By saying "evolution isn't interested in this outcome" you're not so subtly anthropomorphizing evolution, but evolution does not have to have an "interest".
3 things are required for evolution to manifest
1. Variation
2. Heritability
3. Selection
where "Selection" often comes in the form of a change in environmental conditions such that certain variations can no longer successfully reproduce compared to other variations.
Evolution has no "interest" in things that are "beneficial for a species". Evolution is an epiphenomenon of the existence of the three factors of variation, heritability, and selection. [0]
EDIT: Just a comment that I didn't see one of my sibling replies whose first sentence I practically duplicated. Clearly at least two of us do not like anthropomorphizations of evolution.
I don’t see the harm in anthromorphizing. Fluids want to move faster when they move from wide to narrow tubes. My computer isn’t happy if it’s too hot inside the case. Evolution wants to make genes that successfully reproduce.
If someone else reads higher order intentionality to it than that, why should that stop me from using a convenient turn of phrase? Sure, if someone wants to think that I’m implying my computer is sentient then they’re odd and incorrect but I’m not going to stop saying it. It’s convenient.
The harm is just misunderstanding. Attributing a interest in dying "for the good of the species" shows a breakdown in usefulness of the metaphor, as attributes not associated with the process of evolution are being applied to it because of the anthropomorphization.
Species is a nebulous conflation of genetics, behavior and habitat. Some like to say that ability to bear fertile offspring is the limit to determine speciation. This definition allows ignoring the mule offspring of horses and donkeys, strengthening the position that the latter are different species, but fails on the liger, which can be fertile with few people claiming tigers and lions to be of the same species. So breeding is insufficient to determine species.
Species is then more a measure of the human perception of things being different than any more specific quality.
The idea that a species could somehow convince its constituent individuals to act for the benefit of the species isn't useful. Individual members of the species will each act with self-interest in the pursuit of resources, mates and territory. Altruistic behaviors will propagate by out-competing "cheating" behaviors, and most often multiple simultaneous behavior strategies will exist within a population. Even within an individual, which might choose different actions in different situations.
If there was more benefit to living longer in the species, cheaters would certainly exploit it in the face of "dying for the good of the species". However, if the detriments of living longer cause the individual to be unable to compete with shorter living individuals, the species will continue to tend to a shorter lifespan.
Suggesting that the creatures will conspire to die and make room for their offspring suggests that the anthropomorphized idea of species is causing faulty assumptions about the nature of the subject to be held, and that the metaphor should be discarded as detrimental to understanding.
> Suggesting that the creatures will conspire to die and make room for their offspring suggests that the anthropomorphized idea of species is causing faulty assumptions about the nature of the subject to be held, and that the metaphor should be discarded as detrimental to understanding.
I wasn't suggesting that, nor was anyone else. I really think you're reading too much into it. I'm merely suggesting, the rather obvious thought that you and everyone else here probably understands, that a group of animals where the weak and old die to make way for the new (obviously not in a self-sacrofice way, but just how the animals are) will probnably be more successful, on average, that a group of animals where the old very slowly, or indeed even never, die.
Now, I apologise that the use of language "evolution is not interested in this outcome" caused such confusion.
I apologize for being so gung-ho in my attack on your original comment. The criticism really wasn't worth the paragraphs I poured into it. I think it struck a chord because I somewhat recently read Dawkins' "The Selfish Gene" and I, as many holders of a head full of fresh new ideas are wont to do, swung them like a hammer at the first thing that might, in a particular light, from a particular angle, look like a nail.
Of coruse I don't literally think evolution is a "thing" that is "interested" in anything. Hopefully it is clear what I'm saying from context. It's just the use of language. I'm sorry for the confusion.
Evolution isn't "interested" in any outcome. There's no need to anthropomorphize it.
There doesn't need to exist some conspiracy in a species to explain death.
The new compete with the old for resources, mates and avoiding predators ( don't need to be faster than a bear, just faster than your friends ). The old have a lifetime of cellular damage, injuries, diseases etc having done damage to their bodies. These things make them more susceptible to predators and dying, being unable to mate do to body problems, being unable to compete for mates and being unable to compete for resources and dying.
Evolution can only select for that which leads to reproduction and survival of progeny. Whatever happens to an animals body after it passes on genetic material is of no matter to the new animal, excepting where interactions with the existing creature can be of benefit and detriment to the young. A mother crocodile protecting her young will have more surviving young than one that eats them, and the former will tend to out-compete the latter and continue existing.
Assuming a long-lived effectively-immortal species that only reproduces when resources are available for doing so exists, what would happen if a single gene for fast reproduction arose? Resources would run out, and animals would have to start competing with one another over them. Assuming the old and the young are both 50/50 for living or dying in any given fight, the creatures that reproduce slower would be at a disadvantage because there would always be more and more of the fast reproducers.
The only stay for the fast reproducers would be whether they can keep their young alive. So perhaps if they have young one or two at a time instead of twelve at a time, their one or two might be more likely to survive to adulthood whereas the twelve would tend to die well before then.
In the end a balance would emerge where members of the species would tend to reproduce as much as possible where they expect to be able to properly nuture the offspring. Those reproducing slower would fail to compete for resources. Those reproducing faster would fail to keep their offspring alive.
But certainly, those that are steadfastly not reproducing for "the good of the species"? These would be out-competed in short order by the rest.
Yeah, more resources for the newer generation and more adaptability from generations occurring more frequently. The extreme of this might be HIV or the common cold.
Another possibility is that aging is actually a side effect of some other important process. This would make it difficult to evolve ways to slow down aging without affecting the original process. My guess is that aging is somehow related to growth rates since organisms with longer life spans like humans or turtles often take a long time to reach maturity. Most forms of life need to reach full size as quickly as possible followed by a rapid stop in growth once full size is reached. Perhaps the rapid stop in growth causes problems with the body's repair mechanisms which ultimately lead to aging. This would be kind of like a business or city which experiences a sudden stop in growth that eventually leads to breakdowns as there is no longer enough money to maintain the infrastructure built up during the growth phase. The physics based theory in the article can't explain why similar forms of life age at very different rates (i.e. dogs aging 7x faster than humans) so something else must be going on.
Actually it is much more direct: evolution benefits from sex (using the DNA of multiple individuals when producing offspring), and sex does not work without death (the destruction of the parent DNA). Or perhaps it simply does not work as well.
If you analyze death in humans you will quickly see it's not as simple as you might think. Cells die in humans all the time, in fact millions of your cells will have died before you finish reading this post. Some organs, such as the skin and the colon, depend on killing (ie. triggering programmed cell death) large amounts of their own cells to function, and even internally it is used as a tool where more gentle means would probably work, such as bone growth and repair, which involves large amounts of cells dying.
Second if you analyze what do humans die from if they die "peacefully in their sleep" ? Well they die of "natural causes". That's awfully noninformative. What do you die from, really ? Well, you die from energy exhaustion in your blood, causing multiple organ failure, leading to poisoning, leading to more organ failure, leading to more organ failure, leading to a relatively slow and orderly shutdown of your body. At this point there are certainly things that your body could do to stay alive (all it takes is accelerating energy dumping in the blood), but it doesn't. Your body chooses to die at a certain point, and it very gently kills itself at a certain point. There's a feedback mechanism that makes this happen. It takes something like a few weeks to actually die. People often report that they can feel this happening and the timeframe seems to be such that you have plenty of time to say goodbye or do whatever needs doing.
Because this is how death works in animals, it does mean that if someone dies from natural causes, the organs are thoroughly poisoned and have had to take extreme measures to avoid dieing completely before the body dies. This usually includes sacrificing significant parts of the organs. This means you cannot safely transplant organs from people who die slowly. But this is another subject.
Thirdly while everybody focuses on death, there are pretty serious symptoms that occur, frankly they start happening before you're even born, but by the time you're 60 there will be very obvious external symptoms of aging. Most of the ones we focus on boil down to cell senescence: your cells choose to systematically become less active as they age, and at a certain cell age (measured in generations) they kill themselves, and they are mostly, but not entirely replaced (that's the function of stem cells: replace senescenced cells that have killed themselves, and that's why they're such a big focus for anti-aging research). This is a mechanism that, essentially, stores your age, and the total energy use of the environment of the cell, into every DNA chain in every cell, and responds to it. Your age gets too big, and it kills itself. You use a certain amount of energy over time, and your cells kill themselves. Long before they kill themselves, they will force themselves to use less energy, even when it means things go wrong (this is why you should -and will- systematically eat less as you age).
And of course there are exceptions to death. There is a continuous cell line from every living human (even clones and the like) to the first human pair, and probably even to the very first living organism. So specific cell types, most notably the procreation related cells, are exempt from death. They do age, as in they measure their age, in years and energy, and they do kill themselves (even a lot quicker than normal cells) but they reset their age every time procreation happens. So, assuming you've got children, not all of your cells will die when you die.
There is a clear evolution to death, as a mechanism. Early lifeforms did not age (some are still alive, so we should say "do not age" in a few cases. Some were alive the first time Eve proverbially smiled at Adam and may still be alive when the last human dies). They would die from disease, getting eaten, or simply by getting themselves into a situation where they could not survive (getting buried was pretty popular). Of all of life's "kingdoms", there's 5.
* The Monera (mostly bacteria, mostly single cellular organisms, with many interesting exceptions), do not die of old age. A curious exception is that a number of them have a built-in self destruct (ie. death) if they do not reproduce.
* The Protoctista and Fungi (2 kingdoms). Have chromosomes and a cell nucleus. Some living protocta are hundreds of thousands, maybe even millions, of years old. They are mostly single cellular organisms, but some of them are very big, for example some algae can be 40 meters or longer. The general rule seems to be that sexually reproducing protoctista die, but there are many interesting mechanisms of death found in these cells, rather than just the one we see in higher lifeforms.
Many can "pause" their death clocks. Only time spent eating causes the death countdown to tick and various forms of hibernation do not.
Quite a few are "optionally" sexually reproducing and they disable and reset the death counter when they switch to the asexual mode.
Some have inherited death clocks: organisms can switch to asexual reproduction but their death clocks do not reset upon reproduction. If they, and their offspring, do not switch back before a hundred or so generations, they age, grow weak, and die.
Keep in mind that when single cellular organisms sexually reproduce, they start with 2 cells and end with 4 cells. Mostly, there is no difference between parent and child. They change their own DNA and then divide. So "parents" don't die sooner than their children, and mostly you simply cannot tell the difference between parent and child at all. And all of the cells have their death clocks reset.
Despite being single cellular organisms, they actually have sexual "organs" (parts of the cell dedicated to reproduction alone). Both outer and inner ones : a way to connect the cell membranes together, and dedicated "micronuclei" that actually reproduce. The cell then "kills" (eats-sort of) the "old" cell macronucleus. Generally the new cells immediately recreate their "sexual organs", which are deactivated immediately after creation, and the newly formed cells go about their business under the direction of their new macronucleus.
The "death" of the old nucleus is the first form of death that is encountered in evolution.
The defining feature of death seems to be that DNA is split into two parts: DNA that is used exclusively for reproduction and DNA that is used for, well, anything else. The reason you die is that a human being falls into that second category.
The obvious variant that must have existed yet is missing is the variant we all want to exist: sexual reproduction where the death clock is reset in both parent and child, and the parent DNA is not destroyed. We do not know of any lifeforms that do this.
So there is a simple and inescapable conclusion : sex (the sharing of genetic information of multiple individuals in a species) does not work without death. That is why you die.
Extremely interesting book on the subject: "Sex and the origin of death" [1]
that sounds right. evolution needs to iterate and iteration stops when generations don't die out? Unless perhaps we figure out how to evolve single generation in progress.
Or evolution isn't interested in this outcome. It is probably benefitical for a species if members die once they get old, to make way for the new.