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Biological Immortality
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Biological Immortality refers to a stable or decreasing rate of mortality from senescence,
thus decoupling it from chronological age. Various unicellular and multicellular species,
including some vertebrates, achieve this state either throughout their existence or after living
long enough. A biologically immortal living being can still die from means other than
senescence, such as through injury or disease.
This definition of immortality has been challenged in the new Handbook of the Biology of
Aging, because the increase in rate of mortality as a function of chronological age may be
negligible at extremely old ages, an idea referred to as the late-life mortality plateau. The rate
of mortality may cease to increase in old age, but in most cases that rate is typically very
high. As a hypothetical example, there is only a 50% chance of a human surviving another
year at age 110 or greater.
The term is also used by biologists to describe cells that are not subject to the Hayflick limit.
Cell lines
Biologists chose the word "immortal" to designate cells that are not subject to the Hayflick
limit, the point at which cells can no longer divide due to DNA damage or shortened
telomeres. Prior to Leonard Hayflick's theory, Alexis Carrel hypothesized that all normal
somatic cells were immortal.
The term "immortalization" was first applied to cancer cells that expressed the telomerelengthening enzyme telomerase, and thereby avoided apoptosis—i.e. cell death caused by
intracellular mechanisms. Among the most commonly used cell lines are HeLa and Jurkat,
both of which are immortalized cancer cell lines. HeLa cells originated from a sample of
cervical cancer taken from Henrietta Lacks in 1951. These cells have been and still are
widely used in biological research such as creation of the polio vaccine, sex hormone steroid
research, and cell metabolism. Normal stem cells and germ cells can also be said to be
immortal (when humans refer to the cell line).
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Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor
suppressor genes. One way to induce immortality is through viral-mediated induction of the
large T‑antigen, commonly introduced through simian virus 40 (SV-40).
Organisms
According to the Animal Ageing and Longevity Database, the list of organisms with
negligible aging (along with estimated longevity in the wild) includes:

Rougheye rockfish (Sebastes aleutianus) – 205 years

Olm (Proteus anguinus) – 102 years

Painted turtle (Chrysemys picta) – 61 years

Blanding's turtle (Emydoidea blandingii) – 77 years

Eastern box turtle (Terrapene carolina) – 138 years

Red sea urchin (Strongylocentrotus franciscanus) – 200 years

Ocean quahog clam (Arctica islandica) – 507 years

Great Basin bristlecone pine (Pinus longaeva) – 4,713 years
Bacteria and some yeast
Many unicellular organisms age: as time passes, they divide more slowly and ultimately die.
Asymmetrically dividing bacteria and yeast also age. However, symmetrically dividing
bacteria and yeast can be biologically immortal under ideal growing conditions. In these
conditions, when a cell splits symmetrically to produce two daughter cells, the process of cell
division can restore the cell to a youthful state. However, if the parent asymmetrically buds
off a daughter only the daughter is reset to the youthful state - the parent isn't restored and
will go on to age and die. In a similar manner stem cells and gametes can be regarded as
"immortal".
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Hydra
Hydras are a genus of the Cnidaria phylum. All cnidarians can regenerate, allowing them to
recover from injury and to reproduce asexually. Hydras are simple, freshwater animals
possessing radial symmetry and no post-mitotic cells. All hydra cells continually divide. It
has been suggested that hydras do not undergo senescence, and, as such, are biologically
immortal. In a four-year study, 3 cohorts of hydra did not show an increase in mortality with
age. It is possible that these animals live much longer, considering that they reach maturity in
5 to 10 days. However, this does not explain how hydras are consequently able to maintain
telomere lengths.
Jellyfish
Turritopsis dohrnii, or Turritopsis nutricula, is a small (5 millimeters (0.20 in)) species of
jellyfish that uses transdifferentiation to replenish cells after sexual reproduction. This cycle
can repeat indefinitely, potentially rendering it biologically immortal. This organism
originated in the Caribbean sea, but has now spread around the world. Similar cases include
hydrozoan Laodicea undulata and scyphozoan Aurelia sp.1.
Lobsters
Research suggests that lobsters may not slow down, weaken, or lose fertility with age, and
that older lobsters may be more fertile than younger lobsters. This does not however make
them immortal in the traditional sense, as they are significantly more likely to die at a shell
moult the older they get.
Their longevity may be due to telomerase, an enzyme that repairs long repetitive sections of
DNA sequences at the ends of chromosomes, referred to as telomeres. Telomerase is
expressed by most vertebrates during embryonic stages but is generally absent from adult
stages of life. However, unlike vertebrates, lobsters express telomerase as adults through
most tissue, which has been suggested to be related to their longevity. Contrary to popular
belief, lobsters are not immortal. Lobsters grow by moulting which requires a lot of energy,
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and the larger the shell the more energy is required. Eventually, the lobster will die from
exhaustion during a moult. Older lobsters are also known to stop moulting, which means that
the shell will eventually become damaged, infected, or fall apart and they die. The European
lobster has an average life span of 31 years for males and 54 years for females.
Planarian flatworms
Planarian flatworms have both sexually and asexually reproducing types. Studies on genus
Schmidtea mediterranea suggest these planarians appear to regenerate (i.e. heal) indefinitely,
and asexual individuals have an "apparently limitless (telomere) regenerative capacity fueled
by a population of highly proliferative adult stem cells". "Both asexual and sexual animals
display age-related decline in telomere length; however, asexual animals are able to maintain
telomere lengths somatically (ie during reproduction by fission or when regeneration is
induced by amputation), whereas sexual animals restore telomeres by extension during sexual
reproduction or during embryogenesis like other sexual species... homeostatic telomerase
activity observed in both asexual and sexual animals is not sufficient to maintain telomere
length, whereas the increased activity in regenerating asexuals is sufficient to renew telomere
length... "
Lifespan: For sexually reproducing planaria: "the life span of individual planarian can be as
long as 3 years, likely due to the ability of neoblasts to constantly replace aging cells.".
Whereas for asexually reproducing planaria: "individual animals in clonal lines of some
planarian species replicating by fission have been maintained for over 15 years"
Attempts to engineer biological immortality in humans
Although the premise that biological aging can be halted or reversed by foreseeable
technology remains controversial, research into developing possible therapeutic interventions
is underway. Among the principal drivers of international collaboration in such research is
the SENS Research Foundation, a non-profit organization that advocates a number of what it
claims are plausible research pathways that might lead to engineered negligible senescence in
humans.
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In 2015, Elizabeth Parrish, CEO of BioViva, treated herself using gene therapy, with the goal
of not just halting, but reversing aging. She has since reported feeling more energetic, but
long-term study of the treatment is ongoing.
For several decades, researchers have also pursued various forms of suspended animation as a
means by which to indefinitely extend mammalian lifespan. Some scientists have voiced
support for the feasibility of the cryopreservation of humans, known as cryonics. Cryonics is
predicated on the concept that some people considered clinically dead by today's medicolegal
standards are not actually dead according to information-theoretic death and can, in principle,
be resuscitated given sufficient technological advances. The goal of current cryonics
procedures is tissue vitrification, a technique first used to reversibly cryopreserve a viable
whole organ in 2005.
Similar proposals involving suspended animation include chemical brain preservation. The
non-profit Brain Preservation Foundation offers a cash prize valued at over $100,000 for
demonstrations of techniques that would allow for high-fidelity, long-term storage of a
mammalian brain.
Immortalism and immortality as a political cause
In 2012 in Russia, and then in the United States, Israel, and the Netherlands, pro-immortality
transhumanist political parties were launched. They aim to provide political support to antiaging and radical life extension research and technologies and want to ensure the fastest
possible—and at the same time, as least disruptive as possible—societal transition to radical
life extension, life without aging, and ultimately, immortality. They aim to make it possible to
provide access to such technologies to the majority of people alive today.
Other life extensionists
Biogerontologist Marios Kyriazis suggested that biological immortality in humans is an
inevitable consequence of natural evolution. His theory of extreme lifespans through
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perpetual-equalising interventions (ELPIs) proposes that the ability to attain indefinite
lifespans is inherent in human biology, and that there will come a time when humans will
continue to develop their intelligence by living indefinitely, rather than through evolution by
natural selection. Finite telomere regeneration would enable such a theory in biological
models upcoming.
Future medicine, life extension and "swallowing the doctor"
Future advances in nanomedicine could give rise to life extension through the repair of many
processes thought to be responsible for aging. K. Eric Drexler, one of the founders of
nanotechnology, postulated cell repair devices, including ones operating within cells and
utilizing as yet hypothetical molecular machines, in his 1986 book Engines of Creation.
Raymond Kurzweil, a futurist and transhumanist, stated in his book The Singularity Is Near
that he believes that advanced medical nanorobotics could completely remedy the effects of
aging by 2030. According to Richard Feynman, it was his former graduate student and
collaborator Albert Hibbs who originally suggested to him (circa 1959) the idea of a medical
use for Feynman's theoretical micromachines (see nanobiotechnology). Hibbs suggested that
certain repair machines might one day be reduced in size to the point that it would, in theory,
be possible to (as Feynman put it) "swallow the doctor". The idea was incorporated into
Feynman's 1959 essay There's Plenty of Room at the Bottom.
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