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The world has come to regularly use genetic modification for cosmetic purposes, hair colour, eye colour, height, etc, relatively useless stuff. A breakthrough has been made that has produced the first functionally useful genetic modification, one that extends the repair/regeneration ability of the liver in the event of physical damage to the rest of your vital organs.

A far cry from immortality, since people still age, but it's a start and might do more for a person's total years of life than most current practices are capable of. Some people doubt its ability to extend a person's life on its own precisely because people still age despite it, but it might end up proving extremely effective once mods(the genetically modified) eventually prove to live longer than normal people.

Would human life expectancy increase by a significant amount due to this or would it prove to not be that effective in the end?

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  • $\begingroup$ Probably yes, on average, but life expectancy is a statistical value measured over an entire population. It depends on child birth, the most common cause of death, medical care quality and lots of other things having to do with culture and life style (food related habits). So please specify the population, what country are we talking about ? Rich, poor.. cold.. tropical.. also keep in mind the liver is quite vulnerable, despite of its self-repair ability. $\endgroup$
    – Goodies
    Dec 8, 2021 at 13:33
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    $\begingroup$ People will recover fully after a heart attack or a stroke. Accidents which don't kill the person outright will see full recoveries -- the demand for wheel chairs will fall. Luxottica will see its revenues plumet, because men will no longer need glasses in their old age. Cosmetics manufacturers will panic, because nobody will get wrinkles any more. Hip and knee replacements will no loner be needed. Overall, the length of fully active life will be greatly extended, which is what really counts in the end, doesn't it? (But note that this will require extensive engineering...) $\endgroup$
    – AlexP
    Dec 8, 2021 at 13:42
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    $\begingroup$ @Goodies Well... most of the world can be described as 'first world', with the cosmetic genetic engineering being of a price equivalence to really expensive makeup or similar cosmetics. As for this functional modification, it's equivalent in cost to a liver transplant in the US, $520,000 if I remember correctly, but genetic modification is, well, genetic and might to be passed on to offspring so globally the modification might spread $\endgroup$
    – Lemming
    Dec 8, 2021 at 13:53
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    $\begingroup$ Could you elaborate a bit on self-repair ability? $\endgroup$
    – Otkin
    Dec 8, 2021 at 18:56
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    $\begingroup$ @Lemming Could you edit your query to include this clarification? Hopefully, it would lead to getting answers that are more helpful to you. $\endgroup$
    – Otkin
    Dec 8, 2021 at 19:22

5 Answers 5

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Most death is not from cellular wear and tear.

Joints wear out. But it is unusual for wear and tear to be a cause of death. For orientation: causes of death in the US.

https://www.statista.com/statistics/248622/rates-of-leading-causes-of-death-in-the-us/

cause of death graph

#1 and #2 are heart disease and cancer.

It is not clear to me that cardiovascular disease (and death from heart attack or stroke) is related to the self-renewal ability of cells in the arteries. I do not think making those cells turn over like epithelial linings will reduce plaque. But maybe.

If heart disease incidence falls, cancer becomes #1. As is the case in Japan where people live 10-15 years longer and die of cancer.

Self-renewal for all cells will increase cancer risk. A look at cancer mortality shows that common cancers arise in epithelial linings that are renewing themselves. Cancers can arise in non-renewing tissues (brain, bone, muscle) but those cancers are rare and do not make the list. Expanding the pool of cells which are renewing themselves will increase cancer rates for those cancer types.

https://gco.iarc.fr/today/data/factsheets/cancers/40-All-cancers-excluding-non-melanoma-skin-cancer-fact-sheet.pdf cancer deaths

-- I am not sure about dementia and not sure about kidney disease. Kidney disease might actually be from wear. Maybe a self-renewing kidney will take kidney diseases out of the running for mortality risk.

Dementia has not historically been considered a cause of death because it is usually something else that strikes the final blow. I am not sure if self renewing brain cells would sidestep dementia.

For a fiction you could have self renewing artery, kidney and brain cells get rid of cardiovascular disease, renal failure and dementia. You could have improvements in cancer detection and then immunotherapy and other cancer treatments to nip cancer in the bud.

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  • $\begingroup$ Self-repairing arteries and brain cells would help people with dementia. It progresses very slowly. Restoring brain cells underways would certainly make the deterioration even more slower.. $\endgroup$
    – Goodies
    Dec 8, 2021 at 17:18
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    $\begingroup$ @Goodies problems of the arteries is a kind of dementia yes but that is not the most common one. Alzheimers is the most common one by 70% to 80% if i remember correctly. that disease is caused by the buildup of plaques (debris) around the nerve cells. boosting the existing self cleaning ability would alleviate that problem. $\endgroup$
    – Postlim Fort
    Dec 8, 2021 at 19:10
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    $\begingroup$ A decent share of accidental deaths are geriatric falls which are really just cellular decay. $\endgroup$
    – ohwilleke
    Dec 8, 2021 at 19:15
  • $\begingroup$ @PostimFort treatment is impossible, either you postpone, or alleviate the symptoms. Little is known about it, or how these plaques be countered. The British Altzheimer society supports stem cell research alzheimers.org.uk/about-us/policy-and-influencing/what-we-think/… stating newly formed cells could repair damage, and on the other hand recent insights point at a defect in brain cells, allowing cholesterol in form the plaques.. newsroom.uvahealth.com/2021/09/13/… in that case extern cells can help. $\endgroup$
    – Goodies
    Dec 8, 2021 at 20:25
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    $\begingroup$ Having read one book about cancer and now being an expert :-), more active cells leading to cancer is a big, big deal. This feels like an X-Files episode where ultra-healthy rich people start dropping like flies from mega-cancer and we find they were all treated at a secret rejuvenation clinic 8 years ago. $\endgroup$
    – Owen Reynolds
    Dec 9, 2021 at 15:45
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The body is pretty bad at repairing fine structure. When you remove lobes of the liver, the lobes don't recover, the cells just replicate and fill the gaps. Because the cells just all filter blood it doesn't matter so much that they lack much structure.

That's pretty useless for the heart. The heart has a fine structure, and it doesn't work well if you just fill it with lots of cells. It's pretty useless for the brain, which relies on a precise structure to function.

So, it would probably do more harm than help, since most organs don't function well with cells just generating to fill all the gaps.

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    $\begingroup$ "cells just generating to fill all the gaps." Isn't that called cancer?? Well..assuming the cells don't know where the gap ends it probably is. $\endgroup$
    – Michael Kutz
    Dec 8, 2021 at 14:01
  • $\begingroup$ @Michael Kutz Yes, that IS called cancer, and odds are with regenerating organs, cancer would be more prevalent and virulent. Likely it would become the leading cause of death. $\endgroup$
    – DWKraus
    Dec 8, 2021 at 18:00
  • $\begingroup$ From my understanding of the question, OP specified that all organs now are able to repair fine structure. $\endgroup$
    – Alexander
    Dec 8, 2021 at 19:13
  • $\begingroup$ They said that in comments, but not in the main post. $\endgroup$
    – Nepene Nep
    Dec 8, 2021 at 23:45
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    $\begingroup$ And it doesn't even have to be particularly fine structure - in general, we have the code to produce a human being from a human embryo. We do not have a code for, say, regrowing a limb on an adult with a missing arm. And genetic code is really a lot more like a baking recipe than a blueprint. That said, it would probably go a long way towards fixing senescence - not damage from something like, say, getting stabbed or smoking. $\endgroup$
    – Luaan
    Dec 9, 2021 at 12:57
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Short answer, no.

There is a new process being looked into that links DNA to aging. A component of our genes, telomere is the genetic end caps of our genes and act as a type of internal clock in the body. Each time cells in the body divide, ie replace other old and dying cells, these telomere's get shorter.

Over time, these telomere will shorten to nothing and the cell could no longer reliably duplicate itself without errors. This does not happen across the body all at once, but eventually, there will be a significant number of cells through out the body that it could not repair damage, cannot duplicate itself or are creating erroneous copies of itself at a quick pace (cancer).

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    $\begingroup$ Telomere limit is just a limit, not a showstopper here. Let's say a heart muscle cells hit it at 85 years - but before that the heart would have an advanced ability to repair itself, which would inevitably increase life expectancy. $\endgroup$
    – Alexander
    Dec 8, 2021 at 19:20
  • $\begingroup$ All your cells have the code to fix the telomeres. They have to, since our sperm cells certainly do that - otherwise your kids would start out with cells effectively as old as yours. Certainly not a way to make a successful germ line ;) Of course, producing and activating those enzymes is one of the things any (dangerous) cancer cell has to do to really become (dangerously) cancerous. Heck, looking form the point of view of a cancerous cell, it's doing the same thing millions of generations of cells in their line did - all the ones that didn't aren't ancestors to modern cells! $\endgroup$
    – Luaan
    Dec 9, 2021 at 13:01
  • $\begingroup$ if you read the link, it does talk about the fact that sperm telomere's lengthen with age as cellular telomere shorten. The sperm telomere do play a role in the health of the subsequent children. There was a study involving fruit flies (I cant find it now unfortunately) that demonstrated that if they are allowed to breed later than usually, future generations tend to live longer, and thus can breed later, possibly extending the lifespan of fruit flies. However, studies such as this have not been conducted on humans $\endgroup$
    – Sonvar
    Dec 9, 2021 at 15:00
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Really good regeneration is what axolotls do and they live about 20 years, which is pretty much the same as other salamanders (and much less than the really, really long-lived species but those are typically metabolically slower). So the "natural experiment" does not support an increase in lifespan, although regeneration has other advantages.

As others have pointed out, the principal causes of death for humans aren't necessarily going to be improved by better cellular/organ repair, and at least one (cancer) is probably going to get worse, nullifying any gains from limiting the damage from cardiovascular events. You may however see an increase in healthy life expectancy or "healthspan", as in the fraction of one's life unencumbered by age-related health problems. Joint pain, osteoporosis, muscle loss, cataracts/loss of visual acuity, hair loss, all could be improved resulting in a more youthful-looking (and feeling) population (see AlexP's similar comment above).

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Coupled with Modern Society, it Would Increase Life Expectancy

When you look at Willk's answer, you see that the 2 leading causes of death are by far heart disease and cancer with heart disease exceeding all forms of cancer combined. It is true that the heart is the 3rd most resistant organ in the human body to cancer; so, making it regenerative would increase the rate of heart cancer pushing the cancer death rate up a notch ... but this could also massively reduce deaths from heart disease. While cholesterol buildup is often blamed for pulmonary illness, various studies over the past couple decades suggest that this is probably a symptom, not a cause. When an artery becomes weakened or damaged, our bodies coat our arteries with cholesterol on purpose to reinforce and protect it, but our heart and arteries have limited actual healing capabilities due to poor regeneration. If the pulmonary system could better heal itself, then our bodies would not need to respond with cholesterol buildup which means that heart disease as we know it could be all but eliminated. So, you could trade a lot of prevented heart disease for a little bit of heart cancer.

Then you look at the next 3 lowest things: Accidents, Chronic Lower Respiratory, & Stroke. Many accidents cause chronic, unrecoverable injuries. With our current bodies, most major accidents end not with instant death, but being put on various types of life support and waiting to see if the body can heal itself. Many people who go onto life support never recover, but with better regeneration, life-support would become far more successful at saving lives and allowing a person to return to full health. Chronic Lower Respiratory diseases are normally caused by scaring of the lower lungs from smoking or major infections. With better regeneration, your lungs could fully heal following these events making later life respiratory issues far less common. Strokes would also not necessarily become less common, but making full recoveries would become more common.

But the biggest life saver of all here is improved quality of life. People who are not in chronic pain live happier lives. Of all health factors that determine how long you will live, happiness is probably the most important due to its direct relationship with pulmonary heath and your immune system, and better regeneration helps you maintain better happiness as you age.

So what does this all have to do with Modern Society?

Human biology is designed to optimize our survival to how our ancestors lived.

Our medial pulmonary systems don't regenerate very well because physically active humans living off of a natural diet can live a very long time as is; so, no need for better regeneration there. But now that we are living longer and eating worse, a regenerative heart would become more practical. Modern medical interventions also mean that we are MUCH better at stopping a simple wound from killing you quickly. If getting a leg cut off is rapidly fatal to pre-modern man, then there is no reason to care if your body has a long-term plan for recovery, but if you can consistently stop the fast death, then better regeneration helps prevent slow death.

We are also a lot better now at treating cancer than our ancestors were. To premodern man, cancer was an absolute death sentence; so, our biology tries to avoid it by reducing cell divisions to minimal requirements. But with modern medicine, we can cut it out, irradiate it, chemo it, etc. Ironically, better regeneration may actually decrease the chance of dyeing of cancer despite higher cancer rates because more invasive treatment options would open up.

So, if you went back to 50,000BCE and made humans super regenerative, it would not be very beneficial, but do it today, I am pretty sure it would help a lot.

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