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Author Topic:   Humans are losing.
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 8 of 58 (308642)
05-02-2006 10:43 PM
Reply to: Message 3 by Wepwawet
05-01-2006 8:06 PM


I largely agree with Brennakimi. Sexual selection is probably a lot more important than natural selection for the continued progression of the human gene pool at this point.
There is a lot of truth in your post that I think is well stated, but there is also an element of truth in what the OP stated. We are severely suppressing selection on the human gene pool by enhancing everyone's reproductive success. That much is obvious on many levels. However, simpler organisms such as bacteria and viruses will always be able to evolve faster than us, necessitating 'management strategies' on our part.
Also, re: the OP, the increase in allergy syndromes only emerged in the 1970's and 80's after we started to try and raise our children in completely sterile environments. I can dig up some info if you're interested...
This message has been edited by EZscience, 05-02-2006 09:47 PM

This message is a reply to:
 Message 3 by Wepwawet, posted 05-01-2006 8:06 PM Wepwawet has not replied

Replies to this message:
 Message 11 by crashfrog, posted 05-03-2006 12:43 AM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 13 of 58 (308736)
05-03-2006 11:08 AM
Reply to: Message 11 by crashfrog
05-03-2006 12:43 AM


Crash writes:
In what sense is our reproductive success being "enhanced?"
I was thinking more along the lines of medical interventions that enhance survival of premature babies and other individuals bearing faulty genetics that otherwise would not live to reproductive age.
Crash writes:
it's easy to see what the selective forces on human evolution are right now
These are true for developing countries, but are these really going to be the genetic lineages that come to represent the future of the human race? We'll have to wait and see.
Crash writes:
...my wife is on birth control, and I'm nearly 30 years old with no children. If there's any selection going on, it's selecting against people like me. From an evolutionary perspective, we're failures, likely doomed to extinction. Certainly not the pinnacle of human evolution.
I would say you have plenty of time left to achieve biological fitness. I think your judgement is a little premature. My first daughter wasn't born until I was 40. What if it turns out that having fewer children later in life actually increases their 'fitness' in terms of success in human society?
Crash writes:
...you have to start with the reality of what fitness means in an evolutionary context
Definitely. I just think that fitness is relative and for humans it is coming to be defined differently than for other organisms. It is not simply the number of offspring you produce that matters so much as their quality - determined by their success in society. I have to question your assumption that evolution is progressing faster among the dis-advantaged simply because they are having more kids. Who is more likely to be taken out by the next Ebola outbreak or bird flu epidemic? My two daughters in Canada, or the 14 kids of Emilio Sanchez in Nicaragua? We don't need to produce as many shildren in the developed world to have greater fitness than those people because our juvenile mortality rates are much lower.
This message has been edited by EZscience, 05-03-2006 10:10 AM

This message is a reply to:
 Message 11 by crashfrog, posted 05-03-2006 12:43 AM crashfrog has replied

Replies to this message:
 Message 14 by crashfrog, posted 05-03-2006 11:40 AM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 15 of 58 (308784)
05-03-2006 1:27 PM
Reply to: Message 14 by crashfrog
05-03-2006 11:40 AM


Crash writes:
Is premature birth a genetically-influenced condition?
By enhancing the survival of premature babies, we are necessarily improving the survival of any genes that are associated with premature birth. You know enough about evolution to see that. We are essentailly preventing natural selection from acting against premature birth as it would otherwise.
Crash writes:
what makes you think that it's our genetics that will represent the future of the human race?
I didn't say that, though. I left it an open question.
I am just not as confident as you that simple *numbers* of offspring are going to translate directly into the best genetic representation across multiple generations ofr all human beings, regardless of their situation. As they destroy their ecosystems locally in some of these countries they may all end up killing each other in wars over the last remaining resources. However, some may succeed in emigrating before that occurs...
Crash writes:
"Fitness" is a measure of how an individuals genes come to dominate a population. If you have only one child, you are substantially less fit than the couple down the street with many, many children.
Yes, I know how fitness is conventionally defined sensu Sewall Wright. But reproductive success has a qualitative component (fertility) as well as a quantitative component (fecundity). Both are important. An extreme example is an insect diet that allows females to lay lots of eggs, but they don't hatch. Another diet that has less protein (but better amino acid complementation) might permit fewer eggs to be produced, but with higher fertility (hatching rates). Those individuals laying fewer eggs end up with the higher fitness in this scenario. There are lot of other ways this sort of thing can occur.
An example in humans is Kwashiorkor syndrome. Protein deficiency is exacerbated in the second child when the women gets pregnanat again too quickly, leading to substantially reduced survival and fitness of the second born.
The point I am getting at is that in humans, I think we are seeing a lot of different factors start to influence fertility, and some of these may be outside the tradional biological ones we are used to considering for animals. Social status and (as you point out) country of residence may be important factors determining who among use leaves any descendants at all in a few generations as the biosphere becomes severely depleted. I don't like the odds for those in developing countries.
Crash writes:
Fitness is fitness, if we're talking about evolution. It's not a measure of your wealth, or your place in life...
Are you saying that wealth or social status cannot, or will never, influence human fitness? I suggest it already is influencing it. Out of all the soldiers dying in Iraq, how many are grunts versus highly-educated officers? How many rich Republicans like old dubya have avoided the draft entirely or been posted to safe places because of their family connections? These types of effects could prove more important in the future as the human race gets more desperate for diminishing resources. If there was a third world war, don't you think those with the best weapons would end up with all the fitness, even if they had far fewer children?
Crash writes:
Among children, a reasonable estimate is 50% mortality. So you'll have 1 kid left, maybe none; Emilio will have around 6-7.
I don't think you can generallize that easily, but you're missing the point. If there is a vaccine available, whose kids do you think are going to get it?
Crash writes:
Their populations are growing markedly; ours are in decline.
Yes, that much is true, although I would say ours are stabilizing, not declining. What is in question is whether their high population growth will increase or reduce the fitness of their future generations. Our lower rate of population growth could easily translate long term into better regional stabilization of our society (with continued survival of the genetics it contains). In contrast, their ecology and economies could collapse from the burden of overpopulation and their populations plummet from pestilience, disease and starvation (just as in Africa right now).
Always a pleasure to hear from you Crash
This message has been edited by EZscience, 05-03-2006 12:31 PM

This message is a reply to:
 Message 14 by crashfrog, posted 05-03-2006 11:40 AM crashfrog has replied

Replies to this message:
 Message 16 by crashfrog, posted 05-03-2006 1:39 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 17 of 58 (308795)
05-03-2006 2:09 PM
Reply to: Message 16 by crashfrog
05-03-2006 1:39 PM


Numbers aren't everything.
That's all I'm saying.
Crash writes:
What genes are, though? I'm asking because I don't know.
Neither do I. But its quite likely there are some.
Crash writes:
If not numbers, then what?
Differential survival rates, however caused.
Crash writes:
...the latter organism still has more copies of their genes in the gene pool. That's not happening to individuals living in the West.
At the moment. We can't extrapolate that too far in the future because, as I have pointed out, a lot of things may change and the most rapidly reproducing populations may be ultimately disadvantaged because of it, so they finally end up with less genetic representation. You are just observing a temporary trend specific to our particular generation. The is no reason to expect this trend to be sustainable or to continue indefinitely.
Crash writes:
...the wealthy reproduce a lot less. Wealth is maladaptive.
The first part is generally true, but the second part doesn't necessarily follow. Ever think that the wealthy might be able to afford to reproduce less without a loss of much fitness because the survival and reproductive success of their offspring is far more assured? I don't think wealth is at all maladaptive. It secures resouces essential for human fertility, even if it happems to correlate with reduced fecundity.
Crash writes:
...our biomes could support many, many more human beings than they do now, particularly in America.
All that does is give us some breathing room to find was to stbilize our resource consumption before K is reached. And it will inevitably be reached. But it will happen other places first and thats where you will see big fitness reductions for all the 'breeder' populations.
But really, Crash - I can't spell it out any better.
Its not just how many children you have, but how many survive to produce children that also have a chance to survive to reproduce.
We can't fully analyze the population-level consequences of high human reproductive rates within one or two generations and link that to long term fitness functions of these populations.
If I have two cages in a wheat field and I infest each with equal numbers of a different strain of greenbug aphids (a high reproductive rate vs. a low) for a fixed period before opening the cage, which will have higher fitness when the cage is opened ?
The cages will prevent predation and parasitism so the aphids virtually grow uncontrolled (like humans, pretty much) and eventually kill all their wheat.
The answer is it depends entirely on how long I leave them protected. If I open the cages in one week, the high rep. strain will have produced the largest number of alate migrants and have the higher fitness. If I leave them for 4 weeks, the high rep. strain will all be dead because it only took them 2 weeks to kill their plants, and the low rep. strain, having used less of their resources, will still be alive and have higher fitness.
So I guess that's how I see us as humans in some ways - a bunch of insects breeding uncontrolled in different cages
Now I *really* have to finish this MS review....

This message is a reply to:
 Message 16 by crashfrog, posted 05-03-2006 1:39 PM crashfrog has replied

Replies to this message:
 Message 18 by crashfrog, posted 05-03-2006 2:34 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 19 of 58 (308804)
05-03-2006 2:59 PM
Reply to: Message 18 by crashfrog
05-03-2006 2:34 PM


Re: Numbers aren't everything.
Crash writes:
That's evidence of reduced fitness.
In the immediate sense, for those individuals, yes.
Crash writes:
If the avaliability of better health care etc. to the wealthy was offsetting their lower birth rates, they'd have comparible population growth.
I would argue that achieving comparable population growth would not be in the best interest of our long term fitness. These high reproducing populations haven't yet faced the real crunch they are headed for.
Crash writes:
we know that being wealthy in the West isn't enough to offset the reduced birth rate.
Fine, but that reduced birth rate may be what saves our 'fitness' in the longer term. Surely you're not in favor of indefinite, unlimited population growth? The planet's 'sustainable' carrying capacity has been estimated at around 2-3 billion. We are over 6 and heading for 8.
Crash writes:
The greater percentage of offspring that survive to parenthood in the West still doesn't offset the greater absolute birth rate in developing nations.
You seem totally fixated on birth rates.
Yes, number of children is an important (primary) determinant of 'individual fitness'.
But it is our 'population fitness' we should be more concerned with.
I have pointed out that there are many other factors that will ultimately limit the fitness of various populations above and beyond their birth rate, and that a high population birth rate may be ultimately detrimental to the future fitness of individuals within those populations.

This message is a reply to:
 Message 18 by crashfrog, posted 05-03-2006 2:34 PM crashfrog has replied

Replies to this message:
 Message 20 by crashfrog, posted 05-03-2006 3:25 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 21 of 58 (308813)
05-03-2006 3:52 PM
Reply to: Message 20 by crashfrog
05-03-2006 3:25 PM


New story, in that case
Crash writes:
Evolution doesn't plan ahead, so our "long-term fitness" is irrelevant. We're shaped by the environment we live in now, not the environment future individuals might inhabit.
This makes no sense.
No one said anything about evolution being prescient.
Of course we are shaped by our current environment.
If we are talking about the trajectory of human evolution, how is our long term fitness in geographically separate populations NOT relevant?
We are quite capable of predicting the impact of a lot of our activities on the planet and on its ability to sustain human life in various regions.
Crash writes:
I'm "fixated" on the relevant facts, something you seem prepared to completely dismiss.
Please show me a fact that I am dismissing.
Crash writes:
...the alleles of the developing world are increasining in frequency across the human gene pool, while the alleles of the West are decreasing in frequency.
Only if you consider the 'human gene pool' to be one effective population 'N(sub)e', which it isn't. You are OK until you say 'across the human gene pool'. These high rates of reproduction are largely localized in the basket-case countries.
Except for the fortunate emigrants that get to join the gene pool in developed countries, most of their progeny remain 'in situ' with increasingly bleak prospects for the survival of their alleles, regardless of how quickly they replicate them.
Crash writes:
Our alleles represent less fitness because they're being selected out of the population over time.
Now Crash, you're getting careless. You haven't said one word about 'selection' yet. Your entire argument has hinged on differential birth rates.
*I* am the one arguing that differential survival through various forms of selection can potentially render current differences in birth rates ultimately meaningless.
Crash writes:
Our environment right now selects against alleles whose carriers live in the West.
So tell me please, what is this environmental force that is causing our genes to be 'selected out' of the population?
Because all you have done so far is talk about their relative rates of replication.
Crash writes:
That's it. End of story.
That seems a bit arbitrary. Fond of the last word are we ?
This message has been edited by EZscience, 05-03-2006 02:54 PM

This message is a reply to:
 Message 20 by crashfrog, posted 05-03-2006 3:25 PM crashfrog has replied

Replies to this message:
 Message 22 by crashfrog, posted 05-03-2006 5:11 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 23 of 58 (308922)
05-03-2006 10:15 PM
Reply to: Message 22 by crashfrog
05-03-2006 5:11 PM


Re: New story, in that case
Crash writes:
You're speculating from things you cann't possibly know.
Really. The earth isn’t approaching unsustainable population growth. Global warming and habitat destruction isn’t going to make survival more difficult for those in developing countries? You sure you want to contest this?
Crash writes:
. the facts of what populations are now increasing, and what populations are now decreasing.
I feel I have clearly addressed the question of how differences in birth rates can have little bearing on the long term fitness of disparate geographic populations. Current differences in rates of population increase may have little to do with the ultimate genetic makeup of the future human race.
Crash writes:
It's a "global village."
Maybe on a technological level, but not on a genetic level. You’re saying that everyone has an equal chance to mate with anyone else of the opposite sex wherever they are in the world? Because that’s the definition of effective population size. That group of individuals that has a non-zero possiblity of interbreeding.
Crash writes:
There's no reproductive isolation for any but the most marginal subpopulations.
You mean the ones with the highest birth rates you referred to? You are only helping to prove my point here.
Crash writes:
Regions like Africa have had consistently high growth rates for generations, now. Prospects for the survival of a large number of progeny are very high in those countries.
But for how much longer can this be sustained before it reaches an asymptote, in your educated opinion ?
Crash writes:
How do you think we detect selection?
We hypothesize a selective force and design an experiment to test for its influence, neither of which you have managed to do.
Crash writes:
The change in populations.
Which could be due to random drift or stochastic events that influence survival in a density-independent manner.
Many explanations other than selection are possible.
What is your hypothesis regarding the mechanism of *selection* that dooms us to genetic extinction in the western world? You haven’t answered this question.
You are trying to infer the action of selection a posteriori without even postulating a mechanism.
Crash writes:
. the reality is, there's no such counterselection occuring. This is proven by the differential in population growth.
Which you apparently conclude can continue ad infinitum. How can you be so sure there is no counterselection against profligate reproduction ? (Oh, that the selective force could be stronger here!). If it were acting, but currently affecting population growth less than birth rates, how would you detect it?
You assume its absence without testing for it.
Crash writes:
The "environment" is that people are choosing to have less children, and have them later in life
Fine. Now you need to provide convincing evidence that these behavior patterns will inevitably lead to reduced average fitness of the local human population. I have already provided convincing reasons why this may not necessarily be the case.
This message has been edited by EZscience, 05-03-2006 09:20 PM
This message has been edited by EZscience, 05-03-2006 09:23 PM

This message is a reply to:
 Message 22 by crashfrog, posted 05-03-2006 5:11 PM crashfrog has replied

Replies to this message:
 Message 24 by crashfrog, posted 05-03-2006 10:47 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 27 of 58 (308938)
05-03-2006 11:16 PM
Reply to: Message 24 by crashfrog
05-03-2006 10:47 PM


Re: New story, in that case
Crash, I have read every word of your posts and you haven't postulated any selective mechanism. If you did what is it? You have only paid lip service to selection after you failed to defend your argument based on differential birth rates alone.
Crash writes:
What makes you think that the factors you're talking about will be the last factors to influence human genetics?
Again, you're putting words in my mouth. I simply meant that the proximal trends you point to cannot be used to imply long term outcomes.
Effective population size
quote:
...for the theory of population genetics what matters is the chance that two copies of a gene will be sampled as the next generation is produced, and this is affected by the breeding structure of the population.
Since the genes of a Zimbabwe hooker have little chance of recombining with yours (presumably) you are both members of different 'effective' populations. Technically, you amay belong to the same gene pool, but functionally you don't. That's the point.
Crash writes:
An equal chance? Or a non-zero chance?
Pick either. Your effective population size of 'planet earth' fails both criteria.
Crash writes:
Because it's starting to look like you're more interested in jerking me around.
I am not yet aware of any lack of respect on my part, although this could be considered to approach it on yours.
Crash writes:
We're talking about what's going on now, not what might happen in the future.
Sorry. You lost me completely. I thought one of the main reasons we were interested in evolutionary biology was because it gave us some insights into what to expect of living things in the future, based on what we understand about the forces shaping their biology. Is this not the case?
Crash writes:
Are you even reading my posts?
Yes, and its getting boring because you don't answer direct questions.
With every post your replies seem to get more flippant.
What is this selective force you refer to that is eliminating the alleles of western people from the global gene pool?
You are not going to slip out of this careless statement.
Crash writes:
What on Earth gave you the idea that I thought this would go on forever?
Your inference that higher birth rates rates in certain populations would inevitably translate into higher fitness in those populations.
This message has been edited by EZscience, 05-03-2006 10:17 PM
This message has been edited by EZscience, 05-03-2006 10:19 PM

This message is a reply to:
 Message 24 by crashfrog, posted 05-03-2006 10:47 PM crashfrog has replied

Replies to this message:
 Message 29 by crashfrog, posted 05-03-2006 11:37 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 32 of 58 (309147)
05-04-2006 5:43 PM
Reply to: Message 29 by crashfrog
05-03-2006 11:37 PM


Re: New story, in that case
Crash writes:
What's wrong here?
Let me clarify. In post 20 you said:
Crash writes:
Our environment right now selects against alleles whose carriers live in the West.
In post 22 your only reference to selection is:
Crash writes:
How do you think we detect selection? The change in populations.
Which is a completely nebulous statement that doesn’t identify any selective force.
Differences between populations and their growth rates can arise for many reasons other than selection - your heavily-touted difference in birth rates for example. We don't 'detect selection' by comparing populations, but by identifying causative influences that affect survival or reproductive success of individuals differentially. Like industrial melanism in Biston betularia. Like disease and parasitism. These are selective forces. What selective force are you postulating?
So while I accept that we currently have lower birth rates in the west than in the developing world, I really would like you to clarify how you think that "our environment is selecting against our alleles". Their replication might be slower, but that doesn't amount to any form of selection against them. Your refering me back to post 22 just seems like an attempt to obfuscate and avoid this question.
In regard to selection you also said:
Crash writes:
I haven't disagreed with the potential of that being the case. But the reality is, there's no such counterselection occuring. This is proven by the differential in population growth.
I accept that we don’t see an impact of such selection on population growth rates yet, but that doesn’t allow us to conclude that no such selection is occurring - only that the net effects of such selection are not yet sufficient to counter the birth rate.
Crash writes:
...that's changing the allele frequencies in the human species and isn't being counteracted by a ecologically-driven population crash in the developing world because that isn't happening yet.
'Yet' being the pivotal word. I agree with you here, but I think you will agree there are many independent lines of evidence to suggest that many of these populations will have to crash eventually. What happens to the alleles they contain at that point is uncertain and will depend on emigration, survivorship, etc. but I predict some severe bottlenecks.
Crash writes:
Are you telling me that we don't belong to any reproductive population at all? That we're, essentially, our own species?
You seem to view the human species as one large homogenate, whereas I see it more as a series of ecologically separate populations that have potentially very different fates, regardless of a little gene fow between them, hence my comments on effective population size. No, we are not separate species, but we are functionally separate societies in relatively separate ecosystems and hence our gene pools, even with some gene flow, are subject to locally specific differences in selective forces. I have spoken about some of these selective forces I think will affect these populations differentially. I am still waiting for you to identify the selective force you think is “selecting against our alleles.”
Crash writes:
I mean, you pretty much seem to have completely abandoned this position
Not at all. It was a different issue, one of medical intervention increasing the ”genetic load’ of our population.
Crash writes:
. choosing to argue, ludicrously, that selection is working against people who live in Africam, despite their genes increasing in frequency in the human gene pool.
As I have pointed out, there is every reason to believe that all kinds of negative selective forces are starting to affect survival in Africa, but until they start reducing more of the survival prior to reproductive age, you are not going to see much effect on population growth.
Crash writes:
. you've chosen to repay my attempt to engage you in interesting debate with nonsense.
I’m sorry you feel that way. At least I have managed to refrain from insulting you.
Crash writes:
. start addressing the discussion honestly.
Oh. You mean like your clumsy attempt to evade your blunder about the ”environment selecting against our alleles? Please.
Crash writes:
Post 22. 5 posts ago. How hard is it to read?
Post 22 contains no such information. Stop trying to obfuscate.
Crash writes:
Those populations are growing. Ours are declining. Their alleles are more frequent, and ours are less, over time. That's fitness.
Fine. That is true if you consider the human race as one large homogeneous population. Theoretically, it can be viewed that way, but in practical terms whole populations often either survive or die as ethnic groups or societies. Look at all the examples of genocide. All I’m saying is there are lots of types of selective forces that can affect the survival of entire geographic populations differentially. Like war for example. I guess I don’t accept your inference that somehow we in the west will inevitably lose genetic representation in the human race just because there are poor countries breeding faster than we are. Yes, they technically have higher Darwinian fitness measured by current rates of reproduction. Will that be the case for much longer is the question. I doubt it.

This message is a reply to:
 Message 29 by crashfrog, posted 05-03-2006 11:37 PM crashfrog has replied

Replies to this message:
 Message 33 by Quetzal, posted 05-04-2006 9:37 PM EZscience has replied
 Message 38 by crashfrog, posted 05-05-2006 12:02 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 34 of 58 (309239)
05-04-2006 10:13 PM
Reply to: Message 33 by Quetzal
05-04-2006 9:37 PM


Re: A VERY Interesting Conceptualization
Let he who is without fear of recompense cast the first stone...
AbE: You realize, of course, that this could open a rather ugly can of worms ? I will particpate, of course, but I am not sure I want the responsibility of initiating...
This message has been edited by EZscience, 05-04-2006 09:21 PM

This message is a reply to:
 Message 33 by Quetzal, posted 05-04-2006 9:37 PM Quetzal has replied

Replies to this message:
 Message 35 by Quetzal, posted 05-05-2006 9:22 AM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 36 of 58 (309347)
05-05-2006 10:22 AM
Reply to: Message 35 by Quetzal
05-05-2006 9:22 AM


Re: A VERY Interesting Conceptualization
Quetzal writes:
Ya mean we have to be unemployed?
It would help. I find myself borrowing a lot of time from my writing and editing responsibilities to participate here, but it is fun and intellectually stimulating.
Perhaps a good discussion could be had by raising the question of just how relevant or meaningful the strict Darwinian definition of ”fitness’ is for the further evolution of humans at this point. This came to me in the course of this discussion with Crash where he seemed so concerned about the rate at which non-western, UD countries were gaining genetic representation in the human race, as he sees it ”at the expense of our alleles’. Numerically, I guess that’s true, but my gut reaction is, so what? How many truly unique alleles do each of us carry, if any? All my alleles are all likely present in multiple copies in many other individuals. The only thing ”unique’ about me is my genotype - and genotypes are completely destroyed by recombination every generation. However, what a unique human genotype is able to create can live on .
Can't individual humans influence their species' evolution in permanent and lasting ways without making a genetic contribution?
I am thinking of science, culture, and intellectual creation/invention. Who cares about how many stinkin’ genes you are leaving behind if you can bequeath a hefty publication record to the enterprise of science that forms the basis of future discoveries and advances for the human race? (My true life’s goal, laid bare ).
The significance of DNA to nature is two-fold. First, it holds the information needed for the construction of all lifeforms during their development and, in this regard, will never have a substitute. But it is also the only means of preserving any kind of information across generations for most animals. In this context, humans have many alternatives not available to other animals - language and a record of history and science.
So the next question becomes, which will be more important to our human destiny as a species - our genetic information or our cultural information ? I would argue the latter.
The strongest forms of selection currently acting on humans are almost all either directly or indirectly the result of other human activities (wars, mismanagement of the environment, overpopulation etc.). We (human societies) are now the primary cause of most selection acting on our own species and are, thus, largely responsible, consiously or unconsciously, for our own evolution. The fate of humanity (extinction vs. continued existence) rests on our ability to evolve a culture of sustainable existence on this planet - NOT on mutation + NS resulting in dramatic changes to our genetic makeup.
I suppose this could be transposed to form the OP of a new thread (Does Darwinian fitness even matter for human evolution?) if admins feel I am ranging too far afield in this one.
Here I go again spending a half hour on a post when I just got a MS back from review. Where are my priorities ...?

This message is a reply to:
 Message 35 by Quetzal, posted 05-05-2006 9:22 AM Quetzal has not replied

Replies to this message:
 Message 41 by crashfrog, posted 05-05-2006 2:44 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 39 of 58 (309403)
05-05-2006 2:11 PM
Reply to: Message 38 by crashfrog
05-05-2006 12:02 PM


Re: New story, in that case
Crash writes:
The avaliability of birth control and social factors that lead people to believe that having fewer children is better than having many, or that having them later in life is better than having them sooner. The "environment" is that people are choosing to have less children, and have them later in life, here in the West.
Its hard for me to view voluntary reproductive restraint as a form of 'selection', but I agree that birth control is a choice more available in the west. But it's a choice individuals can make to voluntarily reduce their fitness - so is abstinance and suicide. So now I am pondering whether we would have to accept abstinance and suicide as forms of 'selection' if we accept birth control availability.
A more interesting question might be to ask why this is occurring, apparently in direct contradiction to the expectations of NS. Such non-adaptive behavior should be selected against.
Crash writes:
Humans in the West are being selected against, detectable by the fact that our genes represent a decreasing frequency within the human gene pool.
You are inferring the action of selection without demonstrating it.
I refuse to accept that a simple difference in rate of reproduction equates to any form of selection. Recall Darwin's original inference that animals produced more offspring than could survive. Selection is the process whereby certain ones die and others don't. Higher rates of reproduction are normally advanatageous under selection, but reproductive rate alone does not constitute any form of selection. It just provides the raw materials. There are situations where both reduced fecundity and delayed onset of reproduction can evolve as a consequence of selection acting on other traits and actually be favored under selection. If not, we wouldn’t see such trends evolve in so many taxa of large animals. Most evolved from smaller ancestors with higher reproductive rates.
Under your reasoning, reduced fecundity and/or delayed reproduction cannot evolve because, by your definition of selection, such traits can only be evidence of a selective disadvantage.
Crash writes:
Non-random differential reproduction is selection, by definition.
You are using the term in its broadest sense without identifying any 'selective force'. For example, if I isolate two aphid clones from field collections and clone A has twice the rate of reproductive rate of clone B, under your broad definition clone A will be selected for and clone B, against. I would say there is no selection acting - we have just compared reproductive rates and found them to be different. I don't see any need to use the term 'selection' unless there is some detectable, external force that is limiting to survival or reproduction. I am still finding it difficult to accept your view of voluntary reproductive restraint as such a force, but I don’t want to belabor the point any further.
Crash writes:
The fitness of these genes in a future environment is irrelevant to their fitness in this environment.
Definitely. But I think that as humans we have a pretty good picture of some of these future environments that evolution doesn't have. Given that, it doesn't seem unreasonable to project certain changes in the mean fitness of particular populations based on their geographic locations.
Crash writes:
The evidence indicates that genetic differences between these populations are decreasing, not increasing
This is true, but we are far from being one large homogenate yet. I was merely emphasizing ecological, political and with the potential to affect the survival of large populations and the specific genetic structure they contain.
Crash writes:
transportation technologies mean that these populations are becoming decreasingly geographically seperated.
I think you mean less genetically separated. The geography doesn’t change. But yes, this is true.
Crash writes:
It's merely my position that that is what is happening now, and you've presented nothing to rebut that.
I never intended to mis-represent you. These were impressions I got from your argument. I don’t dispute that they are currently achieving higher Darwinian fitness, so I don’t need to rebut that. I am just not accepting that there is any selection acting specifically against us. A higher reproductive rate is not invariably adaptive.
Crash writes:
Are we done, now?
I'm ready to move on if you are.
I'd like to hear what you have to say about post 36.

This message is a reply to:
 Message 38 by crashfrog, posted 05-05-2006 12:02 PM crashfrog has replied

Replies to this message:
 Message 40 by crashfrog, posted 05-05-2006 2:40 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 42 of 58 (309435)
05-05-2006 3:21 PM
Reply to: Message 40 by crashfrog
05-05-2006 2:40 PM


Re: New story, in that case
Crash writes:
Posts 22 and 38. The selective force has been specifically identified to you, twice now.
Yes. I understand now what you are construing as a selective force. I am just not convinced that it constitutes one. We may just have to settle for respectful disagreement here.
Crash writes:
What effect on our population is reduced fecundity and delayed reproduction having in reality?
That's the $6 million dollar question, isn't it?
You seem concerned that we are losing Darwinian fitness in the west relative to UD countries. The current data definitely support that position, I agree. I am just not sure it is a cause for much concern given the other factors I can see coming into play which will have differential influences on whole populations. Despite our currently lower fitness, I predict that most our genes have pretty good odds of survival just based on where we live. And I still claim that reduced fecundity and delayed reproduction can be adaptive under various scenarios, particularly group selection - and group selection is really what humans are going to be facing from here on. Our survival as individuals (and the alleles we carry) is far more likely to be determined by the group we belong to, than by ourselves as individuals.
So the only remaining 'bone of contention' is your definition of selection :
Crash writes:
The changing gene frequencies demonstrates it, and I've provided the mechanism.
But changes in gene frequencies can occur by random drift, without selection, as you well know I am sure. Don't you see any problem here?
Leaving the mechanism aside for a moment, you are still inferring selection simply by differences in rates of reproduction. That's your evidence, right? I have pointed out that both reduced fecundity and delayed reproduction can and have evolved naturally in various lineages. Might you explain how this is possible if reduced reproduction alone is to be considered sufficient evidence of selection acting against a sub-group? By this logic, every lineage should evolve to reproduce faster and faster and earlier and earlier to their physiological limits. We don't see this. We see higher organisms headed in exactly the oppsite direction.
I will suggest that both reduced fecundity and delayed reproduction are traits that will highly adaptive for the human race to evolve in coming generations. We should expect to see them favored by group selection in future generations.

This message is a reply to:
 Message 40 by crashfrog, posted 05-05-2006 2:40 PM crashfrog has replied

Replies to this message:
 Message 44 by crashfrog, posted 05-05-2006 5:53 PM EZscience has replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 43 of 58 (309436)
05-05-2006 3:25 PM
Reply to: Message 41 by crashfrog
05-05-2006 2:44 PM


Re: A VERY Interesting Conceptualization
Hey, can this be possible?
Virtually complete agreement?
*snap* Fizzzzzz. glug, glug (gulps beer)

This message is a reply to:
 Message 41 by crashfrog, posted 05-05-2006 2:44 PM crashfrog has not replied

  
EZscience
Member (Idle past 5154 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 45 of 58 (309710)
05-06-2006 2:28 PM
Reply to: Message 44 by crashfrog
05-05-2006 5:53 PM


Evolution of reduced fecundity happens
Crash writes:
Because that isn't reduced reproduction.
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?
Crash writes:
You're conflating two entirely seperate things - strategies such as smaller brood size or strategic delays in mating to increase offspring survival, and overall change in population size.
No, you are the one confused and talking about two things I never mentioned. Firstly, fecundity is the not the same as brood size - the latter is simply the number of offpsring produced in a single bout of reproduction, not the lifetime. Secondly, a 'stategic delay in mating' is not the same as 'age at first reproduction', which is the age at which the first offspring is produced. For example, females of many insects mate once and store sperm for their entire lifetime, producing offspring much later. Mating can occur at any time - it's the physiological cost of producing the offspring that has a much bigger impact on life history. In semelparous creatures, they die.
Crash writes:
The strategies you mention wouldn't be successful if they didn't result in population growth for the offspring of those individuals.
Just so we're clear, the *life history traits* I mentioned (not strategies - that's a term for behavior) were :
1. evolution of reduced fecundity (fewer offspring in the lifetime).
2. evolution of delayed onset of reproduction (later birth of first offspring).
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. You concluded that our slower population growth was evidence our genes were being selected against. I disagreed and said I thought it was simply evidence of slower reproduction and that there was no evidence of any selection. You said that because our genes were being replicated more slowly, that was evidence of selection. I said you can't define selection like that.
Now I am pointing out that many lineages, over evolutionary time, have actually evolved reduced fecundity and delayed onset of reproduction.
I don't think that is disputable. Higher organisms reproduce at later ages and produce fewer progeny per individual.
So here is the question again. If slower population growth (produced by summing the reduced fecundity of many individuals and their waiting longer to reproduce) is evidence of negative selection against that population, by your definition of 'selection', then how can either of these traits possibly evolve? They are, by your definition, evidence of selective disadvantage and can have no advantage. And yet evolve they did.
They only answer is that selection CANNOT be adequately defined the way you have defined it. Selection has actually favored reduced fecundity and delayed onset of reproduction independently in many lineages over evolutionary time. Otherwise, an elephant would reproduce as quickly as a house fly. Reproductive rate is just one life history feature of an individual, (or a demographic statistic of a population - we must distinguish these) that has to be interpreted within the much larger context of the species' adaptive topology, sensu Sewall Wright. Faster rate of reproduction is not always going to correlate with greater fitness in all contexts.
Crash writes:
Reducing fecundity is only a successful strategy if it increases your population growth.
You have now abandoned brood size and returned to fecundity, but now you have made a completely paradoxical statement.
By definition, reduced fecundity leads to a lower rate of population growth. It CANNOT, by definition, possibly increase population growth. However, it can increase population *survival*. The only way reduced fecundity can evolve is if populations with lower rates of reproduction are more sucessful in surviving than populations with higher fecundity. 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).
So finally, how can we possibly say for sure that reduced fecundity and delayed onset of reproduction are not being selected for in humans today? We can't. 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. For example, the civil wars in Congo and Darfur are examples of strong group selection occurring right now that are severely reducing average fitness in some high RR populations.
As RazD would say, 'Enjoy'
EZ
AbE for new subtitle
This message has been edited by EZscience, 05-06-2006 01:35 PM

This message is a reply to:
 Message 44 by crashfrog, posted 05-05-2006 5:53 PM crashfrog has replied

Replies to this message:
 Message 46 by crashfrog, posted 05-06-2006 7:09 PM EZscience has replied

  
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