Are We Designed to Age?

[sciborg]

Did we evolve aging as part of our design because it performs some needed function? This site (http://www.azinet.com/aging/) provides numerous arguments that aging is necessary to the process of evolution, especially to the evolution of certain traits such as intelligence.

 

What do you think?

 

If we are designed to age would that have implications for medical research?

[Tormod]

Absolutely every living thing we know about ages. The "reason" may be simple - consumption of energy requires expenditure of energy and in the end the machinery fails. The outcome is maybe what you state, that evolution gets an upper hand because individuals die and as such changes the sum of the gene pool.

[Boerseun]

Yes.

 

It's to the offspring's advantage if the parents age and eventually die, otherwise the parents with the older, not so efficient genes would be competing with the kids with potentially better genes for the same resources.

 

However, it's not a universal truth, seeing as everyday things like bacteria are actually immortal beings!

[Biochemist]

Most cells in most species had a predefined number of generations they run before stopping. Rat lung fibroblasts (so called 3T3 cells, a standard cell culture model) divide 50 times before stopping. The chromosomes have markers on them (consuming one marker per generation) to preclude division beyond that, ergo cell death at 50 generations.

 

Some cancers have no such limitation, and grow interminably. As you might note, that is generally not a good thing. In the case of the 3T3 cells referenced above, a Simeon virus will transform the 3T3 cells into a cancerous culture. Those little beggars are SV3T3 cells, also a standard in tissue culture.

[sciborg]

Tormod: Some species (Pacific Rockfish, Sturgeon, some turtles) apparently do not age according to some researchers. Generic degradation theories ("machinery fails") do not explain why some species have drastically different life spans than other similar species (e.g. different varieties of salmon, different birds, etc.). There are other problems with generic degradation theories.

 

Biochemist: Yes. But the $64 billion question is are the cell division limitations a fundamental limitation (unlikely for reasons stated above) or part of a "programmed death" biological suicide mechanism. Cell division is thought to stop because telomeres shorten each division. However, an enzyme, telomerase, can repair the telomeres. Possibly the suicide mechanism controls the availability of telomerase? As you point out there does not appear to be any fundamental limitation on cell division since cancer cells can divide indefinately. Normal cells need to be regulated in their division.

 

Boerseun: Yes. That is essentially the Weismann theory of 1882. Unfortunately, it is incompatible with Darwinian evolution theory. This has caused 145 years of argument!

[Biochemist]

Tormod: Some species (Pacific Rockfish, Sturgeon, some turtles) apparently do not age .... There are other problems with generic degradation theories.

 

Biochemist: Yes. But the $64 billion question is are the cell division limitations a fundamental limitation ...

 

Boerseun: Yes. That is essentially the Weismann theory of 1882. Unfortunately, it is incompatible with Darwinian evolution theory...!

All good points, sciborg.

 

The empirical answer is that most (all?) higher life forms have a statictical life span (as opposed to life expectancy) and that life span is pretty tight by species. Whether one thinks that it was an evolutionary value (as Boersen suggested) or not (I don't), it appears to be true. Mitigation of damage to an organism (or to a population) does not do much to improve life span. All it does is elevate life expectancy for a species toward its intrinsic life span. Life expectancy for humans is about 75 years in the US, life span is about 95 years for the species. As we improve medical science, we are essentially "rectangularizing" the life expectancy curve so that more people approach their intrinsic life span.

 

There are so many separate systems that are "timed" for coincident burn-out, that it is hard to argue that the "design" of the system did not specify it. It does not mean that we can't reverse it, but it does suggest that we would need to manipulate the embryo (or the germ cells) before differentiation to have much effect on the life span of the overall organism.

 

On the telomerase issue, you are correct that the enzyme does reverse some effects of telomere reduction. But it doesn't usually, which suggests that it is there more for repair than for life span management. Complex little beggars, really.

[Boerseun]

Boerseun: Yes. That is essentially the Weismann theory of 1882. Unfortunately, it is incompatible with Darwinian evolution theory. This has caused 145 years of argument!

Why would this be incompatible with Darwin?

 

In my opinion, for most organisms to die of old age is a very good mechanism to enforce genetic betterment and variation in the next generation, seeing as that generation only has to compete with itself for resources, and not have to compete with the previous, "genetically less advanced" generation.

 

If this wasn't a built-in factor, like it is in bacteria, we'd multiply exponentially untill all resources have been consumed - and suffer a total population crash. Like bacteria does in a petrie dish once the growth medium has been consumed.

 

I think most species have evolved over time to find the perfect balance between resources, reproduction and longevity, (humans found that balance as well - but with our increase in technology over the last two hundred years, our ceiling have been raised quite a lot; with the resultant increase in population).

[sciborg]

Why would this be incompatible with Darwin?

 

In my opinion, for most organisms to die of old age is a very good mechanism to enforce genetic betterment and variation in the next generation, seeing as that generation only has to compete with itself for resources, and not have to compete with the previous, "genetically less advanced" generation.

 

If this wasn't a built-in factor, like it is in bacteria, we'd multiply exponentially untill all resources have been consumed - and suffer a total population crash. Like bacteria does in a petrie dish once the growth medium has been consumed.

 

 

Darwin's theory says that traits that cause organisms to live longer and therefore to breed more, or just to breed more are the traits that are "selected". Mutational changes that cause an organism to die earlier or breed less are "selected out". Therefore there cannot be an evolved trait that causes an organism to live less long and/or breed less. Aging and some other observed traits conflict with this view resulting in 145 years of argument among biologists. Aging theories have had to work around this difficulty.

 

Darwin's view was that all organisms (not just bacteria) are driven to survive and breed to absolutely the greatest extent possible and all the limitations such as starvation, predators and disease were externally imposed. Any internal restraint such as you describe is incompatible with the preceeding paragraph.

 

This leads to the idea that Darwinian evolution requires "individual" benefit and cannot support the evolution of traits that provide "genetic betterment" or other future benefit at the expense of a breeding or life span disadvantage to current organisms. See http://www.azinet.com/evolution/ for a brief overview of this issue.

 

I think that you are right and Darwin was wrong. Evolution is more complicated than just survival of the fittest.

[HydrogenBond]

Aging and death probably serve the purpose of peaceful progressive change. Picture if humans could live forever. Culture would stop evolving because those in power wouldn't want to change anything. It would be way too much work to change with the times and retain power every 20-30 years. The new generations, during their idealism stage of life where change seems possible, would be censor.This would lead to war causing death to the immortal stagnation.

[HydrogenBond]

The telemere or ends of the chromosomes are an interesting angle for cellular life expectancy. These ends are not genetically active, except during cell cycles, implying that maybe junk genes may not be junk at all, but serve some quiet static purpose that is important to cells. They may store energy that is needed for the potential of active genes and cell cycles.

[CraigD]

Absolutely every living thing we know about ages.

You’re absolutely right about large, specialized-tissued multicellular life. Though there’re some pretty old things still living (eg: olive trees with documented lifespans of over 1,000 years) or recently deceased (eg: a tortoise known to have lived from at least 188 years, 1777-1965), all show detectable biological signs of an aging process headed toward certain death.

 

Many simple, single-celled organism, though, simply don’t age. Reproduce asexually (clonally), cells of this king will die only due to mishap or starvation. Genetically and anatomically simple, they seem to lack the necessary biological mechanisms (eg: “fuse” telemeres, free radicals, or mitochondria to be damaged by same) for aging. Though it’s hard to support the claim experimentally, it’s theoretically possible that a simple, single-celled organism, protected from environmental hazards and assured an uninterrupted supply of nutrients, could live for tens of thousands of years. There exist decade-old cultures of single-celled organisms that show no detectable biochemical sign of aging.

 

In my amateur opinion, there’s no inherent demand in biological systems for cell mortality. A complex, multi-cellular organism built out of cells that lack senility mechanisms could, in principle, be as immortal as the atoms it is made of (~10^40 sec), which is to say, have a vastly longer life expectancy longer than the environment required to sustain it (~10^24 sec). Such an organism could, in principle, be grossly and neurologically anatomically similar to a human being, or any other higher animal.

 

Whether the apparent total lack of a large, immortal plant or animal means such organism have, at various times, existed, but were out-competed by mortal contenders for their nitches, or never existed, is beyond my power to even guess.

 

PS: There are extremophiles that can survive in such places as buried dry rock, volcanic vents, and even, arguably, hard vacuum. Even humble Streptococcus managed to hang on to life on the surface of the moon (inside a camera on Surveyor 5) until brought back to Earth 3 years later by Apollo 12!

 

I think it’s necessary, though, to disqualify these interesting oddballs from this discussion – while technicall alive, they’re just too weird to justify normal labels like “age”, and “mortal”. They’re also hard for a naïve H.Sapiens to even recognize as alive.

[Biochemist]

It seems to me that the best candidates for immortal life forms are the large fungi. The Honey Mushroom fungus here in Oregon is a single entity that is over five kilometers long. It covers over 2000 acres, and extends down several hundred feet. As I recall, it is thought to be between 2000 and 7000 years old, but I suspect those numbers are pretty hypothetical. Odd to think of an entity that has been around for all of recorded human history.

 

I think this would count as immortal. Anyone want to come back as a fungus?

[sciborg]

Aging and death probably serve the purpose of peaceful progressive change. Picture if humans could live forever. Culture would stop evolving because those in power wouldn't want to change anything. It would be way too much work to change with the times and retain power every 20-30 years. The new generations, during their idealism stage of life where change seems possible, would be censor.This would lead to war causing death to the immortal stagnation.

 

Yes. Aging and death have a number of plausible benefits for the species, society, culture, tribe, etc. The difficulty has been in developing a sequence of events that could explain how an individually adverse characteristic could propagate regardless of its greater benefit. Wouldn't the individuals that live longer have more descendents? Wouldn't aging select out according to Darwin's theory. Therefore, the currently most accepted theories of aging all postulate that aging and death are not desirable traits and did not evolve.

[CraigD]

It seems to me that the best candidates for immortal life forms are the large fungi. The Honey Mushroom fungus here in Oregon is a single entity that is over five kilometers long. It covers over 2000 acres, and extends down several hundred feet. As I recall, it is thought to be between 2000 and 7000 years old, but I suspect those numbers are pretty hypothetical. Odd to think of an entity that has been around for all of recorded human history.

 

I think this would count as immortal. Anyone want to come back as a fungus?

According to this wikipedia section, some marine corrals may have lived for over 100,000 years, making your Oregon Honey Mushroom fungus seem an baby in comparison (though it’s surely a big baby – 9 km^2 – wow!).

 

I think it’s necessary to draw a practical line between “true individual” organisms and organism that seem more like colonies, like corral and fungi. Rather than messing with difficult-to-understand genetic distinctions :Waldo:, I propose the “can anyone imagine every having a conversation with it” criteria. I guess prime criteria are some sort of information processing system – a “brain” or some kind – and metabolic speediness.

[Mr. Potato Head]

Maybe we get to choose before we get here. Quality or quantity. Clearly, cats and dogs have better lives than humans. But they only live 1/7 of the time. The 100K year old corral doesn't seem to have a very stimulating life, but it's here for a long time. Maybe we are the ones that saw "Human" as an option and said, "Hey, that looks like a nice mix."

[Biochemist]

According to this wikipedia section, some marine corrals may have lived for over 100,000 years, making your Oregon Honey Mushroom fungus seem an baby in comparison (though it’s surely a big baby – 9 km^2 – wow!).

Great factoid. I bet your coral is pretty massive as well. And one heckuva lot more attractive.

I think it’s necessary to draw a practical line between “true individual” organisms and organism that seem more like colonies, like corral and fungi. Rather than messing with difficult-to-understand genetic distinctions :surprise:, I propose the “can anyone imagine every having a conversation with it” criteria. ...

This criterion would rule out most of the US Congress.

[goku]

very good question

adam and eve were not designed to age, but what about us?

i guess so because babies don't get around that well.

however death is proof of god, think about it, life is nothing but chemical reactions. why do they stop?

name another chemical reaction that gets sick and dies.