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[P]
Plague Time: A Review

By DesiredUsername in Technology
Wed Jun 13, 2001 at 12:07:12 PM EST
Tags: Books (all tags)
Books

Plague Time
by Paul Ewald

From the magazine articles you'd conclude Paul Ewald is a wacko. Even the cover of his own book highlights the kook-factor. But this book really has two orthogonal ideas in it.


The book's subtitle reads "How STEALTH INFECTIONS Cause CANCERS, HEART DISEASE, and Other DEADLY AILMENTS". It's this idea, chronic conditions being caused by infectious pathogens, that the media seems to have latched onto. But that concept really plays a minor role in Ewald's thesis.

His basic point is that microscopic organisms obey the same evolutionary laws that fruit flies, rabbits and pea plants do. He suggests using biology's most fundamental theory, natural selection, to inform and guide biology's most practical application, medicine. On this topic he is extremely convincing.

For instance, he has several sections on mosquitos as vectors for malarial infection. If a patient in America has a severe case of malaria, they are bed-ridden in a house or hospital that is mosquito-proof (screens, etc). A lack of mosquitos means a virulent strain of malaria has no vector to infect someone else. On the other hand, with a milder case of malaria the patient could be walking around outside (if only periodically) where there are mosquitos and the disease could propagate itself. These conditions constitute selection pressure on the malaria pathogen(s) to evolve toward a more benign state.

However, in a country with poor mosquito-proofing, bed-ridden malaria victims are still subject to mosquito bites, which serve as a vector for the more virulent strain. In fact, bed-ridden victims may be especially vulnerable since they have no strength to slap away stinging insects. So there is either no pressure or there is slight pressure towards more virulence in a country with poor mosquito-proofing.

Ewald makes similar points about diarrheal diseases and also HIV. He also backs up his "just-so stories" with data gathered from the field. He has examples of cholera infection in Peru (with a poor water supply) vs Chile (with an adequate one). He has examples of mosquito-proofing campaigns in Alabama from the 1930's. And he goes on at length about the selection pressures on various strains of HIV.

So where does the "heart disease is infectious" idea come from? The book doesn't make it clear what line of reasoning convinced him of this. He has three basic arguments, only two of which are convincing (although the third is suggestive). The first (and most prevalent but least scientifically valid) argument for infectious causation of chronic disease is via simple induction. Many times throughout the book he almost derisively mentions how peptic ulcers and cervical cancer were once thought, by dimwitted and blinkered medical scientists, to be non-infectious. But now they have finally seen the light. If they were wrong about that, the illogical argument runs, what else could they be wrong about? Less derisively, and therefore more convincingly, in this same vein he points out that many diseases, for instance syphilis, have an acute phase *and* a chronic phase. We traditionally think of acute-phase diseases as infectious, but just because it is "missing" that phase doesn't guarantee, he says, that it is *not* infectious.

The second argument is from evolution and is somewhat more plausible. If human genes caused the "diseases of old age" like Alzheimer's and heart disease, why hasn't evolution eliminated these diseases by now? Obviously old people don't have children, but this argument has two flaws. First, you don't need to be actively reproducing to affect your genes' chances of survival. For instance, children with a living, on-the-ball grandparent are probably more likely to survive than children without one. Even this slight selection pressure should have removed some of these diseases from the gene pool. Second, "old people don't have children" is circular. The *reason* they don't have children is that they are either dead, too sick or infertile. Why did their genes allow them to become so? No, says Ewald, the situations wrought by these conditions reek of a predator-prey relationship. Some outside agent is causing the problems these old people have and the available data points to infection.

But his third reason for suspecting infection in the case of chronic disease is most plausible of all: data. For instance, there is a virus that is known to cause breast cancer in mice. This same virus has been found in women with breast cancer and is rarely found in women without breast cancer. The geographic distribution of the mice in question roughly matches the geographic distribution of the breast cancer. It seems to Ewald (and to me) as though it would at least be worth checking out if women can "catch" certain kinds of breast cancer from mice the way we used to catch plague from rats. He has other example ranging from the nearly-conclusive as above to the slightly-suggestive as his theories about schizophrenia.

There are two unfortunate things about this book. The first is the poor separation between the actual main idea, evolutionary theory applied to medicine, and it's most controversial off-shoot, "stealth infections". His plausible and inexpensive ideas for improving medical care through simple evolutionary insights are probably being masked by his more outrageous-seeming claims and may go unheeded because of that. The second unfortunate thing about the book is that Ewald is not a particularly good writer. Much of the text, especially the HIV-related text, is hard to follow and a lot of the details of his reasoning are left up to the reader to fill in.

Therefore my rating:

Idea: 9/10
Execution: 7/10

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Plague Time: A Review | 35 comments (33 topical, 2 editorial, 0 hidden)
Worse to your heart than tobacco, alcohol, coke (2.00 / 7) (#1)
by nictamer on Wed Jun 13, 2001 at 09:32:11 AM EST

... It's JUNK FOOD.

And it's legal, too.

It's not an infectious sort of plague, tho. More of a social plague.

Red wine is believed to prevent heart disease, by the way. So much for the anti alcohol fanatics.
--
Religion is for sheep.
Not according to Ewald (4.00 / 1) (#3)
by DesiredUsername on Wed Jun 13, 2001 at 09:42:37 AM EST

Ewald is more careful about labelling junk food, smoking, high blood pressure, etc as "risk factors" rather than "causes". He even speculates about how these factors could exacerbate an existing artherosclerosis "infection". For instance, the proposed virus that he says causes the disease, C. pneumoniae, is lipophilic. So your eating fatty food just provides them with food. But if you weren't infected you wouldn't have (as much of) a problem.

Play 囲碁
[ Parent ]
Um... (3.00 / 1) (#8)
by i on Wed Jun 13, 2001 at 10:14:57 AM EST

HIV is also a lipophilic virus. So people who eat junk food should have more chance to get AIDS, right?

and we have a contradicton according to our assumptions and the factor theorem

[ Parent ]
I don't know (3.00 / 1) (#12)
by DesiredUsername on Wed Jun 13, 2001 at 10:49:01 AM EST

Not being a biologist or even a physician I can't answer the question. And Ewald doesn't address it so I can't say how he'd answer.

Play 囲碁
[ Parent ]
kook theories (4.00 / 3) (#2)
by Signal 11 on Wed Jun 13, 2001 at 09:41:16 AM EST

The problem with kooks are that they can be amazingly logical... to a point. As you point out, the author makes some good points. But it's rather like the mathematical proof that 2+2=0... it's all logical, except buried halfway into the proof is a single innocuous line - divide by zero. Science is like that too - and scientists screw up an awful lot, I'll give him that...

But the fact is that we have rigorous standards and testing for a reason - and this is why the scientific community seemingly moves so 'slow' compared to the rest of the world. When the media sounded the alarm on the so-called 'cold fusion' in a test tube experiments, the scientific community remained silent for a couple weeks... after which, upon conducting their own experiments around the world, came back with the answer - False. What's important to note here is that it was only a small experimental error - an error in methodology, that made these fantastic results seem possible.

If one wishes to call something science, one should adhere to all of the rules of it, not just the ones that are easy and convenient to do. A theory about 'infectious agents' causing all kinds of human ailments is fine.. but the simpler explanation (ockhams razor) is the one that the scientific community has embraced, because it fits all the data, and is simpler.




--
Society needs therapy. It's having
trouble accepting itself.

Totally Offtopic (none / 0) (#20)
by FatRatBastard on Wed Jun 13, 2001 at 04:55:24 PM EST

... but 2 + 2 = 0 can be perfectly valid without resorting to Div0.

2 + 2 (Mod 4) = 0.

Sorry to be obtuse, but I love a good math problem.

[ Parent ]
"kook" (4.83 / 6) (#5)
by ucblockhead on Wed Jun 13, 2001 at 10:03:52 AM EST

I wouldn't label this guy as a kook. "Wrong", probably, but not "kook".

Here's his homepage, by the way. Scientific American also did a profile of him a couple months back.

Anyway, science needs mavericks to challenge the conventional wisdom from time to time. Often they are wrong, but sometimes, as in "plate tectonics" and the foreign origins of mitochondria, they turn out to be correct.

Oh, and his "old age" arguments are missing something very important. Accidents and such will keep many people from reaching a certain age. You don't design a car with a muffler that is good for 500,000 miles if the engine is good for only 100,000 miles. That is, if, statistically speaking, the chances where high that the average prehistoric person died around age 40 from accidental causes (or disease, or famine, whatever), there'd be little evolutionary pressure to fix diseases that generally occurred after that.
-----------------------
This is k5. We're all tools - duxup

age & evolution (4.66 / 9) (#7)
by codemonkey_uk on Wed Jun 13, 2001 at 10:13:07 AM EST

The reason we reproduce, age and die is because its less expensive & less risky for our genes than to maintain the body indefinitely, and provides opportunity for improvement through mutation*. It is the at the core of what life is.

Once this high level strategy for survival has been established, along with the emergence of life on earth, changing the fundamental structure in an attempt to extend an individuals life by a few years in the hope of a altruistic advantage is practically impossible.

Death is a fundamental design decision in the structure of life. To use it as an evolutionary argument in support of a predator-prey relationship with disease is fundamentally wrong headed.

*Note: When I say an "improvement through mutation" I'm talking about a gene improving its enviroment (the body) by "teaming up with" (via cross over) better genes.
---
Thad
"The most savage controversies are those about matters as to which there is no good evidence either way." - Bertrand Russell

"Fundamental Design" (4.40 / 5) (#14)
by ucblockhead on Wed Jun 13, 2001 at 11:43:05 AM EST

I'd take issue with some of that. I don't think that we are "designed to die" in that we are designed to live a certain amount of time and then, *poof*. I think it is more that we have a "design lifetime" like a car does. A car might be built to last 150,000 miles. It might go further if we're lucky. It might fall apart far too early. It's just that it's cheaper to simply buy another car ever 150,000 miles than to build one that goes significantly farther. And we could stretch the lifetime out by replacing parts that fail, but eventually we'd just be spending way too much.

Bodies are much like that. I am convinced that we can, in theory, extend human lifetimes further and further out. But as we do, it will become more and more expensive. At what point is it no longer worth it?

I personally think that the idea that we die to make way for the next generation is overrated in that it doesn't really explain why some species live for over a hundred years and others last only a few days. I think that a better explanation is that the reason mice die of old age at three years is because in the wild, chances are most mice are going to get stepped on, eaten by a snake, or something else before they hit three. There's not much point in making a mouse last longer if that's the case.
-----------------------
This is k5. We're all tools - duxup
[ Parent ]

Good analogy, etc (4.00 / 1) (#15)
by codemonkey_uk on Wed Jun 13, 2001 at 11:48:26 AM EST

I wasn't advocating the idea that "we die to make way for the next generation". I was saying, basically, what you said, except, it seems, less clearly.
---
Thad
"The most savage controversies are those about matters as to which there is no good evidence either way." - Bertrand Russell
[ Parent ]
Bogus genetic argument (4.14 / 7) (#10)
by streetlawyer on Wed Jun 13, 2001 at 10:22:45 AM EST

The second argument is from evolution and is somewhat more plausible. If human genes caused the "diseases of old age" like Alzheimer's and heart disease, why hasn't evolution eliminated these diseases by now? Obviously old people don't have children, but this argument has two flaws. First, you don't need to be actively reproducing to affect your genes' chances of survival. For instance, children with a living, on-the-ball grandparent are probably more likely to survive than children without one. Even this slight selection pressure should have removed some of these diseases from the gene pool. Second, "old people don't have children" is circular. The *reason* they don't have children is that they are either dead, too sick or infertile. Why did their genes allow them to become so?

Quite clearly mixes up selection at the group, population and gene levels. Even if a tribe with grandparents is likely to be more prosperous than a tribe without grandparents, this says nothing about the adaptive fitness of the individuals within that group; it certainly doesn't imply that there would be sufficient "selective pressure" (a concept in poor evolutionary standing anyway) to drive out genes for post-reproductive degeneration. After all, this sort of "selective pressure" would be bad news for praying mantises and black widow spiders, who appear to have survived generation after generation of their behaviour.

It's also an entirely unwarranted assumption that there _could_ be such a thing as a gene for "no dementia" or "no reproductive decline". It's known that all existing mammals are born with a finite supply of ova, which suggests to me that the impossibility of indefinite fertility is rather like that of a unicorn; there is no single-gene (or non-combinatorially huge number of genes) mutation which could produce it at all, meaning that this sort of possibility is effectively locked off from natural selection forever.

And furthermore, the idea that "children with a living, on-the-ball grandparent are probably more likely to survive than children without one" introduces a whole lot of utterly speculative and unwarranted evolutionary psychology and sociobiology with the assumption that nurturing ancestors is directly selected for as adapted behaviour. If one considers the alternative hypothesis -- that nurturing ancestors is a not-directly-adaptive consequence of two adaptive traits (a strong desire to survive and kin selection), then there is no evidence to support the rather woolly idea that "ancestors are a source of advice and knowledge". As far as I am aware, the only human populations which have frequently been in such a situation for resources that it genuinely had to make a costly sacrifice to maintain the supposedly vital wisdom of the ancestors are the Bedouin and Inuit, both of whom practice euthanasia.

So, an interesting thesis spolit by the tendency of biologists to abandon all pretence of rigour when trying to expand the boundaries of Dawkinsism to encompass sociology.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever

no group selection problem (4.66 / 3) (#11)
by DesiredUsername on Wed Jun 13, 2001 at 10:46:13 AM EST

"Quite clearly mixes up selection at the group, population and gene levels. Even if a tribe with grandparents is likely to be more prosperous than a tribe without grandparents..."

Who said anything about tribes? Parents are multi-functioned (food, protection, "wisdom", etc). Having one parent instead of zero is clearly advantageous. If that single parent is killed by a defective gene, the child is less likely to survive--and is somewhat likely to have carried the defective gene. Result: Selection pressure away from the gene. Having two parents instead of one would presumably be even more advantageous and having three possibly even more s--at the very least so that there are "spares" around, i.e. one or two parents die from accidents, older kin are around to take care of the child. There is no group selection problem here.

"And furthermore, the idea that "children with a living, on-the-ball grandparent are probably more likely to survive than children without one" introduces a whole lot of utterly speculative and unwarranted evolutionary psychology and sociobiology with the assumption that nurturing ancestors is directly selected for as adapted behaviour."

No, it doesn't. It doesn't matter why the grandparents are nurturing--it could be adaptive it could be random. The point is that no matter how nurturng the grandparents are, they can't do diddly if they are dead or senile.

Play 囲碁
[ Parent ]
too weak (4.66 / 6) (#13)
by streetlawyer on Wed Jun 13, 2001 at 11:08:26 AM EST

At most, that is an argument for the genetic adaptiveness of survival until one's offspring can fend for themselves. And the point is that we know human beings are tribal animals, so the group level has to be taken into account. If all tribe members look after the offspring of all, then the number of people around to look after babies is determined by the number of people the territory can support, and the age to which individuals survive only determines the average age of (and therefore the average accumulated accidental damage sustained by) the pool of parent-figures.

The vast variety of parental models which actually exist among different animal species should give us a clue that the "selective pressures" involved are likely to be comparatively weak -- Ewald seems to need them to be so strong as to have potentially been the determining factor in human survival during the period of historical time over which epidemic diseases developed, which is implausible.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

When *who* can fend for themselves? (4.00 / 2) (#16)
by DesiredUsername on Wed Jun 13, 2001 at 11:48:41 AM EST

"At most, that is an argument for the genetic adaptiveness of survival until one's offspring can fend for themselves."

I agree, assuming "one's offspring" includes grandchildren, etc. Clearly being a grandparent is less useful than being a parent but I wouldn't call it useless. Arguing that the effect is "too weak" is pointless at this stage since the effect hasn't been measured to see if it jibes with when genetic diseases start to take their toll.

In any case, Ewald doesn't "need" them to be strong at all. If heart disease and Alzheimer's are infectious, the genetic usefulness of grandparents will be unaffected.

Play 囲碁
[ Parent ]
disagree and disagree (4.25 / 4) (#17)
by streetlawyer on Wed Jun 13, 2001 at 11:59:14 AM EST

The usefulness of grandparents has been measured using a suitably "evolutionary" test by observation of the Bedouin and Inuit. In the rare cases where human societies have to make a sacrifice of resources to keep grandparents around, they practice euthanasia. Presumably, Artic and Saharan tribes which reasoned that old people were still really useful and should get their share of the water/whale blubber died out long ago.

In any case, Ewald doesn't "need" them to be strong at all. If heart disease and Alzheimer's are infectious, the genetic usefulness of grandparents will be unaffected.

No, he needs the selective pressure to be important in order for his evolutionary argument to have explanatory power. If the selective pressure to evolve continued fertility and non-dementia is weak, then one cannot argue that they would have evolved away had the predator/prey relationship been absent. In other words, if the pressure is not strong, then the infectious agent hypothesis is an explanation in search of an anomaly.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Usefulness (4.50 / 2) (#28)
by ucblockhead on Thu Jun 14, 2001 at 12:26:50 PM EST

That argument really just says that the "elders" are of less use than other, younger members of the tribe. It doesn't really show that the "elders" are a net negative in all environments, only that they are a net negative in certain environments. For evolution to work on the traits involved here, it would require that they be a net negative in most environments. (Most of this assumes that no human group, including the eskimos and the bedouin, have been in place long enough to evolve significantly in these respects. Aging is something that isn't as easy to change as skin color or facial features.)

It's like the arctic explorers who eat their dogs when they run out of food. It doesn't mean that their dogs were a burden before that point.

But anyway, it is probably a mistake to get too fixated on humans here, because all animals age, not just humans. A theory that purports to explain a bunch of age related diseases in terms of genetics has to explain why it occurs in all animals, from rats to whales, as well as humans. Adding mysterious infectious agents doesn't really change this.

That's my real problem with "need to keep the elders around to pass on knowledge" explanations. Why are there old rats, then? To pass on rat wisdom? Yet rats show all the same sorts of aging problems as humans do.
-----------------------
This is k5. We're all tools - duxup
[ Parent ]

Ova (4.33 / 3) (#18)
by ucblockhead on Wed Jun 13, 2001 at 12:01:19 PM EST

I don't disagree with you, mostly, but you might be reading to much into the finite number of ova and its potential effect on aging. There are a wide variety of lifespans in mammals, from a year or two to over a hundred. It also means that the selective effect on aging is going to be sex-biased, as male fertility does not have the same dead drop-off that female fertility does. And you do see some differences in this area, with a things like heart disease, which can effect men at any time, but tend to hit women only after menopause.

The thing about "Selective pressure" is that it can't really "drive genes out" unless they are invariably fatal. Instead, they tend to drive them to some low level, below the statistical "noise" of the randomness of deaths. Usually it is the slowest in the tribe that gets taken by the lion, but sometimes it is the guy who had the misfortune to trip. I suspect a lot of diseases are like this. The heart disease rate may seem high to us moderns, but to a primitive proto-human, it would likely seem minimal to the death rate do to accidents, predators and the like. If only ten percent of the population even makes it to fifty, another 1 in 20 dying from heart attacks isn't likely going to make much difference to the tribe in general, regardless of how important the "nurturing" and "knowledge transference" might be. (As you say, wholly speculative in itself.)

Anyway, you are likely right, there likely is no gene for "no reproductive decline". But there very likely is a set of genes that controls when the genetic decline occurs. But it is not likely to be a nice simple timer like most people imagine. Not a thing that you can simply turn up if you want. The human reproductive life span ends at about 45-50 the same way the paint on my house lasts about ten years.

Finally, I think it is a mistake to look at any society we have access to and look for evolutionary effects. Our bodies evolved over millions of years, and evidence for any but the most primitive societies runs back only about 40,000. Society, even primitive society, hasn't had enough time to have much of an effect.
-----------------------
This is k5. We're all tools - duxup
[ Parent ]

Re: Bogus genetic argument (4.66 / 3) (#23)
by sigwinch on Wed Jun 13, 2001 at 07:58:33 PM EST

Even if a tribe with grandparents is likely to be more prosperous than a tribe without grandparents, this says nothing about the adaptive fitness of the individuals within that group; it certainly doesn't imply that there would be sufficient "selective pressure" (a concept in poor evolutionary standing anyway) to drive out genes for post-reproductive degeneration.
First, "selective pressure" is not in poor standing; the only other options are Lamarkism and/or divine intervention. Second, "driving out" genes takes extreme selective pressure; small pressures operating over time create small genetic tendencies. Regardless, I don't think there has been enough time for post-reproductive health to have evolved much. It's only in the past few hundred thousand years that humans had the lifespan and intellectual sophistication for elders to be a giant selective factor.
After all, this sort of "selective pressure" would be bad news for praying mantises and black widow spiders, who appear to have survived generation after generation of their behaviour.
People are not bugs; the labor and knowledge value of human males considerably outweighs their one-time nutrition value.
It's known that all existing mammals are born with a finite supply of ova, which suggests to me that the impossibility of indefinite fertility is rather like that of a unicorn; there is no single-gene (or non-combinatorially huge number of genes) mutation which could produce it at all, meaning that this sort of possibility is effectively locked off from natural selection forever.
Until recently, the ova supply only had to sustain a dozen back-to-back pregnacies. And what did evolution do? It gave women hundreds of ova, enough that even if they never got pregnant, they were more likely to die before running out. Let homo industrialis evolve for a million years and you'll see the fertile period lengthen.
And furthermore, the idea that "children with a living, on-the-ball grandparent are probably more likely to survive than children without one" introduces a whole lot of utterly speculative and unwarranted evolutionary psychology and sociobiology with the assumption that nurturing ancestors is directly selected for as adapted behaviour.
Grandparents exist. They eat food, drink water, and generally compete for resources that could go to their grandchildren, yet evolution created them anyway. The mere existence of a trait that costs significant energy is conclusive evolutionary proof that the trait is a beneficial adaptation. Q.E.D.
If one considers the alternative hypothesis -- that nurturing ancestors is a not-directly-adaptive consequence of two adaptive traits (a strong desire to survive and kin selection), then there is no evidence to support the rather woolly idea that "ancestors are a source of advice and knowledge".
No evidence besides our own overwhelming experience that if you need complex knowledge (how to cultivate maize, how to break a horse, how to make an arrowhead, which herbs best treat septic infection, how to resolve a dispute), you go ask an elder. You can learn the motions to do a craft by the age of 15, but becoming a master who can improve the craft itself takes much longer. With mere fecundity, we would be nothing more than the hominid analog of rabbits.

You also don't consider a third non-wisdom selection factor: possessing old people is unambiguous proof that a group is prosperous and healthy, and has been that way for three consecutive generations (kind of like a peacock's feathers prove he is neither starving nor diseased). All other things being equal, the girl with more living grandparents is a better proposition.

As far as I am aware, the only human populations which have frequently been in such a situation for resources that it genuinely had to make a costly sacrifice to maintain the supposedly vital wisdom of the ancestors are the Bedouin and Inuit, both of whom practice euthanasia.
Those examples merely show that a harsh, resource-poor environment can support less intellectual sophistication.

--
I don't want the world, I just want your half.
[ Parent ]

this is presumably some sort of joke (4.00 / 3) (#24)
by streetlawyer on Thu Jun 14, 2001 at 02:07:50 AM EST

The mere existence of a trait that costs significant energy is conclusive evolutionary proof that the trait is a beneficial adaptation. Q.E.D.

Are you sure about this one?

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Energy cost of traits (none / 0) (#29)
by sigwinch on Thu Jun 14, 2001 at 06:17:25 PM EST

Are you sure about this one?
Yes, with the qualifications that the organisms be close to evolutionary equilibrium with their environment, and that they occassionally experience starvation. I think that most species substantially meet these qualifications. Occassional starvation selects against resource-intensive traits that have no survival benefits. Traits that prevail in the face of starvation must therefore have beneficial value.

Of course, the strict 'energy law' only holds for traits that are hard-wired in the activated state. Nearly all real traits deactivate to some extent during starvation, so what you really want to look at is the deactivation-starvation curve. A more positive slope implies that the trait is less beneficial, while a less positive slope implies that the trait is more beneficial. A negative slope implies that the trait is proactively starvation avoiding.

--
I don't want the world, I just want your half.
[ Parent ]

the trouble with that... (5.00 / 1) (#30)
by ucblockhead on Thu Jun 14, 2001 at 07:51:46 PM EST

The trouble is that the organism may be at a local minima. In other words, even though a trait costs the organism more than it brings, any potential mutation brings the organism into a state where the new trait costs the organism even more then the old bad trait. If the only way the organism can get to a state with a trait that costs less than it is worth is to go through this even worse state, then it will stay stuck at the local minima.

Being stuck at such a local minima could easily cause a species to die out rather than evolve.

People usually ignore the intricities when talking evolution, but sometimes they can't be ignored. Traits are made up of sections of DNA, which mutate in certain ways, and therefore some mutations are easier than others. As an example, you could easily cause the human race to evolve a dark brown skin color simply by preventing all light skinned humans from breeding. You could not, however, cause the human race to evolve a green skin color because there is no simple set of mutations that will get them there. You'd be waiting forever for a "green skin" mutation to occur. Parrots, on the other hand...

So you can imagine a situation where "brown skin" was a trait that cost more than it was worth but green skin cost less than it was worth. Even if this were the case, the human race would be brown, and not green, if white skin cost even more than brown skin. It doesn't matter than green skin would help the organism as there is simply no path for that trait to evolve. The species will go extinct before it evolves the trait. One reason why species go extinct in the real world all the time.


-----------------------
This is k5. We're all tools - duxup
[ Parent ]

FYI (4.66 / 3) (#27)
by ucblockhead on Thu Jun 14, 2001 at 12:15:09 PM EST

It gave women hundreds of ova, enough that even if they never got pregnant, they were more likely to die before running out.
Pregnancy has little to do with it. A woman loses one or two ova every cycle, whether fertilization takes place or not. That works out to a few hundred over the woman's fertile lifetime, regardless of the number of pregnancies.

Anyway, the trouble with your "grandparent" argument is that no one can really say with any assurity how many adults past the age of fertility there were in prehistoric times, so you can't really make any meaningful statements about the resource cost. But the bigger error is assuming that evolution is an engine that inevitibly arrives at a perfect solution. It isn't, and it is very susceptible to local minima. Evolution seeks a low energy point the way water seeks the lowest physical point. This doesn't mean lakes aren't found in the Himalayas.

It may well be that the older folks were a significant resource drain, yet that there were also no easy genetic paths to a sort of "Logan's Run" gene that caused people to instantly croak when they reached a certain age. In other words, any genetic change that would weaken the "elders" to the point where they wouldn't exist would also effect younger, still fertile members of the tribe, reducing overall fitness.

It is also important to remember that only half the elders would actually be infertile. Male fertility doesn't stop the way female fertility does. This means that any such gene would have to be sex linked, which means that it would be much less likely to arise.

And finally, evolution is a dynamic thing. While in theory, every species evolves to "perfectly" fit its environment, that environment is constantly changing. This means that many traits may exist because they were useful at one time, but not now.

None of this is to say that the "elders" didn't positively effect the tribe. But I don't think the evidence is strong enough to make conclusive changes.
-----------------------
This is k5. We're all tools - duxup
[ Parent ]

The true evolutionary purpose behind aging... (4.83 / 6) (#22)
by Kasreyn on Wed Jun 13, 2001 at 07:07:15 PM EST

...is to further the speed of evolution itself. Consider: If previous generations die out faster, this has many effects. One is that there will be more resources left to support younger generations. One is that they will produce fewer offspring before death. Another is that their offspring will have their protection and care for less amounts of time. However, the main effect is that generations will be shorter.

I do not believe that 74 years, or whatever the current lifespan is, is all that can be managed by our mortal tissue. I believe human beings have been evolved to self destruct by that age, evolved to be eliminated before they're that old. If the generations come quicker, the organism evolves faster. (more generations = more chances for natural selection to eliminate bad genes from the gene pool. We shouldn't think of our ancient single celled ancestors in terms of years ago; we should think of them in terms of generations ago)

An organism that evolves faster adapts faster to changing environments, and will thus outperform and supplant other organisms that evolve more slowly. End result? Faster generations, thus shorter lifespans, are strongly selected for. Therefore, we all come with a built in time bomb. Mother Nature, to use a phrase, wants us to reproduce, to dump our mutations into the gene pool, and then get the heck out of the way. If not for this pressure from competing with other evolving organisms, I think our natural lifespan might be in the 200's or 300's, and other animals on Earth might be even longer-lived.


-Kasreyn


"Extenuating circumstance to be mentioned on Judgement Day:
We never asked to be born in the first place."

R.I.P. Kurt. You will be missed.
not quite (none / 0) (#36)
by theantix on Mon Jul 09, 2001 at 02:17:41 AM EST

You were right in your first paragraph when you said: "One is that there will be more resources left to support younger generations." But your main point that organisms die off to speed up the evolutionary process is based on flawed logic.

I've been reading a lot of Richard Dawkins lateley (Selfish Gene, Blind Watchmaker, etc) and he spends a lot of effort fighting the very idea that you are indirectly proposing: that organisms develop for the sake of the species. Infact it seems to be the case that natural selection works on the level of the gene (in some cases even smaller than that!). I think your process is indirectly tied to that misconception, because a particular organism would not see the benefits of dying young in order to "eliminate bad genes from the gene pool".

Dawkins' argument, from "River out of Eden", is extremely simple: your direct ancestors were all young at one point in their lives, but only some of them were old. (I told you it was simple) Thus the genes that provided reproductive / survival success for the young folks would win out over genes that benefited the elderly.

And of course you were right: organisms would live as long as needed to to properly raise their offspring and help them along through life. For humans, it seems about 40-50 years at the maximum, before the body starts to fall apart (of course through medical technology we have stretched that out a bit to 70-80 on average). Which is conveniently just enough to raise one or two generations of offspring. If they die at 45, but have passed on their genes -- that's all that is needed for that trait to continue to survive, no reason to ever get weeded out via natural selection. There is little reason to continue reproducing past that point, because you would have already started a genetic spiral with your first generation.

--
You sir, are worse than Hitler!
[ Parent ]
You would be right... (none / 0) (#37)
by Kasreyn on Thu Aug 02, 2001 at 12:14:49 AM EST

...were evolution a closed system with only one species of organism growing, and not in competition with other species for the same ecological niches.

Were there only one species of life, the rate of evolution would not matter enough to make dying young viable. Consequently I predict evolution would be slower.

I realize that no individual organism is selected upon, based on the concept of decreased longevity. However, evolution also works on a macro-scale - that of evolving species pitted against each other in a struggle for resources and survival. Consider Lions vs Leopards - both top-level carnivores, both occupy the same geographical areas, both highly specialized for the role of carnivore and hunter par excellence. Species like this compete with each other, because they consume the same resources.

Now, if the lions were to die younger and mutate (thus, eventually, evolve) faster than the leopards, what will happen? It will make no real difference to the lions. The individual lion might think (if he ponders it) that it kinda sucks. But it's good for the species. And the leopards are not evolving and adapting as quickly. Result, the lions win out. Over enough time, Natural selection will begin to prefer creatures who are long-lived enough to be efficient and reproduce, yet short-lived enough not to slow the march of evolution. The end result is a delicate balance.

I suppose one way to study this might be through paleontological or archeological studies of fossilized animals, such as the giant mammals of the Quaternary Period. One might study the different niches and which were more fiercely competed for, and whether the more fiercely contested ones had animals with apparently shorter lifespans and faster adaptation. If anyone else can think of a viable experimental format, let me know.


-Kasreyn


"Extenuating circumstance to be mentioned on Judgement Day:
We never asked to be born in the first place."

R.I.P. Kurt. You will be missed.
[ Parent ]
one thing you are missing: (none / 0) (#38)
by theantix on Tue Aug 14, 2001 at 03:43:44 PM EST

Now, if the lions were to die younger and mutate (thus, eventually, evolve) faster than the leopards, what will happen?

Ah, I see where we differ. I have read that mutations occur within the lifespan of the creatures (often from exposure to radiation such as sunlight). According to the book I am reading just now (The Third Chimpanzee, I forget the authors) this means that the rate of mutation will be constant no matter what the lifespan of the creature.

If anyone else can think of a viable experimental format, let me know.

Actually, what they did do was very interesting as well. They took known dated fossil records and calculated the amount of mutations that occurred with the creatures, and figured that they were very equivent across species, and actually developed a "clock" which could measure evolutionary progress. Pretty interesting stuff, and it seems to be up your alley so I'd check it out if I were you.

--
You sir, are worse than Hitler!
[ Parent ]

Aging (3.00 / 1) (#25)
by DoubleEdd on Thu Jun 14, 2001 at 04:16:20 AM EST

Thought I'd post this as a new topic, since there are a couple of threads that this could be attached to.

I don't know what the current thinking is, but I remember some fairly recent stuff suggesting that the kind of aging that occurs due to programmed cell death is due to a mechanism which evolved to protect against cancers. If you program a cell to die after so many divisions (germ-line cells excluded obviously, or there'd be a limit to the number of generations) then it can't keep multiplying out of control unless the gene governing this mechanism mutates.

Of course this doesn't easily explain a number of degenerative conditions or the difference in lifespan of a number of creatures. I expect the latter might be due to a trade-off between the effectiveness of such a mechanism and the time and number of divisions needed to reach maturity -so big animals would need more divisions and would live longer, perhaps....

Red Herrings (none / 0) (#26)
by ucblockhead on Thu Jun 14, 2001 at 12:00:26 PM EST

I've long thought that the fact that most human cells will only divide a certain number of times is a red herring in the search for the cause of aging. There's no evidence that I know of that any of the observed symptoms of aging are at all linked to the division limit.

If I recall correctly, most cells in the body don't even reach have that devision limit before the person dies.
-----------------------
This is k5. We're all tools - duxup
[ Parent ]

Certainly not a wacko (4.00 / 2) (#31)
by cp on Fri Jun 15, 2001 at 02:08:54 PM EST

As someone who's taken a biology class or two with Ewald, I can assure you he's not a wacko. Though I haven't read his book yet, I can assure you the man is quite articulate in lecture format, so if his writing is poor in execution, then that is a deviation from his better grasp of other media.

Similar thinks have been found already. (4.00 / 1) (#32)
by SnowBlind on Tue Jun 19, 2001 at 04:27:55 PM EST

Ulcers were once thought to be caused solely by enviromental factors. Now we know that they are caused by microbes as well. It a good thing too, because if I had to give up spicy food, I would have to kill myself.
I seem to remember some forms of heart disease and cancer(lukemia in cats for sure) are caused by virii, it is certianly worth looking into.

Finding out that it is caused by a virus is *not* a good thing either. Vaccines cannot always be developed (AIDS) and there are few "medications" for virii.

There is but One Kernel, and root is His Prophet.
Similar things have been found already. (none / 0) (#33)
by SnowBlind on Tue Jun 19, 2001 at 04:28:05 PM EST

Ulcers were once thought to be caused solely by enviromental factors. Now we know that they are caused by microbes as well. It a good thing too, because if I had to give up spicy food, I would have to kill myself.
I seem to remember some forms of heart disease and cancer(lukemia in cats for sure) are caused by virii, it is certianly worth looking into.

Finding out that it is caused by a virus is *not* a good thing either. Vaccines cannot always be developed (AIDS) and there are few "medications" for virii.

There is but One Kernel, and root is His Prophet.
Clarify... (none / 0) (#35)
by kezgin on Sat Jun 23, 2001 at 10:55:42 AM EST

Finding out that it is caused by a virus is *not* a good thing either. Vaccines cannot always be developed (AIDS) and there are few "medications" for virii. So you would rather stay with conventional treatment than find out that some of these diseases were caused by virii, and then work towards finding a vaccine?

[ Parent ]
Minor nit (4.00 / 1) (#34)
by weirdling on Thu Jun 21, 2001 at 05:12:24 PM EST

Alzheimer's disease et. al. are old-people's diseases, only recently unmasked by good nutrition and decent health care. Essentially, when people had to struggle much harder for life, they often only lived 30 years or so, just long enough to reproduce at eighteen and get their children to a point where they could survive. Parts of the world even now have average ages in the 40s. Sure, there were grandparents, but it only takes a few elders to provide wisdom for the whole tribe, while it takes many young warriors to keep the birth rate up high enough to keep the tribe alive.

I'm not doing this again; last time no one believed it.
Plague Time: A Review | 35 comments (33 topical, 2 editorial, 0 hidden)
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