Biological immortality (sometimes referred to as bio-indefinite mortality) is a state in which the rate of mortality from

senescence Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence inv ...

is stable or decreasing, thus decoupling it from

chronological Chronology (from Latin ''chronologia'', from Ancient Greek , ''chrónos'', "time"; and , ''-logia'') is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. It ...

age. Various unicellular and multicellular species, including some vertebrates, achieve this state either throughout their existence or after living long enough. A

biologically Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

immortal

living Living or The Living may refer to: Common meanings *Life, a condition that distinguishes organisms from inorganic objects and dead organisms ** Living species, one that is not extinct *Personal life, the course of an individual human's life * ...

being can still die from means other than senescence, such as through

injury An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, o ...

poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

, predation, lack of available resources, or changes to

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. This definition of

immortality Immortality is the concept of eternal life. Some modern species may possess biological immortality. Some scientists, futurists, and philosophers have theorized about the immortality of the human body, with some suggesting that human immorta ...

has been challenged in the ''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 age Old age refers to ages nearing or surpassing the life expectancy of human beings, and is thus the end of the human life cycle. Terms and euphemisms for people at this age include old people, the elderly (worldwide usage), OAPs (British usage ...

s, an idea referred to as the

late-life mortality plateau In gerontology, late-life mortality deceleration is the disputed theory that hazard rate increases at a decreasing rate in late life rather than increasing exponentially as in the Gompertz law. Late-life mortality deceleration is a well-establ ...

. The rate of mortality may cease to increase in old age, but in most cases that rate is typically very high. The term is also used by biologists to describe cells that are not subject to the Hayflick limit on how many times they can divide.

Cell lines

Biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...

s 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 DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...

or shortened

telomere A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature mos ...

s. Prior to

Leonard Hayflick Leonard Hayflick (born 20 May 1928) is a Professor of Anatomy at the UCSF School of Medicine, and was Professor of Medical Microbiology at Stanford University School of Medicine. He is a past president of the Gerontological Society of America and ...

's theory,

Alexis Carrel Alexis Carrel (; 28 June 1873 – 5 November 1944) was a French surgeon and biologist who was awarded the Nobel Prize in Physiology or Medicine in 1912 for pioneering vascular suturing techniques. He invented the first perfusion pump with Charle ...

hypothesized that all normal

somatic Somatic may refer to: * Somatic (biology), referring to the cells of the body in contrast to the germ line cells ** Somatic cell, a non-gametic cell in a multicellular organism * Somatic nervous system, the portion of the vertebrate nervous sys ...

cells were immortal. The term "immortalization" was first applied to

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

cells that expressed the telomere-lengthening

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

telomerase Telomerase, also called terminal transferase, is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most euka ...

, and thereby avoided

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

—i.e. cell death caused by intracellular mechanisms. Among the most commonly used cell lines are

HeLa HeLa (; also Hela or hela) is an immortalized cell line used in scientific research. It is the oldest and most commonly used human cell line. The line is derived from cervical cancer cells taken on February 8, 1951, named after Henrietta La ...

and

Jurkat Jurkat cells are an immortalized line of human T lymphocyte cells that are used to study acute T cell leukemia, T cell signaling, and the expression of various chemokine receptors susceptible to viral entry, particularly HIV. Jurkat cells can prod ...

, both of which are immortalized cancer cell lines.

HeLa cells HeLa (; also Hela or hela) is an immortalized cell line used in scientific research. It is the oldest and most commonly used human cell line. The line is derived from cervical cancer cells taken on February 8, 1951, named after Henrietta L ...

originated from a sample of

cervical cancer Cervical cancer is a cancer arising from the cervix. It is due to the abnormal growth of cells that have the ability to invade or spread to other parts of the body. Early on, typically no symptoms are seen. Later symptoms may include abnormal ...

taken from

Henrietta Lacks Henrietta Lacks (born Loretta Pleasant; August 1, 1920 – October 4, 1951) Note: Some sources report her birthday as August 2, 1920, vs. August 1, 1920. was an African-American woman whose cancer cells are the source of the HeLa cell line ...

in 1951. These cells have been and still are widely used in biological research such as creation of the

polio vaccine Polio vaccines are vaccines used to prevent poliomyelitis (polio). Two types are used: an inactivated poliovirus given by injection (IPV) and a weakened poliovirus given by mouth (OPV). The World Health Organization (WHO) recommends all chil ...

, sex hormone steroid research, and cell metabolism.

Embryonic stem cell Embryonic stem cells (ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre- implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consi ...

s and

germ cell Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embry ...

s have also been described as immortal. Immortal cell lines of cancer cells can be created by induction of

oncogenes An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.

or loss of

tumor suppressor gene A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a cell during cell division and replication. If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated, it results in a loss or red ...

s. 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 Aging and Longevity Database, the list of animals with negligible aging (along with estimated longevity in the wild) includes: *

Blanding's turtle Blanding's turtle (''Emydoidea blandingii'') is a semi-aquatic turtle of the family Emydidae. This species is native to central and eastern parts of Canada and the United States. It is considered to be an endangered species throughout much of i ...

(''Emydoidea blandingii'') – 77 years *

Olm The olm or proteus (''Proteus anguinus'') is an aquatic salamander in the family Proteidae, the only exclusively cave-dwelling chordate species found in Europe. In contrast to most amphibians, it is entirely aquatic, eating, sleeping, and br ...

(''Proteus anguinus'') – 102 years *

Eastern box turtle The eastern box turtle (''Terrapene carolina carolina'') is a subspecies within a group of hinge-shelled turtles normally called box turtles. ''T. c. carolina'' is native to the eastern part of the United States. The eastern box turtl ...

(''Terrapene carolina'') – 138 years *

Red sea urchin The red sea urchin (''Mesocentrotus franciscanus'') is a sea urchin found in the northeastern Pacific Ocean from Alaska to Baja California. It lives in shallow waters from the low-tide line to greater than deep, and is typically found on rocky ...

(''Strongylocentrotus franciscanus'') – 200 years * Rougheye rockfish (''Sebastes aleutianus'') – 205 years * Ocean quahog clam (''Arctica islandica'') – 507 years *

Greenland shark The Greenland shark (''Somniosus microcephalus''), also known as the gurry shark, grey shark, or by the Kalaallisut name ''eqalussuaq'', is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and souther ...

(''Somniosus microcephalus'') - 250 to 500 years In 2018, scientists working for

Calico Calico (; in British usage since 1505) is a heavy plain-woven textile made from unbleached, and often not fully processed, cotton. It may also contain unseparated husk parts. The fabric is far coarser than muslin, but less coarse and thick than ...

, a company owned by

Alphabet An alphabet is a standardized set of basic written graphemes (called letters) that represent the phonemes of certain spoken languages. Not all writing systems represent language in this way; in a syllabary, each character represents a syll ...

, published a paper in the journal ''

eLife ''eLife'' is a not-for-profit, peer-reviewed, open access, scientific journal for the biomedical and life sciences. It was established at the end of 2012 by the Howard Hughes Medical Institute, Max Planck Society, and Wellcome Trust, follow ...

'' which presents possible evidence that '' Heterocephalus glaber'' (Naked mole rat) do not face increased mortality risk due to aging.

Bacteria and some yeast

Many unicellular organisms age: as time passes, they divide more slowly and ultimately die. Asymmetrically dividing

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

also age. However, symmetrically dividing

and

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 Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

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 cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s and

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s can be regarded as "immortal".

Hydra

Hydras ''Hydra'' ( ) is a genus of small, freshwater organisms of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions. The genus was named by Linnaeus in 1758 after the Hydra, which was the many-headed b ...

are a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of the

Cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...

phylum. All cnidarians can regenerate, allowing them to recover from injury and to reproduce asexually. Hydras are simple,

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

animals possessing

radial symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pla ...

and contain post-

mitotic In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

cells (cells that will never divide again) only in the extremities. All hydra cells continually divide. It has been suggested that hydras do not undergo

, 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 subsequently able to maintain

lengths.

Jellyfish

Turritopsis dohrnii ''Turritopsis dohrnii'', also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to ...

'', or ''

Turritopsis nutricula ''Turritopsis nutricula'' is a small hydrozoan that once reaching adulthood, can transfer its cells back to childhood. This adaptive trait likely evolved in order to extend the life of the individual. Several different species of the genus ''Tur ...

'', is a small () species of

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

that uses

transdifferentiation Transdifferentiation, also known as lineage reprogramming, is the process in which one mature somatic cell is transformed into another mature somatic cell without undergoing an intermediate pluripotent state or progenitor cell type. It is a type ...

to replenish cells after

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

. This cycle can repeat indefinitely, potentially rendering it biologically immortal. This organism originated in the

Caribbean sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, but has now spread around the world. Key molecular mechanisms of its

rejuvenation Rejuvenation is a medical discipline focused on the practical reversal of the aging process. Rejuvenation is distinct from life extension. Life extension strategies often study the causes of aging and try to oppose those causes in order to slow ...

appear to involve

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...

and

repair The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential installa ...

, and stem cell renewal, according to a

comparative genomics Comparative genomics is a field of biological research in which the genomic features of different organisms are compared. The genomic features may include the DNA sequence, genes, gene order, regulatory sequences, and other genomic structural lan ...

study. Similar cases include hydrozoan '' Laodicea undulata'' and scyphozoan ''

Aurelia Aurelia may refer to: People * Version of feminine given name Aurélie * Aurelia (mother of Caesar) * Aurelia gens, a Roman family * Aurelia Browder, American civil rights activist * Astrud Aurelia, American drag queen Science * ''Aurelia'' (c ...

'' 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 (as detailed below). Their longevity may be due to

, an

that repairs long repetitive sections of

DNA sequence DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...

s at the ends of chromosomes, referred to as

telomeres A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature mos ...

. 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 In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

which requires considerable energy, 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 ''Homarus gammarus'', known as the European lobster or common lobster, is a species of clawed lobster from the eastern Atlantic Ocean, Mediterranean Sea and parts of the Black Sea. It is closely related to the American lobster, ''H. ameri ...

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 ''Schmidtea mediterranea'' is a freshwater triclad that lives in southern Europe and Tunisia. It is a model for regeneration, stem cells and development of tissues such as the brain and germline. Distribution ''Schmidtea mediterranea'' is foun ...

suggest these planarians appear to regenerate (i.e. heal) indefinitely, and asexual individuals have an "apparently limitless elomereregenerative 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 (i.e. during reproduction by fission or when regeneration is induced by

amputation Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on indi ...

), 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... " For sexually reproducing planaria: "the lifespan 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".Archived a
Ghostarchive
and th
Wayback Machine

References

Bibliography

James L. Halperin James L. Halperin (born October 31, 1952) is an American businessman and author, who is the co-founder and co-chairman of Heritage Auctions, now the largest American auction house with 2022 sales in excess of $1.45 billion. In 1985 Halperin author ...

. ''The First Immortal'', Del Rey, 1998. *

Robert Ettinger Robert Chester Wilson Ettinger (December 4, 1918 – July 23, 2011) was an American academic, known as "the father of cryonics" because of the impact of his 1962 book ''The Prospect of Immortality''. Ettinger founded the Cryonics Institute ...

. ''The Prospect of Immortality'', Ria University Press, 2005. * Dr. R. Michael Perry. ''Forever For All: Moral Philosophy, Cryonics, and the Scientific Prospects for Immortality'', Universal Publishers, 2001. * Martinez, D.E. (1998) "Mortality patterns suggest lack of senescence in hydra." ''Experimental Gerontology'' 1998 May;33(3):217–225
Full text.
* {{DEFAULTSORT:Biological Immortality Emerging technologies Immortality Senescence