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#48015 - 02/16/13 02:51 AM 'The Scars of Human Evolution'
Bill Offline
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phys.org:'The Scars of Human Evolution'
A preview of a talk to be given at the AAAS meeting. Basically he says a lot of our physical problems are because of the way evolution translated quadrupeds to bipeds. He particularly will be discussing our back problems, which quadrupeds don't have.

Bill Gill
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#48020 - 02/16/13 05:15 PM Re: 'The Scars of Human Evolution' [Re: Bill]
Bill S. Offline
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Interesting article, Bill.

Presumably, if left to itself, evolution would eventually sort out these problems, but modern medical techniques probably militate against that.
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#48021 - 02/16/13 06:05 PM Re: 'The Scars of Human Evolution' [Re: Bill S.]
Bill Offline
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Originally Posted By: Bill S.
Presumably, if left to itself, evolution would eventually sort out these problems, but modern medical techniques probably militate against that.

Actually no, evolution wouldn't necessarily correct the problems. The way it works is that for any change to be incorporated into a genome it has to produce a positive difference in the ability for individuals to have offspring. If you can have sufficient children despite things that appear to be negatives, such as our backs, then your species can continue without having the problem corrected. After all we all have back problems, but those problem don't shorten our life spans enough to significantly affect the production of children. So there is no great reason that corrected backs would catch on from the point of natural selection.

It has been suggested that modern medicine will produce an end to evolution of the human race. However in my opinion the biggest force stopping continued evolution is the sheer mass of humanity alive. Significant evolutionary changes tend to take place more in isolated small populations. We don't have those any more. That doesn't say that we won't evolve any more. It just means that we probably won't see any significant physical changes.

Bill Gill
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#48032 - 02/19/13 04:53 PM Re: 'The Scars of Human Evolution' [Re: Bill S.]
ImagingGeek Offline
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Originally Posted By: Bill S.
Interesting article, Bill.

Presumably, if left to itself, evolution would eventually sort out these problems, but modern medical techniques probably militate against that.

Two different issues here.

Evolution will not fix my/your/our bad backs. Evolution is a "good enough" mechanism, not an optimization mechanism. Unless having a sore back has a fitness cost (i.e. leads to fewer offspring), there will be no selective pressure to 'fix' the issue. In other words, evolution doesn't care if you hurt; it only cares if you reproduce.

As for medicine preventing evolution, that is simply a mistaken belief based on the general poor understanding of evolution common in society. Evolution is measured as the rate of genetic change in a population. Selection *slows* this process - it is a break on evolution - as it limits the rate of genetic change by selecting for or against certain genotypes. In the western world we've greatly reduced the impact of selection - ergo, we as a species are accumulating mutations faster, and thus are evolving faster than before.

Bryan
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#48037 - 02/20/13 12:17 AM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Orac Offline
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Originally Posted By: ImagingGeek

As for medicine preventing evolution, that is simply a mistaken belief based on the general poor understanding of evolution common in society. Evolution is measured as the rate of genetic change in a population. Selection *slows* this process - it is a break on evolution - as it limits the rate of genetic change by selecting for or against certain genotypes. In the western world we've greatly reduced the impact of selection - ergo, we as a species are accumulating mutations faster, and thus are evolving faster than before.


Not my area but I know the above is an older hypothesis more recent evolutionary studies use a slightly different hypothesis

http://en.wikipedia.org/wiki/Effective_evolutionary_time

Both are unproven but the newer hypothesis has had some success where the older hypothesis fails.

Originally Posted By: http://en.wikipedia.org/wiki/Effective_evolutionary_time

Gillman et al. (2010) extended their earlier study on plants [21] by determining whether the effect is also found within highly conserved DNA. They examined the 18S ribosomal gene in the same 45 pairs of plants. And indeed, the rate of evolution was 51% faster in the tropical than their temperate sister species. Furthermore, the substitution rate in 18S correlated positively with that in the more variable ITS. These result lend further very strong support to the hypothesis.[22] Wright et al. (2010) tested the hypothesis on 188 species of amphibians belonging to 18 families, using mitochondrial RNA genes 12S and 16S, and found substantially faster substitution rates for species living in warmer habitats at both lower latitudes and lower elevations.[23] Thus, the hypothesis has now been confirmed for several genes and for plants and animals.
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#48050 - 02/21/13 01:27 PM Re: 'The Scars of Human Evolution' [Re: Orac]
ImagingGeek Offline
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Originally Posted By: Orac
Originally Posted By: ImagingGeek

As for medicine preventing evolution, that is simply a mistaken belief based on the general poor understanding of evolution common in society. Evolution is measured as the rate of genetic change in a population. Selection *slows* this process - it is a break on evolution - as it limits the rate of genetic change by selecting for or against certain genotypes. In the western world we've greatly reduced the impact of selection - ergo, we as a species are accumulating mutations faster, and thus are evolving faster than before.


Not my area but I know the above is an older hypothesis more recent evolutionary studies use a slightly different hypothesis

http://en.wikipedia.org/wiki/Effective_evolutionary_time

No, the above is exactly what those of us doing work predicated on evolution (i.e. me) use as a definition. Your link refers to a concept that isn't even relevant to the discussion at hand.

But, since you brought it up, the effective evolutionary time hypothesis is fundamentally flawed - it only holds true for a very small subset of species. Most domains of life do not show latitude-based biases in species number distributions. Its only a few exceptions (large plants, some exothermic animals) that do.

Originally Posted By: Orac
Both are unproven but the newer hypothesis has had some success where the older hypothesis fails.

No, the statements I made are proven, and are concepts derived in the new synthesis (circa 1936) that has stood the test of time. Selection limits the rate of acquiring new genetic material, and the maximum rate you acquire new genetic material is determined by your mutation rate.

Bryan
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#48055 - 02/21/13 03:01 PM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Bill Offline
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Originally Posted By: ImagingGeek
Selection limits the rate of acquiring new genetic material, and the maximum rate you acquire new genetic material is determined by your mutation rate.

Bryan, can you discuss that in a little more detail? I don't quite understand what you are saying.

Bill Gill
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#48058 - 02/21/13 07:23 PM Re: 'The Scars of Human Evolution' [Re: Bill]
ImagingGeek Offline
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Registered: 05/19/10
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Bill, no problem.

The speed of evolution is measured by the rate new genetic traits are accumulated. Ignoring single-celled organisms (quite chauvinistic, as they account for the vast majority of life on earth, but lets keep things simple for now), the only route we have to gain new genetic material as a species is mutation. Note that mutation would include "real" mutations (changing the 'letters' of a DNA sequence) as well as other mutagenic processes (duplications, insertions, etc).

Ergo, the fastest we can evolve as a species (i.e. acquire new genetic material) is equal to our mutation rate.

Selection slows this process - by selecting for or against a trait, you reduce the amount of genetic diversity in a species - either by removing an allele (negative selection) or by promoting the spread of an allele at the expense of others.

This gets a little more complex with single-celled organisms, as many of them are able to acquire genes from other species - one of the better examples of this is the spread of antibiotic resistance genes between unrelated species of bacteria. This horizontal gene transfer represents a very fast form of evolution, and is a mechanism that exists outside of conventional mutation. But again, selection limits even this source of new genetic material.

Bryan
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#48059 - 02/21/13 07:33 PM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Bill Offline
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Thanks Bryan, I think I understand what you mean now. That is one more small step towards my better understanding of evolution.

Bill Gill
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#48063 - 02/22/13 12:51 AM Re: 'The Scars of Human Evolution' [Re: Bill]
Orac Offline
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This seems to be your area ImagingGeek so I will ask some questions because your BLACK/WHITE answer for a scientist always gets my attention

I believe you adhere to the strict evolution teaching of the five recognized causes of biological evolution are:

1. mutation
2. migration also known as gene flow
3. random genetic drift (small populations)
4. non-random mating
5. natural selection


So perhaps if you can comment on these

epigenetics:
http://www.time.com/time/magazine/article/0,9171,1952313,00.html
http://www.sciencedaily.com/releases/2012/02/120229091844.htm
http://www.sciencemag.org/content/338/6108/758.full
http://en.wikipedia.org/wiki/Epigenetics


Biased gene conversion:
http://www.annualreviews.org/doi/abs/10.1146/annurev-genom-082908-150001
http://www.sciencedaily.com/releases/2009/01/090126203207.htm
http://www.sciencedaily.com/releases/2012/09/120917151721.htm
http://www.sciencedaily.com/releases/2012/05/120518132832.htm


Edited by Orac (02/22/13 12:54 AM)
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#48065 - 02/22/13 03:27 AM Re: 'The Scars of Human Evolution' [Re: Orac]
ImagingGeek Offline
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Originally Posted By: Orac
This seems to be your area ImagingGeek so I will ask some questions because your BLACK/WHITE answer for a scientist always gets my attention

I believe you adhere to the strict evolution teaching of the five recognized causes of biological evolution are:

1. mutation
2. migration also known as gene flow
3. random genetic drift (small populations)
4. non-random mating
5. natural selection

I'm not sure what you mean by "non-random mating"; that certainty is not an accepted element of evolutionary theory. Indeed, sexual reproduction is the exception to how organisms reproduce (the bulk of life on earth reproduces asexually).

There are more mechanisms than those - horizontal gene flow, genetic recombination, etc, etc, etc. And there are mechanisms which are not yet proven to be involved - but which could be. Kin/group selection, for example. The fundamentals of evolution have not changed much since darwins time, but there are a handful of new mechanisms which have been discovered since then, and a few which have question marks around them.

Originally Posted By: Orac

So perhaps if you can comment on these

epigenetics:

Epigenetics are inheritable changes in gene expression which does not modify the underlying genetic material. Epigenetic changes usually only last a couple of cellular generations. In metazoans [animals] most (perhaps all) epigenetic changes are "reset" in the embryo - i.e. they are not inherited parent->child. Thus they are unlikely to have a significant evolutionary effect, as they are not inherited over generations.

There is a caveat to this - some "simpler" single-celled organisms appear to pass on some epigenetic changes from generation-to-generation. These epigenetic changes remain quite plastic, so their effect on evolution would likely be weak (compared to mutation, which is permanent), but they could, in these rare cases, be inherited and thus have a evolutionary effect.

Originally Posted By: Orac
Biased gene conversion:

Gene conversion is a form of mutation, and would be accounted for in the "mutation" stuff I mentioned earlier. Gene conversion is simply an error in genetic recombination (which occurs during sperm/egg production) which results in either exchange genetic between alleles/gene, or which produces an unbalanced exchange of DNA between two loci. Similar mechanisms also occur in non-sexually reproducing species; for example, sometime bacteria take up DNA for food and accidentally cross-over with it, thus converting a part of their genome to whatever was encoded in the 'food'.

Bryan
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#48070 - 02/22/13 12:17 PM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Orac Offline
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Originally Posted By: ImagingGeek

I'm not sure what you mean by "non-random mating"; that certainty is not an accepted element of evolutionary theory. Indeed, sexual reproduction is the exception to how organisms reproduce (the bulk of life on earth reproduces asexually).


WOW David Attenborough lied to me about all those animals that evolve exagerated traits because they prefer certain traits in mates.

Weirdly it is still listed in wikipedia

http://en.wikipedia.org/wiki/Mate_choice

Quote:

Mate choice, or intersexual selection, is an evolutionary process in which selection of a mate depends on attractiveness of its traits.


Sorry I must have missed the memo when it was overturned by science. I know Darwin included this selection process under natural selection but it generally got shifted out because the evolution it creates is not neccessarily the fitess of survival driven.

Originally Posted By: ImagingGeek

Epigenetic changes usually only last a couple of cellular generations. In metazoans [animals] most (perhaps all) epigenetic changes are "reset" in the embryo - i.e. they are not inherited parent->child.


WOW again can you cite evidence for those statements.

See again here is wikipedia

http://en.wikipedia.org/wiki/Transgenerational_epigenetics

Quote:

Inherited epigenetic effects on phenotypes have been documented in bacteria, protists, fungi, plants, and animals.



Originally Posted By: ImagingGeek

Gene conversion is a form of mutation, and would be accounted for in the "mutation" stuff I mentioned earlier.


You view Biased gene conversion as a form of gene mutation???????

For me mutation is generally defined as a failure to store genetic information faithfully while genetic recombination is exactly that.

I certainly don't equate those two things but I guess it is not my area so it must be me.


Edited by Orac (02/22/13 12:33 PM)
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#48071 - 02/22/13 03:04 PM Re: 'The Scars of Human Evolution' [Re: Orac]
ImagingGeek Offline
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Registered: 05/19/10
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Originally Posted By: Orac
WOW David Attenborough lied to me about all those animals that evolve exagerated traits because they prefer certain traits in mates.

No one lied to you; you used an incorrect term to describe part of sexual selection. That would fall under the umbrella of selection in general - i.e. one of the founding principals originally described by Darwin.


Originally Posted By: Orac
Sorry I must have missed the memo when it was overturned by science. I know Darwin included this selection process under natural selection but it generally got shifted out because the evolution it creates is not neccessarily the fitess of survival driven.

Actually, Darwin never considered it part of natural selection - indeed, he wrote a whole book on the topic.

Originally Posted By: Orac
Originally Posted By: ImagingGeek

Epigenetic changes usually only last a couple of cellular generations. In metazoans [animals] most (perhaps all) epigenetic changes are "reset" in the embryo - i.e. they are not inherited parent->child.


WOW again can you cite evidence for those statements.

See again here is wikipedia

http://en.wikipedia.org/wiki/Transgenerational_epigenetics

You may want to read your own source, it says exactly the same as I just did - In sexually reproducing organisms, much of the epigenetic modification within cells is reset during meiosis

If you continue to read your own source you'll see it says exactly what I did - that in simpler organisms we do see inheritance of inter-generational epigenetic inheritance, but it is rare in "higher" organisms, and that such inheritance is often temporary, and is lost over multiple generations.



Originally Posted By: Orac
Originally Posted By: ImagingGeek

Gene conversion is a form of mutation, and would be accounted for in the "mutation" stuff I mentioned earlier.


You view Biased gene conversion as a form of gene mutation???????

Because it is; or at least, its how it is treated by biologists. A few examples:
http://www.ncbi.nlm.nih.gov/pubmed/12454074
http://mcb.asm.org/content/13/7/4374
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC555444/
http://genome.cshlp.org/content/22/3/429.full

As an example, a quote from the abstract of the last article: However, pathological mutations can also be introduced by nonreciprocal recombination events between paralogous sequences, a phenomenon known as interlocus gene conversion (IGC).

Originally Posted By: Orac
For me mutation is generally defined as a failure to store genetic information faithfully while genetic recombination is exactly that.

Your personal definition is irrelevant. Scientific terms have set & concrete definitions so that when we (scientists) discuss things there is no ambiguity. As I demonstrated above, gene conversion* is treated by biologists as a form of mutation.

And, I would point out, that gene conversion fullfills your incorrect definition of mutation as well - you loose the "faithfulness" of the genetic information.

*we have to be careful with this term, as another form of gene conversion - antigen switching via gene conversion - is arguably not a mutation and rather an evolved mechanism of gene regulation. Hence, the gene conversion you are talking about should be called "interstrand gene conversion" (if tlaking about conversion between two alleles) or "interlocus gene conversion" (if talking about conversion between separate genes) to separate it from the other forms of gene conversion.

Bryan
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#48075 - 02/22/13 06:21 PM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Orac Offline
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Originally Posted By: ImagingGeek

No one lied to you; you used an incorrect term to describe part of sexual selection.


I see so non random mating does not equal sexual selection ... to select something is by definition NON RANDOM smile


Originally Posted By: ImagingGeek

If you continue to read your own source you'll see it says exactly what I did - that in simpler organisms we do see inheritance of inter-generational epigenetic inheritance, but it is rare in "higher" organisms, and that such inheritance is often temporary, and is lost over multiple generations.


No it doesn't and infact the latest publications in nature and other science journals highlights the controvesy.

http://www.nature.com/news/epigenetics-posited-as-important-for-evolutionary-success-1.12179
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3434969/

On the status quo that epigenetic changes eventually fade out there are also a number of reasonable papers

http://www.sciencedaily.com/releases/2011/09/110920132628.htm
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710163/

HOWEVER the controversy is still raging and is far from settled.

This month Nature they have 5 leading researchers and none of them can agree

http://www.nature.com/nrg/journal/v14/n3/full/nrg3435.html

Quote:

Their responses highlight the mixture of excitement and caution that surrounds transgenerational epigenetic inheritance and the wide gulf between species in terms of our knowledge of the mechanisms that may be involved.


To you it may be settled but to the rest of science this is far from settled.



Originally Posted By: ImagingGeek

Your personal definition is irrelevant. Scientific terms have set & concrete definitions so that when we (scientists) discuss things there is no ambiguity.


That is a load of rubbish any term in science has ambiguity because you are trying to break a very complex concept and bring it down to a word. Pick any scientific word and I will give you ambiguity on it, your example above just shows that feature in science.

I still think you are dancing around the big difference between the two that actual true mutation you can get a something that was never present in any form prior to the event. Recombination is exactly that a simple mixing of existing items.


Edited by Orac (02/22/13 06:22 PM)
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#48077 - 02/22/13 08:27 PM Re: 'The Scars of Human Evolution' [Re: Orac]
Bill Offline
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Originally Posted By: Orac
I still think you are dancing around the big difference between the two that actual true mutation you can get a something that was never present in any form prior to the event. Recombination is exactly that a simple mixing of existing items.

I of course am not an expert but I'm not sure that what you say there is completely true. A simple mixing of existing items could produce something that is unique, which would be classified as a mutation.

Bill Gill
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#48081 - 02/23/13 01:24 AM Re: 'The Scars of Human Evolution' [Re: Bill]
Orac Offline
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Originally Posted By: Bill

I of course am not an expert but I'm not sure that what you say there is completely true. A simple mixing of existing items could produce something that is unique, which would be classified as a mutation.


To me the issue is in mixing you will be able to backtrack the genetic sequences for a transcription mutation that will not be possible because you suddenly have a sequence that has no history ... perhaps I am wrong this is not my area either.

I just did a quick bit of studying and it appears they break mutation into 4 classes

Originally Posted By: Human Genome Variation Society (standard human sequence variant nomenclature)

Four classes of mutations are

(1) spontaneous mutations (molecular decay)
(2) mutations due to error prone replication by-pass of naturally occurring DNA damage (also called error prone translesion synthesis)
(3) errors introduced during DNA repair, and
(4) induced mutations caused by mutagens.

.... The nomenclature then goes on to specifies the type of mutation and base or amino acid changes and how to write them .....


So I am happy to conceed that I am wrong on that point.

As an aside when I was reading up on how science determines what constitutes a mutation I ran across the public reaming of the ENCODE paper. Quite funny they suffered my problem only they are supposed to know better ... worth a quick read smile

http://scienceblogs.com/pharyngula/2013/02/22/encode-gets-a-public-reaming/

I guess I would have been reamed for not including enough laugh


Edited by Orac (02/23/13 02:42 AM)
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#48106 - 02/25/13 04:26 PM Re: 'The Scars of Human Evolution' [Re: Orac]
ImagingGeek Offline
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Registered: 05/19/10
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Originally Posted By: Orac
Originally Posted By: ImagingGeek

If you continue to read your own source you'll see it says exactly what I did - that in simpler organisms we do see inheritance of inter-generational epigenetic inheritance, but it is rare in "higher" organisms, and that such inheritance is often temporary, and is lost over multiple generations.


No it doesn't

Actually it did - I even gave you the relevant quotes.

Originally Posted By: Orac
and infact the latest publications in nature and other science journals highlights the controvesy.

http://www.nature.com/news/epigenetics-posited-as-important-for-evolutionary-success-1.12179
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3434969/

Your first paper doesn't say what you think it does - its arguing that epigenetic changes may alter gene expression to allow invasive species to thrive in a different environment; i.e. epigenetics as a evolutionary strategy. It does not support the reverse - i.e. epigenetics as a mechanism of evolution.

Your second paper is about the effects of environmental contamination, and presents a hypothesis that is not widely held in the field. I'd also point out that their support for epigenetics in evolutionary responses consisted of one reference - to another hypothesis paper.

Originally Posted By: Orac
On the status quo that epigenetic changes eventually fade out there are also a number of reasonable papers

http://www.sciencedaily.com/releases/2011/09/110920132628.htm
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710163/

The science daily article repeated what I said verbatim - epigenetic change is rarely inherited over multiple generations and thus has a minimal evolutionary effect. The second article deals with a long-term issue of heritability (i.e. we often see a degree of inheritance of traits beyond what would be accounted for by identified genetics). All the paper does is provide a mathematical framework in which a role for epigenetics could be detected in "missing" heritability.

If you follow up on the papers citing your last paper, you'll find this study, which took the math from your paper and applied it to real-world data:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268279/

They found that unknown genetic interactions (i.e. gene regulation, protein interactions) account for the missing heritability, not epigenetic phenomena.

Originally Posted By: Orac
HOWEVER the controversy is still raging and is far from settled.

Funny, I've worked in the biomedical field for over 2 decades and never noticed the raging controversy - because there isn't one. The role of epigenetics in evolution is pretty well established; minimal effect on "higher" organisms, some effect on "lower" (I hate those terms, but I digress). While the exact degree to which epigenetic impacts the evolution of those organisms remains to be clarified, the net trend is extremely unlikely to change.


Originally Posted By: Orac
This month Nature they have 5 leading researchers and none of them can agree

http://www.nature.com/nrg/journal/v14/n3/full/nrg3435.html

The degree of conflict there is minimal; if you look closely you'll see the major difference in 'opinion' is time frame and species under consideration. Those looking at "higher" species were more muted, those looking at "lower" were more exuberant. Those considering long-term evolution were the most exuberant - which makes sense given that a) over long periods of time, rare events become "common", and b) in our deep history, we were all "lower" organisms and therefore likely more influenced by epigenetic changes.

To put the "controversy" into context, its equivalent to car-fans arguing over whether a 4-barreled carborator or multi-chanel fuel injector produces a faster car - no one is arguing over whether they work, how they work, that they work, or their imprtance in making a car go (i.e. a "real" controversy). All they are arguing over is which one makes it go faster.

Originally Posted By: Orac

To you it may be settled but to the rest of science this is far from settled.

Again, nothing in your links was contrary to what I wrote. I never said it never happened in "higher" orgnaisms - only that it was rare. And indeed, that is exactly what your articles stated. I also said it was more common in "lower" organisms - too which your papers also agreed. And lastly, I said its overall role was likely minor due to its transitory nature - to which all but your last article agreed with. And 4 of the 5 interviewees agreed in your last article - the one "hold-out" was discussion transposons in deep-time; to which he was very likely correct.


Originally Posted By: Orac
That is a load of rubbish any term in science has ambiguity because you are trying to break a very complex concept and bring it down to a word. Pick any scientific word and I will give you ambiguity on it, your example above just shows that feature in science.

No, there is no ambiguity. Epigenetics has a strict definition, as does evolution, selection, mutation, etc. as I stated, we need strict definitions to avoid confusion.

And just to highlight how well this works, consider your last article. They used "transgenerational epigenetic", rather than "epgenetics" for a reason - epigenetics covers a broad swath of processes, most of which are not inherited and thus have no evolutionary impact. They used a term which quite specifically relates to one very distinct form of epigenetics - the rare ones which may be inherited.

Our discussion of mutation is the same - mutation simply is defined as a "change in the nucleotide sequence of a genome". That is it - so any process which modifies the sequence is, by definition, a mutation. Meaning that gene conversion is a mutational mechanism.

If we want to be more specific, we use different terminology. "Gene covnersion" being one such term; other examples would be single-nucleotide polymorphisms, synonymous mutations, insertions, deletions, inversion, tri-nucleotide expansions, recombination, etc. All are mutations - they change the nucleotide sequence - but all are very different processes with very different mechanism.

Originally Posted By: Orac
I still think you are dancing around the big difference between the two that actual true mutation you can get a something that was never present in any form prior to the event. Recombination is exactly that a simple mixing of existing items.

Recombination is very much capable of creating new things. Indeed, it is far better at it than simple point-mutations. Recombination can copy genes, whciha re then free to undergo additional change without a fitness cost. Even solo - recombination is powerful - most new genes arise through recombination events - gene fusion and exon swapping can both occur during recombination, and both spontaneously create new genes with a previously non-existing sequence, structure and (potentially) function.

Moreover, you are assigning a purpose where none exists. Mutation doesn't have a purpose - it doesn't exist to create new variability or new genetic information. To the contrary, mutational mechanisms simply exist. What occurs downstream - be they adaptive or harmful, neutral or non-neutral, information-creating or information-destroying (or information-neutral), is a consequence of the mutation; rather than the function of it. A synonymous mutations, which has no effect on protein sequence, is still a mutation - despite have no biological impact what-so-ever.

I think you're over-anthropomorphising biology.

Bryan


Edited by ImagingGeek (02/25/13 04:30 PM)
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#48108 - 02/25/13 05:59 PM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Bill Offline
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Originally Posted By: ImagingGeek
Funny, I've worked in the biomedical field for over 2 decades and never noticed the raging controversy - because there isn't one. The role of epigenetics in evolution is pretty well established; minimal effect on "higher" organisms, some effect on "lower" (I hate those terms, but I digress).

That is a problem for me too. I keep using words and phrases like that, then thinking what in the world does that mean? In evolutionary terms "lower" and "higher" are really difficult to defend.

Bill Gill
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#48110 - 02/25/13 09:55 PM Re: 'The Scars of Human Evolution' [Re: Bill]
ImagingGeek Offline
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Originally Posted By: Bill
That is a problem for me too. I keep using words and phrases like that, then thinking what in the world does that mean? In evolutionary terms "lower" and "higher" are really difficult to defend.


And they're incorrect - any existent organism, no matter how many cells/genes it has, has successfully passed through the gauntlet for ~4 billion years. All are successful - it is with quite a bit of hubris that we call ourselves "higher" than bacteria and other single celled organisms.

Bryan
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#48114 - 02/26/13 01:04 AM Re: 'The Scars of Human Evolution' [Re: ImagingGeek]
Orac Offline
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I have several problems with that and sort of agee with you in part but to me you see the world far to black and white.

My problems is probably the same as most people no organism we see around us today has survived the 4.5 billion years their genetic sequences arguably has but not them unchanged. The oldest organism I know of unchanged is a stromatolite but I guess there may be some simple cell stuff that really does go across the 4.5 Billion years and so really has been successful as you define it. Certain genetic sequences and approaches may be successful if we are defining existing for 4.5 Billion years but you can't really extend that to the organism.

Secondly you equate bacteria and more complex multi-cellular organism as the same based on one criteria that we are here today so we are all successful. In itself nothing wrong with that from a survival point of view but it overlooks the battle the more complex organisms underwent to be here. The more complex an organism the more thing there are to be attacked so the more advanced must be the mechanisms to protect it. It is therefore natural to view complex organism as more advanced because they face tougher risk/reward equations.

I guess the way to pose the question back to you both is why do complex organisms exist at all, what is the payoff for being a complex organism and why did it come about?


Edited by Orac (02/26/13 01:04 AM)
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