Natural evolution does not "want" eternal organisms, not even eternal species; it "wants" life to constantly evolve.
Death is a feature, not a bug. It evolved in the last billion years together with sex and reproduction, as a way to clear up space for new individuals.
You provide no arguments that eternal youthfulness is not feasible, you only state that it is indesirable for a species.
I would not say "undesirable". I put "want" in quotes because species and natural evolution have no desires (thanks Lamb for seeing that
) It is just that being mortal is part of being what we are.
Personally, I think it is very desirable for an individual, and probably for society as well.
It may be hard to believe, but, after a certain point in life, that desire usually goes away.
But yes, we generally hate succumbing to old age and death, just like we hate getting sick and weak. That wish must be a naturally evolved trait too, like "you must leave soon, but, as long as you are here, you must try to be as useful as you can" --- and that includes remaining as fit and healthy as you can.
It is not different from how companies treat their older employees. Indeed, retirement is the corporate version of natural death. It was invented not for the good of the individual, but for the good of the company: a barely delicate way to remove the old guys whom no one dares to fire, and open space for new blood.
2) Aging is not a 'planned removal of individuals'. Please describe how the gradual loss of strength, memory functions, etc.. is evolutionary positive. How does the presence of elderly people that need help for everything benefit society? Wouldn't evolution program death in a way that individuals suddenly drop dead after a certain time?
A finite lifetime is nature's solution to make space for new individuals. Aging is a consequence of that.
I do believe that the evolutionary need for a long-living individual wasn't very high (partially because most individuals died much sooner), so our metabolic programming isn't perfected to keep cells functioning forever, resulting in wear and tear.
Yes.
Natural evolution is constrained by the laws of physics. Organisms in most species are optimized to very tight margins, the result of millions of tradeoffs. We cannot have bigger brains, for example, because that would require many structural changes to the body, different wiring plans, longer learning times. A bigger brain would need more oxygen and food, hence better ways to get those things there, and would consume more energy. Anyone who knows something about computers knows that you cannot make a modern processor by taking the design of a 386 and merely tacking more transistors to it, or increasing its clock speed.
A bigger brain might even make us dumber, because signals would take longer to propagate between different parts. (The data processing part of brain is actually the gray matter, a bladder about 1 foot across and 2-3 mm thick; the white matter is just wiring between different parts of this bladder, and the bladder is crumpled up into our skulls both for mechanical reasons and to keep those wires as short as possible.)
The body must not only function, it must also build, adjust, and repair itself. Thousands of our genes get turned on only on specific cells for specific number of generations, or when those cells get specific chemical signals or other stimuli. Some genes get turned on only when we are 13-14 years old, to set up and turn on the reproduction machinery; and some may get turned on at later age when that machinery is not longer needed and should be shut off.
For each body part, nature must choose between making that part more durable and repairable, or using the necessary resources for some other purpose. So, the cells that are destined to become sperm and eggs get better materials, more protection, more redundancy than cells that are destined to die with the individual. Bones, muscles and skin are capable of repairing some damage; but only to a certain extent --- not every possible kind of damage, not damage that is too extensive or repeated too often. Apparently, building the brain and nervous system is already such a demanding task that nature basically gave up on making it self-repairing, other than provide some redundancy and fungibility.
So, once nature "invented" the death of the individual, all parts of the body, and the mechanisms for development, maintenance and repair, got optimized assuming about the same mean lifetime. That happens with human desiged objects, too: each part of a car is made only as durable as needed to last for the expected lifetime of the car. It would not make sense to make seats of a high-tech material that could last 50 years, if the engine, crankcase, and metal shell are unlikely to be usable in 10 years.
In many species, that have been evolving for millions of years in the same environment, things have evolved to the point that death comes suddenly at a fixed age. For other species, mostly plants (and perhaps some fish), evolution apparently has found it unnecessary to provide for natural death, since long life happened to have advantageous (e.g. taller trees get more light) and accidental death was sufficient to open space. For most vertebrates, however, the tradeoffs implied a finite but not strictly determined design lifetime.
Actually it seems that, for millions of years, we evolved for a lifestyle like that of chimpanzees, only perhaps in a more open environment like a savannah. The invention of hunting weapons, fire and clothing changed our lifestyle a lot; we only had a couple hundred million years to adapt our bodies to that change, when the invention of agriculture some 12000 years ago turned our life upside down again. Our bodies and mind are totally not adapted to our present evironment, and may never have a chance to become so.
Nature does not care for our sadness at seeing out bodies and mind falter. However, in the millions of years before the first technological explosion, life did end suddenly for most hominids. As soon as some key function became to falter, the probability of an accidental death -- being eaten by a lion, or falling from a cliff, or catching a fatal infection -- would skyrocket. The expected lifetime for early humans may have been as low as 35 years or even less. For the species, it was good (and sufficient) to let a few lucky survivors reach a more advanced age, to keep memories that might be useful in case of rare events like droughts and earthquakes.
(The Andaman islands between India and Myanmar are the home of the Pigmy-like Negritos, one of the few human populations that have changed little since the last ice age. The islands were devastated by the tsunamis caused by the big Indonesian earthquake, years ago. People feared that the Negritos may have been wiped out; but they survived fine, because their elders knew that tsunamis often come after a earthquake, so they all fled to high ground well before the waves arrived.)
Your reasonings sound like rationalisations to calm the mind to me ("I shouldn't worry, everything is as it should be, everything has a reason")
Not at all. I am as unhappy at getting old as anyone else. I am just pointing out that eternal youth (which implies eternal life) is a rather complicated concept, perhaps a meaningless one.
Does it make sense to wish for a car that will last forever?
Does it make sense to wish for your dear Volkswagen Beetle to last forever?
Poll
