Evolutionary Value of Specific Traits

[Rasori]

I've been wondering for the past few days about this--evolutionarily speaking, we (humans, though it's true of everything) have traits that are supposed to help us in surviving, and, (probably more importantly) reproducing.

 

So what, then, is the evolutionary advantage to being left-handed? Surely if there was no advantage, that particular mutation would've disappeared, but if there was an advantage it should be dominant, no?

 

Of course, I suppose it's pretty stupid to ask for the advantages of tiny details, but I still question why we don't have toes with full movement, like our fingers, or what makes finger and toenails useful.

 

Taste is another thing--sight, hearing, and smell are useful for hunting (even in the average-level capabilities humans have in comparison with many other animals), and touch is useful because it allows us to better coordinate ourselves and, through pain, alert us to problems. Along the same lines, you'd think that something that tastes bad must be harmful to the body. That could be fitting (dunno about you, but I've never actually tasted a poison to test that) except that many people perceive healthy foods to taste horrible, preventing them from eating them, and yet other people absolutely love the taste of foods they're allergic to (causing a bad reaction = bad taste, or at least that's how things should work).

 

So, on an evolutionary level, are we evolving in whole towards something better, even if some things seem useless, or is there a reason behind these things that I'm missing, or does evolution just allow for some things that don't, in the end, help or hurt the being?

[Mokele]

So what, then, is the evolutionary advantage to being left-handed? Surely if there was no advantage, that particular mutation would've disappeared, but if there was an advantage it should be dominant, no?

 

It might have none, or even be detrimental (though I can't see how it could be), yet still persist because it's linked to an advantage that outweighs any problems. Given that both right and left handed people are still around, clearly the advantge is not universal, but rather situational, if there is any at all. Of course, it might just be a bit of neurological randomness.

 

Interestingly, other animals also display 'handedness' in terms of manipulating prey and the like. Even snakes, ironicly, prefer to coil in a particular direction (clockwise or counterclockwise).

 

Of course, I suppose it's pretty stupid to ask for the advantages of tiny details, but I still question why we don't have toes with full movement, like our fingers, or what makes finger and toenails useful.

 

Evolution is often constrained by developmental pathways. Fingers and toes use the same genes as penii, and many alterations to those can adversely effect the most important finger of all, if you get my drift. That's why 6 fingers hasn't become the standard.

 

Taste is another thing--sight, hearing, and smell are useful for hunting (even in the average-level capabilities humans have in comparison with many other animals), and touch is useful because it allows us to better coordinate ourselves and, through pain, alert us to problems. Along the same lines, you'd think that something that tastes bad must be harmful to the body. That could be fitting (dunno about you, but I've never actually tasted a poison to test that) except that many people perceive healthy foods to taste horrible, preventing them from eating them, and yet other people absolutely love the taste of foods they're allergic to (causing a bad reaction = bad taste, or at least that's how things should work).

 

Basically, that just boils down to evolutionary novel environment (we haven't had time to adapt to how our evironment has changed) and lack of selection (food allergies would be selected against and mostly eliminated in the past).

 

So, on an evolutionary level, are we evolving in whole towards something better, even if some things seem useless, or is there a reason behind these things that I'm missing, or does evolution just allow for some things that don't, in the end, help or hurt the being?

 

The last option. Neutral traits and those constrained by development or lack of variation are suprisingly infuential in evolution.

 

Mokele

[stubighead]

Yes, of course if handedness is genetic, i dont know about that and a neurological factor seems more likely, left handedness doesnt have to have an advantage to exist in a population just so long as it isnt a disadvantage in reproducing. It would be just another variation in the human species. This of course is a fundamental principle of evolution, variation must exist to allow evolution to move in any particular direction if need be.

 

There are humans with plenty of movement in their toes but i think this is generally a good thing for those wishing to swing through trees ie. monkeys!!

Humans are humans cos it was an advantage to lose that ability and replace it with feet better for walking and running than gripping tree branches.

 

Yes, evolution allows variation to occur so long as it is not detrimental to the organisms ability to reproduce. If this wasnt the case natural selection would have nothing to work on.

[Ophiolite]

Interestingly, other animals also display 'handedness' in terms of manipulating prey and the like. Even snakes, ironicly, prefer to coil in a particular direction (clockwise or counterclockwise).

Interesting. Is that species specific. Are there mixes of sinisters and dexters in each species? Does it appear to provide any advantages? Slightly OT, but perhaps a good illustration of Rasori's underlying theme.

[shenzhou]

So what' date=' then, is the evolutionary advantage to being left-handed? Surely if there was no advantage, that particular mutation would've disappeared, but if there was an advantage it should be dominant, no?

[/quote']

 

There is an explanation of the persistance of left handedness that invokes frequency dependant selection. Basically in a majority right handed population lefties would have an advantage in combat increasing chances of survival. This advantage would decrease as left handers became more common and righties became accustomed to lefties. A proxy for this effect can be seen in professional sports such as tennis where there is a disproportionately high number of left handers, this is not seen in games where there is not direct competition such as golf.

 

There is an excellent book entirely devoted to issues of handedness and symmetry if you want to learn more: http://www.righthandlefthand.com/

 

see: Proc Biol Sci. 1996 Dec 22;263(1377):1627-33. Frequency-dependent maintenance of left handedness in humans. Raymond M, Pontier D, Dufour AB,

 

Moller AP. http://www.isem.univ-montp2.fr/GE/Adaptation/Bibliographie/raymond96.pdf

 

http://www.isem.univ-montp2.fr/GE/Adaptation/Raymond.php

 

Proc Biol Sci. 2005 Jan 7;272(1558):25-8. Handedness, homicide and negative frequency-dependent selection. Faurie C, Raymond M.

 

http://www.isem.univ-montp2.fr/GE/Adaptation/Bibliographie/fauriePRSLB2004.pdf

 

http://www.isem.univ-montp2.fr/GE/Adaptation/Faurie.php

[Mokele]

Is that species specific. Are there mixes of sinisters and dexters in each species? Does it appear to provide any advantages? Slightly OT, but perhaps a good illustration of Rasori's underlying theme.

 

I really have no idea. I know that most bears are left-handed, while in other species there is more of a mix, but that there seem to be both in all species we've looked at. However, that's about all I know of it, since it's so far outside my field. Shenzhou's links probably contain some good info, though.

 

Mokele

[Kyrisch]

Regarding the claim that without an advantage, left-handedness would vanish due to natural selection and human evolution:

 

Presently, the human race is deteriorating at a frightening rate. We are no longer evolving, thanks to medical “innovations” and inventions that save lives everyday. We are DE-volving.

 

Take the common vestigial organ, the appendix. Appendices are vestigial organs that are not only useless, but in some rare cases, deadly. Appendicitis strikes an average 15 people out of 20,000 in the United States each year. Not a very high number, but, still, one would think the number of people with appendices is decreasing because of natural selection. This is not the case, however, because each year about the same amount of appendices are removed, allowing the individual with the faulty appendix (and faulty genes) to live and reproduce, passing those genes down to his/her kids. Children without appendices have been born in the world today, and five million years ago (if the organ was vestigial then, which it was not), the appendix-free population would immediately flourish while the percentage of people with appendices would plummet until the appendix was abolished forever. Now, in this age of mapping the human genome and other great medical advances, the appendix will never be abolished completely.

 

It is the same with near- and farsightedness. Glasses and contacts repair these problems that would have horribly inhibited the daily function of our ancestors. Not being able to hunt, these individuals inflicted with problems such as this would be forgotten and would die off, natural selection at work once more.

 

So you see, as long as we keep fixing these genetic defects* that manifest themselves in our bodies as physical problems, the human race will continue deteriorating.

 

*This obviously does not include genetic defects that are incurable or untreatable, or are completely devastating such as cystic fibrosis.

[rbp6]

I don't understand how that would be deevolution though. We're gaining the ability to cure diseases, thus, they're not really defects anymore, so it doesn't affect the survivability of the species to have them. I.E if you can cure a swollen appendix easily, why doesn't it matter that people are born with them any more? If anything its sort of an evolution because it increases the survival rate of our species.

[Kyrisch]

But soon everyone in the world will be suffering from appendicitis or wearing glasses five feet thick (Ok, I'm exaggerating there, but you get my point).

 

We're growing in quantity but decreasing in quality. Each generation is born with worse and worse genes. We're tinkering with natural selection itself.

[Skye]

The appendix may be useful as part of the immune system.

[Halucigenia]

Presently, the human race is deteriorating at a frightening rate. We are no longer evolving, thanks to medical “innovations” and inventions that save lives everyday. We are DE-volving.

We're growing in quantity but decreasing in quality. Each generation is born with worse and worse genes. We're tinkering with natural selection itself.

It's still evolution though, not de-evolution (no such thing IMO), evolution is directionless so you can't de-evolve. It's just un-natural selection

[PhDP]

We live longer, taller, stronger, and, even without natural selection, IQ are rising at a fast pace. We are certainly not decreasing in quality. Natural selection isn't always a good thing, it's the enemy of diversity, if we compare the human species to other mammals, our genetic diversity is already low. About "the world will be suffering from appendicitis". Why ? Nearly all human have an appendix. Nearly all human HAD an appendix. Appendicitis is an random infection due to the mechanic of our digestive system, it's not genetic. Have you proofs appendicitis is more frequent now ? I don't think it is...

[Kyrisch]

I never said it was more common now. I never said appendicitis is genetic. I did say that having an appendix is genetic.

 

We live longer because our medicine and technology. The same stuff that is ruining the quality of our genes. The same stuff that is ruining the quality of life as well. Would you rather live a full, happy life and die with content, or would you like to die in a hospital that has been your home for twenty years on top of a bed pan where they feed you? I'd take the first one, personally.

 

We are taller, true, but that does not improve quality of life. That is a quantitative characteristic.

 

We are most certainly not stronger. Our ancestors had to hunt everyday and bring their kill home... we have to get up and get in our car to go to work.

 

IQ and intelligence is the only thing that Natural Selection has apparently given us that is useful. In all other aspects, I still say the human race is deteriorating.

[PhDP]

We live longer because our medicine and technology. The same stuff that is ruining the quality of our genes. The same stuff that is ruining the quality of life as well. Would you rather live a full, happy life and die with content, or would you like to die in a hospital that has been your home for twenty years on top of a bed pan where they feed you? I'd take the first one, personally.

 

I agree that, because of exagerated therapeutic eagerness, people often die in very poor condition. That doesn't mean technology and medicine is ruining our genes. We don't need to have a good sight, we don't need to loose our appendix, we live in an environement where these things doesn't matter to our survival. Most of the genes have no intrinsec value, they only have a value in a particular context. Sure, life is very easy for people in occident, and sure, natural selection (which is not the only mecanism of evolution, maybe not even the most important) isn't affecting us very much, like many other species in the wild, but we have a strategy oriented toward the use of our intelligence. We might even be able to enhanced our own genome.

 

True, some illness could have been discared in the wild. It's the consequence of society and human empathy, what can we do about it except waiting for genetic engineering ?

 

IQ and intelligence is the only thing that Natural Selection has apparently given us that is useful.

 

It's certainly not because of natural selection that the average IQ is rising today.

[Kyrisch]

Really, I assumed that's what you were implying by putting it in your initial list. I was skeptical but I did not know for sure and therefore did not challenge you, but now I am curious. What is the cause of the steadily increasing IQ of our race?

[LucidDreamer]

Really, I assumed that's what you were implying by putting it in your initial list. I was skeptical but I did not know for sure and therefore did not challenge you, but now I am curious. What is[/i'] the cause of the steadily increasing IQ of our race?

Education mostly, possibly some nutrition as well.

[Mokele]

Presently, the human race is deteriorating at a frightening rate. We are no longer evolving, thanks to medical “innovations” and inventions that save lives everyday. We are DE-volving.

 

As others have pointed out, there is no such thing as 'de-evolving'.

 

This is not the case, however, because each year about the same amount of appendices are removed, allowing the individual with the faulty appendix (and faulty genes) to live and reproduce, passing those genes down to his/her kids. Children without appendices have been born in the world today, and five million years ago (if the organ was vestigial then, which it was not), the appendix-free population would immediately flourish while the percentage of people with appendices would plummet until the appendix was abolished forever. Now, in this age of mapping the human genome and other great medical advances, the appendix will never be abolished completely.

 

Why do we have one, then? We didn't have the ability to treat appendicitis until the last 200 years, tops, which leaves over 249,800 years of human evolution (and possibly more, esp. if we include other hominids in our line) for us to solve this problem. Why hasn't it been solved?

 

Lack of variation. If nobody has ever been born without an appendix, then there is no trait to select *for*. Given that the formation of the appendix is no doubt a result of complex developmental pathways, and that such pathways rarely can be tinkered with without lethal or highly damaging results, it is entirely possible that the genetic combination for 'no appendix' simply hasn't happened.

 

We live longer because our medicine and technology. The same stuff that is ruining the quality of our genes. The same stuff that is ruining the quality of life as well.

 

Flat out wrong. Ever had malaria? Tapeworms? Been through a famine? Those are large parts of ancient life. Call that quality? Because I don't.

 

---------

 

Frankly, I fail to see a problem with the effects of medical technology. So what if the genes for our eyes suck; so long as we can get that corrected, we can still see, so there's no difference. Only the end result matters in nature, not how you get there. It doesn't matter if Mr. Primitive is strong because he worked so much, while I'm strong because I had 4 giant mechanical Dr. Octopus tentacles implanted into my back. Only the end result matters, and that I can kick his puny, un-enhanced butt.

 

Mokele

[Rasori]

That actually brings me to a question--only the end result matters, but wouldn't evolution try to make the end result itself? The evolutionary process (as far as I know) isn't sentient, so clearly it can't know "oh, they don't need good eyesight--they have laser eye surgery and glasses," and thus let eyesight die out. Wouldn't it instead try to create better eyesight as much as it could (and I know that talking about the evolutionary process this way is awfully tough, as "it," again, isn't sentient) and then we would correct it in the long run?

 

Or is it that "Oh, this person survived just fine without good eyesight, so the next one in their line could probably do the same?" Basically, that natural selection isn't quite so natural anymore, but we're practically leading it along. Perhaps someone with an evolutionarily good trait then gets shot and killed in the streets of New York, so "natural" selection leads to that good trait fizzling, while worse traits such as bad eyesight are corrected and thus don't need fixing.

 

As confusing as that last paragraph probably was, I think I get it now lol.

[Kyrisch]

Really' date=' I assumed that's what you were implying by putting it in your initial list. I was skeptical but I did not know for sure and therefore did not challenge you, but now I am curious. What is the cause of the steadily increasing IQ of our race?[/quote']

 

Education mostly, possibly some nutrition as well.

 

Isn't IQ Intelligence Quotient, meaning the potential you have of being smart, and not the knowledge you already posses? Therefore education would have no effect on IQs. If the tests that are given favour those with higher educations, they are faulty, are they not?

 

Given that the formation of the appendix is no doubt a result of complex developmental pathways, and that such pathways rarely can be tinkered with without lethal or highly damaging results, it is entirely possible that the genetic combination for 'no appendix' simply hasn't happened.

 

You are wrong. People without appendices have been born in this world, and that is basically upon what I based my argument.

[rakuenso]

If only we had the genetic imprinting abilities of the Gua'old, but then again you wonder how giant their genomes must be.

[atinymonkey]

Isn't IQ Intelligence Quotient, meaning the potential you have of being smart, and not the knowledge you already posses?

If it were only a measure of potential, it would be called Intelligence Potential and not IQ.

Therefore education would have no effect on IQs.

Education is related to IQ. Teaching someone how to think is part of an education.

If the tests that are given favour those with higher educations' date=' they are faulty, are they not?

[/quote']

No. It is a fair assessment of intelligence. Complete ignorance and inability to solve logic puzzles is not a great indicator of intelligence.

You are wrong. People without appendices have been born in this world, and that is basically upon what I based my argument.

It's still a pretty crap argument, isn't it? Honestly? Crap? Isn't It?

[LucidDreamer]

Isn't IQ Intelligence Quotient' date=' meaning the potential you have of being smart, and not the knowledge you already posses? Therefore education would have no effect on IQs. If the tests that are given favour those with higher educations, they are faulty, are they not?

[/quote']

I don't want to get too off topic so if someone wants to disagree maybe we should start a new thread. IQ tests are dependent on education, but education is not the sole determinant. Education will improve IQs, especially in children. In fact, if you wanted to you could practice taking lots of IQ tests and improve your IQ. However, if two people practice taking IQ tests the smarter one will improve faster and have a higher maximum cap on their performance. Just like the ability to run fast is partly genetic, but you can improve your performance by practicing.

 

Damn you monkey! You beat me to it.

[PhDP]

What is the cause of the steadily increasing IQ of our race?

 

It's called the "Flynn" effect. We don't know exactly why it's happening, it's a fast increase in the average IQ of a population. But it's certainly not natural selection. Generally, people with high IQ have few children and they often have them late, while people with high IQ have many children. It lead some eugenicist to the catastrophic conclusion that IQ would decrease because "high IQ" wasn't as fit as "low IQ". In theory, IQ isn't supposed to be influenced by education. However, nutrition and stimulation can affect the IQ. It's generally accepted that about 50% of the IQ results are explained by genes, the other half is explained by a combination of environment and genetics. Many think the increase is du to a more complex/stimulating environment and better healthcare (technology). A very recent research show that Heterosis is maybe partially responsible for the rise. Heterosis happen when the 2 parents are from different ethnic background, it was shown their offspring have higher IQ than suspected (heterosis = hybrid vigor).

 

So my point is; we don't really care about sight and appendix, but we do care about thing like intelligence, which are increasing, certainly not because of natural selection, but as a consequence of the environment technology and medicines has created. You seem to think genes have an intrinsic value, they don't. If having no appendix isn't an advantage, if it doesn't improve your fitness, then you aren't degenerate to have an appendix. It's a question of context.

 

However, if two people practice taking IQ tests the smarter one will improve faster and have a higher maximum cap on their performance. Just like the ability to run fast is partly genetic, but you can improve your performance by practicing.

 

I really doubt you could enhanced your IQ as much as you could improve an athletic performance. The brain isn't a muscle. However it's true that you can improve your IQ, and IQ result are not accurate at high level (beyond 2 standard deviance, in most test it mean more than 130 or less than 70).

[LucidDreamer]

Phil, I think part of our disagreement might have to do with definition. When I say education, I am thinking of all forms of mental stimulation from birth to death.

[[Tycho?]]

Isn't IQ Intelligence Quotient' date=' meaning the potential you have of being smart, and not the knowledge you already posses? Therefore education would have no effect on IQs. If the tests that are given favour those with higher educations, they are faulty, are they not?

[/quote']

 

No. One of the most important aspects of schooling is learning how to learn. A person who has gone through school and done well probably has reasoning, math, language and logic skills that someone who did not attend school would be less likely to posses.

 

If Einstein had been born 10 000 years ago, he would not have had as high an IQ, because he never would have learned how to read, write, do math etc. Education plays a huge role in intelligence and IQ.