Thehuman skull is used universally as a symbol of death.[1]
Death is the end oflife, theirreversible cessation of allbiological functions that sustain a livingorganism.[2] Death eventually and inevitably occurs in all organisms. The remains of a former organism normally begin todecompose shortly after death.[3] Some organisms, such asTurritopsis dohrnii, arebiologically immortal; however, they can still die from means other thanaging.[4] Death is generally applied to whole organisms; the equivalent for individual components of an organism, such ascells ortissues, isnecrosis.[5] Something that is not considered an organism can be physically destroyed but is not said to die, as it is not considered alive in the first place.
As of the early 21st century, 56 million people die per year. The most common reason isaging,[6] followed bycardiovascular disease, which is adisease that affects theheart orblood vessels.[7] As of 2022, an estimated total of almost 110 billion humans have died, or roughly 94% of all humans to have ever lived.[8] A substudy ofgerontology known asbiogerontology seeks to eliminate death by natural aging in humans, often through the application of natural processes found in certain organisms.[9] However, as humans do not have the means to apply this to themselves, they have to use other ways to reach themaximum lifespan for a human, often throughlifestyle changes, such ascalorie reduction,dieting, andexercise.[10] The idea oflifespan extension is considered and studied as a way for people to live longer.
Determining when a person has definitively died has proven difficult. Initially, death was defined as occurring when breathing and the heartbeat ceased, a status still known asclinical death.[11] However, the development ofcardiopulmonary resuscitation (CPR) meant that such a state was no longer strictly irreversible.[12]Brain death was then considered a more fitting option, but several definitions exist for this. Some people believe that all brain functions must cease. Others believe that even if thebrainstem is still alive, thepersonality and identity are irretrievably lost, so therefore, the person should be considered entirely dead.[13] Brain death is sometimes used as a legal definition of death.[14] For all organisms with a brain, death can instead be focused on this organ.[15][16] Thecause of death is usually considered important, and anautopsy can be done to determine it. There are many causes, from accidents to diseases.
Many cultures and religions have a concept of anafterlife. There are also different customs for honoring the body, such as afuneral,cremation, orsky burial.[17] After a death, anobituary may be posted in a newspaper, and the "survived by" kin and friends usually go through thegrieving process.
There are many scientific approaches and various interpretations of the concept. Additionally, the advent of life-sustaining therapy and the numerous criteria for defining death from both a medical and legal standpoint have made it difficult to create a single unifying definition.[18]
Defining life to define death
One of the challenges in defining death is in distinguishing it from life. As a point in time, death seems to refer to the moment when life ends. Determining when death has occurred is difficult, as cessation of life functions is often not simultaneous across organ systems.[19] Such determination, therefore, requires drawing precise conceptual boundaries between life and death. This is difficult due to there being little consensus on how to define life.
A flower, a skull, and an hourglass symbolize life, death, and time in this 17th-century painting byPhilippe de Champaigne.[20]
It is possible to define life in terms ofconsciousness. When consciousness ceases, an organism can be said to have died. One of the flaws in this approach is that there are many organisms that are alive but probably not conscious.[21] Another problem is in defining consciousness, which has many different definitions given by modern scientists, psychologists and philosophers.[22] Additionally, many religious traditions, includingAbrahamic andDharmic traditions, hold that death does not (or may not) entail the end of consciousness. In certain cultures, death is more of a process than a single event. It implies a slow shift from one spiritual state to another.[23]
Other definitions for death focus on the character of cessation of organismic functioning and human death, which refers to irreversible loss of personhood. More specifically, death occurs when a living entity experiences irreversible cessation of all functioning.[24] As it pertains to human life, death is an irreversible process where someone loses their existence as a person.[24]
Definition of death by heartbeat and breath
Historically, attempts to define the exact moment of a human's death have been subjective or imprecise. Death was defined as the cessation ofheartbeat (cardiac arrest) andbreathing,[11] but the development ofCPR and promptdefibrillation have rendered that definition inadequate because breathing and heartbeat can sometimes be restarted.[12] This type of death where circulatory and respiratory arrest happens is known as the circulatory definition of death (CDD). Proponents of the CDD believe this definition is reasonable because a person with permanent loss of circulatory and respiratory function should be considered dead.[25] Critics of this definition state that while cessation of these functions may be permanent, it does not mean the situation is irreversible because if CPR is applied fast enough, the person could be revived.[25] Thus, the arguments for and against the CDD boil down to defining the actual words "permanent" and "irreversible," which further complicates the challenge of defining death. Furthermore, eventscausally linked to death in the past no longer kill in all circumstances; without a functioning heart or lungs, life can sometimes be sustained with a combination oflife support devices,organ transplants, andartificial pacemakers.
Today, where a definition of the moment of death is required, doctors and coroners usually turn to "brain death" or "biological death" to define a person as being dead;[26] people are considered dead when the electrical activity in their brain ceases.[27] It is presumed that an end of electrical activity indicates the end ofconsciousness.[28] Suspension of consciousness must be permanent and not transient, as occurs during certainsleep stages, and especially a coma.[29] In the case of sleep,electroencephalograms (EEGs) are used to tell the difference.[30]
The category of "brain death" is seen as problematic by some scholars. For instance, Dr. Franklin Miller, a senior faculty member at the Department of Bioethics, National Institutes of Health, notes: "By the late 1990s... the equation of brain death with death of the human being was increasingly challenged by scholars, based on evidence regarding the array of biological functioning displayed by patients correctly diagnosed as having this condition who were maintained on mechanical ventilation for substantial periods of time. These patients maintained the ability to sustain circulation and respiration, control temperature, excrete wastes, heal wounds, fight infections and, most dramatically, to gestate fetuses (in the case of pregnant "brain-dead" women)."[31]
French 16th-/17th-century ivory pendant, Monk and Death, recalling mortality and the certainty of death (Walters Art Museum)[32]
While "brain death" is viewed as problematic by some scholars, there are proponents of it[who?] that believe this definition of death is the most reasonable for distinguishing life from death. The reasoning behind the support for this definition is that brain death has a set of criteria that is reliable and reproducible. Also, the brain is crucial in determining our identity or who we are as human beings. The distinction should be made that "brain death" cannot be equated with one in a vegetative state or coma, in that the former situation describes a state that is beyond recovery.[33]
EEGs can detect spurious electrical impulses, while certain drugs,hypoglycemia,hypoxia, orhypothermia can suppress or even stop brain activity temporarily;[34] because of this, hospitals have protocols for determining brain death involving EEGs at widely separated intervals under defined conditions.[35]
Neocortical brain death
One view is that theneocortex of the brain is necessary for consciousness, and that therefore only electrical activity of the neocortex should be considered when defining death. Eventually, the criterion for death may be the permanent and irreversible loss ofcognitive function, as evidenced by the death of thecerebral cortex. All hope of recovering human thought andpersonality is then gone, given current and foreseeable medical technology.[13] Even by whole-brain criteria, the determination of brain death can be complicated.
Total brain death
At present, in most places, the more conservative definition of death (irreversible cessation of electrical activity in the whole brain, as opposed to just in the neo-cortex) has been adopted. One example is theUniform Determination Of Death Act in the United States.[36] In the past, the adoption of this whole-brain definition was a conclusion of the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research in 1980.[37] They concluded that this approach to defining death sufficed in reaching a uniform definition nationwide. A multitude of reasons was presented to support this definition, including uniformity of standards in law for establishing death, consumption of a family's fiscal resources for artificial life support, and legal establishment for equating brain death with death to proceed withorgan donation.[38]
Problems in medical practice
Aside from the issue of support of or dispute against brain death, there is another inherent problem in this categorical definition: the variability of its application in medical practice. In 1995, the American Academy of Neurology (AAN) established the criteria that became the medical standard for diagnosing neurologic death. At that time, three clinical features had to be satisfied to determine "irreversible cessation" of the total brain, including coma with clear etiology, cessation of breathing, and lack of brainstem reflexes.[39] These criteria were updated again, most recently in 2010, but substantial discrepancies remain across hospitals and medical specialties.[39]
Donations
The problem of defining death is especially imperative as it pertains to thedead donor rule, which could be understood as one of the following interpretations of the rule: there must be an official declaration of death in a person before starting organ procurement, or that organ procurement cannot result in the death of the donor.[25] A great deal of controversy has surrounded the definition of death and the dead donor rule. Advocates of the rule believe that the rule is legitimate in protecting organ donors while also countering any moral or legal objection to organ procurement. Critics, on the other hand, believe that the rule does not uphold the best interests of the donors and that the rule does not effectively promote organ donation.[25]
The death of a person has legal consequences that may vary between jurisdictions. Most countries follow the whole-brain death criteria, where all functions of the brain must have completely ceased. However, in other jurisdictions, some follow the brainstem version of brain death.[39] Afterward, adeath certificate is issued in most jurisdictions, either by a doctor or by an administrative office, upon presentation of a doctor's declaration of death.[42]
There are many anecdotal references to people being declared dead by physicians and then "coming back to life," sometimes days later in their coffin or whenembalming procedures are about to begin. From the mid-18th century onwards, there was an upsurge in the public's fear of being mistakenly buried alive[43] and much debate about the uncertainty of the signs of death. Various suggestions were made to test for signs of life before burial, ranging from pouring vinegar and pepper into the corpse's mouth to applying red hot pokers to the feet or into therectum.[44] Writing in 1895, the physician J.C. Ouseley claimed that as many as 2,700 people were buried prematurely each year in England and Wales, although some estimates peg the figure to be closer to 800.[45]
As medical technologies advance, ideas about when death occurs may have to be reevaluated in light of the ability to restore a person to vitality after longer periods of apparent death (as happened when CPR and defibrillation showed that cessation of heartbeat is inadequate as a decisive indicator of death). The lack of electrical brain activity may not be enough to consider someone scientifically dead. Therefore, the concept of information-theoretic death has been suggested as a better means of defining when true death occurs, though the concept has few practical applications outside the field ofcryonics.[47]
The leading cause of human death indeveloping countries isinfectious disease. The leading causes indeveloped countries areatherosclerosis (heart disease and stroke), cancer, and other diseases related toobesity andaging. By an extremely wide margin, the largest unifying cause of death in the developed world is biological aging,[48] leading to various complications known asaging-associated diseases. These conditions cause loss ofhomeostasis, leading to cardiac arrest, causing loss ofoxygen and nutrient supply, causing irreversible deterioration of the brain and othertissues. Of the roughly 150,000 people who die each day across the globe, about two thirds die of age-related causes.[48] In industrialized nations, the proportion is much higher, approaching 90%.[48] With improved medical capability,dying has becomea condition to be managed.
According toJean Ziegler, the United Nations Special Reporter on the Right to Food, 2000 – Mar 2008, mortality due tomalnutrition accounted for 58% of the total mortality rate in 2006. Ziegler says worldwide, approximately 62 million people died from all causes and of those deaths, more than 36 million died of hunger or diseases due to deficiencies inmicronutrients.[53]
American children smoking in 1910.Tobacco smoking caused an estimated 100 million deaths in the 20th century.[54]
Tobacco smoking killed 100 million people worldwide in the 20th century and could kill 1 billion people worldwide in the 21st century, aWorld Health Organization report warned.[54]
Many leading developed world causes of death can be postponed bydiet andphysical activity, but the accelerating incidence of disease with age still imposes limits on humanlongevity. Theevolutionary cause of aging is, at best, only beginning to be understood. It has been suggested that direct intervention in the aging process may now be the most effective intervention against major causes of death.[55]
Selye proposed a unified non-specific approach to many causes of death. He demonstrated thatstress decreases the adaptability of an organism and proposed to describe adaptability as a special resource,adaptation energy. The animal dies when this resource is exhausted.[56] Selye assumed that adaptability is a finite supply presented at birth. Later, Goldstone proposed the concept of production or income of adaptation energy which may be stored (up to a limit) as a capital reserve of adaptation.[57] In recent works, adaptation energy is considered an internal coordinate on the "dominant path" in the model of adaptation. It is demonstrated that oscillations of well-being appear when the reserve of adaptability is almost exhausted.[58]
Natural disasters kill around 45,000 people annually, although this number can vary from thousands to millions on a per-decade basis. Some of the deadliest natural disasters are the1931 China floods, which killed an estimated 4 million people, although estimates widely vary;[65] the1887 Yellow River flood, which killed an estimated 2 million people in China;[66] and the1970 Bhola cyclone, which killed as many as 500,000 people inEast Pakistan (present-dayBangladesh).[67] If naturally occurringfamines are considered natural disasters, theChinese famine of 1906–1907, which killed 15–20 million people, can be considered the deadliest natural disaster in recorded history.
In animals,predation can be a common cause of death. Livestock have a 6% death rate from predation. However, younger animals are more susceptible to predation. For example, 50% of young foxes die tobirds,bobcats,coyotes, andother foxes as well. Young bear cubs in theYellowstone National Park only have a 40% chance to survive to adulthood from other bears and predators.[68]
An autopsy, also known as apostmortem examination or anobduction, is amedical procedure that consists of a thoroughexamination of a humancorpse to determine the cause and manner of a person's death and to evaluate any disease or injury that may be present. It is usually performed by a specializedmedical doctor called apathologist.[69]
Autopsies are either performed for legal or medical purposes.[69] A forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes.[70] Autopsies can be further classified into cases where external examination suffices, and those where the body is dissected and an internal examination is conducted.[71] Permission fromnext of kin may be required for internal autopsy in some cases.[72] Once an internal autopsy is complete the body is generally reconstituted by sewing it back together.[41]
A necropsy, which is not always a medical procedure, was a term previously used to describe an unregulated postmortem examination. In modern times, this term is more commonly associated with the corpses of animals.[73]
Death before birth
Death before birth can happen in several ways:stillbirth, when thefetus dies before or during the delivery process;miscarriage, when theembryo dies before independent survival; andabortion, the artificial termination of the pregnancy. Stillbirth and miscarriage can happen for various reasons, while abortion is carried out purposely.
Stillbirth can happen right before or after the delivery of a fetus. It can result fromdefects of the fetus orrisk factors present in the mother. Reductions of these factors,caesarean sections when risks are present, and early detection of birth defects have lowered the rate of stillbirth. However, 1% of births in the United States end in a stillbirth.[74]
A miscarriage is defined by theWorld Health Organization as, "The expulsion or extraction from its mother of an embryo or fetus weighing 500g or less." Miscarriage is one of the most frequent problems in pregnancy, and is reported in around 12–15% of allclinical pregnancies; however, by including pregnancy losses duringmenstruation, it could be up to 17–22% of all pregnancies. There are many risk-factors involved in miscarriage; consumption ofcaffeine,tobacco,alcohol, drugs, having a previous miscarriage, and the use of abortion can increase the chances of having a miscarriage.[75]
An abortion may be performed for many reasons, such aspregnancy from rape, financial constraints of having a child,teenage pregnancy, and the lack of support from asignificant other.[76] There are two forms of abortion: amedical abortion and an in-clinic abortion or sometimes referred to as a surgical abortion. A medical abortion involves taking a pill that will terminate the pregnancy no more than 11 weeks past the lastperiod, and an in-clinic abortion involves a medical procedure using suction to empty the uterus; this is possible after 12 weeks, but it may be more difficult to find an operating doctor who will go through with the procedure.[77]
Senescence refers to a scenario when a living being can survive all calamities but eventually dies due to causes relating to old age. Conversely, premature death can refer to a death that occurs before old age arrives, for example, human death before a person reaches the age of 75.[78] Animal and plant cells normally reproduce and function during the whole period of natural existence, but the aging process derives from the deterioration of cellular activity and the ruination of regular functioning. The aptitude of cells for gradual deterioration and mortality means that cells are naturally sentenced to stable and long-term loss of living capacities, even despite continuing metabolic reactions and viability. In the United Kingdom, for example, nine out of ten of all the deaths that occur daily relates to senescence, while around the world, it accounts for two-thirds of 150,000 deaths that take place daily.[79]
Almost all animals who survive external hazards to their biological functioning eventually die frombiological aging, known in life sciences as "senescence." Some organisms experiencenegligible senescence, even exhibitingbiological immortality. These include the jellyfishTurritopsis dohrnii,[80] thehydra, and theplanarian. Unnatural causes of death includesuicide andpredation. Of all causes, roughly 150,000 people die around the world each day.[48] Of these, two-thirds die directly or indirectly due to senescence, but in industrialized countries – such as the United States, the United Kingdom, and Germany – the rate approaches 90% (i.e., nearly nine out of ten of all deaths are related to senescence).[48]
Physiological death is now seen as a process, more than an event: conditions once considered indicative of death are now reversible.[81] Where in the process, a dividing line is drawn between life and death depends on factors beyond the presence or absence ofvital signs. In general,clinical death is neither necessary nor sufficient for a determination oflegal death. A patient with workingheart andlungs determined to bebrain dead can be pronounced legally dead without clinical death occurring.[82]
Life extension refers to an increase inmaximum oraverage lifespan, especially in humans, by slowing or reversingaging processes throughanti-aging measures. Aging is the most common cause of death worldwide. Aging is seen as inevitable, so according toAubrey de Grey little is spent on research into anti-aging therapies, a phenomenon known aspro-aging trance.[48]
The average lifespan is determined by vulnerability toaccidents and age or lifestyle-related afflictions such as cancer orcardiovascular disease. Extension of lifespan can be achieved by gooddiet, exercise, and avoidance of hazards such assmoking. Maximum lifespan is determined by the rate of aging for a species inherent in itsgenes. A recognized method of extending maximum lifespan iscalorie restriction.[10] Theoretically, the extension of the maximum lifespan can be achieved by reducing the rate of aging damage, byperiodic replacement of damaged tissues,molecular repair, orrejuvenation of deteriorated cells and tissues.[83]
A United States poll found religious and irreligious people, as well as men and women and people of different economic classes, have similar rates of support for life extension, while Africans and Hispanics have higher rates of support than white people. 38% said they would desire to have their aging process cured.[84]
Researchers of life extension can be known as "biomedicalgerontologists." They try to understand aging, and develop treatments to reverse aging processes, or at least slow them for the improvement of health and maintenance of youthfulness.[9] Those who use life extension findings and apply them to themselves are called "life extensionists" or "longevists." The primary life extension strategy currently is to apply anti-aging methods to attempt to live long enough to benefit from a cure for aging.[85]
Technicians prepare a body for cryopreservation in 1985.
Cryonics (fromGreek κρύος 'kryos-' meaning 'icy cold') is thelow-temperature preservation of animals, including humans, who cannot be sustained by contemporary medicine, with the hope that healing andresuscitation may be possible in the future.[86][87]
Cryopreservation of people and other large animals is not reversible with current technology. The stated rationale for cryonics is that people who are considered dead by current legal or medical definitions, may not necessarily be dead according to the more stringent 'information-theoretic' definition of death.[47][88]
Some scientific literature is claimed to support the feasibility of cryonics.[89] Medical science andcryobiologists generally regard cryonics with skepticism.[90]
Around 1930, most people in Western countries died in their own homes, surrounded by family, and comforted by clergy, neighbors, and doctors makinghouse calls.[93] By the mid-20th century, half of all Americans died in a hospital.[94] By the start of the 21st century, only about 20 to 25% of people in developed countries died outside of a medical institution.[94][95][96] The shift from dying at home towards dying in a professional medical environment has been termed the "Invisible Death."[94] This shift occurred gradually over the years until most deaths now occur outside the home.[97]
Death studies is a field withinpsychology.[98] To varying degrees people inherently fear death, both the process and the eventuality; it is hard wired and part of the 'survival instinct' of all animals.[99] Discussing, thinking about, or planning for their deaths causes them discomfort. This fear may cause them to put off financial planning, preparing awill and testament, or requesting help from ahospice organization.
Mortality salience is the awareness that death is inevitable. However,self-esteem and culture are ways to reduce theanxiety this effect can cause.[100] The awareness of someone's own death can cause a deepened bond in theirin-group as adefense mechanism. This can also cause the person to become very judging. In a study, two groups were formed; one group was asked to reflect upon their mortality, the other was not, afterwards, the groups were told to set abond for aprostitute. The group that did not reflect on death had an average of $50, the group who was reminded about their death had an average of $455.[101]
Different people have different responses to the idea of their deaths. PhilosopherGalen Strawson writes that the death that many people wish for is an instant, painless, unexperienced annihilation.[102] In this unlikely scenario, the person dies without realizing it and without being able to fear it. One moment the person is walking, eating, or sleeping, and the next moment, the person is dead. Strawson reasons that this type of death would not take anything away from the person, as he believes a person cannot have a legitimate claim to ownership in the future.[102][103]
Commemoration ceremonies after death may include variousmourning, funeral practices, and ceremonies of honoring the deceased.[105][106] The physical remains of a person, commonly known as acorpse orbody, are usuallyinterred whole orcremated, though among the world's cultures, there are a variety of other methods ofmortuary disposal.[17] In the English language, blessings directed towards a dead person includerest in peace (originally theLatin,requiescat in pace) or itsinitialism RIP.
Death is the center of many traditions and organizations; customs relating to death are a feature of every culture around the world. Much of this revolves around the care of the dead, as well as theafterlife and the disposal of bodies upon the onset of death. Thedisposal of human corpses does, in general, begin with thelast offices before significant time has passed, and ritualistic ceremonies often occur, most commonly interment or cremation. This is not a unified practice; inTibet, for instance, the body is given asky burial and left on a mountain top. Proper preparation for death and techniques and ceremonies for producing the ability to transfer one's spiritual attainments into another body (reincarnation) are subjects of detailed study in Tibet.[107]Mummification orembalming is also prevalent in some cultures to retard the rate ofdecay.[108] The rise ofsecularism resulted in material mementos of death declining.[109]
Some parts of death in culture are legally based, having laws for when death occurs, such as the receiving of a death certificate, the settlement of the deceasedestate, and the issues ofinheritance and, in some countries,inheritance taxation.[110]
Capital punishment is also a culturally divisive aspect of death. In most jurisdictions where capital punishment is carried out today, the death penalty is reserved for premeditated murder, espionage,treason, or as part ofmilitary justice. In some countries, sexual crimes, such asadultery andsodomy, carry the death penalty, as do religious crimes, such asapostasy, the formal renunciation of one's religion. In manyretentionist countries, drug trafficking is also a capital offense. In China,human trafficking and serious cases of corruption are also punished by the death penalty. In militaries around the world,courts-martial have imposed death sentences for offenses such ascowardice,desertion,insubordination, andmutiny.[111] Mutiny is punishable by death in the United States.[112]
Death in warfare andsuicide attacks also have cultural links, and the ideas ofdulce et decorum est pro patria mori, which translates to "It is sweet and proper to die for one's country", is a concept that dates to antiquity.[112] Additionally, grieving relatives of dead soldiers anddeath notification are embedded in many cultures.[113] Recently in theWestern world—with the increase in terrorism following theSeptember 11 attacks but also further back in time with suicide bombings,kamikaze missions inWorld War II, and suicide missions in a host of other conflicts in history—death for a cause by way of suicide attack, includingmartyrdom, have had significant cultural impacts.[114]
Suicide, in general, and particularlyeuthanasia, are also points of cultural debate. Both acts are understood very differently in different cultures.[115] In Japan, for example, ending a life with honor byseppuku was considered a desirable death,[116] whereas according to traditional Christian and Islamic cultures, suicide is viewed as a sin.
Santa Muerte, the personification of death in Mexican tradition[117]
In Brazil, death is counted officially when it is registered by existing family members at a cartório, a government-authorized registry. Before being able to file for an official death, the deceased must have been registered for an official birth at the cartório. Though a Public Registry Law guarantees all Brazilian citizens the right to register deaths, regardless of their financial means of their family members (often children), the Brazilian government has not taken away the burden, the hidden costs, and fees of filing for a death. For many impoverished families, the indirect costs and burden of filing for a death lead to a more appealing, unofficial, local, and cultural burial, which, in turn, raises the debate about inaccuratemortality rates.[119]
Talking about death and witnessing it is adifficult issue in most cultures. Western societies may like to treat the dead with the utmost material respect, with an official embalmer and associated rites.[108] Eastern societies (like India) may be more open to accepting it as afait accompli, with a funeral procession of the dead body ending in an open-air burning-to-ashes.[120]
Much interest and debate surround the question of what happens to one's consciousness as one's body dies. The belief in the permanent loss of consciousness after death is often calledeternal oblivion. The belief that thestream of consciousness is preserved after physical death is described by the termafterlife.
Near-death experiences (NDEs) describe thesubjective experiences associated with impending death. Some survivors of such experiences report it as "seeing the afterlife while they were dying". Seeing a being of light and talking with it,life flashing before the eyes, and the confirmation of cultural beliefs of the afterlife are common themes in NDEs.[126]
Microorganisms also play a vital role, raising the temperature of the decomposing matter as they break it down into yet simpler molecules.[131] Not all materials need to be fully decomposed.Coal, afossil fuel formed over vast tracts of time inswamp ecosystems, is one example.[132]
The contemporaryevolutionary theory sees death as an important part of the process ofnatural selection. It is considered that organisms lessadapted to their environment are more likely to die, having produced fewer offspring, thereby reducing their contribution to thegene pool. Their genes are thus eventually bred out of a population, leading at worst toextinction and, more positively, making the process possible, referred to asspeciation. Frequency ofreproduction plays an equally important role in determining species survival: an organism that dies young but leaves numerous offspring displays, according toDarwinian criteria, much greaterfitness than a long-lived organism leaving only one.[133][134]
Death also has a role incompetition, where if a species out-competes another, there is a risk of death for the population, especially in the case where they are directly fighting over resources.[135]
Inquiry into the evolution of aging aims to explain why so many living things and the vast majority of animals weaken and die with age. However, there are exceptions, such asHydra and the jellyfishTurritopsis dohrnii, which research shows to bebiologically immortal.[136]
TheVolvox algae are among the simplest organisms to exhibit that division of labor between two completely different cell types, and as a consequence, include the death of somatic line as a regular, genetically regulated part of itslife history.[138][139]
Grief in animals
Animals have sometimes shown grief for their partners or "friends". When twochimpanzees form a bond together,sexual ornot, and one of them dies, the surviving chimpanzee will show signs of grief, ripping out their hair in anger and starting to cry; if the body is removed, they will resist, they will eventually go quiet when the body is gone, but upon seeing the body again, the chimp will return to a violent state.[140]
Furthermore, anthropologist Barbara J. King has suggested that one way to evaluate the expression of grief in animals is to look for altered behaviors such as social withdrawal, disrupted eating or sleeping, expression of affect, or increased stress reactions in response to the death of a family member, mate, or friend.[141] These criteria do not assume the ability to anticipate death, understand its finality, or experience emotions equivalent to those of humans, but at the same time do not rule out the possibility of those abilities existing in some animals or that different kinds of emotional experiences might constitute grief.[142] Based on these criteria, King gives examples of observed potential mourning behaviors in animals such as cetaceans, apes and monkeys, elephants, domesticated animals (including dogs, cats, rabbits, horses, and farmed animals), giraffes, peccaries, donkeys, prairie voles, and some species of birds.[141][143]
Overview of signal transduction pathways involved inapoptosis
Cell death is the event of abiological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as inprogrammed cell death, or may result from factors such asdiseases, localizedinjury, or the death of the organism of which the cells are part.Apoptosis or Type I cell-death, andautophagy or Type II cell-death are both forms of programmed cell death, whilenecrosis is a non-physiological process that occurs as a result of infection or injury.[144]
The term "cell necrobiology" has been used to describe the life processes associated with morphological, biochemical, and molecular changes which predispose, precede, and accompany cell death, as well as the consequences and tissue response to cell death.[145] The word is derived from theGreek νεκρό meaning "death", βìο meaning "life", andλόγος meaning "the study of". The term was initially coined to broadly define investigations of the changes that accompany cell death, detected and measured by multiparameter flow- and laser scanning- cytometry.[146] It has been used to describe the real-time changes during cell death, detected by flow cytometry.[147]
Death of abiotic factors
Somenon-living things things can be described as "dead" when they stop functioning or undergo destruction. For example,volcanoes,batteries,electrical components, and stars are often said to "die" once they reach the end of their active state.
A volcano, a break in the earth's crust that allowslava,ash, and gases to escape, has three states that it may be in, active, dormant, and extinct. Anactive volcano has recently or is currentlyerupting; in adormant volcano, it has not erupted for a significant amount of time, but it may erupt again; in an extinct volcano, it may be cut off from the supply of its lava and will never be expected to erupt again, so the volcano can be considered to be dead.[citation needed]
A battery can be considered dead after the charge is fully used up. Electrical components are similar in this fashion, in the case that it may not be able to be used again, such as after a spill of water on the components,[149] the component can be considered dead.
Stars also have a life-span and, therefore, can die. After it starts to run out of fuel, it starts to expand, this can be analogous to the star aging. After it exhausts all fuel, it may explode in asupernova,[150] collapse into ablack hole, or turn into aneutron star.[151]
In Buddhist doctrine and practice, death plays an important role. Awareness of death motivatedPrince Siddhartha to strive to find the"deathless" and finally attainenlightenment. In Buddhist doctrine, death functions as a reminder of the value ofhaving been born as a human being. Rebirth as a human being is considered the only state in which one can attain enlightenment. Therefore, death helps remind oneself that one should not take life for granted. The belief in rebirth among Buddhists does not necessarily removedeath anxiety since all existence in thecycle of rebirth is considered filled withsuffering, and being reborn many times does not necessarily mean that one progresses.[152]
InDante'sParadiso, Dante is with Beatrice, staring at the highest heavens.
While there are different sects of Christianity with different branches of belief, the overarching ideology on death grows from the knowledge of the afterlife. After death, the individual will undergo a separation from mortality to immortality; their soul leaves the body, entering a realm of spirits. Following this separation of body and spirit (death),resurrection will occur.[153] Representing the same transformationJesus Christ embodied after his body was placed in the tomb for three days, each person's body will be resurrected, reuniting the spirit and body in a perfect form. This process allows the individual's soul to withstand death and transform into life after death.[154]
Illustration depicting Hindu beliefs aboutreincarnation
InHindu texts, death is described as the individual eternal spiritualjiva-atma (soul or conscious self) exiting the current temporary material body. The soul exits this body when the body can no longer sustain the conscious self (life), which may be due to mental or physical reasons or, more accurately, the inability to act on one'skama (material desires).[155] During conception, the soul enters a compatible new body based on the remaining merits and demerits of one'skarma (good/bad material activities based ondharma) and the state of one's mind (impressions or last thoughts) at the time of death.[156]
Usually, the process ofreincarnation makes one forget all memories of one's previous life. Because nothing really dies and the temporary material body is always changing, both in this life and the next, death means forgetfulness of one's previous experiences.[157]
The Islamic view is that death is the separation of the soul from the body as well as the beginning of the afterlife.[158] The afterlife, orakhirah, is one of the six main beliefs in Islam. Rather than seeing death as the end of life, Muslims consider death as a continuation of life in another form.[159] In Islam, life on earth right now is a short, temporary life and a testing period for every soul. True life begins with the Day of Judgement when all people will be divided into two groups. The righteous believers will be welcomed tojanna (heaven), and the disbelievers and evildoers will be punished injahannam (hellfire).[160]
Muslims believe death to be wholly natural and predetermined by God. Only God knows the exact time of a person's death.[161]The Quran emphasizes that death is inevitable, no matter how much people try to escape death, it will reach everyone. (Q50:16) Life on earth is the one and only chance for people to prepare themselves for the life to come and choose to either believe or not believe in God, and death is the end of that learning opportunity.[162]
The word "death" comes fromOld Englishdēaþ, which in turn comes fromProto-Germanic *dauþuz (reconstructed by etymological analysis). This comes from theProto-Indo-European stem *dheu- meaning the "process, act, condition ofdying."[164]
The concept and symptoms of death, and varying degrees of delicacy used in discussion in public forums, have generated numerous scientific, legal, and socially acceptable terms or euphemisms. When a person has died, it is also said they have "passed away", "passed on", "expired", or "gone", among other socially accepted, religiously specific, slang, and irreverent terms.
As a formal reference to a dead person, it has become common practice to use theparticiple form of "decease", as in "the deceased"; another noun form is "decedent".
Bereft of life, the dead person is a "corpse", "cadaver", "body", "set of remains", or when all flesh is gone, a "skeleton". The terms "carrion" and "carcass" are also used, usually for dead non-human animals. The ashes left after acremation are lately called "cremains".
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