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One Day More
2005-Mar-12, 11:23 PM
I was wondering if Homo sapiens could ever stop evolving at all (both physically and culturally). I mean look how far we've come:
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->Homo erectus-->Neanderthals-->Hello, Homo sapiens. We've come a long way from stone tools in the developed world (knives, forks, etc), and of course-we've got clothing. Our skulls have had changed dramatically over those years as well.
But...can we ever stop evolving physically and culturally? I can't imagine how mama nature could ever find another reason for us to improve, as we have all this technology around us.
And...is evolution just a theory and/or hypotheses?

Lycus
2005-Mar-12, 11:32 PM
Yes it's a theory, but nothing is "just" a theory. For something to be considered a theory, it has to have repeatedly and successfully stood up to the scrutiny of the scientific method.

01101001
2005-Mar-13, 12:11 AM
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->Homo erectus-->Neanderthals-->Hello, Homo sapiens.
Are the arrows are meant to imply that Homo sapiens descended from Neaderthal?

Wikipedia: Homo neaderthalensis (http://en.wikipedia.org/wiki/Homo_neanderthalensis):


It is generally accepted that both Neanderthals and Homo sapiens evolved from earlier "archaic" Homo sapiens, but the classification of Neanderthals depends on when in the timeline these modern humans are considered a separate species from the "archaic" forms. This complication is introduced because the "archaic" forms are a chronospecies.
I would put them on a parallel branch -- cousins, not parents -- descending from a common ancestor.

One Day More
2005-Mar-13, 12:20 AM
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->Homo erectus-->Neanderthals-->Hello, Homo sapiens.
Are the arrows are meant to imply that Homo sapiens descended from Neaderthal?

No, I just put them there :oops: . No, I think Neanderthals was a branch off, just like wikipedia had said. Thanks for the little link :) (URL that is).

frogesque
2005-Mar-13, 12:57 AM
With modern technology I don't see any reason why we should be as big as we are. 1/3 or 1/4 the size with sufficient strenght to bear the skull and contents would be a huge benefit. We would consume far less food, our vehicles could be smaller and our dwellings could be much more efficient and cost effective to build. We could also loose some of those features of ours that evolution didn't do such a great job of like teeth - what a pain they are! We should have teeth like sharks that rip raw flesh and can grow a new set when the old ones become loose or damaged.

Ultimately this will enable us all to evolve into lawyers but unfortunately we will spend so much time countersuiting that when the little green men come to take over the planet we will be so busy arguing with eachother that no one will notice. We are truely a doomed race. :cry:

ToSeek
2005-Mar-13, 01:06 AM
People still engage in an incredible amount of self-destructive behavior. Seems to me as if there's lots of room for improvement there.

Crazieman
2005-Mar-13, 02:28 AM
As it stands, there is tangible evidence humans continue to be taller and taller.

Gullible Jones
2005-Mar-13, 02:40 AM
Yep... AFAIK that's not evolution though, just better nutrition.

Maksutov
2005-Mar-13, 11:22 AM
[edit]Ultimately this will enable us all to evolve into lawyers but unfortunately we will spend so much time countersuiting that when the little green men come to take over the planet we will be so busy arguing with eachother that no one will notice. We are truely a doomed race. :cry:
LOL!! =D>

Then again, perhaps those LGM will be surprised when they're attacked by catfish (bottom-feeders) with shark's teeth!

Mainframes
2005-Mar-13, 11:23 AM
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversly as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted.....

Maksutov
2005-Mar-13, 11:30 AM
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversly as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted.....
Therefore, given your condition and your view of the adverse effect of technology and medical science, I trust you have never contributed nor plan to contribute to the gene pool.

swansont
2005-Mar-13, 11:49 AM
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->


Lucy was A. afarensis, not H. habilis.

edit: correct Lucy to be an Australopithecine

mickal555
2005-Mar-13, 11:52 AM
I suppose if technology was advanced enough that we could live forever, that would stop evolution.



Mainframes wrote:
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversely as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted..... Therefore, given your condition and your view of the adverse effect of technology and medical science, I trust you have never contributed nor plan to contribute to the gene pool.
I plan too. I don't care about "contaminating" the gene pool...

um3k
2005-Mar-13, 02:24 PM
I suppose if technology was advanced enough that we could live forever, that would stop evolution.



Mainframes wrote:
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversely as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted..... Therefore, given your condition and your view of the adverse effect of technology and medical science, I trust you have never contributed nor plan to contribute to the gene pool.
I plan too. I don't care about "contaminating" the gene pool...
I have quite good vision. Maybe I'll contribute a few times, and set humankind on their way to super vision! :D :lol:

Candy
2005-Mar-13, 02:45 PM
I suppose if technology was advanced enough that we could live forever, that would stop evolution.



Mainframes wrote:
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversely as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted..... Therefore, given your condition and your view of the adverse effect of technology and medical science, I trust you have never contributed nor plan to contribute to the gene pool.
I plan too. I don't care about "contaminating" the gene pool...
I have quite good vision. Maybe I'll contribute a few times, and set humankind on their way to super vision! :D :lol:
I'm content on being a non-reproducing recipient? Just for fun, no other reason. :wink:

Mainframes
2005-Mar-13, 02:48 PM
I suppose if technology was advanced enough that we could live forever, that would stop evolution.



Mainframes wrote:
In my opinion, all the technology we have and the advances in medical science to date will mean that evolution will now affect the human race adversely as natural selection has all but been eliminated in the case of humanity. Junk DNA that would caused harmful mutations is now not being selected out and is proliferating.......

For example I myself am quite badly short sighted..... Therefore, given your condition and your view of the adverse effect of technology and medical science, I trust you have never contributed nor plan to contribute to the gene pool.
I plan too. I don't care about "contaminating" the gene pool...
I have quite good vision. Maybe I'll contribute a few times, and set humankind on their way to super vision! :D :lol:
I'm content on being a non-reproducing recipient? Just for fun, no other reason. :wink:

I won't object to trying. It's succeeding that's the difficult part...! :wink:

Human
2005-Mar-13, 03:03 PM
I don't think we will stop to evolve, but I know we evolve slowly. So it takes many years before we change.

tbm
2005-Mar-13, 04:58 PM
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->


Lucy was H. afarensis, not H. habilis.

I saw recently (on TV) that "Lucy" has been demoted to being, in reality. a member of the chimapanzee family, and the researchers that originally pushed her as being an ancestor of man had backtracked and re-evaluated their theories about her. Does anybody have any more info along those lines?

tbm

sohvan
2005-Mar-13, 05:06 PM
I don't think humanity has stopped evolving, but rather the genetic evolution has slowed down considerably. I think the ideas left behind by invidual people have had a far greater effect for a long time, than contributions to the gene pool.

Candy
2005-Mar-13, 05:27 PM
I don't think humanity has stopped evolving, but rather the genetic evolution has slowed down considerably. I think the ideas left behind by invidual people have had a far greater effect for a long time, than contributions to the gene pool.
Could being aware of ourselve contribute to this..

I chose not to have children, because I don't want dysfunction to continue.

Just wondering.. 8-[

DreadCthulhu
2005-Mar-13, 06:27 PM
Well, it is likely that by the end of the century, humanity will be tinkering with our own DNA. I predict the next couple of centuries will see the fastest period of human evolution to date, due to our own selection.

Lance
2005-Mar-13, 06:36 PM
Well, it is likely that by the end of the century, humanity will be tinkering with our own DNA. I predict the next couple of centuries will see the fastest period of human evolution to date, due to our own selection.

"Gee, what happens if we cross these two genes? Ah, we get much stronger. Good, good. But now oxygen is pois{THUD}"

beskeptical
2005-Mar-13, 07:37 PM
I don't think humanity has stopped evolving, but rather the genetic evolution has slowed down considerably. I think the ideas left behind by invidual people have had a far greater effect for a long time, than contributions to the gene pool.And what on Earth would account for evolution slowing?

Evolution is very slow but the mechanisms for genetic changes are relatively constant over time. When populations become isolated, when there are significant selection pressures such as a global catastrophe, (since humans populate all continents), then new species can emerge.

Our gene pool was reduced to a few thousand members about 70,000 years ago but no truly new race or species evolved. It left us with less genetic diversity. Chimpanzees have much greater genetic diversity than humans. We have room for expanding our genetic diversity without significantly changing our human characteristics.

Bottom line, evolutionary changes march continually on. Other factors determine when we will see a considerably different species evolve.

As to the increasing size, there is more evidence that is the result of nutrition than genes but there is some genetic basis for taller and shorter body types. Zulus vs Pygmys tribes' size would be genetic diversity but increased size of Americans from the 1700s to the 1900s would be more from nutritional effects.

Reacher
2005-Mar-13, 08:09 PM
Punctuated Equilibrium theory (I have no idea if it's still valid) states that evolution goes through stages of acceleration... So I guess it's possible that we're in a stage of slowness relative to the stages of speed...

The Red Queen theory (named for the Red Queen from Alice in Wonderland) says that a creature needs to continue to evolve constantly in order to simply maintain it's position in the food chain, the way that Alice had to keep running as fast as she possibly could in order to remain in the same place.

That doesn't really explain creatures who have evolved very little for long periods of time, like sharks, but as long as a single one with a mutation who does exactly as well as each other shark in it's generation will not encourage evolution, I guess there's no reason for them to change.

sohvan
2005-Mar-13, 08:16 PM
And what on Earth would account for evolution slowing?

With better medical technology and welfare states, the quality of your genes have a less significant effect on whether you survive to pass on your genes. Only extremely harmful mutations are weeded out. Humanity has built everything it's accomplished on the ideas and knowledge of the previous generation. I'm claiming that the contribution an invidual makes to the growing database of ideas has a greater effect on the development of mankind, than the genetic material passed on through children. A large part of this is passing on your ideas to your children through their ubringing. How much has our gene pool evolved in the last few thousand years? How much has our society evolved in that same time?

Madcat
2005-Mar-13, 08:24 PM
I tend to disagree. It seems logical that certain genes still result in people being more likely to reproduce, and over millenia, they should still become more common. They might not be the same genes that would have been favored before civilization, but it's still evolution.

Grendl
2005-Mar-13, 08:36 PM
Well, it is likely that by the end of the century, humanity will be tinkering with our own DNA. I predict the next couple of centuries will see the fastest period of human evolution to date, due to our own selection.
I don't see any reason to believe we have stopped evolving. Sharks have existed for 350 million years--we have a lot of time to evolve. As BestSkeptical said, we are one of the most "un-diverse" species on the planet. What Dread says above I think will be true; if people come to choose the "perfect" genes for the "perfect" offspring we will manipulate the gene pool. Those, who for moral reasons oppose that, will weaken their gene pool. Selection will still exist. I can't see us forestalling that from happening. But, I think environmental factors will affect us mostly and sooner--nutrition, medical technology, chemicals and toxins in our food, drugs...we already see that when we compare people in First and Third World nations.

I don't think you can put a value on our evolution as far as it being positive or negative--we either go extinct or change and survive. The technology we have to fool around with genes may become necessary for survival (and I'm not talking eugenics of yore). Aside from moral reasons, is there not a reason we shouldn't build a better mousetrap if we are capable of doing so? We're talking years and years from now and we don't know what could happen--a huge chunk of the population could be wiped out for all we know, requiring a better stronger, more efficient version of who we are now. It seems "tinkering with our DNA" is inevitable.

sohvan
2005-Mar-13, 09:13 PM
I tend to disagree. It seems logical that certain genes still result in people being more likely to reproduce, and over millenia, they should still become more common. They might not be the same genes that would have been favored before civilization, but it's still evolution.

I'm not saying that genetic evolution no longer happens or has an effect, but rather it seems insignificant compared to the evolution of ideas. Society and technology is changing too fast for regular evolution to have a significant effect any more. What one generation considers as the characteristics of a good mate, will probably change in a few generations. What we consider beautiful might be considered plain in a hundred years. If the characteristics people look for in mates change with a rapidly developing society, how will any particular genes be favored?

To clarify, I think we change as a species mostly depending on the ideas passed on than the genes passed on.

swansont
2005-Mar-13, 11:15 PM
Homo afranseis--->Homo habiliis (I think that was "Lucy" IIRC)-->


Lucy was H. afarensis, not H. habilis.

I saw recently (on TV) that "Lucy" has been demoted to being, in reality. a member of the chimapanzee family, and the researchers that originally pushed her as being an ancestor of man had backtracked and re-evaluated their theories about her. Does anybody have any more info along those lines?

tbm

My typo. Lucy was Australopithecus afarensis, not Homo.

Gillianren
2005-Mar-13, 11:22 PM
surviving is not enough for evolution. as has been referenced, passing on the genes is what counts.

my best friend has reached the painful decision (for her, anyway) to avoid having children so as to avoid passing on her mental illnesses. if all mentally ill people decided this . . . well, we'd get a definitive answer to the "nature vs. nurture" question on the subject, at least.

I think the mistake people make is assuming that all evolution is what a human would emotionally consider "beneficial." there are some really gross survival strategies on Earth, after all, and if you were to choose, you'd never consider most of them. besides, we as a species have unprecedented control over our environment, so there are certain "negative" traits that will get passed on anyway because we can correct for them. certainly that's the only reason I've survived this long. if I had to catch my own food, I'd be dead of starvation by now. as would Stephen Hawking, come to that.

Sheki
2005-Mar-14, 01:57 PM
If modern evolutionary theory is correct, the only ways for a species to stop evolving are:

1. To become extinct.
2. To cease to reproduce (which for all intents and purposes is equivalent to #1).
3. To evolve into a form that relies exclusively on clonal reproduction (but only assuming that the clonal progeny is free of genertic errors).
4. To cease to be subject to selection pressure (which for all intents and purposes is not possible).

I would also second what Gillianren said about "negative" traits. Positive traits improve survival and fecundity. Negative traits impair survival and reproduction. Whether those traits meet humanity's subjective evaluation of what should be considered "positive" or "negative" is another matter entirely.

I leave it to the reader to examine our present society and make generalizations about which traits are being selected for and which are not... (which segments of the population have the most children? Which traits correlate with lower life expectancy and fewer children?)

Personally, on my more pessimistic days, I presume that we are evolving toward rather lazy, dimwitted, fat creatures with a propensity for abusive behaviour among adult males. Other times I am slightly more charitable - but only slightly.

On the bright side, we can count on evolution to be self-correcting. Which is to say, that should humanity ultimately evolve to a point where we no longer have the wherewithal to sustain the institutions and technology upon which we relied to allow us to evolve into that state...


Sheki

Argos
2005-Mar-14, 02:22 PM
Random mutations is what drives Evolution. Most mutations are harmful, not contributing to the "improvement" of the individual. Paradoxically, "evolution" tends to lead a species to extinction most of the times. More than ninety per cent of all species that ever existed are extinct now.

Humankind is beginning to control its genome, so the random character of evolution belongs to the past, as far as humans are concerned. We are on the verge of stopping evolving naturally.

archman
2005-Mar-14, 08:24 PM
We are on the verge of stopping evolving naturally.
I believe we're already well past that, and have been for hundreds of years. Once you start seeing widespread propagation of deleterious traits (i.e. nearsighedtness, allergies), the cat's out of the bag.

Given proper nutrition and medical care throughout life, the general consensus among anthropologists is that "man" from hundreds to thousands of years ago would overall have had greater genetic fitness. The gene pools of those times would be far healthier than our existing one.

The evolution of man nowadays is virtually (if not totally) up to us now. Many argue that the widespread propagation of bad recessive genes is "devolving" us, or at the very least undoing the work of natural evolutionary processes. I'm a firm member of this camp, possessing many such "devolved" traits myself. Boo! #-o

beskeptical
2005-Mar-14, 09:46 PM
... As BestSkeptical said, we are one of the most "un-diverse" species on the planet.Perhaps you misunderstood me since this is not what I said. I said genetic evidence indicates the human population hit a bottleneck ~ 70,000 years ago and dwindled to a few thousand members. Chimpanzees, who presumably didn't hit the same bottleneck, have much more genetic diversity than humans. We can imply from this that there is room for a lot more diversity among us genetically without changing our similarities that place us in the same species.


What Dread says above I think will be true; if people come to choose the "perfect" genes for the "perfect" offspring we will manipulate the gene pool. Those, who for moral reasons oppose that, will weaken their gene pool. Selection will still exist. I can't see us forestalling that from happening. But, I think environmental factors will affect us mostly and sooner--nutrition, medical technology, chemicals and toxins in our food, drugs...we already see that when we compare people in First and Third World nations.

I don't think you can put a value on our evolution as far as it being positive or negative--we either go extinct or change and survive. The technology we have to fool around with genes may become necessary for survival (and I'm not talking eugenics of yore). Aside from moral reasons, is there not a reason we shouldn't build a better mousetrap if we are capable of doing so? We're talking years and years from now and we don't know what could happen--a huge chunk of the population could be wiped out for all we know, requiring a better stronger, more efficient version of who we are now. It seems "tinkering with our DNA" is inevitable.We already have begun 'tinkering'. Genetic tests in the womb are used to make some decisions to abort the fetus and gene insertion is being tried to correct some genetic defects.

Controlling the direction of evolution has been done for millenia by breeding animals and plants. We can perhaps do it more efficiently now. Mistakes might have bigger potential for bad outcomes but successes also have bigger potential for good outcomes. I think the more we learn in genetic science the more we will advance as a species no matter how we use it.

We face hazards with our impact on the environment, on weapons development, in genetic manipulation, and with our use of resources. At the same time we have many benefits from those same developments. Even nuclear weapons development has created a deterrent to large wars for a time, though whether that will always be the case is certainly questionable today.

I see no reason genetic science is any more or less hazardous than other technologies. It certainly has promise for incredible medical advances.


Back to the evolution question...I reiterate, evolution mechanisms march along. Whether the genetic changes result in more diversity within a species or result in new species is the result of external influences acting upon those genetic changes.

beskeptical
2005-Mar-14, 10:00 PM
We are on the verge of stopping evolving naturally.
I believe we're already well past that, and have been for hundreds of years. Once you start seeing widespread propagation of deleterious traits (i.e. nearsighedtness, allergies), the cat's out of the bag.

Given proper nutrition and medical care throughout life, the general consensus among anthropologists is that "man" from hundreds to thousands of years ago would overall have had greater genetic fitness. The gene pools of those times would be far healthier than our existing one.

The evolution of man nowadays is virtually (if not totally) up to us now. Many argue that the widespread propagation of bad recessive genes is "devolving" us, or at the very least undoing the work of natural evolutionary processes. I'm a firm member of this camp, possessing many such "devolved" traits myself. Boo! #-oThis is a bit of a science fiction version of reality here. The fact we keep some people alive through medicines that would have perished from their genetic make up in the past would only have a minor impact on the gene pool. It's no different now than when humans first benefited from caring for debilitated members of their groups. There are advantages as well as drawbacks. Grandma can't pull her weight in the fields but she can watch the babies so Mom can work, for example. So, did it weaken or improve the gene pool when we evolved to take care of members that would otherwise have met their end when their genes led to aging bodies?

For every medical intervention that stops a genetic based illness from ending a life prematurely, we maintain that much more genetic diversity in the gene pool. We know that genetic diversity plays a role in species survival. When some major environmental change occurs that threatens survival, the more diversity you have, the more likely there is for someone to have a genetic makeup that survives the change.

Lack of diversity in food crops that have been bred to produce more has been one of the setbacks since such crops are more vulnerable to being completely wiped out by a new disease. Some people are on a campaign to save biodiversity in crops by maintaining seed banks of as many varieties as possible. You have a set back....you go forward again.

beskeptical
2005-Mar-14, 10:12 PM
Random mutations is what drives Evolution. Most mutations are harmful, not contributing to the "improvement" of the individual. Paradoxically, "evolution" tends to lead a species to extinction most of the times. More than ninety per cent of all species that ever existed are extinct now.

Humankind is beginning to control its genome, so the random character of evolution belongs to the past, as far as humans are concerned. We are on the verge of stopping evolving naturally.I'm not sure anyone has done the research showing most mutations to be harmful. It is possible but maybe we shouldn't assume that. We may never know since a very serious defect might never be born. On the other hand, the rate of spontaneous miscarriage is 10-15% and the rate of birth defects combined with miscarriage wouldn't be greater that 50%. Since mutations should be expected to be the same in both groups, we might conclude a greater number of mutations were neutral or beneficial. This is all complicated by the fact we have 2 sets of genes which often, if one is defective, the other replaces. So then we'd have to add the % of recessive genes that had defects from mutations into the calculations.

Anyway, if I were going to make a statement most mutations are harmful, I want to do the actual calculations first. Perhaps they have been done?

And how are you pinning extinction on evolution as opposed to pinning it on external forces evolution was unable to overcome?

beskeptical
2005-Mar-14, 10:16 PM
I'm not saying that genetic evolution no longer happens or has an effect, but rather it seems insignificant compared to the evolution of ideas. Society and technology is changing too fast for regular evolution to have a significant effect any more. What one generation considers as the characteristics of a good mate, will probably change in a few generations. What we consider beautiful might be considered plain in a hundred years. If the characteristics people look for in mates change with a rapidly developing society, how will any particular genes be favored?

To clarify, I think we change as a species mostly depending on the ideas passed on than the genes passed on.Perhaps. But this may be a premature assumption. If a comet or massive plague hits the Earth before our 'ideas' evolve to deal with it, evolution may turn out to be more prominent than you are predicting.

Gillianren
2005-Mar-14, 10:59 PM
It's no different now than when humans first benefited from caring for debilitated members of their groups. There are advantages as well as drawbacks. Grandma can't pull her weight in the fields but she can watch the babies so Mom can work, for example.

actually, it is different. Grandma's already done her reproducing, whereas people who survive genetic diseases long enough to reproduce who wouldn't, say, a thousand years ago, are actually having an impact on the gene pool. there are certain conditions that strike in childhood where the person can be brought up to adulthood, but the pivotal step is the reproducing, and whether or not the trait is inheritable. (because I'm specifically thinking of Creb from Clan of the Cave Bear when you refer to debilitated members of the group, and being mauled by a bear is not an inheritable trait, even if he had reproduced.)

Argos
2005-Mar-14, 11:13 PM
Random mutations is what drives Evolution. Most mutations are harmful, not contributing to the "improvement" of the individual. Paradoxically, "evolution" tends to lead a species to extinction most of the times. More than ninety per cent of all species that ever existed are extinct now.

Humankind is beginning to control its genome, so the random character of evolution belongs to the past, as far as humans are concerned. We are on the verge of stopping evolving naturally.

I'm not sure anyone has done the research showing most mutations to be harmful. It is possible but maybe we shouldn't assume that. We may never know since a very serious defect might never be born. On the other hand, the rate of spontaneous miscarriage is 10-15% and the rate of birth defects combined with miscarriage wouldn't be greater that 50%. Since mutations should be expected to be the same in both groups, we might conclude a greater number of mutations were neutral or beneficial. This is all complicated by the fact we have 2 sets of genes which often, if one is defective, the other replaces. So then we'd have to add the % of recessive genes that had defects from mutations into the calculations.

Anyway, if I were going to make a statement most mutations are harmful, I want to do the actual calculations first. Perhaps they have been done?

I thought that it was common knowledge. Ive been hearing of that ever since I was schooled. I should have said that most significant mutations are harmful, since the bulk of them in fact are neutral or never get expressed. Most of the sources I´ve read seem to agree with that. Unfortunately, I couldn´t find premium (and free) web references to the subject. I´m aware that this is claimed by some creationists, but I remember reading serious persons of science (including C. Sagan) saying that.



And how are you pinning extinction on evolution as opposed to pinning it on external forces evolution was unable to overcome?

Isn´t it all the same thing?

eburacum45
2005-Mar-15, 12:27 AM
Humans do not seemed to have changed very much over the last ten thousand years.

Ten thousand years from now humans may well have split into hundreds of different species, living in different environments on and (probably) off the Earth. Some people call ths autoevolution; self directed evolution is more accurate.

If this occurs, evolution will certainly not have stopped. But will there still be natural selection in such a diverse world? Yes, if we decide that it is desirable.
A new artificial species of humans (perhaps Merpeople (http://www.orionsarm.com/clades/merpeople.html), for example) would have to survive in the face of evolutionary pressures; but in many, if not all cases, constant planned adjustments to the genome will be more important than natural evolutionary selection of the fittest. I can imagine the creation of vast gene banks, which ensure that traits are never entirely lost (but they might instead go out of fashion).
However if a population of humans (of whatever kind) decide to opt out of autoevolution, they will experience the same sort of evolutionary processes that we have experienced in the past. In all probability. if these hypothetical new human species were left to evolve without interference, it may become apparent that many would not be viable in the long term.

beskeptical
2005-Mar-15, 06:30 AM
I thought that it was common knowledge. Ive been hearing of that ever since I was schooled. I should have said that most significant mutations are harmful, since the bulk of them in fact are neutral or never get expressed. Most of the sources I´ve read seem to agree with that. Unfortunately, I couldn´t find premium (and free) web references to the subject. I´m aware that this is claimed by some creationists, but I remember reading serious persons of science (including C. Sagan) saying that.I'm not saying it is or isn't true. I'm saying maybe we shouldn't assume it is true. We might not be correct.




And how are you pinning extinction on evolution as opposed to pinning it on external forces evolution was unable to overcome?

Isn´t it all the same thing?No. Saying evolution eventually leads to extinction because 90% of life forms are extinct is a bad interpretation. I'd say evolution allowed at least 10% of the evolved life forms to still be here against all odds.

archman
2005-Mar-15, 07:40 AM
We are on the verge of stopping evolving naturally.
I believe we're already well past that, and have been for hundreds of years. Once you start seeing widespread propagation of deleterious traits (i.e. nearsighedtness, allergies), the cat's out of the bag.

Given proper nutrition and medical care throughout life, the general consensus among anthropologists is that "man" from hundreds to thousands of years ago would overall have had greater genetic fitness. The gene pools of those times would be far healthier than our existing one.

The evolution of man nowadays is virtually (if not totally) up to us now. Many argue that the widespread propagation of bad recessive genes is "devolving" us, or at the very least undoing the work of natural evolutionary processes. I'm a firm member of this camp, possessing many such "devolved" traits myself. Boo! #-oThis is a bit of a science fiction version of reality here. The fact we keep some people alive through medicines that would have perished from their genetic make up in the past would only have a minor impact on the gene pool. It's no different now than when humans first benefited from caring for debilitated members of their groups. On the contrary, this is by no means science fiction. It’s classic biology, at least a few decades old. Didn’t you ever do genetic mapping in high school or college?

Currently, man is not following selection pressures from normal evolutionary processes. And when a population is no longer subject to such pressures, you get individuals that...
1. normally would have died from genetic ailments before attaining sexual maturity
2. attain sexual maturity, but would normally never be able to conceive children due to genetic ailments

What either of these scenarios leads to is propagation and enhancement of deleterious traits within the target population. Which is what we’ve been seeing for quite some time now. A veritable nest of dangerous recessive and/or rare dominant traits is popping up out of the woodwork, and doing so at an alarming rate. There are very few checks in place anymore, and most are manmade (i.e. genetic counseling).


For every medical intervention that stops a genetic based illness from ending a life prematurely, we maintain that much more genetic diversity in the gene pool. We know that genetic diversity plays a role in species survival. When some major environmental change occurs that threatens survival, the more diversity you have, the more likely there is for someone to have a genetic makeup that survives the change.

Lack of diversity in food crops that have been bred to produce more has been one of the setbacks since such crops are more vulnerable to being completely wiped out by a new disease. Some people are on a campaign to save biodiversity in crops by maintaining seed banks of as many varieties as possible. You have a set back....you go forward again.
Domesticated crops have the luxury of their “evolution” being controlled by man. WE prune and snip out the individuals that suffer reduced fitness. But we’ve become so bloody good at it lately, one of the natural “checks” to genetic purity (disease) has become a significant concern. This same thing happens naturally in homeostatic environments, by the way. So now man is attempting a compromise between genetically pure stocks that perform their function admirably, and some measure of genetic heterogeneity that imparts a certain degree of disease resistance.

With man, genetic diversity is not an issue, and is likely never to be in the forseeable future. We have NO selective controls driving our evolution currently in place, either natural or artificial. We’re a genetic loose cannon. This fosters remarkably high genetic diversity (and thus resistance to disease). That’s the only real advantage, and only advantageous to certain individuals.

You can very easily simulate population genetics using computer models, fruit flies, or a honking big piece of paper and some crayons. When selective pressures against deleterious phenotypes are no longer permitted in such models, what you end up with (most of the time) are lower-fitness populations overall, and very high ratios of individuals possessing debilitating traits.

This is what is happening in humans, most notably in developed countries. Populations with reduced genetic fitness, and high percentages of individuals with debilitating traits. And the condition worsens with every generation. That’s why we need to strongly support gene therapy research. That, or institute selective breeding. Most folks would frown on the latter course, nowadays. We're not corn.

archman
2005-Mar-15, 07:55 AM
Regarding mutations being mostly harmful or uesless, yes that's the "dogma" taught in modern biology. :lol:

Let me see if I can remember this right. Basic mutations occur via loss/addition/change of genetic material, either at the DNA/RNA amino acid level, or the allele/chromosome level.

Messing with genetic information usually doesn't do anthing discernible or bad to the organism, 'cuz we tend to have:
1. a lot of DNA that doesn't seem to do much, or anything
2. multiple copies of genes
3. redundant DNA on our sister chromosome (except for boy humans with that pesky Y)

So finding useful areas in the genetic code to "mutate" aren't quite so easy, and the more DNA you have in a critter, the harder it tends to be (I think ferns have more DNA than us). Master control genes are good places to hit if you want to see a mutation expressed. The geneticists in my department are particularly good at it. They foster all sorts of horrible mutations in fishes and plants... sick.

Sheki
2005-Mar-15, 12:34 PM
Archman wrote:


Currently, man is not following selection pressures from normal evolutionary processes.

I would challenge you to back up this assertion. Humanity is most certainly still subject to selection pressures. There are diseases for which there are no cures, others of the species behave violently and unpredictably towards us, some people never mate even though they want to, we cannot mate with whomever we choose (our choices are limited based on our resources, biology, location, and ability), there are risks inherent in modern living (car crashes, plane crashes, etc) that can be avoided through caution, their are opportunities that can be exploited through taking risk, although (in advanced societies) our immediate needs are taken care of (welfare) we are not egalitarian - there is an inequity of resources where the rich are much more capable of providing for their progeny.

People die every day, many in the womb, many in childhood, many before reproducing, many during their reproductive years, and many post-reproduction - but leaving behind children that still need parental care.

I would also note that there are nearly 6 billion members of our species, and just because you are living a cushy life in your little corner of the world does not mean that the rest of humanity isn't stuggling for their next meal.

So long as there is inequity in the world there is selection pressure.

Sheki

beskeptical
2005-Mar-15, 10:59 PM
On the contrary, this is by no means science fiction. It’s classic biology, at least a few decades old. Didn’t you ever do genetic mapping in high school or college? Yes, didn't you keep your education current after high school? I realize you meant to make a particular point but we all do each other a disservice here attacking a person's education or experiences.


Currently, man is not following selection pressures from normal evolutionary processes. And when a population is no longer subject to such pressures, you get individuals that...
1. normally would have died from genetic ailments before attaining sexual maturity
2. attain sexual maturity, but would normally never be able to conceive children due to genetic ailments

What either of these scenarios leads to is propagation and enhancement of deleterious traits within the target population. Which is what we’ve been seeing for quite some time now. A veritable nest of dangerous recessive and/or rare dominant traits is popping up out of the woodwork, and doing so at an alarming rate. There are very few checks in place anymore, and most are manmade (i.e. genetic counseling).The fallacy in this premise is the presumption man's influences on the environment do not contribute to selection pressures. As in my example of the grandmother, humans have been 'over riding' what you refer to as natural selection since we first evolved into humans. In fact, it is often pointed out as something separating us from 'animals' though other great apes also assist injured members of their groups.

I could have just as easily pointed out keeping a young injured member alive until they healed and later went on to reproduce fails to remove weaker members from the gene pool. However, naturally selected traits that increase survival of a group, also increase survival of the individuals.


With man, genetic diversity is not an issue, and is likely never to be in the forseeable future. We have NO selective controls driving our evolution currently in place, either natural or artificial. We’re a genetic loose cannon. This fosters remarkably high genetic diversity (and thus resistance to disease). That’s the only real advantage, and only advantageous to certain individuals. I always find it interesting that because evolution is on such a slow timetable we are often unable to see the movement as it applies to us. Is the climate never going to change? Will new diseases never again emerge? Will our food supplies and exposure to environmental toxins never be an issue in human species survival? And more importantly, which goes to the underlying premise of your argument, will we always have adequate shelter, a medical cure, another food source that these conditions will never again affect our species?

I direct you to current research in genetics of the "CCR5 deletion" which affects a certain protein on the surface of white blood cells. This mutation first occurred several hundred (several thousand?) years ago in Europe and was believed to have been amplified by being a benefit in some way to plague survivors. It now affords the inheritor some resistance to HIV infection.


You can very easily simulate population genetics using computer models, fruit flies, or a honking big piece of paper and some crayons. When selective pressures against deleterious phenotypes are no longer permitted in such models, what you end up with (most of the time) are lower-fitness populations overall, and very high ratios of individuals possessing debilitating traits. Sounds good, just isn't happening on quite the scale you seem to think it is. There are lots of people taking medications or who have had corrective surgeries for genetic diseases. Why I say your version is science fiction is that version is grossly inaccurate in scale and in significance of impact on the human gene pool.


This is what is happening in humans, most notably in developed countries. Populations with reduced genetic fitness, and high percentages of individuals with debilitating traits. And the condition worsens with every generation. On what do you base this sweeping indictment?

I think the problem here is understanding the complexity of the human genome, the time scale on which human evolution occurs, the critical role genetic diversity plays in species survival, and the actual rate at which modern medicine is impacting the gene pool.

I have wondered in the past how we as a species will progress in technological development given the high birth rate of people who live in under developed regions of the world. Then something comes along like HIV which disproportionately affects the third world. I am reminded that over crowding enhances disease transmission. So having the most babies is not necessarily going to mean intellectuals are going to be overtaken in the gene pool in the long run. It is possible but not inevitable. The process of natural selection and genetic diversity is not a simple one.

(No claim here, BTW, that there is an inherently smaller intellect in the third world, just that more babies vs smarter babies is a possible genetic trait that natural selection processes can be acting on.)

beskeptical
2005-Mar-15, 11:05 PM
1. a lot of DNA that doesn't seem to do much, or anything
....Currently, the fact these long repeating strands are inactive is doubted. Since the same strands are present from generation to generation, it means mutations along the repeating strands are either not occurring or the organism is not surviviing when they do occur.

archman
2005-Mar-18, 01:44 AM
Archman wrote:


Currently, man is not following selection pressures from normal evolutionary processes.

I would challenge you to back up this assertion. Humanity is most certainly still subject to selection pressures. There are diseases for which there are no cures, others of the species behave violently and unpredictably towards us, some people never mate even though they want to, we cannot mate with whomever we choose (our choices are limited based on our resources, biology, location, and ability), there are risks inherent in modern living (car crashes, plane crashes, etc) that can be avoided through caution, their are opportunities that can be exploited through taking risk, although (in advanced societies) our immediate needs are taken care of (welfare) we are not egalitarian - there is an inequity of resources where the rich are much more capable of providing for their progeny.
Compared to "wild" conditions, all of those arguments either do not apply or their effects are now greatly diluted. And for any of them to classify as selection pressures, there has to be genetically-based predispositions for/against them. Not personal choice, geography, culture/economic level, or the like.


People die every day, many in the womb, many in childhood, many before reproducing, many during their reproductive years, and many post-reproduction - but leaving behind children that still need parental care.

I would also note that there are nearly 6 billion members of our species, and just because you are living a cushy life in your little corner of the world does not mean that the rest of humanity isn't stuggling for their next meal.

We currently have runaway population growth, and the current human population size is unprecedented. A nullifying of many "natural" selection pressures has most certainly contributed to this growth. The advent of modern medicine and health care is one of the biggest examples. It has allowed many individuals to live and/or reproduce that under normal circumstances would not occur. That's not advantageous to the genetic fitness of the overall population, hence it runs counter to natural evolution.

archman
2005-Mar-18, 06:51 AM
1. a lot of DNA that doesn't seem to do much, or anything
....Currently, the fact these long repeating strands are inactive is doubted. Since the same strands are present from generation to generation, it means mutations along the repeating strands are either not occurring or the organism is not surviviing when they do occur.

The whole issue of "junk DNA" is highly in doubt. You don't have to tell me about it, I work in a department that's 90% geneticists. :lol:

However, we're still fairly certain that most of the protein-making genes comprise only limited portions of genomes. And that's the most important stuff. The other DNA... theories and recent research studies abound. Much of this DNA is endlessly repetitive in sequence... AGCG-AGCG-AGCG over and over again. Some folks argue that the DNA is leftover material no longer used. Others claim that they act as protective buffers around the protein-making gene segments. Actually, here's a link that talks about the newest possibilities for junk DNA.
http://www.godandscience.org/evolution/junkdna.html

Don't take that article to heart, it merely outlines some current research. The consensus on these non-coding DNA regions is not likely to be resolved anytime soon. We still have no idea if most of this DNA does anything at all, we've just shown that some portions do.

Regarding DNA replication from generation to generation, let me assure everyone that changes very much do occur, on a continuous basis. The DNA you possessed at childhood is not the same as at age 80. The most significant change in your DNA is the shortening of your telomeres. Telomeres protect the protein-coding genes; they’re repetitive “junk DNA” segments of TTAGGG (and AATCCC). Anyway, you start off with a lot of telomere in your cells, and steadily lose the stuff every time your cells divide. Losing telomeres is not considered a good thing.

Your DNA is subject to good old fashioned mutations too. Here’s a pretty thorough link describing all the fun ways you can and will thrash your genetic code. At the bottom, there’s a listing of self-healing techniques. The ability to self-repair is one of the critical hallmarks of DNA; we’d all be screwed else. Self-repair is by no means perfect, however. Mutations creep in that aren't corrected, all the time. But like most mutatations, they don't seem to do anything.
http://www-personal.ksu.edu/~bethmont/mutdes.html

Dang, I should bookmark this site. It’s an easier read than the stuff in my office. Lord I hate genetics...

archman
2005-Mar-18, 07:14 AM
Let me try to enhance on some of your excellent counterarguments beskeptical. I apologize if you interpreted some of my comments as insulting or demeaning... they were not intended to be. I don’t use smilie faces nearly as much as I should... here's one. :P


Currently, man is not following selection pressures from normal evolutionary processes. And when a population is no longer subject to such pressures, you get individuals that...
1. normally would have died from genetic ailments before attaining sexual maturity
2. attain sexual maturity, but would normally never be able to conceive children due to genetic ailments

What either of these scenarios leads to is propagation and enhancement of deleterious traits within the target population. Which is what we’ve been seeing for quite some time now. A veritable nest of dangerous recessive and/or rare dominant traits is popping up out of the woodwork, and doing so at an alarming rate. There are very few checks in place anymore, and most are manmade (i.e. genetic counseling).


The fallacy in this premise is the presumption man's influences on the environment do not contribute to selection pressures. As in my example of the grandmother, humans have been 'over riding' what you refer to as natural selection since we first evolved into humans. In fact, it is often pointed out as something separating us from 'animals' though other great apes also assist injured members of their groups.

I could have just as easily pointed out keeping a young injured member alive until they healed and later went on to reproduce fails to remove weaker members from the gene pool. However, naturally selected traits that increase survival of a group, also increase survival of the individuals.
Assuming man’s influences on the environment is contributing to natural selection pressures, what are examples of such selection pressures? I completely agree that humans have been “overriding the system” for a very long time now; I don’t know a single biologist that doesn’t believe this. But in order to have a selection pressure, there has to be a phenotypically expressed advantage regarding mate selection. From a genetics standpoint, modern man is not pursuing this nearly so much as in the distant past.

Sociobiological traits like parental care are very tricky to pin down at the genetic level, so it’s very difficult to measure them within evolutionary contexts. But remember, parents aren’t thinking of their youngs’ genetic fitness when they protect and nurture them; the parent is “thinking” only of propagation of its own genes. Those genes can still be “bad”. And in many animals, social altruism is a learned behavioral trait, not a genetically inherited one. Remove the learning context, and the altruism often goes with it, or it’s made far less effective. That’s what happens with isolated humans and apes. Their genetic fitness may still be perfectly fine, but their behavioral fitness might not be.



With man, genetic diversity is not an issue, and is likely never to be in the forseeable future. We have NO selective controls driving our evolution currently in place, either natural or artificial. We’re a genetic loose cannon. This fosters remarkably high genetic diversity (and thus resistance to disease). That’s the only real advantage, and only advantageous to certain individuals.


I always find it interesting that because evolution is on such a slow timetable we are often unable to see the movement as it applies to us. Is the climate never going to change? Will new diseases never again emerge? Will our food supplies and exposure to environmental toxins never be an issue in human species survival? And more importantly, which goes to the underlying premise of your argument, will we always have adequate shelter, a medical cure, another food source that these conditions will never again affect our species?
All of those pressures can (and are) dealt with not by natural darwinian evolution processes anymore, but by advents in modern technology and industrialization. Some of us have “help” from our genes against certain diseases and environmental toxins/stresses, but by and large man directs its own fate now. We can even piddle around with our genes now, albeit on an extremely primitive level. The technology is ramping us very quickly.


I direct you to current research in genetics of the "CCR5 deletion" which affects a certain protein on the surface of white blood cells. This mutation first occurred several hundred (several thousand?) years ago in Europe and was believed to have been amplified by being a benefit in some way to plague survivors. It now affords the inheritor some resistance to HIV infection.
Well, I don’t know about CCR 5, but I’ll discuss some other genetic-based disease resistances. Let’s take the sickle-cell gene, and the bipolar disorder genes. With the sickle cell gene, you get increased malarial protection. With the advent of antimalarial medications, man no longer has a need to foster the sickle cell gene (it has some nasty side effects with anemia). With bipolar disorders, similar processes are hypothesized.

Here’s a cutesy article from some psychiatrists, talking about bipolar disorders from an evolutionary perspective. Everything they’re saying falls into line with modern theory.
http://www.psycheducation.org/depression/fitness.htm

Here’s one excerpt that explains loss of genetic fitness in a specific context (bipolar disorder):

Having a few too many (bipolar) genes begins to decrease reproductive success, because the behaviors they cause are becoming too extreme -- in other words, a person with that many genes is becoming "symptomatic". If you get a few more genes than that, you may have so many symptoms that you cannot function well. This is what we regard as "mental illness".

Assuming we get a better handle on HIV (or at least one of the major strains), the “CCR 5” deletion won’t have much value, either. It might still be fostered in endemic populations with limited health care, but such selection pressures will be increasingly diluted as the “need” for it drops. The only way it might be retained in modern societies is in the form of retroviral-type gene therapies, which is directed by us.

There are many diseases found throughout the world which are stymied/attenuated by particular genetic resistances... folks that inherit such resistances have higher genetic fitness. Folks that take vaccinations to ward off the disease may/may not have the resistant genes, and they very likely no longer face selection pressures to maintain such genes. Therefore the gene that favors the particular disease resistance is no longer favored for, and you suffer reduced genetic fitness (relevant to the disease).

Take away the medical care, and the difference between folks that are fit/less fit become readily apparent.



You can very easily simulate population genetics using computer models, fruit flies, or a honking big piece of paper and some crayons. When selective pressures against deleterious phenotypes are no longer permitted in such models, what you end up with (most of the time) are lower-fitness populations overall, and very high ratios of individuals possessing debilitating traits.


Sounds good, just isn't happening on quite the scale you seem to think it is. There are lots of people taking medications or who have had corrective surgeries for genetic diseases. Why I say your version is science fiction is that version is grossly inaccurate in scale and in significance of impact on the human gene pool.


This is what is happening in humans, most notably in developed countries. Populations with reduced genetic fitness, and high percentages of individuals with debilitating traits. And the condition worsens with every generation.
On what do you base this sweeping indictment?

Basic gene mapping, simple statistics, and classical evolutionary theory is my “sweeping indictment”. If there aren’t evolutionary pressures to weed out deleterious traits, those traits persist. If parents retaining such deleterious traits (but the trait is medically treated for them) produce offspring, they pass on and possibly magnify the presence of such genes. It’s that simple. Corrective surgeries and/or medications don’t pass on to offspring (although some medications taken by the mother during pregnancy can damage offspring’s DNA). Regarding short-term significance of impact on the human gene pool, here you may be correct. There is so little quantifiable information available at present, theory is mostly all we have to go on. The theory however is quite firm... it’s the time-scale factoring that’s not well predictable. This may possibly be what is being implied with the “scifi” remarks. I am not insinuating we’re all about to keel over and die from gross genetic damage, and I apologize if my earlier remarks were interpreted as such. But developed nations have the higher risk associated with them, as they’ve got the lowest natural selection pressures operating on them. And we really cannot back much up with cold hard facts at the present time. Developed nations depend much more heavily on modern medical care to maintain (relatively) high numbers of people with serious genetically-based ailments. Those alleles persist in the gene pool, where normally they would not. There’s very good reason to visit your genetic counselor nowadays; you’d hardly credit how many kids with genetic diseases are popping up in cities. Much of this is due to women delaying childbirth until their 30’s or later. Statistics on increased offspring born with genetic defects IS something well documented.

Regarding scale, there are two factors to contemplate, the global gene pool, and localized “breeding” gene pools. It’s the latter that is easier to simulate on the computer (fewer people), and in fact which mirrors human community structure more accurately. Despite our massive global population, the majority of individuals still interbreed within the regional/local level. People that propagate within smaller breeding groups (i.e. inner city slums, hierarchical castes, ethnic groups) can and do propagate deleterious genotypes much faster than in larger groups. For very small, isolated populations, the effects of such inbreeding are well disseminated. But the principle works the same in larger ones; it just takes longer to manifest.

Take for example the relatively isolated (in terms of breeding) populations of lower-class, inner-city African Americans. There’s a sharp rise in asthma being reported from that moderate-sized demographic. Some of that rise is believed to be the result of genetic propagation of asthmatic genes (specifically those that cue into cockroach feces, which African Americans tend to be predisposed against). Unfortunately, pinning down asthmatic genes has been less than fruitful, so it’s impossible to directly test this. But it follows the simulation pattern quite nicely, and there aren’t many alternative theories (air quality is one).

The problem with scale is that smaller breeding populations carrying a lot of deleterious genes can wreak havoc on larger breeding populations, when the two are mixed. In some cases, the deleterious genes simply aren’t present in the larger populations, in other cases, the genes are present but sufficiently rare and/or masked by other genes. Either way, you still end up with deleterious genes.

Regarding impact to the human gene pool, you don’t need a significant phenotype expression in high numbers to sound alarm bells. If a population already sees that, it’s very likely far too late for a simple fix. Ecosystem health (which I study ad nauseum) works the same way... minor but persistent damages can be just as bad as major ones. With unchecked propagation of deleterious genes in one’s DNA, you get a slow but steady (and cumulative!) drop in genetic fitness. Sneaky minor changes actually tend to be worse, ‘cuz you’re less likely to notice their inception and spread. This is called “Shifting Baseline Syndrome” in the ecological community, and it’s nasty stuff.

There are two common examples of genetically-based ailments that I will touch on, that do get overhyped in the media. Allergies, and Vision.

Vision. Most of the common vision maladies in people are genetically based. Strabismus, amblyopia, myopia, hyperopia for example. There’s a huge upswing in myopia popping up in developed nations, but most of that has been found to be due to watching TV or hitting the books. NOT genetic pooping out in the general population. That doesn’t mean that our eyeball genes are still following natural selection pressures to stay in tip-top shape, but we’re not all going blind in fifty years (due to genetic degradation) either.

Allergies. This is tougher, as it’s strongly based not just on genes, but the environment. Allergies are reported on the high upswing throughout the world, mostly in western nations. Increasing problems with air and water quality is thought to be the major contributor here. Many allergies are genetic in origin, and something like 20-30% of the world’s population carries allergy genes. Many of these genes are “atopic”, inducing immediate hypersensitivity. Most people don’t consider their “atopic risk” when they bear children, for the simple reason that even the worst allergies currently known are medically treatable. That’s perfectly valid, but it also nullifies any evolutionary selection pressures to keep atopic genes as few as possible in offspring. Fortunately, not a single doctor will advise against rearing children due to atopic predispositions... of course those doctors will assume there’s proper medical care also. There’s a lot of allergies that can kill ya’. Ugh.



I think the problem here is understanding the complexity of the human genome, the time scale on which human evolution occurs, the critical role genetic diversity plays in species survival, and the actual rate at which modern medicine is impacting the gene pool. Yes, all of those are huge question marks, and major areas of current research. We seem to know a little bit about each of these topics; enough to formulate plenty of theories. I study evolution on large-scale populations myself, albeit my test subjects aren’t humans. A lot of the theories that work on animals just fine seem to fizzle out when we try them out on modern humans. This highlights man as a potentially unnatural animal. I doubt any evolutionary biologists still consider man “natural”, however. Even we generic biologists do not.


Looks like I got to rambling. Oh God this is bloody HUGE... I didn't mean to write so much garbage. I don't even LIKE genetics. #-o

Be merciful, oh BA viewers! I'm on a lot of caffeine!

Plat
2005-Mar-18, 07:27 AM
Wow archman, you could write your own book...

And doesnt natural selection drive evolution too?

archman
2005-Mar-18, 07:38 AM
Wow archman, you could write your own book...


I was supposed to be running regression analyses for my dissertation, but nooooo... Blah.

Can one become addicted to message boards? What's the prescribed treatment?

Plat
2005-Mar-18, 07:46 AM
I think the reason why we have slowed down evolving or stopped completely (which I doubt) is because there is no more environmental pressures to make us evolve, the environment doesnt force us to change we now have the ability to force the environment to change.

Sheki
2005-Mar-18, 08:35 PM
Archman wrote:


Compared to "wild" conditions, all of those arguments either do not apply or their effects are now greatly diluted.

Again I ask you to back up your assertions, why do those arguments "not apply", how are the effects "greatly diluted", and why would that necessarily matter?


And for any of them to classify as selection pressures, there has to be genetically-based predispositions for/against them.

Agreed


Not personal choice,

Are you stating that there is no genetic component to personal choice? Is not one's ability to percieve the world linked to the choices that they make? Would not an individual that is genetically predisposed toward high intelligence be more likely to make certain types of decisions than others? Can we assume that there is no genetic predisposition with respect to the acceptance of risk? Are there no genotypes/phenotypes that exihibit different physiological responses to different situations? Has one's physiology no affect on the choices they make? No affect on their response to stressful events?


geography,

Geography is one of the most important selection pressures. Speciation is often linked to adaptation to match ones environment. I would argue that indeed humans change their environment to suit them, however this does not relieve the species from environmental/geographic selection pressures. On the contrary. The species has a tendency to modify the environment in the same way, all the time. We make cities, and live in apartment's and houses. Thus, we can expect that those who fair well in urban environments might be selected for. A three year-old child, forced to live in the city, intensely allergic to diesel fumes is obviously selected against.


culture/economic level, or the like.

Is not our culture an extension of our biology? Would not our culture be rather different if humanity had a predominantly hermaphroditic sexaul habit? (for instance)

Anything that influences an individual's reproductive success is selection pressure. It need not even be terribly obvious, as even very small, seemingly innocuous advantages can have a huge influence over geological timescales. For example, consider two groups of people -athsmatics and non-athsmatics. If their reproduction success is even only slightly different, say 1 or 2% (ie. 1 or 2% of athmatics not reproducing, or having fewer children for some reason (say they died of an athsma attack before reproductive age, or they couldn't become captain of the football team, etc)). That is a significant disadvantage.


We currently have runaway population growth, and the current human population size is unprecedented. A nullifying of many "natural" selection pressures has most certainly contributed to this growth. The advent of modern medicine and health care is one of the biggest examples. It has allowed many individuals to live and/or reproduce that under normal circumstances would not occur.

Agreed, but this does not mean that evolution has stopped, just that some very extreme selection pressures have been removed or eliminated. That is very different than saying ALL selection pressures have been eliminated.


That's not advantageous to the genetic fitness of the overall population, hence it runs counter to natural evolution.

Not so. The situation is quite normal, and is well understood within even the most basic formulation of "Evolution". Perhaps a quick refresher on Hardy-Weinberg equilibrium would be of assistance:
http://anthro.palomar.edu/synthetic/synth_2.htm

As noted in the Hardy-Weinberg list of the seven prerequisite conditions for stopping evolution, you have only identified one:
1. The elimination of natural selection

However, as identified above, I dispute even that claim. It might be argued that humanity is no longer subject to Natural selection, if it could be shown that humanity was in concious control of the selection pressures that it places on itself...but even then it would still be subject to selection pressure, just not natural selection pressure. (However, given that natural selection would have given rise to a creature that can choose its own selection, could we really separate our own concious selection decisions from those of nature?)

You also seem preoccupied with the "runaway" population growth, and the proliferation of individuals with deleterious genes. However, even this is predicted by evolutionary theory. Take a population, provide it with unlimited resources and the population will explode, with all members participating to a great extent and producing offspring like crazy. Once the resources are gone, or the population has exceeded the carrying capacity, that is when the serious competition starts. This is all part of evolution, not just the cutthroat competition at the end.

Elsewhere you noted that you did not know any biologists that think humanity is still subject to selection pressure. Note that this is an argument from authority. Even worse, an argument from pressumed authority. It prooves nothing. And for the record, you now know of one.

Sheki

fossilnut2
2005-Mar-18, 10:45 PM
As a paleontologist I have to point out that evolution isn't magical or spiritual but very simple: the perpetuation of genetic material. Those with the most viable offspring that in turn reproduce will determine future human evolution.

The myth from science fiction movie, etc. is that brains become bigger, limbs atrophy, etc. This all assumes that people with bigger brains have more offspring who in turn have more offspring...etc.

Ask yourself this: in your own society, wherever you live, do the most intelligent people have the most children? an argument can be made than in the most technologically advances societies it is the less intelligent who multiply in higher numbers and therefore humans are becoming less intelligent and not more intelligent.

The big wrench thrown into evolution is genetic engineering of various flavors. Is generic engineering performed by man part of Nature or outside of Nature? Is Nature a closed system that includes everything man does? Is there really such a thing as natural or artificial or is the dichotomy just a superficial division imposed my man?

beskeptical
2005-Mar-19, 09:07 AM
I think the reason why we have slowed down evolving or stopped completely (which I doubt) is because there is no more environmental pressures to make us evolve, the environment doesnt force us to change we now have the ability to force the environment to change.But there is no evidence we have "slowed down evolving". It just looks that way because human evolution is so slow. Bacteria evolve more quickly so we can see it happen.

Think about how many copies of a single bacteria are made per day. Millions or billions. Now think how many years it takes for the same number of new generations in a single human's offspring. See the different time scale. It isn't that evolution of humans is slower, it's that evolution of humans was always very slow.

Argos
2005-Mar-23, 01:11 PM
Anyway, if I were going to make a statement most mutations are harmful, I want to do the actual calculations first. Perhaps they have been done?


Well, It looks like there´s something new (http://www.nytimes.com/2005/03/23/science/23gene.html?hp&ex=1111640400&en=8f3d930c9f478eac&e i=5094&partner=homepage). With these findings I´m unable to make the case for my position on harmful mutations. On the flip side, creationists, who use the harmful mutation argument to defend the thesis of the impossibility of evolution, will face hard times.

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