigate this factor. Being the seat of consciousness, the brain cannot be risked to trauma if a continuous physical life is to be maintained. This aversion to trauma risk to the brain would naturally result in significant behavioral changes that would render physical immortality undesirable.
may restore sight to the blind. Drugs are being developed to treat a myriad of other diseases and ailments. nervous system and certain types of cancer have been discovered, allowing for new therapies to be developed. Artificial devices attached directly to the type 1 diabetes. Genes associated with tuberculosis and AIDS are being researched for Vaccines. cancer research are leading to treatments for telomere and cell biology. Breakthroughs in stem cells may soon be curable with the use of Alzheimer's and Parkinson's is becoming better understood. Neurodegenerative diseases like Preventative medicine is leading to cures and treatments for myriad previously incurable diseases. The mechanisms by which other diseases do their damage are becoming better understood. Sophisticated methods of detecting diseases early are being developed. genetics Human understanding of