Did death evolve?
Death - everyone save a child knows about it. I don't know the history of death in culture but I do know that people are, well, disappointed, to put it mildly, that we have a finite life-span. I'm not going into the fringes of social existence - the extremes of pain (mental/physical)- where death may be considered a relief because I want to focus on th majority. Most of us want to live - we find pleasure in existence.
That said, I have a small doubt...
Scenario 1: We, our genes, are equipped for immortality. It's just that our environment (exposure to so-called free radicals and toxins) cause the aging process, eventually leading to death.
Scenario 2: Our genes are actually time-bound. Death is programmed into our genes. We die not because of exposure to mutagens and toxins but because our genes shut off the life force.
Scenario 1 would mean that reproduction (renewal of life) is an adaptive response to environmental stress-induced death. Death didn't evolve as an adaptive response but rather it's forced onto us by external forces.
Scenario 2 would mean death evolved as an adaptive response. Possibly to kill off damaged organisms or to make space available for new, more well-adapted, versions of organisms, etc.
So, what does the Theory of Evolution say about death?
Did it evolve or is it forced onto us by the environment?
That said, I have a small doubt...
Scenario 1: We, our genes, are equipped for immortality. It's just that our environment (exposure to so-called free radicals and toxins) cause the aging process, eventually leading to death.
Scenario 2: Our genes are actually time-bound. Death is programmed into our genes. We die not because of exposure to mutagens and toxins but because our genes shut off the life force.
Scenario 1 would mean that reproduction (renewal of life) is an adaptive response to environmental stress-induced death. Death didn't evolve as an adaptive response but rather it's forced onto us by external forces.
Scenario 2 would mean death evolved as an adaptive response. Possibly to kill off damaged organisms or to make space available for new, more well-adapted, versions of organisms, etc.
So, what does the Theory of Evolution say about death?
Did it evolve or is it forced onto us by the environment?
Comments (44)
If you propagate - i.e. if your sperm cells win - then you outwit it. You personally will die but your line will live on. Beyond that, there is no ‘why’.
"The scientific literature is full of explanations for aging: Protein aggregation, DNA damage, inflammation, telomeres. But these are the biological responses to an underlying cause, which is accumulating damage through thermal and chemical degradation.... If this interpretation of the data is correct, then aging is a natural process that can be reduced to nanoscale thermal physics—and not a disease."
The whole article is worth a read, it's pretty breezy, and relates quite nicely to the OP. As to weather death 'evolved', well, no, death is a condition of evolution, so cannot have evolved; This is a logical/defintional point. Also, the question mixes up levels up analysis: death is what happens to individual organisms, evolution is what happens to species and their environments (the correlate of the latter is extinction, not death).
You're right. Seems I mixed up death with extinction but there is an analogy to be had. Don't you think?
After all death on a large scale is the mode of extinction.
Quoting StreetlightX
I guess there's a difference between natural death (old age) and premature death (infection, trauma, etc.). It feels right not to consider the former a malady but not the latter.
However this doesn't sit well with the general perception of death. Most people prefer to live long and, if possible, indefinitely. So, despite science explaining death as a natural process we still have, perhaps a psychological propensity, an impression that ALL death is unnatural.
According to Peter Hoffmann (Nautilus), death is just the laws of nature progressing to their inevitable ends. That means his belief is a mix of the two scenarios I described in my OP. Death has both genetic and environmental components. We die because it's programmed in our genes and also because we succumb to environmental stresses.
What about cancer cells? Dysfunctional though they are they seem to be immune to both genetic signals and environmental stress. Immortality is possible. We don't really have to die even within the context of, I quote, "thermal and chemical degradation". This seems to suggest that it's the environment that has the greater say in death and not our genes which are fully capable of immortality.
Why not? There must be a reason we die, right? Death is the anti-thesis of life and yet it appears that it's programmed into our cells. That's paradoxical and I'd like to question it.
Cancer is fascinating and terrifying because it is literally a kind of superabundence of life itself: life without the limits that normally constrains and, in the last analysis, sustains life. Cancer is pathological life that is indifferent to limits: it's only imperative is to propagate, irrespective of whether this propagation will kill off the very environment that sustains it. The sociologist Melinda Cooper has a great discussion of this, in which she cites the work of Aurel Kolani:
"The specific sickness of cancer lies in the metastasizing overproduction of life rather than its simple negation. If cancer kills, it is not so much through a direct decomposition of the organism, as an extortion of the vital life force of organic life (cellular division), which it deflects from all ends — other than its own accumulation. There is overproduction of life, writes Kolnai, when the generative processes of growth, reproduction, and regeneration escape the boundaries of organic space and time." (Cooper, Life as Surplus)
Cancer lifes you to death. But the point is that those boundaries are what, at the end of the day, allow life to continue. Cancer, precisely because it does not respect those boundaries, ends up putting an end to life. So the so-called immortality of the cancer cell is a double-edged sword: it buys its immortality at the price of... life (which should tell you something about how life and death cannot be as cleanly separated as I think you'd like).
:up:
Quoting StreetlightX
"how life and death cannot be as cleanly separated as I think you'd like'' - interesting!!
You mean death is a part of life itself?
I also thought so but the direction modern medical research is going I think biologists don't think so.
All medical research is about delaying or even completely stopping the aging process. The business, so to speak, is to help people live longer and fuller lives.
I think a time will come (not any time soon) when we can overcome death. I don't know if that's a good thing or not but the trend in medical research suggests such a goal.
I think much of the current perception about life is, even now, very much outdated. I don't like saying his but religion has a lot to do with it. Religion, playing on our deeepest fears and hopes, forces us to cling to ancient notions of life. For instance, Buddhism believes life is suffering, an idea that seems preposterous now that life spans have increased and modern medicine has almost conquered pain.
The future will surely(?) be radically different from the present. Life could be pleasurable, even to the extent that we could create heaven on Earth.
I'm not sure talk of 'parts' and 'wholes' is very appropriate here; I'd perhaps like to think about it in terms of Kant's dove - Kant imagined a dove which, feeling the resistance of air on its wings, figured that it would be much better off without the air getting in its way. But you'd know how that story ends.
Once you are past the age of reproduction, evolution doesn't care about you at all. That's how it works. It only matters what you pass off to your offspring. Why would evolution, the world, anything, anyone, care if you lived forever?
Makes me think the first organism (life form) had to be adapted to the environment without ever evolving. What an incredible stroke of luck that must have been. I mean how does non living material evolve to produce a life form adapted to the conditions existing at that time? I'm thinking there was an incredible amount of proto-life under construction prior to that first organism (one that could eat, reproduce, store energy, evolve etc) emerging from the primordial ooze. There could have been no death before life. With its environment in a state of flux it appears as if death for the life form did indeed evolve....maybe.
Be careful what you wish for, especially when you lack wisdom. Right.
Perhaps death is necessary. I take it you mean that. But what if it's contingent? What if?
Quoting tim wood
If it evolved then death is necessary as opposed to contingent. The reason(s) why would be interesting to know.
Quoting T Clark
I'm under the impression that evolution is about survival - life. If death is necessary for survival (paradox) then it's interesting to know why.
Quoting Codger
Yes, in the dark we must fumble. I guess somethings are unknowable.
I read in biology that cells undergo what is called apoptosis which basically means suicide. Cells do this when they sustain irreparable damage to their chromosomes (thus preventing cancer or viral infection) or if other crucial cellular mechanisms fail.
What do you make of that?
Welcome to the forum. If you're interested, there have been some really good scientific discussions of abiogenesis, how life developed from non-living material, on this forum. The one I remember is called "On the transition from non-life to life."
I've rethought my response a bit. The general principle is still the same - if a characteristic, e.g. longevity, doesn't impact reproductive success, it will have no impact on evolution by natural selection. So, once a person leaves their reproductive years, natural selection becomes blind to their longevity. I rethought my response because, historically, men can continue fathering children longer than than women can bear.
It would seem that everything has a finite life span, a temporal state of affairs. Would evolution or creative evolution (Bergson) make sense if permanence or unending growth were the case? A transition from non-living material to living does not cancel entropy, or a global homeostasis. Death is a necessary condition of procession.
But there are some organisms that don't age, and our reproductive cell line is immortal and doesn't age. So aging is not necessary, at least for some types of cells, and there is ongoing research showing some promise into slowing or even stopping the aging process in various animals, including humans.
I remain sceptical. After all, germ cells are not organisms, and the reason that they don't age is that they - exactly like cancer, actually - remain undifferentiated, retaining their pluripotential so they may turn into other cells. And organisms just are differentiated beings (among other things).
The Water Hydra is a little creeper that seemingly doesn't age at all. It's stem cell can apparently self-rejuvenate as needed without the cap to division that apparently affect almost all other cellular life.
https://en.wikipedia.org/wiki/Hydra_(genus)
So what exactly, are it's limits?
Well, for the longest time, it was thought to be the length and substraction of the telomeres, small tubular "hair" located at the end of chromosomes, which would shrink after every cell-division. When the telomeres are too small ; no more cell-division.
The number of cell-division possible in humans is called the Hayflick limit, and stands for 40 to 60 cell-division before senescence.
I can't find many mentions of living beings with the same degree of never-ending morphallaxis as the Water Hydra, but there are quite a few animals in which the process of senescence is negligible, to a degree which makes us long-lived humans look like ephemerals. A Proteus is a form of worm/salamander that has been observed to go to 200 years old. Clams have been found to go up to 500 years old. And sharks can grow over 400 years old.
But reproduction seems to be related to death. Organisms can't survive death due to chemical/physical degradation and so reproduction does two things:
1. Replenishes the pool with younger individuals who must go through the entire process again
2. Gives an opportunity for mutations to occur; thereby giving life the chance to adapt to changing environments.
Look what happened to the dinosaurs. The natural process of adaptation was just too slow with respect to catastrophic change in the environment and so they died out. I'm only guessing here but if they had longer life spans (ceteris paribus) they could've survived the asteroid impact. Right?
Quoting tim wood
Have a read above. It's a chicken-egg problem. Did reproduction evolve because we die or do we die because of reproduction. I mean reproduction seems to be a way for life to survive death and, taken another way, death seems to make space for the new generation.
Quoting Monitor
Why? It is a paradox isn't it? Death is necessary for life. Afterall they're diametrical opposites.
Jacques Maritain, http://thomasofaquino.blogspot.com.au/2017/07/god-and-science.html
All the photo-cells in the experiments eventually run out of energy. I sat there wondering if these droplets were actually alive, even if for a few seconds? And do they die when energy is depleted and the chemicals return from the biochemical state to the physiochemical? If there are limits to a lifetime then I see no reason for a few seconds to be excluded from any chronologic scale that records lifespans. If proto-cells were alive then I think their dying played no role in evolution other then ensuring the organism's remains were available for recycling.
One fact that is interesting is that most other Hydrazoa (the larger family to which the water Hydra belongs) have a latter state as a polyp. The Hydra, in comparison to other members of it's family, never reaches full maturity. It's not a larval stage, because it can reproduce sexually and asexually, but I've always wondered if the Hydra didn't "trade in" ever reaching it's maturity stage in order to keep the super-morphallaxis that it has in earlier stages.
Quoting TheMadFool
Yes. The theory is that evolvability itself evolves. If you want to achieve greater biological complexity, there is an advantage in dividing things sharply between a mortal body and an immortal germ-line.
So the reason is to allow evolution to access the possibilities of greater structural complexity. Like sex, it had to happen to allow the step from simple bacteria to complex multicellular organisms.
So sex and death do go together.
Bacteria are messy analog creatures. They are promiscuously sexless - forever swapping gene kits even across so called species boundaries. And they are immortal - forever dividing unless hit by some external accident.
But eukaryotes had to create greater digital order. They had to make gene recombination a definite act - a sexual act that divided the flow of evolutionary history into a distinct before and after. And the same for death.
Or rather, it is more subtle. Multicellular organisms needed to separate their immortal germ-line from their developing bodies so that they could start to construct themselves from specialised tissues.
The germ-line - the connecting thread of evolutionary history - had to be tucked away in the gonads or ovaries to allow the other cells get on with their job of turning into lungs, kidneys, brain, muscle, or whatever kind of tissue was their developmental terminus.
So really, the death is the death of alternative developmental possibilities. You can't have lung tissue that wants the autonomy to breed more lungs. Lung tissue that does that is what we call cancer.
But then having specialist reproductive organs - the gonads and ovaries - introduces another problem. As they age, they do accumulate inevitable damage and become too prone to bad mutation.
Now germ-line and stem-line are separated so that one can produce variation while the other avoids it - the stem-line cells just continuing to express the programmed potential to be some kind of tissue like lung. But still, the variation via chromosome recombination is quite different - more tuned and selective in the traits that get exposed to the world - than the kind of brute damage that aging might cause.
So death is an evolved outcome, if a little more indirectly than sex. It is already a de facto presence in the very fact that stem cells are pre-programmed to undergo some certain number of cell-divisions and then - forever - stop. Once our lungs and brains and muscles achieve their proper developmental size, the body is already "dead" so far as its possibilities in that direction goes.
Simpler animals like newts and worms can afford to regenerate limbs and tails. But that stem cell level freedom had to end for good evolutionary reason if nature wanted to access more complex structural possibilities.
So metabolic wearing out is a big reason for death. That is one consequence of achieving complexity - more stuff to go wrong. But also the division of labour - the split between immortal germ-line and disposable soma - is a necessity for achieving complexity of organismic structure.
The lungs can't be allowed to have the ability to live on - spawn away, reproducing themselves - even after the kidneys are shot. The genetics must remain a package deal, tucked away safely, as far from metabolic degradation as possible. The body must perish as a whole so that the immortal part of the business can do its thing of being the continuous historical thread.
Again, the fresh water Hydra is a sexually reproducing animal that is virtually immortal. And there are plenty of animals who'se cells show heightened morphallaxis that have more or less the same putrefaction process that we have.
If death has evolved, it has stopped evolving a long time ago, much before complex sexual reproduction was evolved.
So yes. Simpler animals can afford the luxury of regeneration and metamorphosis. They can recycle cells as the raw material to remodel their structure.
But it is genetically controlled death - the evolution of death as a further now conclusive stage to life - that shows its face even in hydra. Deliberate death was the step underpinning evolutionary access to greater structural complexity.
Well, yeah, but to be fair, so does all form of complex cellular life. All cells are susceptible to cell-suicide if they are exposed to the proper stress value. And I don't think you should read too much "programmed
degradation" into it. The stress vectors which lead the cell to suicide are, notably, the same type of stress which may lead into cellular deregulation and then into cancer.
There is definitely a "cellular death management" function in all living beings. I don't think sufficient homeodynamism for anything else but the simplest vesicle could emerge without it. This doesn't mean that organismal death is itself pre-programmed.
Wasn't that my point? Structural complexity depends on controlled death. And hydra are already complex enough for that to be a factor.
Quoting Akanthinos
Again, it is an evolutionary story. If complex structure depends on controlled death, then control over that death will become increasingly a feature.
There is a vast different between effective waste management and wholesale regulated systematic deregulation. The first one is just a necessary feature of any physical system with an actual physical output. The second one doesn't make sense.
Quoting apokrisis
Controlled death is a sort of exaggeration here. Cell-suicide is not necessarily controlled. It happens all the time accidentally because you decided to smoke, to drink coffee, to expose yourself to some radiation, etc...
The point is that there is a colossal step between cell-suicide and programmed organismal death. Death may very well be virtually unavoidable for beings of our scale and complexity, but the idea that telomeres division or sexual reproduction is somehow what cursed us to death, which was popular in the early 90s and 2000s, is just going the way of the dodo.
Good job I didn't claim that then. That level of eugenic control has only really become possible for human society. ;)
I was talking about the death of possibilities, the termination of development - the positive step of making the soma disposable so as to make the germ-line evolvable.
If you want to make some more simplistic reading of what I wrote, I guess I can't stop you.
Another way of looking at it is the lifecycle model of development - the three natural stages of immaturity, maturity and senescence.
When you are young and stupid, you also have degrees of freedom to burn. You can recover quickly from mistakes, repair any damage, as the body and mind are still in learning mode, not yet established in strong habits.
When you are mature, you have a nice healthy balance of plasticity and stability. You can still recover from perturbations and mishaps, but also you are pretty well efficiently adapted to your environment. You are set up structurally to be doing mostly the right thing.
But this habit-forming - this burning off of the plasticity to lay down confirmed wise habit - keeps on going. Eventually we become so well adapted to our immediate environment - more efficient, less energy consuming, in meeting our survival goals - that we then become more prone to catastrophic breakdown when that environment changes. We have spent all our recovery powers, all our plasticity, to achieve a really good developmental fit with out world. And then it changes on us,
If the whole population becomes a collection of wonderfully adapted old farts - then that works super well until, suddenly, unpredictably, it doesn't.
So yeah. I started with the accidental nature of death. Mostly we would say it is the world that terminates our usefulness.
But then deliberate death also slips into the picture - as the basis for accessing a wider range of complexity-dependent evolutionary possibility. Scheduled, or just statistically reliable, terminations become a useful thing.
Bloody hell, how fucking otiose can someone be???
Yep. I was certainly wondering.
Well, apparently, moments ago, you were talking about structural complexity requiring controlled death. So you aren't have the most coherent of conversation, at the very least.
Organismal immortality does not prevent evolution.
Death did not evolve.
Death is not necessary for sexual reproduction, or vice-versa.
The A Contrario of these are the claims that you made in your post, and they were incorrect, and as usual you tried to deflect by writing a barely-related envolee lyrique.
You are talking right past my point again.
The immortality of the germ-line had to be physically separated from the mortality of the stem-line to achieve even basic multicellular complexity. And while stem cells can just keep growing - turning into whatever tissue they are being told to express by their surrounding mature cells - there is a general framework of regulation that is a kill switch on those possibilities.
The stem cells are stopped from producing the wrong tissues. They are told even when to stop producing. And then mature cells are regulated by similar collective signalling. You have apoptotic control.
So organismic-level immortality did prevent the evolution of complex structure. That is why a germ-line/stem-line dichotomy had to be evolved. The immortality had to be locked away in its own box. And then that made the soma disposable enough that it could become highly adapted as a system of specialised organs - none of which could survive on their own, but which might occasionally slip the leash of regulation to become cancers.
So it might not be the preordained death of an organism because some kind of genetic clock has ticked away the time to the appointed moment for a suicide. But the OP asked in what way might death be evolved as a practical advantage, and I was addressing the OP ... until you butted in.
Quoting Akanthinos
Since you had butted in, I thought I would cover off the senescence issue as well as regeneration/metamorphosis. It might have been of interest.
And your claims about what I claimed are plainly incorrect.
What immortality? Germ-lines can become extinct like anything else.
Clearly the word you intended earlier was obtuse. It is my efforts to enlighten you which have proved otiose.
But if you do have any further interest in the biological arguments, try Nick Lane's The Vital Question. It deals with just this issue.
In a way complex life (eukaryotes?) owes its existence to this trade off.
A year ago I saw this sci-fi movie (forgot the name) where they capture s star-fish like Martian life form whose cells are multi-functional e.g. the skin cells think, see, taste, smell, feel and multiply all at the same time. The cells are even able to contract like muscles.
Do you think that's possible - ''Omnipotent'' cells capable of any possible bodlily function and still able to undego cell division?
"Life". Awesome movie.
The Flying Spaghetti Monster on drugs. :grin:
Cells are omnipotent in that they all carry around the same kitset of genes. But they become specialised in their expression of those genes so as to form specific functional structures like lung tissue or brain tissue. A higher level of intercellular signalling suppresses the generic genetic potential to create the specialised functionalities.
So it is the constraint on that generality that leads to the complexity of a body with an organ system. That makes it "impossible" to have generalist cells that are also, at the same time, specialists at everything. The specialism is what emerges due to the cell being constrained within a context of collective action. The functionality is a property of the higher level of organisation and so cannot inhere in the cell itself.
That's sad to hear. Probably because it's the truth.