Is Aging an Accident of Evolution? -A Galaxy Classic

"Everyone has assumed we age by rust. But how do you explain animals that don't age? Some tortoises lay eggs at the age of 100, there are whales that live to be 200 and clams that make it past 400 years."

Stuart Kim, PhD, Stanford University professor of developmental biology and genetics

Prevailing theory of aging challenged by Stanford University Medical School researchers. Their discovery contradicts the prevailing theory that aging is a buildup of tissue damage similar to rust. The Stanford findings suggest specific genetic instructions drive the process. If they are right, science might one day find ways of switching the signals off and halting or even reversing aging.

“We were really surprised,” said Stuart Kim, who is the senior author of the research.

Kim’s lab examined the regulation of aging in C. elegans, a millimeter-long nematode worm whose simple body and small number of genes make it a useful tool for biologists. The worms age rapidly: their maximum life span is about two weeks.

Comparing young worms to old worms, Kim’s team discovered age-related shifts in levels of three transcription factors, the molecular switches that turn genes on and off. These shifts trigger genetic pathways that transform young worms into social security candidates.

The question of what causes aging has spawned competing schools, with one side claiming that inborn genetic programs make organisms grow old. This theory has had trouble gaining traction because it implies that aging evolved, that natural selection pushed older organisms down a path of deterioration. However, natural selection works by favoring genes that help organisms produce lots of offspring. After reproduction ends, genes are beyond natural selection’s reach, so scientists argued that aging couldn’t be genetically programmed.

The alternate, competing theory holds that aging is an inevitable consequence of accumulated wear and tear: toxins, free-radical molecules, DNA-damaging radiation, disease and stress ravage the body to the point it can’t rebound. So far, this theory has dominated aging research.

But the Stanford team’s findings told a different story. “Our data just didn’t fit the current model of damage accumulation, and so we had to consider the alternative model of developmental drift,” Kim said.

The scientists used microarrays—silicon chips that detect changes in gene expression—to hunt for genes that were turned on differently in young and old worms. They found hundreds of age-regulated genes switched on and off by a single transcription factor called elt-3, which becomes more abundant with age. Two other transcription factors that regulate elt-3 also changed with age.

To see whether these signal molecules were part of a wear-and-tear aging mechanism, the researchers exposed worms to stresses thought to cause aging, such as heat (a known stressor for nematode worms), free-radical oxidation, radiation and disease. But none of the stressors affected the genes that make the worms get old.

So it looked as though worm aging wasn’t a storm of chemical damage. Instead, Kim said, key regulatory pathways optimized for youth have drifted off track in older animals. Natural selection can’t fix problems that arise late in the animals’ life spans, so the genetic pathways for aging become entrenched by mistake. Kim’s team refers to this slide as “developmental drift.”

“We found a normal developmental program that works in young animals, but becomes unbalanced as the worm gets older,” he said. “It accounts for the lion’s share of molecular differences between young and old worms.”

Kim can’t say for sure whether the same process of drift happens in humans, but said scientists can begin searching for this new aging mechanism now that it has been discovered in a model organism. And he said developmental drift makes a lot of sense as a reason why creatures get old.

“Everyone has assumed we age by rust,” Kim said. “But then how do you explain animals that don’t age?”

Some tortoises lay eggs at the age of 100, he points out. There are whales that live to be 200, and clams that make it past 400. Those species use the same building blocks for their DNA, proteins and fats as humans, mice and nematode worms. The chemistry of the wear-and-tear process, including damage from oxygen free-radicals, should be the same in all cells, which makes it hard to explain why species have dramatically different life spans.

“A free radical doesn’t care if it’s in a human cell or a worm cell,” Kim said.

If aging is not a cost of unavoidable chemistry but is instead driven by changes in regulatory genes, the aging process may not be inevitable. It is at least theoretically possible to slow down or stop developmental drift.

“The take-home message is that aging can be slowed and managed by manipulating signaling circuits within cells,” said Marc Tatar, PhD, a professor of biology and medicine at Brown University who was not involved in the research. “This is a new and potentially powerful circuit that has just been discovered for doing that.”

Kim added, “It’s a new way to think about how to slow the aging process.”

Posted by Casey Kazan.

Related Galaxy posts:

Homo Sapiens -The "Time Travelers" -A Galaxy Classic
“Hyper-Speed” Evolution Discovered
Bringing Ancient Human Viruses Back to Life: A Jurassic Park or Salvation?
Robot Evolution: A Parallel to the Origins of Life
Virtual Immortality -How To Live Forever
What do Robots Dream of?
Scientists Create Artificial Brain
A Post-Human Future: Are Humans the Limit of Evolutionary Complexity?

Adapted from the following source:
http://med.stanford.edu/news_releases/2008/july/aging-worm.html

Comments

[Yavor Marichkov]

That's fascinating to say the least. Could this be real?

[marsh]

Hm, interesting speculation, but aging is no accident, but a necessity: Without aging and death, there is no room for the next generation. Without next the generation evolution would never have worked.

Conclusion: No life without aging possible.

[Leah]

Nice thought. There is a difference in environment that needs to be kept in mind....the longest lived creatures live either entirely or for the most part, in the sea. Sea water has an abundance of minerals, which non sea creatures get only through food and drinking, but in which sea creatures are constantly immersed. Also the way in which e.g. oxygen is available to sea creatures differs from the way in which it is available to non sea life.

[Lucifer]

"Everyone has assumed we age by rust. But how do you explain animals that don't age? Some tortoises lay eggs at the age of 100, there are whales that live to be 200 and clams that make it past 400 years." - How do you explain aging in the animals that you claim do not age?

[David]

Evolution,,, ha ha ha lol.

[Michael]

"Conclusion: No life without aging possible."

Ha! Funniest comment all day. Even if animals dont age, they still eat. That means that there is *always* some other animal out there that will eat them.

How many rabbits do you figure died of old age in the era before humans wiped out coyotes and wolves?

They also still get sick. Black Plague, anyone?

[James Fletcher]

How can aging be genetically inbuilt in us when we have already witnessed the average human lifespan rise from around 30 to 70 due to better nutrition and sanitation?

[marsh-rebuttal]

marsh: Well your view asserts some very notable assumptions as well. Perhaps a species might survive just fine if it were to live a very long time instead of experiencing rapid aging based on chemical changes.

The "no room" argument needs to be proven here. It seems like a premise that most people might accept but what about the self-regulatory effect it would have to simply have a longer lifetime and not suffer extreme changes at given ages.

We use chemical changes as humans to signal our bodies to develop sexually as well. This kind of research might help reveal how to help those who do not properly experience those changes - but that is noise to this argument. It's really support for the argument of continuing down this path.

[James Fletcher-rebuttal]

We may simply be experiencing the upper bound of our lifespan as allowed by the time-released genetic changes.

As well, environment may affect how well or how quickly these genetic markers are triggered.

[David]

I love the facts of evolution. They are so fun ny.
I would like at least one of these "evo" scientist to show at least ONE transitional fossil to back up their "facts."
"What is missing are the many intermediate forms hypothesized by Darwin, and the continual divergence of major lineages into the morphospace between distinct adaptive types." (Carroll, Robert L., "Towards a new evolutionary synthesis," in Trends in Evolution and Ecology 15(1):27-32, 2000, p. 27.)

"Given that evolution, according to Darwin, was in a continual state of motion ...it followed logically that the fossil record should be rife with examples of transitional forms leading from the less to more evolved. ...Instead of filling the gaps in the fossil record with so-called missing links, most paleontologists found themselves facing a situation in which there were only gaps in the fossil record, with no evidence of transformational evolutionary intermediates between documented fossil species." (Schwartz, Jeffrey H., Sudden Origins, 1999, p. 89.)

Of course they do not wish to talk about the large gaps in the fossil records which tend to disprove evolution lol...
http://www.genesispark.org/genpark/gaps/gaps.htm

Evolution, fact,theory, or something else? Thats a really good question.

http://emporium.turnpike.net/C/cs/theory.htm

[Qev]

@James Fletcher

You're making the erroneous assumption that people in the past who were dying at age 30 were doing so from old age.

[agethirty]

Here's an interesting factoid which you can feel free to rebute as I have no reference but at age 30, around the later years when human beings have children, muscle density almost halves over their 18 year old selves. They keep the bulk but their body starts to store more as fat even if they are healthy.

Is it that the genetic marker for sexual maturity simply gives us this window and suddenly makes us less and less likely to be able to compete and breed?

Interesting question. I'm not sure what point it may prove other than our life being dictated by a program and that we can only prolong the inevitable with good health practises unless we modify ourselves.

[Patrick]

Aging is and isn't a byproduct of evolution. There is a evolutionary necessity to build in a certain level of aging and growth because larger organisms cannot simply be born fully grown. The consequence is that these genes also cause advance aging because there has never been a evolutionary pressure to build in the mechanisms to prevent that advanced aging; organisms generally die due to disease or predation or falling off something, not old age. It isn't until recently where humans have reduced those other evolutionary pressures to a point where advanced aging becomes prevalent.

[Yaron]

I wonder how this would figure with the ages of people in the bible?

[David-rebuttal]

Well since it is being constantly and properly tested by both sceptics and thsoe who believe in evolution, it would still qualify as a theory.

You don't state a hypothesis and expect it to stay the same forever. Science is fluid. It changes the question as the answers point us in different directions.

Also, when you test a hypothesis you test both the hypothesis and your assumptions made in presenting that hypothesis.

Not finding missing link creatures in the fossil record is not a proof for the non-existence of evolution. It is an opportunity to change the theory and test for that theory's hypothesis. The original theory is not necessarily wrong if its assumptions are sound and nothing has directly proven it wrong, however.

Just because you have never seen a non-black crow doesn't mean that all crows are black. You can be pretty sure, but it only takes one non-black crow to prove you wrong.

Go search the web for white crow. :D

This is how science works. Science is not instantly truth and any self-respecting scientist knows this. Science only has value because it is a record of tests of the natural world which help us better understand it. Science is practical.

Just like we wake up each day and simply expect the sun to be there rather than going nuts all the time wondering if it will, we do rigorous testing to make sure we're pretty close and accept that we will never have all the answers.

[Joe]

Suprised no one mentioned this...

"Without aging and death, there is no room for the next generation."

Yavor: Without aging and death, there is no NEED for the next generation.

[DK]

"Hm, interesting speculation, but aging is no accident, but a necessity: Without aging and death, there is no room for the next generation. Without next the generation evolution would never have worked."

Yeah but this totally speculative in itself. No room for the next generation? Did most creatures evolve in a box, or what? In mountain valleys with no escape?

No doubt every population has a maximum number of creatures that can be supported by the environment, but I think it's a safe bet that the vast, vast majority of animal populations never did reach their upper limit. Young animals crowding out the older ones? The species starts to expand its territory. Not hard to imagine an ageless population getting by just fine, given the resources. And, as Michael correctly points out, there would still be death...

[Seth]

@James Fletcher:

Google "Maiacetus inuus" or "Ambulocetus" for just a couple of examples of fossils that show evolutionary transitions.

[S]

No thank you, I'll rather age. (chumps on huge stack of Oreo cookies)

[Victor Johansson]

@James Fletcher
"I would like at least one of these "evo" scientist to show at least ONE transitional fossil to back up their "facts.""
http://en.wikipedia.org/wiki/Feathered_dinosaurs
http://en.wikipedia.org/wiki/Lucy_(Australopithecus)
http://en.wikipedia.org/wiki/Evolution_of_the_horse
and so on...

Stop trying to fight a battle you already lost a long time ago. If you read about evolution instead of immediately dismissing it you wouldn't be stuck in the intellectual dark ages...

[claudio]

Interesting.....some living species of this planet age with different rate (lower)than us.
An incident of evolution for us humans ???
YES , may be.
And so what ???

We consume an enormous amount of energy only for our brain to work...and think and do usual things..day after day.
More : how complex is our body ???
Reather complex as that of all mammals...nutrition apparatus, blood system transporting oxigen to be 1st inspired.....and then irradiated to burn amminiacids and grease inside us....RUST ??

Yes we rust inevitably...due to the very nature and complexity of our body.....and based on our full dependency from the oxigen.

Is our life style always the same ?? Is it repetitive ???
How emotions shorten our life ??

There may be bipeds in the galaxy less complex than us in their body....simpler nutrition....simpler everything they might have inside.
Could their life span for 400 or 800 Terrestrial years ?? Few metropolitan legends say YES.

How much the sun and the galaxy particles and radiations bombard us daily ??? MUCH.

In the depth of oceans with less apparent gravity force..without the bombardment that we have days and nights...with much simpler bodies and functions...without an energy consuming brain as ours
"SOME species live more than us".

Is this "magics" ??? NO. IT is NORMAL....expected....usual...easily predictable....

So what is the wander of some long living sea species ???

Does this scientist want to change the cycle of our living and death ????

Always we get there...always....these guys are really biased...DNA...trascriptors...and then BLA...bLA...BLA....Genetics engineering and modifications of humans....IT is exactly what these so called scientists always aim to.

WRONG.....

And as many say in the above comments at the end of the day who cares ???

The genetic scientist and who wrote the article.

Sorry for those that have rated the article with many stars...we have to live nearby one star (SUN or SOL...as you like)...and on this miniplanet plenty of oxigen ...vital and deadly for us ...human beings.

Regards....

[SLEZE]

"Yavor: Without aging and death, there is no NEED for the next generation."

What happens when the environment changes? If there is no room for the next generation to promote diversity, and the environment changes in a way that the "old generation" can't adapt to, the whole species dies.

[benburleson]

I think the relative lack of evolution in the cited animals is an artifact of their long life spans. Human lives are shorter, so our evolutionary process is faster. That's my guess, anyway!

[Frank Glover]

"Hm, interesting speculation, but aging is no accident, but a necessity: Without aging and death, there is no room for the next generation. Without next the generation evolution would never have worked."

Evolution works because those who don't possess enough of whatever traits lend themselves to survive in a given environment, long enough to *pass on* those traits...don't pass them on. Nature doesn't 'care' much about the individual after that. 'Room for the next generation' has nothing to do with it.

An ageless rabbit will get caught by a predator, starve or die of something else, *sooner or later.* But if he was good enough at avoiding becoming prey long enough to breed, evolution/natural selection is satisfied.

But if prey-evasion means, say, having a biology or metabolism that isn't supportable (not enough resources put into self-repair and maintenance in order to be fast and responsive, for example) much after passing along successful genes, oh well...

[greg]

The holes in the fossil record have long been explained in the civilized world. The chances of any individual creature leaving behind a fossil are astronomically small, and the number of transitional species is also very small, therefore the chances of finding a transitional fossil are very astronomically small.

Fossils also have a hard time surviving in moist tropical climates, which expand and contract cyclically around the equator throughout the eons. This means that the already low chances of finding fossils are decreased even more during these expansion periods.