A Brief Scientific Introduction to Cryonics

© 1976 by Thomas Donaldson, Ph.D.

[Note: This article was written in 1976 and converted to electronic form by Robert Bradbury in 1999.  It contains many interesting ideas and observations that remain valid to this day.  Nevertheless, it is outdated in some respects.  In particular, our understanding of how memory works is now somewhat different.  For further information see discussions of LTP, Memory and Neural Activity and the Bibliography on Memory at PERIASTRON.]

We can begin with some definitions. Cryonics is the practice of frozen storage of human beings, if necessary, for hundreds of years, until they can be revived and cured of whatever illness or injury caused their legal death. Cryonic suspension is the procedure by which a patient is frozen after legal death.

Some other definitions may also help to understand the practice of cryonics. Legal death is the condition of someone who has been pronounced “dead” by an authority legally qualified to do so. Legal death is a legal and not a biological state. Usually the notion of “death” involves ideas that anyone who is “dead” can never return to life. We will argue here that almost all cases in which people are commonly pronounced “dead” will someday become reversible, treatable conditions. To prevent confusions, therefore, it may help to have a special word for these states. Deanimation is the state in which a person (or animal) no longer shows any of the signs such as heartbeat or brain activity normally associated with life: it as if they have been turned off‘ and stopped working in the same way a phonograph is turned off and stops working. We shall argue in this introduction that almost all cases of legal death are actually different types of this condition of deanimation. However, unlike “death”, deanimation carries no implication of irreversibility or finality to it at all.

Immediately when the possibility of cryonics is raised, all kinds of questions come to mind. Why do we want to do such a thing to ourselves or others? What could someone hope to gain by it Why do we think that we can be stored for so long? What is the chance that we will really come back?

This introduction will give answers to these questions.


I do not wish to belabor this point, which is nevertheless the MOTIVATION for cryonics. It is not proposed to bring back old people only for them to die soon afterwards. It is proposed to keep them frozen until their aging can be significantly REVERSED. Control of growth and development will serve adequately to accomplish this. One excellent short popular article discussing this possibility, which seems far closer than most people think, is:

A. Rosenfeld, The death of old age, TIME-LIFE NATURE-SCIENCE ANNUAL (1975)

At this point it is useful to explicate what would be meant by “immortality” in our terms. Through history the character of those diseases which afflicted people has changed. Many primitive populations show low death rates from cardiovascular diseases: this stems from the fact that few live long enough to develop such problems. I DO NOT BELIEVE THAT THERE WILL EVER COME A TIME IN WHICH WE CAN EXPECT TO LIVE INDEFINITELY WITH NO FURTHER CHANCE OF DESTRUCTION. [Editor’s Note 1] Means to raise lifespan to 400 years may very well come quite soon. Yet there will be still more diseases which do not appear now because no one lives long enough to suffer from them. lt is foolish to expect that we can hope to live indefinitely without taking active steps to acquire this life. No discovery in gerontology is even remotely probable that will give us longevity without subsequent effort.

HOWEVER the combination of gerontology PLUS freezing PLUS vigorous research into means to eliminate all possible fatalities is VERY POWERFUL, and likely to lead to a state not far indistinguishable from “immortality” itself. It would mean that virtually any time YOUR BODY IS FOUND, you can be frozen and hope at some time to be revived. It is only possible to make rough calculations of how long you might expect to live under these conditions. However, complete elimination of aging would imply an average lifespan of about 600 years. Even in most cases of accidental death, the body is recoverable very soon afterwards. A rough estimate of the length of time someone may expect to live before his body is totally destroyed by accident is about 100,000 years. Vigorous attempts to reduce the number of destructive accidents will probably reduce the rate very much, leading to corresponding increases. A reduction of the accident to 1/10 its present value, for instance, would imply, on these figures, an average longevity of 1,000,000 years.


I do not think that repair would be anything so crude as cloning. It seems to me what is most likely is that a new body would be reconstructed from the old.


  1. Ability to design enzymes to produce specific repair functions such as:A. Renaturing denatured proteins.B. Joining broken lipoprotein complexes.

    C. Annealing broken strands of DNA or RNA.

    D. Giving a cell or organism possessing them the ability to metabolize new substrates, use novel cofactors, or construct essential amino acids.

    E. Reading proteins, either existing or special types, onto RNA and replicating them.

  2. Specially constructed bacteria or macrophages able to replicate themselves, spread throughout a specific target tissue, and carry out specific repairs according to the programs designed into their DNA/RNA. These may be so designed to operate at “unnatural” temperatures, as for instance at –70°C, and utilize metabolic pathways not presently found in nature. [Editor’s Note 2]
  3. Ability to introduce into a cell DNA or organelles (such as mitochondria) which it may have lost. This may involve also the ability to introduce entirely new forms of organelles (perhaps to perform specific repair functions) and similarly the ability to introduce into the cell new metabolic capacities.
  4. Ability to modify at will the developmental program of a cell, as for instance to induce postmitotic cells such as neurons to divide, according to a specific program, forming daughter cells with specific properties.
  5. Several different types of repair bacteria (as in 2. above) able to work together in an integrated fashion, and linked together by chemical means (hormones) so as to apply optimal repairs to every body cell.A. To diagnose the precise nature of the damage, call other “repair” bacteria to its location, and report to the attending doctor that new types or repair bacteria other than those already introduced are needed.B. To identify structures which must be preserved (such as memory) and reconstruct them if necessary.


  1. Understanding of the physiology of aging combined with the ability to reverse it.
  2. Control over growth and development, including the ability to program types of growth and development which do not naturally occur, such as:A. Growth of an entire and well–formed body from a head alone.B. Regrowth of injured or lost brain tissue.

    C. Growth of new eyes or other organs which have been lost or damaged.

  3. “Substitute organs” which will take over from others which have been lost. This includes:A. The ability to keep a given tissue alive and healthy in vitro for an indefinite time, and similar abilities for a body part.B. Temporary replacements for any body organ which may have been lost. It is not envisaged that these organs would be permanent. They would be used to support the body while new organs were growing through the techniques of 2., le. as “metabolic crutches”. This capacity specifically includes the ability to make temporary replacements for diffuse systems such as the vascular or nervous systems. For instance, a specially created “plant‘ which will grow an entire vascular system into the patient, down to replacement for the capillaries and venules, from a single seed, always introducing its fibrils between cells and destroying none or very little of the original structure.


There is a voluminous literature on freezing which I will not summarize. A good survey article is:

Robertson, R. D., Jacob, S. N. “The preservation of intact organs” in Advances in Surgery 3. Welch, C., (ed.) (1968)

Present work on freezing continues. The U.S. NIH is funding a study of kidney freezing at the U. of Minnesota. A reader may consult the journal CRYOBIOLOGY or SURGERY for reports of this work.

I have collected together a number of studies of freezing of tissues and organs. Some facts about freezing are relevant in evaluating these reports. At temperatures higher than –196°C, recrystallization of ice occurs slowly over a period of days, causing damage. Temperatures above –130°C are not optimal for long-term preservation. On the other hand, the present consensus of cryobiologists is that most damage in freezing and thawing occurs at the range of –78°C and above. This consensus may help to motivate the fact that so much work has been done on freezing and thawing organs from such (relatively) high temperatures. A second fact to remember is the existence of cryoprotective agents. These prevent or mitigate the damage of freezing. Two particularly effective agents are DMSO and glycerol.

1 mm tissue slices taken from human cadavers, stored in LN2 for months. All showed growth in culture after thawing. Tissues studied were: ovaries, testes, pituitary, thymus, adrenals, liver, thyroid, parathyroid, pancreas, kidney, intestine. No brain tissue studied.

Perry, V. P., Fed. Proc. 22:182 (1963.)
Whole rabbit kidneys frozen in LN, without cryoprotective agents. Kidney epithelium grew in culture after thawing.

Klinke, J., Growth 3:169 (1963)
Whole dog kidneys, perfused with DMSO, stored for one year. Cell cultures taken from the thawed kidney immediately after thawing. Growth in culture of all cell types the same as that of controls.

Robertson, R. S., Jacobs, S. N., op. cit., p.145)
Kidneys perfused and cooled to –50°C. DMSO used. Of 37 kidneys treated, 4 supported life long-term in dog after other kidney was removed.

Halasz, Surgery 61(3):417-21 (1967)
DMSO used, 2 of 14 kidneys functioned long-term.

Mundth E. D., Cryobiology 2(2):62-7 (1965)
Some observations about work on kidneys are worth making. Quite frequently frozen kidneys will function for a short time after thawing. Degeneration occurs later, over a period of days. lt seems to me that this is excellent ground to believe that repair will be possible in future, even if it is not possible now. Our problem is to find a way to prevent this degeneration, not simply to revive the kidney in the first place.
Brains perfused with glycerol and stored at –90°C show no return of electrical activity. Few details of time or storage or treatment given.

Suda, I., Brain Research 70(3):527-31 (1974)
Cat brains, perfused with glycerol and stored for 280 days at -20°C recover electrocortical activity upon rewarming to 39°C and perfusion with fresh donor blood. Techniques of freezing much more crude than those of studies on kidneys. Appearance of tissues in light microscope “almost normal” (original reference contains photograph).

Suda, I., Kito, K., Adachi, C., Nature212(59):268-70 (1966)
Cat brain stored for 7.25 years, thawed slowly over 12 hours. Brains perfused with glycerol before freezing. Spontaneous electrical activity from thalamus and cerebrum.

Suda, I., Brain Research 70(3):527-31 (1974)


The arguments for irreversibility of this so-called “death‘ are CIRCULAR and rest on no scientific grounds whatever. The only support for belief in irreversibility consists of the universal UNEXAMINED belief in it.

It is not possible to argue this question of irreversibility in the terms in which it is usually asked. At present, for most injuries and diseases, the custom is to take those who are afflicted with them, put them in boxes, and bury them. When, because of this treatment, they decline still more until they become dry bones, these dry bones are then exhibited as evidence for the irreversibility of death and the folly of believing that dead people might ever be restored to life. It is one point of cryonics that WE DO NOT INTEND TO ALLOW MATTERS TO GO THAT FAR.

As a general strategy, we systematically attempt to preserve as much as possible. EVERYTHING THAT REMAINS GIVES US MORE TO BUILD ON FOR FUTURE REPAIR. This strategy involves trying to get people as soon as possible. Given present conditions, this may be hours or even days. Even if we cannot perfuse and freeze someone immediately, we CAN do one thing, which is to refrigerate them. By lowering their temperature to 0°C we can slow down all the chemical reactions involved in their deterioration.

In the absence of knowledge of how memories are stored in the brain and therefore of concrete signs of persistence or lack of persistence of identity, we must rely on indirect evidence about the general state of the cells when subjected to various treatments after deanimation of a patient. To give this discussion some empirical content, I have collected together here some information about the state of cells of various types, after remaining at various temperatures, mainly 37°C and 0°C (temperature of refrigeration). Naturally the cells in question are kept at these temperatures without oxygen or nutrients.

The general character of these experiments will be well known to biologists. It has been known for a long time that signs of life persist for hours after “death” has been legally declared. THE SIGNIFICANCE OF THESE FACTS, HOWEVER, SHOULD BE REEVALUATED.

FURTHERMORE, IT SHOULD BE POINTED OUT that there is right now very intensive research going on directed specifically to finding ways to revive the “clinically dead”. Some of this work is described in the table below. The status of being “dead” by present criteria has virtually the same scientific status as that of suffering from acute multiple sclerosis. You will not last long; nonetheless there is very much scientific research directed at the problem, and a general belief that a cure will eventually be possible.

5 to 8 min
16 min
Adult monkeys survive long-term with no neurological deficit when in addition to customary measures of resuscitation they are also given special drugs. 100% survive this treatment: drugs are given AFTER the period in which circulation to the brain has been cut off for 16 min at normal body temperature.

Bleyaert, A. L., et al., Crit. Care Med. 4(2):130 (1976)
38 min
Rat brains kept at 37°C. Using hematoxylin and eosin stains, no abnormalities in cell structure earlier than 38 min. Neurons with swollen mitochondria will be seen in many parts of the brain.

Becker, H., Amer. J. Path. 38:507 (1961)
40 min
Swelling of mitochondria and discontinuities of cell membranes of cat retinal neurons at 40 min without oxygen in vitro at 37°C. All changes will reverse when oxygen is restored.

Webster, N.D., Ames, A., J. Cell Biol. 26:885 (1965)
68 min 
(1 hr)
Monkey and cat brains, deprived of circulation for a period of 1 hr, will recover normal electrical activity and show continued normalization of all other functions for a period of 48 hours. (At present experimental preparation cannot be maintained past that time). Animals given noradrenalin and other drugs after the period of ischemia to promote revival. Both light and electron microscopic studies of brains immediately after 1 hr’s ischemia shows no abnormalities.

Hossmann, K. A., Sato, S., Science 168:375 (1970);
Hossmann, K. A., Kleihues, P., Arch. Neurol. 29(6):375-84 (1973)
2 hrs
Brain slices kept for 2 hrs in Krebs-Ringer solution without oxygen at 37°C show no measurable loss of either RNA or DNA.

Becker, N., Amer. J. Path. 38:587 (1961)
4 hrs
Rabbit cerebellum kept for 4 hrs at room temperature (25°C). Enzyme activities studied using special microscopic stains. Acid phosphatase (lysosomal enzyme), glucose–6–phosphate dehydrogenase (enzyme of glucose metabolism), others studied. Location in cell of all enzymes studied remains the same.

Lazarus, S. S. et al., J. Neurochem. 9:227 (1962)
2 to 6 hrs
Lyzosomal acid phosphatase studied in brain tissue incubated without oxygen or nutrients for periods from 2 to 72 hrs. Enzyme can be distinguished as: “free” = enzyme outside lyzosomes. Control rat brains had 30% free activity. After 1 hr of incubation free activity rises to 32%; at 6 hrs it has risen to 45%. Under light microscope with stains for acid phosphatase, no change in location of enzyme can be seen up to 6 hrs. After (but not before) 6 hrs it tends to concentrate around the nucleus.

Anderson, P. J., J. Neurochem. 12(11):919-25 (1965)
6 to 24 hrs
Brains of adult dogs studied postmortem. Dogs kept at room temperature, cells studied under light microscope using stains luxol fast blue and cresyl echt violet. Progressive agglutination and fragmentation of Nissl substance begins about 6 hrs: Nissl substance disappears by 24 hrs. From 6 to 24 hrs nuclear and cell membranes become progressively irregular and there is an increase in vacuolation.

Haines, D. E., J. Comp. Neurol. 132(3):405-17 (1968)
LIVER For comparison with brain, I include some data on cell changes in livers deprived of oxygen and nutrients.
60 min
Rat liver tissue in vivo. With lack of oxygen mitochondria swell, endoplasmic reticulum becomes fragmented and dilated, vacuoles form, other changes. All changes will reverse to give a normal appearance if the duration of deprivation is not more than 68 min.

Bassi, M., et al., Exp. Molec. Path., 31:332 (1964)
30, 60, 100 min
Mouse liver, removed from mouse and incubated. Control livers had 42% acid phosphatase free; 67.8% free acid phosphatase at 68 min; 82% free at 120 min.

van Lancker, J. L., Amer. J. Path. 35:563 (1959)
30 min
Dog liver may have circulation cut off for 30 min and recover.

Goodrich, E. O., Surgery 39:244 (1956)
2 hrs
Adult rats recover after 2 hrs of complete circulatory arrest and arrest of lung ventilation at 0°C.

Andjus, R. N., Physiology 128:547 (1955)
2.5 hrs
Puppies kept at 10°C to 12°C for periods of 2.5 hrs with circulation arrested. Lungs ventilated artificially despite circulatory arrest. 6 out of 6 chronic survivors, 1 with moderate brain damage, 5 with no persistent disorders.

Kondo, Y. et al., Cryobiology 11(5):446-51 (1974)
4 hrs
Hamsters recover after 4 hrs of cardiac and respiratory arrest at 0°C.

Huggins, C. E., Surg. Forum 12:413 (1961)
4 hrs
Whole dog brains, removed from dog and perfused with Ringer solution, and stored in refrigerator for 4 hrs, recover normal electrical and metabolic activity on rewarming and perfusion with donor blood at 34°C. Electrical activity of brains at 12 and 18 hrs not tested in this experiment.

White R. J., Nature 209(30):1320-2 (1966)
5 hrs 
11 hrs
Infant ground squirrels survive supercooling to -8°C for 5 hrs.
Infant ground squirrels survive supercooling to -4°C for 11 hrs.

Popovic, V. P., and Popovic, S. Amer. J. Physiol. 204:949 (1963)
12 to 24 hrs Tissues removed from human cadavers and stored at 4°C for periods up to 24 hrs. Cultures in vitro will show cellular growth and multiplication. No differences in viability depending on the time of storage from 12 to 24 hrs observed; brain or nervous tissue NOT tested.

Perry, V. P., Fed. Proc. 22:102 (1963)
3 days
Dog kidneys preserved for transplants. Initial perfusion with special solution, storage in ice for 3 days, viable on transplantation.

Sacks, S., Petritsch, P., Kaufman, J., Lancet 1:1024-8 (1973)
3 days
Reflex eye movements of leopard frogs remain good for 3 days.

Sollmann, J., Amer J. Physiol. 149:299 (1947)
3 days
Human embryonic lung cells. More than 50% viable after storage at 4°C for 3 days.

Matsumura, T., Exp. Cell Res. 76(2):297-304 (1973)
15 days
Dogs brains, removed from dog, perfused, and stored in refrigerator for 15 days at 2°C, will show 50X of respiratory activity of normal brains or brains stored for 12 hrs or less. No change in measure of respiration between 18 hrs and 15 days. Cell structure of brain tissue examined with hematoxylin and eosin stains and found to be normal.

White, R. J. loc. cit.


It is a very good question to ask of cryonics exactly what evidence do we have that personality or identity survives after “death”? Since we do not yet know what structures encode our personalities, we cannot yet prove that they survive.

The current best theory as to memory encoding says that it is encoded in the pattern of connections between our neurons, particularly in our brain cortex and cerebellum. A great deal of research on just this question has occurred since 1975, when the first issue of this Bibliography was distributed. [Editor’s Note 3 ] Rather than explain in detail just what might happen to memory during and after freezing I will refer to a second discursive bibliography, distributed at the 1997 Alcor Cryonics Conference in Scottsdale, AZ (I can provide this bibliography upon request).

T. Donaldson, Brief Bibliography on Brain Preservation and Repair (1997); Alcor Cryonics Conference 1997, Scottsdale. AZ

Some further interesting references are:

  • Hershkowitz et al., “The acquisition of dark-avoidance by transplantation of the forebrain of trained newts”, Brain Research 48:366-9 (1972)
  • P. Pietsch, Scrambled salamander brains: a test of holographic theories of neural program storage”, Anatomical Record 172:383 (1972)
  • Craig, P.C. “Musings on brain transplants”, International Surgery57:903 (1972)
  • Pietsch, P., “Shuffle brain”. Harpers Magazine May, 1972

The primary paper here is the Hershkowitz paper. The salamander brains were simply placed in the brain cavity; they worked out how to rearrange themselves by themselves. This suggests that our own brains may retain a good deal of information about their proper structure including the memories they contained, even if we do not now know how to retrieve it. Yes, salamanders are not people. However current work on repairing human brains strongly suggests that our neurons retain much information also. The problem with human (and mammalian) brains comes not from lack of information but from frustration of repair by various other biochemical factors.

It is quite possible, and even to many cryonicists very likely, that cryonics will become widespread NOT when someone is actually revived, but when popular knowledge of our likely ability to recover memory become widespread. For the preservation of memory tells us whether or not revival is possible in PRINCIPLE, rather than merely in PRACTICE, and anyone can see that practice is of all things the most temporary.

However, even here there is a minimum of ignorance which no amount of scientific work on the nature of memory and personality, how it is coded, and the events which can destroy it, is likely to take to zero.

We can certainly make discoveries allowing us to definitely state that some memories survive. But will this, at any given time in the future, be for ALL memories and under ALL circumstances? For some time, at least, we would only be able to test for survival of a representative sample, and the criteria by which we decide it is representative will themselves be faulty. Nor are they likely to work for ALL cases of interest: consider again all the repair methods proposed on page 2: any accident involving such methods will need for its repair still more advanced techniques which will not exist at the time. If we come to understand how memory is coded in the brain, then we will adopt technologies to modify that coding, and sometimes by accident or design such technologies will go awry: not merely or simplistically to ERASE memories, but to invalidate the tests we have for the existence of the memory itself.

Nor can we ever expect definitive means to prove that memory is NOT present. Our memories may leave OTHER traces in chemicals or structure of the cell which could allow us, by a kind of archaeology, to reconstruct them. Revival of someone in such circumstances would consist not just of bringing them back to life and health but of endowing their brain cells themselves with new capabilities to recover the memories which would be lost to normal intact brains.

Certainly if we define our circumstances, we can find cases in which memory is virtually certain to be destroyed. Yet in real life, accidents, mistakes, disease do not present themselves in such a well defined way. There is an IRREDUCIBLE UNCERTAINTY which is basic to cryonics, not merely an adventitious consequence of our ignorance about how memory is stored.

If we seriously proposed to take up the freezing of incurably ill or damaged people, then we will come to freeze people ESPECIALLY if their survival is uncertain, undefined, or suggested only by indirect criteria.

“Life” and Memory

For someone who wants to know about survival of identity and memory. we can point out also that such survival is not at all the same as “life” presently so called. Above, I have given an account of evidence for survival in cases of “death”; but we have only uncertain evidence for survival in many cases of “life”, even now. Conditions, such as late congenital familial amaurotic idiocy, meningitis, Parkinson‘s Disease, Jacob-Creutzfeldt disease, all turn normal thinking people into idiots. Alzheimer’s Disease will do the same. What is the evidence for survival of THEIR memory and identity? Like that of memory after “death”, it is necessarily indirect.


All of the above was devoted to the evidence for survival, often in very bad circumstances. I said that in normal circumstances, we try hard not to let things go that far.

I will now discuss what can happen in good circumstances. The situation, of course. is not nearly so gloomy.

In the first place, equipment for freezing can be set up and ready while the donor is in failing health. Even if hospital cooperation cannot be obtained, the cryonics societies have their own cardiopulmonary resuscitators, so that no serious danger exists that the brain will be for long without oxygen until it has been cooled.

To understand how you would be frozen in good circumstances, you must understand about the “Declaration of Legal Death”. This occurs only by customary practice of physicians, and they have resisted any attempt to define the circumstances legally. Usually it is not discussed openly, even in the medical press.

In general, what happens is that the doctor determines that you are unable to continue breathing and heartbeat on your own. When examined very closely, of course, this criterion becomes very indefinite indeed. lt is certainly NOT the same as “brain death” UNLESS THE PHYSICIAN DELIBERATELY REFRAINS FROM ATTEMPTS TO ARTIFICIALLY SUPPORT BREATHING AND HEARTBEAT. And in fact, most cases of declaration of legal death involve a decision by the physician TO deliberately refrain from artificial support.

1f the cryonics societies are informed, and if they can set up their equipment in advance, and if they have a cooperative doctor on hand, then there will never be ANY QUESTION of brain death. You will be declared legally dead by the cooperating cryonics physician, transferred to the cryonics society CP resuscitator, and then freezing will commence.

What is the chance that you will be frozen in good conditions? A recent book (Life Before Death, by A. Cartwright, L. Hockey, J. L. Anderson; Routledge and Kegan Paul, London and Boston (1973) [HSci: WT 30 C329L]; presents statistics on the warning time available before death. In 83% of all cases, there was more than 1 week’s warning before death. The major cause of sudden deanimations is heart attacks and strokes; accidents play a small role (and in fact, in many accidents the victim actually survives for up to a day or more before succumbing). With preparation, your chances of freezing in good conditions are quite high.

However, take note: “Good conditions” here is always a misnomer. If conditions were really good, you wouldn’t have died, would you?


The ideas of cryonics involve the proposal that people be frozen and stored for periods of hundreds of years. Freezing is not itself a treatment for disease; it merely opens the possibility of future treatment to a patient. A close consideration of the kinds of diseases from which we now suffer, and from which we will in future suffer, strongly suggests that freezing would yield very little real benefit to the frozen if we are only willing to contemplate freezing for short times of 20 years or so. Indeed, if we start to freeze people with the intent of doing so only for 28 years. we will be led to storing them for hundreds of years. IF WE PROPOSE TO FREEZE PEOPLE AT ALL, THEN WE WILL CONTEMPLATE FREEZING THEM FOR HUNDREDS OF YEARS. All of the outrageous proposals of cryonics stem from this basic premise.

This basic premise, however, involves also a BASIC UNCERTAINTY which NO AMOUNT of purely technological discoveries will remove at this time. We are now attempting to found SOCIAL INSTITUTIONS which will last for hundreds of years and provide for the revival of people entrusted to their care NOW. Even if someone is successfully frozen and revived in 30 years time, YOUR situation will not be much changed [Editor’s note 4]. For it will still not be known that the cryonics societies can survive for the length of time required.

If, again, we propose to freeze and store people so that they can take advantage of future medical progress, WE WILL NEVER BE ABLE TO PROVE TO THEN BEFOREHAND THAT THEY WILL BE CURED AND REVIVED.  I do not believe that the prospects of someone facing freezing will be any more predictable on scientific grounds than they are right now, in 1998. It will always be a case of: if we knew how to revive this man then WE WOULD NOT HAVE FROZEN HIM IN THE FIRST PLACE.

To both of these questions, the survival of cryonics societies is essential. Since cryonics has never happened before, we cannot prove that cryonics societies are going to survive by any past history. However, many institutions have lasted a very long time. I collect here some notices of them.

Westminster Abbey Founded 1065. Continuously maintained and occupied since. Earliest tomb, Edward the Confessor (d. 1065), still extant. Many others: Chaucer (d. 1350); many Medieval nobles and bishops still extant.
Longevity 913 years or more.
St. Denis, Paris Line of French kings from Merovingian times until 1792, when during the French Revolution all royal tombs were opened and the bodies destroyed with quicklime.
Longevity about 1288 years.
New Kingdom Egyptian tombs Mummies kept in tombs cut in rock cliffs. Egyptian Earliest 1578 BC. Tombs continuously maintained by tombs priests until the Saite dynasty, about 500 BC.
Longevity about 1000 years.

Europe particularly is crammed with tombs in town cathedrals and monasteries. Many more can be listed than I have given here. For instance, the bodies of all English kings since 1215 are still extant (longevity more than 763 years).

Survival of tombs requires a commentary. I DO NOT COUNT periods in which the tomb was merely existent, but only those in which it was maintained, rites were carried on, bodies protected, etc. That is why I do not credit the Egyptians with more than 1000 years of longevity. These figures are for survival BOTH of bodies AND of an organization to care for them.

St. Catherine,
Mt. Sinai
Founded 538 AD, one of earliest Christian monasteries. Continuously inhabited since that times in Muslim Egypt.
Longevity 1448 yrs or more.
Monasteries of Mt. Athos
Inhabited by anchorites from 830. Great Lavra of Mt Athos founded in 963 AD. Continuously inhabited, including through the period of Turkish rule.
Longevity 1015 yrs.
Monte Cassini
Founded 529 AD. As a corporate body has persisted in the same location since that time. Sacked by Arab raiders about 800 AD, monks escaped; monastery rebuilt the following year. Bombed during W.W. II, rebuilt following the war.
Longevity 1449 yrs or more.
Founded in 361 AD by (St) Martin of Tours, first monastery in Gaul. Persisted until 1792.
Longevity 1615 yrs.

You will have to decide whether it is the fact that these were religious institutions which led to their longevity, or whether it is simply that only religious institutions have existed in the world long enough to have even the possibility of possessing such longevity. For instance, JOINT STOCK COMPANIES in their modern form began only about 1880. it is therefore unreasonable to expect such companies to show a longevity longer than about 178 years. You will also have to decide whether cryonics will produce loyalty to match that of religion.


As mentioned, corporations in their present form do not have a long history. I list here some which began earlier in some form.

  • Amicable Society for Perpetual Life Insurance Office
    First successful life insurance company. Founded 1706 with special royal charter. in 1872 merged with Norwich Office Union Life Ins Co; still extant. Policyholders therefore continued protected.
    Longevity 278 yrs.
  • East India Co. Founded in 1508 to trade with India. Possessions transferred to British government in 1858.
    Longevity 259 yrs.

Survival of corporations is hard to evaluates since they may merge with others while continuing to carry on the same business. lt is not necessary for you to be revived by the same cryonics societies which saw to your freezing.


In evaluating the possibilities of being stored for a very long time, I have not brought up some important probabilities and interactions.

  1. If at ANY time in the future someone is brought back, even if it is not someone frozen at the present time, that fact is likely to STRONGLY REINFORCE the whole custom of freezing and storing people. This includes especially the custom of keeping the bodies of people who were stored now, since their continued existence constitutes proof of one central fact, that storage is possible for a long time. Someone frozen now will therefore benefit by ANY revivals taking place in future, even hundreds of years after his suspension.
  2. We may expect that HUMAN LONGEVITY WILL VASTLY INCREASE. it seems not at all unreasonable to measure periods of storage not in years, but in generations, since someone devoted to keeping people stored will likely remain so for his whole life. A period of 1080 years storage therefore corresponds to about 30 generations. With elimination of aging, we may expect a generation time of about 608 years. We may therefore expect storage if necessary for UP TO 18,000 YRS.


I wrote this bibliography and commentary in 1976 and used it in Australia from that time on. I am up loading it because I think it still has much more than historical value.

In 1978 the American cryonics societies started distributing it. I changed references to dates, and added some citations, for that edition, which is the one presented here. As for history, many cryonics writings by Saul Kent, Mike Darwin, and others still exist only on hardcopy in rare editions. All of this material, done before the age of the PC, deserves transference to computer media. This bibliography is a fragment from the Dark Ages.

In those days, when cryonics was so difficult, everyone expected freezing in bad conditions. That is why the bibliography spends so much time on freezing in bad conditions. But that is still a problem today: not everyone will be frozen in good conditions, not EVER.

We also understand memory a great deal better now than we did then.

Today, when cryonics is moving out of a period of pessimism, the discussion HOW LONG CAN WE EXPECT TO STAY FROZEN seems unnecessary. Many cryonicists believe revival will come in decades, not centuries. I do not feel that this is necessarily WRONG, but I KNOW that things do not always go well. I feel it is still valuable to know that cryonics can survive for centuries if it has to do so.

Editor’s Notes by Robert Bradbury

  1. It would be impossible to live indefinitely if we remain as a biological based intelligence confined to a single planet.  If however we evolved into a distributed replicated intelligence with a size scale of  the order of that of a solar system and the ability to monitor and avoid galactic hazards it is potentially feasible to live indefinately, limited only by the longevity of the universe.
  2. The difficulties to creating biological machines derived from bacteria which operate at temperatures much below freezing are formidable.  It would likely require recreating much of the evolution that occured early in Earth’s history using a fluid that remained liquid at a much lower temperature that water.
  3. In a personal communication in May 1999, the author indicated that our understanding of memory is somewhat different from that available at the time this paper was written.  For further information see discussions of LTP, Memory and Neural Activity and the Bibliography on Memory at PERIASTRON.
  4. When this document was originally written, this was probably a true statement. With the expected advent of computers with human equivalent computational capacity (est. 2008-2020) and progress towards molecular nanotechnology (est. 2010-2020), it is possible to envision that a person cryopreserved in the 21st century might actually be revived in decades rather than centuries.