Questions about aging

Factual Questions
1

Why do some species of animal like lobster and turtle not seem to age? Has anyone figured out what kind of evolutionary benefit there was to that?

Is aging largely determined by when an animal finishes procreating, or by size, or have people not figured it out yet?

I’ve heard larger animals live longer, but a 100 pound woman will live to 80 and a 100 pound dog will live to 15. A thousand pound horse will only live to 35. So is size actually tied to aging or is that just a theory? Larger animals have slower metabolisms pound for pound, but again a horse 10x heavier than a human will die when a human is still relatively healthy.

I’m under the impression the big factor is making sure animals are alive long enough to procreate and create progeny that are autonomous, independent and capable of procreating themselves. After that there is no incentive to keep the parents alive. So in humans our health isn’t terrible up until about early middle age, but then starts to decline. A 17 year old human is in peak health, a 17 year old dog is about to die because of how long it takes for us to obtain autonomy.

So I’m figuring humans reach autonomous procreation age in their late teens (historically menarche happened in mid teens when nutrition wasn’t as good) and if each mother has multiple kids, the parent might be 40 before their children reach full procreation age.

What of the theory that because most of our traits are genetically prescribed we need to cull the old because our environment is constantly changing, is that a factor? Does evolution provide a benefit to not wasting nutrients and energy on the old generation because the environment could change. Of course if that were true, wouldn’t evolution push for the fastest rates of procreation possible?

Its my understanding with procreation there is a balance between having tons of kids with little/no parental involvement vs having few with lots of involvement. Humans to the latter, insects the former.

This feels rambling. Here are my questions:

Does aging and dying provide a benefit by clearing out animals whose genetic material may not be suited to a constantly changing environment? Is there a strong evolutionary incentive to have aging and dying, or is aging just a side effect of evolution saying ‘we don’t need you anymore’? The former is a proactive effort to kill life, the latter is just evolution not giving a shit whether you live or die.

Why do some animals like lobster and turtles not seem to age?

Is aging due to size, how long it takes to reproduce (and see progeny reach autonomous reproductive age), or something else?

Are diseases of old age the same across species? Do they all seem to get CVD, arthritis, diabetes or does it vary by animal? Among humans it ‘seems’ like as we age our sense of sight, smell and hearing goes down but the sense of touch and taste does not. Is that similar to other animals that age?

2

You’re giving way too much credit to evolution, which is not purposeful. Its relevance ends at child bearing/rearing age. After that, evolution is irrelevant.

3

Most animals in the wild will die early in a variety of gruesome ways (disease, infection, being eaten…) . Not aging wouldn’t add much to their average life expectancy and ability to reproduce anyway, I guess.

4

Aging can be pretty complex and it is very difficult to generalize. Even among humans, there is huge variation across peoples, individuals, and organ systems.

Essentially, creatures are not built to any “specs”, just good enough to do the job. In the case of evolution, the job is procreation. Features that help us do that job better are considered ‘adaptive’.

Unfortunately, it is not always easy for us in the trenches to determine which features are ‘adaptive’ or ‘maladaptive’. For example, satisfactory blood clotting may depend upon a certain degree of vascular endothelial reactivity, platelet activity, and the concentrations of numerous clotting and anti-clotting factors in plasma. The job has to be ‘good enough’ to get a good portion of us to reproductive age (and beyond enough to get the kids launched). If this causes vascular disease in many of us as we watch are grand- and greatgrand-kids grow up, this may be a lesser evil.

Also, it’s probably easier to build a biologic machine that wears out, and its probably hard to build one that lasts really long, or forever.

Both these processes may look like aging.

I think we are very long lived for mammals, even large mammals. Some speculate that there is a survival advantage to have elders in the clan and tribe.

I have read other speculations, similar to yours, that evolutionary forces favor “taking out the deadwood”. I don’t believe it myself, but it’s not nuts. After all, the old compete for the same resources as the young.

I got nuthin’ for you as regards lobsters. I’m guessing that they successfully reproduce no matter how old?

5

Why do some animals like lobsters and turtles seem to live far longer than they should based on child bearing rates?

6

Having excess lobsters could possibly provide more targets for predators increasing the odds of breeding lobsters surviving.

7

Nobody knows what causes aging exactly although there is a lot of research going on in that area, What we do know that it is programmed at the genetic level. As you note, mammals of roughly the same size can vary widely in their lifespan due to inborn factors. For example, I have a pet chinchilla that is related to both rats and squirrels. Rats are very smart yet they only live about two years and there is nothing you can do to make them live much longer than that. Squirrels do better at about 15 years but chinchillas can live to be over 20 with good care and a little luck. It is almost genetic variation on the same basic model. Likewise, some species of birds like large parrots can live longer than just about any other warm-blooded mammal at up to well over 100 years while their counterparts like eagles cannot make it past 50 in any demonstrated case.

Most research indicates that telomeres play a crucial role in the aging process. An imperfect analogy is that telomeres are like the aglets (the plastic tips) at the end of your shoelaces that protect DNA during its replication cycles and keep it from falling apart. They wear out during a pre-programmed number of cycles and then you start to get DNA errors that cause protein synthesis failures and other anomalies like cancer that show up as either aging or disease. However, no one fully understands why this, why it varies so much among species or how to prevent it.

http://learn.genetics.utah.edu/content/chromosomes/telomeres/

It may be possible to prevent or cure most of the effects of aging just like any other disease in the future but no one knows how to do that yet. Even if you could fully protect DNA, it still wouldn’t fix or prevent everything. Some aging is earned through wear and tear like osteoarthritis, injuries or dental decay.

8

I’ll age all I wanna. Forget it man. None of your business.

9

http://www.programmed-aging.org/negligible_senescence.html

Apparently lobsters are among a very few species that demonstrates negligible senescence (NS). This is taken by the writers of this web page to be evidence in favor of programmed aging, and they have further links to the whole theory.

An exerpt: "Programmed theories of aging assume that a very long life (relative to age of reproductive maturity) has at least a weak evolutionary disadvantage. (See Evolutionary Value of Life.) It is apparent from its rarity and species diversity that each current NS species individually and independently acquired its NS trait rather than inheriting it from a series of ancestor species. NS is therefore, in evolutionary terms, a recent development. This is consistent with theories to the effect that senescence is the manifestation of a complex life span regulation system (see Aging Mechanisms concept 4). "

10

BTW- this website specifically addresses all your questions. At a glance, it appears credible, but you’ll have to judge. The website name does seem a bit “commercial” to me:

"www.programmed-aging.org

Sponsored by Azinet LLC © 2009"

11

That’s an overstatement. See the Grandmother hypothesis, for example.

12

Another big issue is whether aging is programmed into us or if it is just evolution not caring about us. If you have a car but after 10 years you stop caring about repairing it it will fall apart. On the other hand if you intentionally junk it that is different. I don’t know if aging is because evolution wants to kill us after we procreate and raise kids (to clear out the old genetic deadwood) or if evolution just doesn’t give a damn and as a result there was never any incentive to select for genetic traits that allow us to survive and function past procreation age.

If evolution wants to kill us, why does it take another 40 or so years to die after we finish procreating? If you assume procreation age is about 15-40, and that by a person’s early 40s their kids will all have hit puberty why keep people alive for 40 more years? Is that how long it takes for our bodies to fall apart? Most people die around ages 70-90. Very few people make it to 100 (like 2% of humans). I’ve heard of the grandmother hypothesis, but with dogs I thought they finished procreating around age 7 or 8 but they still live to be 15 or more.

13

Aging has some evolutionary advantage, but lots of debate as to what. My favorite hypothesis is that rapid overpopulation is a clear and real danger to all species. Because good times never last and famine and disease can wipe out a population altogether.

So each species finds a way to modulate population growth in a way that is most beneficial to the entire group. Lots of factors come into play, but reproduction can never be too limited as the species would loose adaptability. So that leaves taking out a certain percentage of the old on a regular basis…

The most interesting creature with respect to all of this is the octopus. Because they are scary smart, but only live a few before before a gland activates and kills them.

But, veterinarians are close to figuring out how to remove the gland surgically (just need to find an anathesia that will work), or engineer the gland out of them completely.

The things seem to learn and remember well, so it will be very interesting to see what they can accomplish once freed from the Logans Run scenario. Perhaps that gland is there for,a very good reason…

14

Could be there is some advantage in having members of a population ones that neither breed nor die. Or could be life is just messy.

15

Issues to factor in:

A certain fraction of a population will die soon after reproduction not of old age but from other factors (predation, conflict, etc.)

In a social animal surviving post-reproductive individuals may have an outsized impact on future generations - contributing resources to a next highly related generation and interfering with the reproductive success of those who are less related. At some point, dependent upon specifics, the negative impact of the older individual on future genration reproductive success outweighs the positive.

Lobsters are not so immortal. They die of many causes, such that “the biggest European lobster males in the wild live an average of 31 years, and the females an average of 54 years …”

The balance of factors for why death when may vary for different circumstances.

16

Reading Jared Diamond’s The World Until Yesterday humans until civilization tended to live in village-sized groups of twenty to one hundred, depending on the availability of food. We can see some signs of aging well before the end of menopause, so it’s apparent that the “quality” of offspring declines with age (i.e. more risk of Downs Syndrome offspring with age). However, with the protection and assistance of a village, even a feeble grandmother can perform a task such as child care to leave more able younger females free to do more heavy lifting. So it would seem that in fact, menopause is a survival trait. It reduces the risk of females dying from the stress of childbirth in their older years, thus allowing them to assist the village with some tasks; and reducing the "waste of resources’ of, for example, the effort spent feeding a 60-year-old through a pregnancy only to have mother and child die at birth because the mother was too old or the child more likely to be unfit.

Men, on the other hand, need only survive the risk of heart attack during the stress of orgasm in old age, so there’s less selective pressure to turn off their reproductive capability which is self-limiting anyway - at least, before Viagra, that is.

But a lot of animals don’t have an old age, simply because it’s not a “necessary” part of their programming - i.e. it confers no great survival advantage. For example, IIRC, the salmon swims vigorously upriver against all odds to reach the spawning grounds, only to roll over and die almost immediately. After all, there’s no evolutionary advantage to sticking around - it’s not like they nurture the little hatchlings, or that they possibly could. I imagine the stress of all those adult salmon competing for scarce resources in the streams for weeks would be a negative. SO… their programming says “Game over” almost immediately.

17

Read a book: Long For This World: The Strange Science of Immortality. It’s a fascinating exploration of human aging and research into longevity. The book focuses on one intriguing character, Aubrey de Grey, who isn’t really a scientist but took up longevity as an interest and sort of became something of an expert on what other people study. Aubrey has kind of classified the various causes of aging into seven categories. They essentially boil down to metabolic processes not being 100% efficient, so things build up, or things break down, or things get clogged, or mutations occur. Telomeres are only one aspect of aging.

Aubrey is fascinating because he proposes that aging can be defeated by fixing each of the above categories of breakdown, and is engaged in trying to drive research to defeat the aging process. It’s controversial but not ridiculous.

I googled Azinet LLC. Apparently this is a two person operation working out of a personal residence in Maryland. They claim to operate several publishing projects. It appears to me to be the author of this book, who also runs the website promoting his ideas. Checking the list of books and articles, they all appear to be written by that one guy, except one ebook.

18

I have a hypothesis that in modern society long lived parents reduce the number of direct descendants. If children wait until they are financially secure before reproducing some of those people are going to miss out on opportunities to have offspring, either through accident or simple age. Had their parents died earlier transferring assets to them they’d have a better chance of having children, and might have more.

It’s the kind of effect that would take a long time to show up so I don’t expect to see any decrease in life expectancy as a result.

19

Our ancestors would rarely have survived for 40 more years. More like 10, if that.

20

I’ve always thought that the longer lifespans of more complex creatures was simply a function of biological inertia. Old age doesn’t kill your entire body at once. Rather individual pieces (e.g. muscles, bones, kidneys, etc.) become less and less effective over time, eventually reaching a level they can no longer sustain the whole organism. At that point, other parts start to fail from lack of proper maintenance (e.g. excess protein in blood from bad kidneys, insufficient oxygen from failing lungs, etc.).

In larger, more complex creatures, there are more cells for each function, so the each component takes longer to reach that point of non-sustainability. Also, it takes longer for the effects of a less-efficient component to damage the entire body (beyond the limits of it’s endurance).