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Author Topic:   Humans are losing.
crashfrog
Inactive Member


Message 46 of 58 (309811)
05-06-2006 7:09 PM
Reply to: Message 45 by EZscience
05-06-2006 2:28 PM


Re: Evolution of reduced fecundity happens
Reduced fecundity is not reduced reproduction?
Fecundity is the total number of offspring produced in an organism's life.
How can you possibly evolve reduced fecundity without reduced reproduction?

If, by virtue of having less offspring, considerably more of them survive to adulthood and mating, then you've reduced your fecundity but increased your reproduction.

I mean, how else do you think that trait gets selected for?

1. evolution of reduced fecundity (fewer offspring in the lifetime).
2. evolution of delayed onset of reproduction (later birth of first offspring).

No, I get what we're talking about. There's no confusion here.

I refered to these life history traits because they are analogous to the current trends that you identified as reducing human fitness in western countries relative to UD countries.

Yes. From the fact that our populations are not growing, we know that these strategies do not increase fitness at this time. They don't result in increased reproduction, which they would, if they were fitness-positive strategies.

Right?

Now I am pointing out that many lineages, over evolutionary time, have actually evolved reduced fecundity and delayed onset of reproduction.

Right. Because, in many environments and situations, those strategies increase reproduction, and increase the population growth rate of populations with those traits compared to populations that don't have those traits.

It CANNOT, by definition, possibly increase population growth.

Nonsense. Of course it can. Here's a simple example:

You have a population of spiders. One subpopulation has an average brood size of 1 million live individuals, but less than 10% survive to adulthood. The other population has half the brood size, but because of the reduced competition, more than 50% of of those individuals survive to adulthood and mating.

The first subpopulation grows by 100,000 individuals in that generation. The second grows by 250,000 individuals. By reducing brood size, the second population grows faster than the first, and those traits come to dominate the population.

They end up *leaving* more offspring because they are *producing fewer*, but perhaps these fewer are larger, more competitive, etc. etc. (More good analogies to western humans here).

Right. No, I get it. You're right on, here, except you keep overlooking the fact that if this were what was happening, our population would be growing faster because, even though we had fewer children, more of them would survive to adulthood and mating.

But that's not what's happening. We have less children, but no more of them survive to adulthood than in the developing world. (In fact, here in America, our rates of infant mortality are about the same as in the developing world.) In the developing world, more individuals are born, and just as many of them survive to adulthood and mating. So their population grows faster than ours, and we can prove that reduced fecundity is not a fitness-positive trait in the environment in which we find it.

In human societies, group selection could easily favor populations with lower reproductive rates and selection could already be acting against those UD countries with high population growth rates.

No, again, I get that. Yes, those populations could be favored.

But the change in allele frequencies that we observe proves that they aren't being favored. That's the reality of the situation, right now.


This message is a reply to:
 Message 45 by EZscience, posted 05-06-2006 2:28 PM EZscience has responded

Replies to this message:
 Message 47 by EZscience, posted 05-07-2006 5:02 PM crashfrog has responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 47 of 58 (310048)
05-07-2006 5:02 PM
Reply to: Message 46 by crashfrog
05-06-2006 7:09 PM


Re: Evolution of reduced fecundity happens
Crash writes:

If, by virtue of having less offspring, considerably more of them survive to adulthood and mating, then you've reduced your fecundity but increased your reproduction.

What you’ve done is increase your ‘fitness’ by reducing your ‘reproduction’.
Crash, you can’t reduce your reproduction *without* reducing your fecundity.
If you refer to the ‘reproduction’ of an individual, it means fecundity, plain and simple.
Your reproduction isn’t comprised of your progeny’s survivorship *after selection*, but rather the total number of offspring you produce in the first place.
That is why individual fitness is defined not simply as the number of offspring produced (simple fecundity) but rather as the number of offspring that survive to reproduce themselves. So you’ve defined fitness here, not reproduction.

Crash writes:

They don't result in increased reproduction, which they would, if they were fitness-positive strategies.

As we have essentially agreed, you can have traits that are favored under selection that actually reduce reproduction if they result in increased fitness.

But what about your earlier claim that differences in relative rates of population growth are evidence of selection? You must admit this is a flawed inference so that we can move on to something more interesting.

Let me propose my definitions for your tentative acceptance:

Individual selection = a force that acts to change the frequency of a particular trait or gene within a population by affecting the survival of individuals differentially.

Group selection = a force that acts to change gene frequencies in a population by affecting the survival of specific groups differentially.

Individual fitness = the number of children an individual has in its lifetime (fecundity) x the proportion of these that survive to reproduce.

Population growth rate (PGR) = (birth rate – death rate) within a specific population.

Some conditions of the human situation we might agree on:

UD countries currently have higher PGR’s than western nations.
This is largely a function of differences in *reproductive behavior* in UD countries relative to ours:

-earlier onset of reproduction
-higher lifetime fecundity

OK. Now let's look at what you said:

Crash writes:

So their population grows faster than ours, and we can prove that reduced fecundity is not a fitness-positive trait in the environment in which we find it.

They have higher average darwinian fitness, comparing *populations* - yes, so what? - are your kids going to compete with kids in Zimbabwe for resources and mates? Your individual fitness is determined locally, not globally (hence the resistance to immigration).
It also doesn't mean that reduced fecundity isn't currently selectively advantageous within our population. It currently appears to be the behavior that is selected *for*, so we need to explain that, on the assumption that higher fecundity is the primitive trait.

One question is whether this higher 'average individual fitness' will translate into a higher *relative population fitness* as determined by group selection forces. This is very much an open question (assuming you accept that group selection is a potentially powerful force in human evolution). Strong group selection can quickly negate high individual fitness if you happen to be in the wrong group.

But more interesting still is this question.
Why is reproductive behavior in western developed countries changing away from the more primitive ‘have all the kids you can’ approach? It must be changing because of some form of selection, and it can’t be simple individual selection for obvious reasons (no apparent payoff in biological fitness).
I suggest that our economically-driven society is a source of cultural selection, and this is the force that is selecting for delayed onset of reproduction and lower fecundity.
We want to make sure we have lots of resouces to provide for our offspring before we have them, and by having fewer, we can provide them with more. We are seeking 'cultural fitness' for our offspring,not biological fitness. The availability of birth control is peripheral to the issue – it’s the * reproductive behavior* of individuals that is being selected, regardless of the mechanisms they use to achieve the end, and behaviors leading to reduced fecundity are actually being favored by cultural, rather than biological, selection. But this is not yet the global norm, and they will only be favored globally in the human race in one of two ways: If populations/countries with reproductive restraint vanquish those with high PGR’s or, OR if economic development improves within UD countries to the point where they experience the same cultural selective forces that we do. There is already some evidence that economic development reduces brith rates. I also think that group selection among human societies will ultimately favor populations that evolve reproductive restraint. Unfortunately, this could mean a lot more war and genocide before the planet’s population stabilizes globally, if it ever does. But that is the only hope for continued human existence on the earth.


This message is a reply to:
 Message 46 by crashfrog, posted 05-06-2006 7:09 PM crashfrog has responded

Replies to this message:
 Message 48 by crashfrog, posted 05-07-2006 6:33 PM EZscience has responded
 Message 55 by Quetzal, posted 05-09-2006 11:41 AM EZscience has responded

  
crashfrog
Inactive Member


Message 48 of 58 (310073)
05-07-2006 6:33 PM
Reply to: Message 47 by EZscience
05-07-2006 5:02 PM


Re: Evolution of reduced fecundity happens
Crash, you can’t reduce your reproduction *without* reducing your fecundity.

Are we having confusion in terms, here? I guess so. You've been kind enough to define terms so I'll try to switch to those.

The way your using terms here doesn't make any sense. Could you make an effort to be clearer?

But what about your earlier claim that differences in relative rates of population growth are evidence of selection? You must admit this is a flawed inference so that we can move on to something more interesting.

If we're defining "fitness" as the number of your offspring that survive to adulthood and mating, then my inference becomes even more obvious. If one population has greater fitness than another, than the first population is being selected for and the second against, by definition.

But I actually think we're heading down the wrong path. "Fitness" as described in biology is a genetic trait, and it refers to the propensity of an individual's genes to duplicate themselves into the next generation of the population. Using it to refer strictly to reproduction might mislead us. And I think trying to construct some model of "group fitness" smacks of group selection, a concept largely dismissed by biologists.

They have higher average darwinian fitness, comparing *populations* - yes, so what? - are your kids going to compete with kids in Zimbabwe for resources and mates? Your individual fitness is determined locally, not globally (hence the resistance to immigration).

The difference between global and local is a mattter of degree. Technological advancements within the decade may very well mean that my children compete with those in Africa or Asia for any number of resources, including mates. Already today we hear of American workers having to compete with Indian and Asian workers, so the idea that conspecific competition for resources could be global doesn't seem farfetched to me.

It also doesn't mean that reduced fecundity isn't currently selectively advantageous within our population.

Within our population? That's a possibility. Just speculating, I'd say that larger families are correllated with lower incomes, and low income is correlated with a number of factors like genetic susceptibility to chemical addiction (detrimental genes) and incarceration (negative selective pressures.) I'd say you're probably not wrong.

Why is reproductive behavior in western developed countries changing away from the more primitive ‘have all the kids you can’ approach?

People don't like kids all that much? I know I don't.


This message is a reply to:
 Message 47 by EZscience, posted 05-07-2006 5:02 PM EZscience has responded

Replies to this message:
 Message 49 by EZscience, posted 05-07-2006 8:48 PM crashfrog has responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 49 of 58 (310120)
05-07-2006 8:48 PM
Reply to: Message 48 by crashfrog
05-07-2006 6:33 PM


Units of selection
Crash writes:

The way your using terms here doesn't make any sense. Could you make an effort to be clearer?

Reproduction, quantified at the level of individual, is equal to fecundity.
After selection acts on that fecundity, you are left with darwinian fitness that cannot be equated to 'reproduction'.

Crash writes:

If we're defining "fitness" as the number of your offspring that survive to adulthood and mating, then my inference becomes even more obvious. If one population has greater fitness than another, than the first population is being selected for and the second against, by definition.

Well I don’t want to belabor this, but its not ‘adulthood and mating’, it’s actually ‘adulthood and leaving progeny’. But I have already killed this argument, unless you wish to take issue with my definition of selection, which I see you haven’t.

The problem is that you are, to use your own terminology, ‘conflating’ population fitness with individual fitness. To say that the “first population is being selected for" is to invoke group selection, by its very definition. And yet you refuse to accept the relevance of group selection here:

Crash writes:

some model of "group fitness" smacks of group selection, a concept largely dismissed by biologists.

Group selection has not been discredited by any means. The good evolutionary biologists of the day (Fisher, Maynard-Smith, Bell, Hamilton) initially struggled to ensure that group selection was treated in the most conservative manner, and not mis-applied where individual selection would suffice for an explanation, because it was clear that individual selection was a far stronger force in most cases for most species. This led to group selection being recognized only in instances where its action could be demonstrated in opposition to individual selection. Now we realize that the two can also work in concert.

It has also been much more difficult to model group selection mathematically than individual selection, but it has been done. Furthermore, humanity is not a ’normal’ species and Alexander has argued quite convincingly that group selection has been of extraordinary consequence to human evolution (refs available upon request). In addition, without the extension of kin selection to the level of group selection, you have no explanation for the evolution of altruism among unrelated individuals.

Crash writes:

”Fitness" as described in biology is a genetic trait

Not entirely. It is, of course, mediated by genetics, by the requirement of heredity, but it can be an attribute of genes, individuals OR populations. There are various units of selection. That’s why its really important to be specific about what kind of ‘fitness’ we are talking about.

Crash writes:

The difference between global and local is a mattter of degree.

No. It’s a matter of scale. And the scale at which selection acts can make all the difference in its effect on population genetics. We could go there, but it gets mathematically messy in a hurry…

Crash writes:

the idea that conspecific competition for resources could be global doesn't seem farfetched to me.

Nor I. Global competition for resources will increase and this will affect us locally. But there are only so many service jobs that can be outsourced, and the outsourced Indians answering telephone help lines aren’t going to be bidding against you for real estate in your home town. Bottom line: we will always have more intense competition locally than globally when we consider things at the level of the individual. Again, we see evolutionary rationale for resistance to immigration.

Crash writes:

People don't like kids all that much? I know I don't.

Neither do I, but the point is to try and explain the trend. Not liking kids maybe simply one symptom of the trend, but why is it we should feel that way? Are we behaving in a maladaptive manner? Or are we behaving in a way that is actually being *selected for* in our present society? You tell me.

AbE: New subtitle.

This message has been edited by EZscience, 05-07-2006 07:52 PM


This message is a reply to:
 Message 48 by crashfrog, posted 05-07-2006 6:33 PM crashfrog has responded

Replies to this message:
 Message 50 by crashfrog, posted 05-07-2006 9:26 PM EZscience has responded

  
crashfrog
Inactive Member


Message 50 of 58 (310135)
05-07-2006 9:26 PM
Reply to: Message 49 by EZscience
05-07-2006 8:48 PM


Re: Units of selection
But I have already killed this argument, unless you wish to take issue with my definition of selection, which I see you haven’t.

I'm sorry, but you haven't killed anything. It's not even clear that you've actually addressed my argument.

It would be better for you to do that, in fact, than make proclamations about your supposed debate victory. It's still not clear to me why you refuse to approach this as an honest debate between interested individuals instead of an excercise where you try to slap me around with your dick.

The problem is that you are, to use your own terminology, ‘conflating’ population fitness with individual fitness. To say that the “first population is being selected for" is to invoke group selection, by its very definition.

No, it's not. Group selection, to the extent that it happens, is the phenomenon where individuals experience selection not based on their own traits but on the traits of others that they're connected to; kind of a "I'm with him" effect.

You, on the other hand, are conflating individual selection on a group of individuals with selection of the group itself. It's not clear that group selection ever actuallly occurs. It's certainly not group selection that I'm proposing in this case - merely the action of individual selection operating, in parallel, on a group of individuals.

Group selection has not been discredited by any means.

I don't know any biologists, personally or by reputation, who take the concept seriously.

In addition, without the extension of kin selection to the level of group selection, you have no explanation for the evolution of altruism among unrelated individuals.

Oh, there's a very simple explanation - nonkin altruism is maladaptive.

No. It’s a matter of scale.

Is this how the debate is going to be? You're going to correct me for using the wrong synonym? Yes. Scale. Degree. That's the difference.

Not liking kids maybe simply one symptom of the trend, but why is it we should feel that way?

It's my guess that most people feel that way, and always have. People have kids not because they like kids (at least, not beforehand) but because they like sex.


This message is a reply to:
 Message 49 by EZscience, posted 05-07-2006 8:48 PM EZscience has responded

Replies to this message:
 Message 51 by EZscience, posted 05-08-2006 9:50 AM crashfrog has responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 51 of 58 (310257)
05-08-2006 9:50 AM
Reply to: Message 50 by crashfrog
05-07-2006 9:26 PM


Group Selection in Human Evolution
Crash writes:

It's not even clear that you've actually addressed my argument.

It’s not yet clear that you have one. Would you care to restate it?

Crash writes:

It would be better for you to do that, in fact, than make proclamations about your supposed debate victory. It's still not clear to me why you refuse to approach this as an honest debate between interested individuals instead of an excercise where you try to slap me around with your dick.

Your colorful metaphor aside, I am trying to do no such thing. I am just trying to get you to tighten up your terminology so we can have a meaningful discussion. Where is your justification for accusing me of dishonesty? I have merely pointed out a number of careless errors in your off-the-cuff definitions of things like ‘selection’ and ‘reproduction’ and it would behoove your own intellectual standing to admit your mistakes at this point, but you just keep trying to circumvent them. It is not about ‘debate victory’ but rather about establishing clarity of terminology so the debate can be constructive.

Crash writes:

No, it's not. Group selection, to the extent that it happens, is the phenomenon where individuals experience selection not based on their own traits but on the traits of others that they're connected to; kind of a "I'm with him" effect.

That is the antiquated conception. Group selection merely implies that groups of individuals can serve as a unit of selection, regardless of the relatedness of the individuals within them, and that the genetic composition of the species can be impacted because of it.

Crash writes:

It's not clear that group selection ever actuallly occurs. It's certainly not group selection that I'm proposing in this case - merely the action of individual selection operating, in parallel, on a group of individuals.

Sorry, Crash, but I can’t make any sense of this statement. Can we please refer back to my definitions of group and individual selection in post 47 that you appear to agree to in post 48? How can individual selection possibly act “in parallel, on a group" ? The units of selection are different. If you mean the two acting 'in concert', then yes it can, but that doesn't dispose of group selection as a separate force to be reckoned with.

Crash writes:

Oh, there's a very simple explanation - nonkin altruism is maladaptive.

How is that a simple explanation? How does a ‘maladaptive’ trait evolve???? If altruism were truly non-adaptive under all forms of selection it would be selected against in all systems. But it isn’t. It occurs with appreciable frequency in many systems, especially those with social structure.

Crash writes:

I don't know any biologists, personally or by reputation, who take the concept seriously.

Really ? I think your information is a bit dated. Group selection has not been discredited by any means and has undergone a considerable revival of late, especially in regards to human evolution.

You should read some of the essays by Dr. Richard Alexander, professor emertius at University of Michigan.

I refer you to this article. Alexander’s hypothesis, from the essay:

quote:

…that humans had in some unique fashion become so ecologically dominant that they in effect became their own principal hostile force of nature, explicitly in regard to evolutionary changes in the human psyche and social behavior. At some point in their evolution humans obviously began to cooperate to compete, specifically against like groups of conspecifics, this intergroup competition becoming increasingly elaborate, direct, and continuous until it achieved the ubiquity with which it has been exhibited in modern humans.

quote:
Team sports seem to me especially significant to the arguments presented so far. To the observer they represent not only the physical and mental "how to" of intergroup competition and intragroup cooperativeness but as well a way of participating in the ceremonial and reinforcing aspects of own-group success. The equivalents of fans and cheerleaders have surely been important for a very long time in the group competitions of humans, and it is no accident that the "home court" gives a significant advantage.

quote:
So now we at least have an hypothesis for why the populations most like our evolving ancestors failed to survive alongside us in the way that many similar species of animals and plants do co-exist. Evidently they were extinguished-the collections of traits that identified them disappeared--as a result of the cooperative group-against-group competition that we conduct so frightfully well.

And what about this article .

quote:
In both biology and the human sciences, social groups are sometimes treated as adaptive units whose organization cannot be reduced to individual interactions…

During the 1960's and 70's most biologists rejected group selection as an important evolutionary force but a positive literature began to grow during the 70's and is rapidly expanding today…

We show that the rejection of group selection was based on a misplaced emphasis on genes as "replicators" which is in fact irrelevant to the question of whether groups can be like individuals in their functional organization. The fundamental question is whether social groups and other higher-level entities can be "vehicles" of selection. When this elementary fact is recognized, group selection emerges as an important force in nature


And here

quote:
Group selection has not won over biology. However, the combination of fission/fusion organization (favoring coalition formation and relatively complex tactical behavior) with weapons (which in conjunction with group and/or ambush attacks greatly reduce the costs to actors of lethal inter- and intragroup aggression) create circumstances which may well have favored group selection in hominid evolution.

You can read a rather interesting counterpoint to Dawkins rather constrained viewpoint on group selection here

The implications of group selection for human evolution are also spilling over into psychology.

quote:
The mechanisms underlying these findings may constitute a biological substrate of ethnocentrism, enabling group selection to occur.

Why don’t you stop being so reactionary and unjustifiably dismissive and start putting a little more care, thought and research into your posts?
I keep trying to appeal to the depths of your insight, but your careless replies continue to do nothing more than reveal the limits of your education.

AbE: My search of Biological Abstracts for 'group selection' generated 212 hits - since 1997 alone. Apparently it is not a dead concept.

This message has been edited by EZscience, 05-08-2006 09:03 AM


This message is a reply to:
 Message 50 by crashfrog, posted 05-07-2006 9:26 PM crashfrog has responded

Replies to this message:
 Message 52 by crashfrog, posted 05-08-2006 2:39 PM EZscience has responded

  
crashfrog
Inactive Member


Message 52 of 58 (310329)
05-08-2006 2:39 PM
Reply to: Message 51 by EZscience
05-08-2006 9:50 AM


Re: Group Selection in Human Evolution
It’s not yet clear that you have one. Would you care to restate it?

If you missed it the first time, go back and re-read. My posts haven't disappeared. I've restated my argument every time that you've misrepresented it; I hardly feel the need to do it again.

I'm not really interested in discussing concepts of "group selection" in this thread. If that's something you want to have a substantive discussion on, open a new thread. And I recall that you conceeded my point several posts ago so I don't see much merit in continuing the discussion.

I keep trying to appeal to the depths of your insight, but your careless replies continue to do nothing more than reveal the limits of your education.

Ah. Since I don't value your speculations and conjecture over measureable reality, I'm the ignoramus:

Where is your justification for accusing me of dishonesty?

Where, indeed.


This message is a reply to:
 Message 51 by EZscience, posted 05-08-2006 9:50 AM EZscience has responded

Replies to this message:
 Message 53 by EZscience, posted 05-08-2006 2:51 PM crashfrog has not yet responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 53 of 58 (310340)
05-08-2006 2:51 PM
Reply to: Message 52 by crashfrog
05-08-2006 2:39 PM


Re: Group Selection in Human Evolution
NWOAR.
(not worthy of a response)
This message is a reply to:
 Message 52 by crashfrog, posted 05-08-2006 2:39 PM crashfrog has not yet responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 54 of 58 (310432)
05-08-2006 11:13 PM


Humans are not losing except to other humans
I suspect the originator of this thread is long gone, but let’s just summarize the implications of the discussion so far, re: the OP.

Douglas writes:

We're losing our arms race with our only predator.

Douglas writes:

Basically, diseases are evolving and we're not.

How can we conclude we are not evolving? Diseases are not our only ‘predator’, nor our most dangerous predator. We humans ourselves are our most dangerous predator via group conflict. Got any antibiotics for war yet? Nothing for war to become resistant to, is there? You just die if you’re on the wrong side in the wrong place at the wrong time.

Douglas writes:

…our environment is too clean

Sterility of developmental environments has now been linked to allergy development. Yes. The immune system needs to be challenged during development. This much is true.

Douglas writes:

… could be the end of our species

This doesn’t follow. Human conflict and environmental degradation are far more imminent threats to our species than disease. Disease is manageable and never kills all of its hosts in an epidemic. The resistant survive. We are seeing this with avian flu and west Nile virus. The human species has a long history of evolving immunity. Why do you think that human flu viruses and diseases have to change? Just because they can evolve *faster* than us doesn’t mean they are necessarily winning the arms race.

This message has been edited by EZscience, 05-08-2006 10:18 PM


  
Quetzal
Member (Idle past 4038 days)
Posts: 3228
Joined: 01-09-2002


Message 55 of 58 (310483)
05-09-2006 11:41 AM
Reply to: Message 47 by EZscience
05-07-2006 5:02 PM


Re: Evolution of reduced fecundity happens
Brilliant! THAT'S the piece I was missing in this discussion. Your last paragraph sums things up nicely. (One of those "duh-oh" moments *smacks forehead*). Selection is local, not global. Allow me to modify your population growth equation a bit:

PG = rN[(K-N)/K]

Where population growth is restricted by the carrying capacity (K) of the local environment (r is effective growth rate or birth - death + immigration - emigration, N is current population). The term (K-N)/K represents the amount of carrying capacity remaining for population growth. When N approaches K, growth approaches zero.

What this implies is that high fecundity may ultimately be negative in terms of fitness for the population. IOW, density dependent factors limiting population growth in the developing world will likely become more and more critical until local K - N is zero. As K in the developing world is much lower than K in the developed world, it is conceivable (all other things being equal), that the fecundity issue that crash discusses may be self-limiting - which is disturbing from a moral standpoint. However, local economic development and technology may be able to reverse both trends - the former by reducing r, the latter by increasing K. Maybe we're not going to hell in a handbasket...


This message is a reply to:
 Message 47 by EZscience, posted 05-07-2006 5:02 PM EZscience has responded

Replies to this message:
 Message 56 by EZscience, posted 05-09-2006 1:06 PM Quetzal has not yet responded

  
EZscience
Member (Idle past 3320 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 56 of 58 (310506)
05-09-2006 1:06 PM
Reply to: Message 55 by Quetzal
05-09-2006 11:41 AM


Re: Evolution of reduced fecundity happens
Quetzal writes:

...Allow me to modify your population growth equation a bit:

By all means. Adding the term for carrying capacity makes my whole point about local population reproductive rate not necessarily being linked to relative population fitness because of factors like evironmental degradation.

Quetzal writes:

...local economic development and technology may be able to reverse both trends

You're an optimist :)
But we have to hope...


This message is a reply to:
 Message 55 by Quetzal, posted 05-09-2006 11:41 AM Quetzal has not yet responded

  
DrFrost
Inactive Member


Message 57 of 58 (310568)
05-09-2006 4:59 PM
Reply to: Message 7 by macaroniandcheese
05-02-2006 10:17 PM


hmmm....
quote:
it's not that good hygiene is bad for us, it's that all these lysol etc are bad for us. i ate dirt as a kid and now the only thing i get sick from is sinus infections and maybe a cold once every couple years. kids raised in immaculate houses haven't built their own immune systems up. but these are not likely to result in germ cell changes, only somatic. but it could still kill a great number of us.

Do you have kids? I had a cold once every 3 to 4 years (food poisoning once which I don't count) from middle of grade school on. And even then it didn't last long. I was so rarely sick that people had literally asked me if I ever got sick. Cold going around the office? I never caught it. As a child my environment was fairly pristine. I was fastidious about keeping my hands and face clean (almost compulsive).

BUT, since I've had kids of my own things have changed. There's much more stress in my life (not just because of the stresses of parenthood but other factors as well) and it seems about half the time that my kids catch something I get to "share" in their new experience.

I'm not an expert on the immune system but it seems logical to me that exsposure amount can play a big role in infection. Your body can fight off a small amount, while an exposure to a larger amount will cause you to succumb. When your kids are sick you know you should restrict your exposure but it simply doesn't work like that. They don't feel good and they want you to hold them, so you hold them. That's how I explain the sudden failings of my immune system anyway.

Any other sample points out there?


This message is a reply to:
 Message 7 by macaroniandcheese, posted 05-02-2006 10:17 PM macaroniandcheese has responded

Replies to this message:
 Message 58 by macaroniandcheese, posted 05-09-2006 6:45 PM DrFrost has not yet responded

  
macaroniandcheese 
Suspended Member (Idle past 2093 days)
Posts: 4258
Joined: 05-24-2004


Message 58 of 58 (310585)
05-09-2006 6:45 PM
Reply to: Message 57 by DrFrost
05-09-2006 4:59 PM


Re: hmmm....
i don't have kids, but i'm a swim instructor. i work with kids in the elements. last year walking pneumonia was going around. got it. but that's about all.

it's more likely the stress in your life than the exposure. although exposure to virus does determine the load and the severity of infection.


This message is a reply to:
 Message 57 by DrFrost, posted 05-09-2006 4:59 PM DrFrost has not yet responded

  
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