Non-Aging Species – Negligible Senescence

Are there species that do not age? Some species apparently lack any internal limitation on their lifespans. What implications does this have for aging theories and dependent medical research on aging and age-related diseases?

Observed Long-Lived Species

We can use the term internal immortality to refer to the absence of any internal limitation on how long members of a species can live. Of course such a species would still be subject to death from external causes such as predators, intra-species warfare, starvation, lack of suitable habitat, and infectious diseases. A number of animal and plant species live extremely long lives and might be internally immortal.

It is infeasible to prove that any such species is or is not internally immortal. For example, we could keep a statistically large number of individuals under zoo conditions for 300 years and see if any survived. Such an experiment would probably require multiple zoos in multiple locations to prevent the entire zoo population from being wiped out by fire, earthquake, or epidemic, would take 300 years to perform, and would only show that a lifespan of 300 years was possible.

Some species have internal indicators of age like tree rings or similar markings on fish scales or internal bones so we can determine the age of a captured wild individual by dissection. Because wild species are subject to myriad external threats a very large number of such examinations would be necessary to demonstrate an even very long lifespan much less demonstrate the presence or absence of internal immortality.

Rougheye Rockfish - Maximum measured lifespan 140 years

Rougheye Rockfish – Maximum measured lifespan 140 years


Giant Sequoia – maximum measured lifespan >3000 years

Giant Sequoia – maximum measured lifespan >3000 years

Negligible Senescence

Another approach to the species senescence issue that avoids the lifespan measurement problem is to measure symptoms of aging. Humans and most other organisms have very obvious multiple senescence symptoms. A negligibly senescent species is one in which no measurable evidence of senescence such as decreased strength, speed, sensory acuity, reproductive ability, or increased incidence of diseases has been observed.

Some have claimed that the mouse-sized naked mole rat (interesting because it is a mammal) is negligibly senescent even though maximum lifespans of about 30 years have so far been observed. Lab mice live about 2.5 years and some mice live less than one year. Naked mole rats have a reproductive scheme similar to colony insects. In any underground colony only one “queen” female reproduces. This behavior and other strange characteristics likely affect their need for lifespan.

Naked Mole Rat – Maximum observed lifespan ~30 years, may be negligibly senescent

Naked Mole Rat – Maximum observed lifespan ~30 years, may be negligibly senescent

Aging Theory Implications of Non-Aging Species

A reader might conclude that trees, fish, and maybe even rats have no significance regarding human aging. However, as explained earlier, modern aging theories attempt to explain why different species have different lifespans and how aging relates to the evolution process and to other characteristics of a particular species.

An individual tree that has lived for more than 3000 years proves that there is not some fundamental limitation on how long an individual living organism can live (at least up to 3000 years). Trees actually share many life processes (such as sexual reproduction) with more complex species such as mammals so this is significant.

Modern non-programmed (non-adaptive) theories assume that each species only has an evolutionary need to live for a certain minimum lifespan but that there is no evolutionary disadvantage from living longer. For example, even if internally immortal, very few wild mice would live as much as three years because of external factors such as predators, starvation and harsh environmental conditions. Therefore having the internal ability to live longer would have very little value for a population of wild mice. This is the logic used by Medawar in 1952 to suggest that each species only needed to evolve the ability to live for a certain species-specific period. Because there is no disadvantage from living longer there is no evolutionary motivation to evolve a suicide mechanism that purposely limits lifespan.

These theories assume that various natural deteriorative processes would limit lifespan beyond the species-specific age at which there was an evolutionary need to live, thus leading to the huge variety of observed lifespans. There is no scientific disagreement that natural deteriorative processes such as oxidation, random mutations, and mechanical wear and tear exist.

However, non-programmed theories make a subtle but important and undefended assumption:  They assume that each increment of lifespan requires a different organism design because living X +1 years is somehow more difficult or otherwise a different task than living X years for any value of X. They further assume that if an organism inherited a longer lifespan than it needed, the natural deteriorative processes would degrade its design to fit its current external world thus resulting in the huge variety of lifespans observed. These assumptions “assume facts not in evidence.” It is not obvious why replacing dead skin cells or hairs would be any more difficult or require a different organism design in an 80-year-old than in an 8-year-old. Similarly why would preventing or repairing the causes of cancer or other age-related condition be more difficult with age?

In addition to this assumption, modern non-programmed theories assume that each species has an evolutionary need to live for a lifespan that is determined by internal design parameters (such as age of puberty) and external conditions (such as predation). Therefore they have the (so far mainly unaddressed) problem of explaining why some apparently non-aging or negligibly senescent species needed to live so long, even possibly indefinitely! Non-programmed proponents typically suggest that apparently non-aging species must actually age. Readers will recognize this as an example of circular logic: It must be true because our theory says it must be true!

Modern programmed (adaptive) aging theories assume that each species has a particular optimum lifespan, similarly determined by internal and external conditions, that living too long creates an evolutionary disadvantage for a population, and that therefore organisms evolved aging mechanisms designed to produce senescence symptoms on a species-specific schedule. Biological programs that stage various life-cycle events are common (e.g. growth, puberty, mating seasons). Programmed aging theories suggest [1] that negligibly senescent species have lost the ability to age and are therefore more likely to become extinct. This could have been caused by mutations that disabled their aging program.

[1] Goldsmith T. The Evolution of Aging 3rd ed. 2014 ISBN 978978870959 Azinet Press

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Non-Science Factors Influence Aging Theory Consensus

Aging TheoriesWHY is it that despite more than 150 years of effort there is still no scientific agreement on even the nature of human aging?  Is aging the result of fundamental limitations that could not be overcome by the evolution process, or a consequence of the lack of an evolutionary need for our ancestors to live longer, or the result of our possessing an aging program or biological suicide mechanism because populations of our ancestors received an evolutionary benefit from limiting individual lifespan? Many non-science factors act to bias thinking about aging and aging theories, mainly toward fundamental limitation theories or more recent non-programmed aging theories even though empirical evidence favors programmed aging theories. This is one of the reasons that no wide scientific agreement on even the nature of aging (much less details) exists today or is likely in the near future.

Education and Training

Most people are trained to believe Darwin’s individual-oriented evolutionary mechanics concept, which does not support more recent population-oriented evolutionary mechanics concepts and dependent modern programmed and non-programmed aging theories. Therefore they are, in effect, trained to believe in fundamental limitation theories. This logically leads to the idea that altering human aging is impossible. Very few of these people go on to obtain training in modern evolutionary mechanics concepts and dependent aging theories. Although modern non-programmed aging theories also conflict with traditional evolution theory, they do not present the gross and diametrically opposed conflict associated with programmed theories. The public is also accustomed to extravagant claims regarding discoveries and developments in medicine.

People who think that altering aging is impossible would logically be against funding research into anti-aging medicine or possibly even in studying aging on the basis that funds and other resources would be wasted. This situation also decreases motivation into studying age-related diseases and conditions. If aging is the result of fundamental limitations isn’t our ability to treat highly age-related diseases likely to be severely limited? Try comparing government funding of research on aging and age-related diseases to the defense budget. Now compare the death rates from age-related diseases to those resulting from enemy attack! We could ask the following question: Would funding for research into aging and age-related diseases increase if it was widely thought that aging, per se, was a treatable condition?

Anti-Science Influences

There are substantial anti-science influences at work in biology and medicine. Possibly the largest single anti-science effort currently extant is religious attacks against evolution theory. This effort strives to show that evolution theory cannot explain various observations without the intervention of supernatural intelligence and publishes pseudoscience articles to that effect. They then cite the pseudoscience in efforts to push teaching of anti-evolution religious concepts like creationism and intelligent design especially in introductory venues. This effort has been so successful that as of 2005 a Harris poll showed that the majority of Americans did not believe in evolution theory. Evolution is extremely central to the nature-of-aging issue and the anti-evolution situation leads to non-science biases toward fundamental limitation theories and non-programmed aging theories:

  • Proponents of fundamental limitation and non-programmed theories have, until recently, been able to dismiss programmed aging theories as non-scientific (and similar to anti-science proposals about evolution such as creationism and intelligent design) because of the conflict with traditional evolutionary mechanics.
  • Efforts to teach evolution, especially in more introductory venues like K-12 biology classes, would like to avoid any indication that there is any scientific disagreement regarding evolution theory and thus avoid giving support to the anti-science effort. This contributes to avoiding any mention of scientific disagreements about evolutionary mechanics or specific modern evolutionary mechanics theories.

The Zero-Sum Game

Funding for medical research tends to be rather flat (after inflation) on a year-to-year basis. Consequently, funding for new areas of research (like programmed aging or anti-aging medicine) must come from reducing funding to existing research avenues. Those researchers can be expected to fight fiercely against the new activities.

Scientific Inertia

Some senior bioscientists have a major public and long-term, even career, commitment to the older non-programmed theories. Such a person might well suspect that they are now betting on the wrong horse. However, for such a person to switch now would in many cases be like an Episcopal Bishop deciding to start over as an entry-level Methodist minister – possible but extremely unlikely.

Ethics and Health Policy Issues with Aging Theories

The fact that humans only live for a certain period is one of the most central and seemingly unalterable aspects of human existence and has profound ethical and policy implications. What happens to annuities, health insurance, pensions, social security, and Medicare if people start living significantly longer? What about the need for term limits for elected and life-time-appointed government officials? How do we increase retirement age? Would wealth imbalance increase?

Many have ethical concerns with altering aspects of human design that are “normal.” Most people would consider it unethical to genetically engineer humans to be taller, stronger, or more intelligent. It is certainly acceptable to the vast majority to attempt to treat or even cure cancer, heart disease, or other massively age-related disease because these conditions are not “normal” in that they do not occur in everybody. A very small part of the population does consider trying to treat cancer or other serious disease as interfering with God’s will and therefore sinful.

However, the more or less universal aspects of aging are certainly “normal” including “dying of old age.” Would it therefore be ethical to try to treat aging, per se? Worse yet, programmed aging theories suggest that humans possess an evolved suicide mechanism that limits their lifespans and that they are consequently designed to age. Aging is a feature of an organism’s design (like height) and not a defect (like a disease or injury).

On the other hand, just as it is obvious that different species age at very different rates, it is widely agreed that the aggressiveness of senescence, per se, varies substantially between individual humans. Therefore if a person inherited relatively aggressive senescence, should that person be able to seek medical aid to delay his senescence in such a way as to be able to enjoy a “normal” lifespan? Extending this idea, should we all be able to ethically enjoy the internally-determined lifespan seen by the longest-lived humans?

Many are concerned with medical advances that might extend the “nursing home stage” of life and favor advances that increase the “healthy” stage and decrease the nursing home stage.

Because they are concerned with the policy, ethics, and religious issues, some are against development of medical technology that would “extend normal lifespan” and are consequently against research in directions that might support lifespan extension – including programmed aging research, and even possibly including research as to the nature of aging such as initiatives specifically designed to determine if aging is programmed or not programmed. Some consider that because aging is a natural and normal aspect of human existence it is not a proper subject for medical research and medicine should be confined to treating dysfunction.

My conversations with thoughtful members of the general public indicate that there is substantial concern over these issues. Informal polling suggests that more than half of the U.S. population has at least some ethics, moral, or policy issues with research into lifespan extension or altering aging.

There is no doubt that senescence is surrounded by serious health policy, ethical, and religious issues. However, in my opinion it does not make logical sense to spend billions on research into treating massively age-related diseases without understanding aging and that doing so amounts to a “fool’s errand.” How can we hope to understand and best treat such a disease without understanding aging? If the majority of deaths due to highly age-related diseases (even in 40-year-olds) are caused by aging, how can we ignore aging in devising treatments for these diseases? Senescence is what it is. Ignoring scientific evidence pointing toward a certain conclusion regarding aging mechanisms is like ignoring global warming or ignoring all the evidence that the Earth orbits the sun.

Average human lifespans have substantially increased in the last century and few would really like to return to a much earlier age. Is it likely that there is going to be such a sudden and large increase in human lifespan that there would be huge social upheaval as a result?

Conclusion: A substantial portion of the U.S. population has issues with research into interfering with human biological aging mechanisms because they think such interference is impossible or because of ethical, religious, or policy issues. These attitudes obviously impact funding and support for research into aging and age-related diseases.

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