Was There a Need for an Extended Evolutionary Synthesis?

[jimmydasaint]

The Modern Synthesis can be thought of as a pulling together of various strands of Biology (hence the 'synthesis' bit) around the Darwinian evolutionary concept of overpopulation --> selection of favourable characteristic--->reproduction (Natural Selection). Population genetics had confirmed that Mendelian genetics showing how genes combined to produce a phenotype was thoroughly consistent with Darwinian theories. Saltationism (from Latin saltus- to leap) which suggested quick drastic genetic changes from one generation to the next, leading to speication was rejected. Paleontology suggested that rate of change in the features or phenotype were not at a constant rate but consistent with the fossil record. Everything was rosy and a central dogma had been suggested for biological evolution.

 

However, remember the date -1942. All I want to do is open up a discussion for why Extended Evolutionary Synthesis is required and to ask if it really adds anything substantial to the Modern Synthesis?

 

http://life.bio.sunysb.edu/ee/pigliuccilab/Papers_files/2007-Evolution-EES.pdf

[foodchain]

The Modern Synthesis can be thought of as a pulling together of various strands of Biology (hence the 'synthesis' bit) around the Darwinian evolutionary concept of overpopulation --> selection of favourable characteristic--->reproduction (Natural Selection). Population genetics had confirmed that Mendelian genetics showing how genes combined to produce a phenotype was thoroughly consistent with Darwinian theories. Saltationism (from Latin saltus- to leap) which suggested quick drastic genetic changes from one generation to the next, leading to speication was rejected. Paleontology suggested that rate of change in the features or phenotype were not at a constant rate but consistent with the fossil record. Everything was rosy and a central dogma had been suggested for biological evolution.

 

However, remember the date -1942. All I want to do is open up a discussion for why Extended Evolutionary Synthesis is required and to ask if it really adds anything substantial to the Modern Synthesis?

 

Well going from an empirical standard I would only think such would have any validity if it could say be understood in such a way.

 

With evo-devo such is a good example I think. Its relatively new, it also is not in perfect accordance with modern theory. Such as with the histone code which I think is very interesting. I don’t know if this requires a new title.

 

The central dogma is really simple. The more complicated thing to it I think was the entire discovery process, its that which has really held the impact with say molecular biology. Darwin was just a genius really, I don’t know about every detail of the guys life but I do know that he also had an impact on geology for instance. I also think the in crowd of the time arranged for him to be buried in the same graveyard as Newton.

 

"A unit of selection is a biological entity within the hierarchy of biological organisation (e.g. genes, cells, individuals, groups, species) that is subject to natural selection. For several decades there has been intense debate among evolutionary biologists about the extent to which evolution has been shaped by selective pressures acting at these different levels. This debate has been as much about what it means to be a unit of selection as it has about the relative importance of the units themselves, i.e., is it group or individual selection that has driven the evolution of altruism? When it is noted that altruism reduces the fitness of individuals, it is difficult to see how altruism has evolved within the context of Darwinian selection acting on individuals; see Kin selection."

 

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

[CharonY]

I think there was similar thread somewhere already, but anyway.

 

I would like to discuss it in some more depth when I got more time (maybe around next wee or so). But I would like to state that it is clear that the modern synthesis clearly needs an update. This has been apparent at least the last decade or so.

The modern synthesis has never been as concise as, say, the darwinistic theory, simply due to the problem of summarizing all the available, very different type of data into one single theoretical work. As such the modern synthesis grew over time, without a real complete update. In my opinion the real need for a new theory is not the fact that new data is available, as these can be integrated rather easily, but rather because some of basic assumptions of the modern synthesis are now generally regarded as wrong.

These include:

-that genomes are well ordered libraries of genes (partially true for prokaryotes, not that much for most eukaryotes)

 

- genes have usually have single functions honed by natural selection

 

-Species are finely adjusted to their ecological circumstances due to efficient adaptive adjustment of biochemical functions. (well due to the fact that species concepts are arbitrary, especially within the realm of prokaryotes this does not make any sense anymore)

 

-The durable units of evolution are species, and within

them the organisms, organs, cells, and molecules, which

are characteristic of the species. (see above)

 

-Given the adaptive nature of each organism and cell, their machinery can be modeled using principles of efficient design. (newer modeling approaches showed that this usually does not work for eukaryotes. Though sometimes it has limited uses in prokaryotes).

 

In any case there has been a rather large discussion to what has to be added into a new synthesis and how it should be called. EES is by no means the only call for an update, though we could use the given paper as a basis and compare it to other similar papers.

 

I do recall that someone here (sorry, forgot who) actually had a nice idea of starting to call it alpha, beta... synthesis.

[Mr Skeptic]

I do recall that someone here (sorry, forgot who) actually had a nice idea of starting to call it alpha, beta... synthesis.

 

That would be me. Everytime something is named Modern Soandso, after a period it becomes obsolete and the name becomes silly and confusing. So I figure, we know the name will become silly, so why not start silly and at least prevent if from being confusing.

[CharonY]

Actually I do like the idea. Main problem is that the guy formulating it of course thinks that his/her theory would be the end of all others

[PhDP]

Shouldn't this tread be in the 'Evolution' section ?

 

Anyway... I think we already had a couple of new syntheses within the field of evolutionary biology; in the 60s-70s, we had the molecular revolution (a true revolution, IMO), right now we're beginning the era of population genomics. Evolutionary quantitative genetics, thanks to people like Russell Lande, finally gets the attention it deserves... and yes, evolutionary developmental biology (evo devo) is an important new field.

 

In fact, it's a field I'm very interested in, especially the relationship between theoretical population genetics and evo devo. But I don't think it's the biggest thing since the modern synthesis, and I'm not even sure it will be the most important subfield in the coming years.

[pioneer]

One modern observation, with continuous, instead of discontinuous data, that is not consistent with darwinism is how the average human height has increased. This is happening across the board and has little to do with the selective advantage of particular animals. It is attribute to diet change with this environmental change causing the entire species to change.

[PhDP]

One modern observation, with continuous, instead of discontinuous data, that is not consistent with darwinism is how the average human height has increased. This is happening across the board and has little to do with the selective advantage of particular animals. It is attribute to diet change with this environmental change causing the entire species to change.

 

Of course it's consistent, the theory of evolution (which is not, BTW, called 'Darwinism') doesn't say that every change is caused by the modification of the genetic structure of a population.

 

Because the phenotype often depends on both the genotype and the environment (a very basic principle of genetics, which is especially well integrated into quantitative genetics), then of course you can see change in the phenotype without any evolution going on.

[CharonY]

I have moved this thread to the evolution area. To PhDP, there have been added syntheses since the forties, however some of the basic tenets simply have to be revised, which I think is at least one of the reasons to call for a new nomenclature

[PhDP]

CharonY,

 

I'm not against the idea of an extended synthesis, but I'm against the view that evo-devo is so big that it should be considered the starting point of THE extended synthesis, IMO we already had a couple of important revisions.

 

Personally, one of my biggest concern is to rehabilitate natural selection in molecular evolutionary biology, which implies a much better integration of genetics in population genetics, and a less naive of view of natural selection (we really have to get rid of that notion that natural selection is everywhere and explains everything from the color of the eyes to all tiny details at the molecular level). And, to me at least, this basic understanding of how the different mechanisms interact to drive evolution; that's the core of theory of evolution.

[CharonY]

I'm not against the idea of an extended synthesis, but I'm against the view that evo-devo is so big that it should be considered the starting point of THE extended synthesis, IMO we already had a couple of important revisions.

No argument from me here. I tried to make clear that the call for a revision (however it is called) is not from a single source (like evo-devo) but from a variety of disciplines. Moreover it is less the need to integrate new findings, but to discard some obsolete one, which is more important in my opinion.

 

Of course due to the fragmentation of biology proposals will always have a big influence from the discipline of the respective proponent.

 

Personally, one of my biggest concern is to rehabilitate natural selection in molecular evolutionary biology, which implies a much better integration of genetics in population genetics, and a less naive of view of natural selection (we really have to get rid of that notion that natural selection is everywhere and explains everything from the color of the eyes to all tiny details at the molecular level). And, to me at least, this basic understanding of how the different mechanisms interact to drive evolution; that's the core of theory of evolution.

 

Just to get it correct, you mean you fear that there is a "selection-centric" view on evolution? Again, no argument from me here. Integration of molecular data is often rather complicated to translate into population genetics as some features were driven towards persistence within an organisms without actually benefiting the organism as whole, but yes I do agree to this point, too.

[pioneer]

I would say yes, because it is just an empirical correlation and more fudge factors are always welcome. I did this example elsewhere. I was wondering how its fits in with the master plan. Over the past 100 years, to use a number, the average height of Americans has increased. This had nothing to do with tall people dominating breeding, as far as I know. It occurred cross the board due to better food. Or the environment pushed all the genes sort of globally. All my siblings are taller than either of my parents. Maybe the basketball team was in town for each of my siblings according to Darwin.

 

The affect is the environment changed, due to better food, shifting the entire population at the same time, more of less. Here is an interesting special affect. If this was an animal population doing the same thing, but our data was discontinuous, with only two samples, with a hundred year separation, would be conclude that a tall critter had selective advantage. It could reach higher food. This caused it to breed more, and through selective advantage, the genes shifted the population to taller. In this case the basketball team did come to town, when we have discontinuous data.

 

With discontinuous data, it looks like jumps or mutations. It looks like key players, etc. With continuous data is looks like the environment is pushing the genetics across the board. Maybe we need more data before adding too many more fudge factors. We need to investigate how genetics can be pushed across the board by a global environmental potential. The current theory is a little thin here. If we thicken this up maybe we overhaul rather than add more patches.

[PhDP]

CharonY,

 

Yea, of course, the current view outside the field of evolutionary genetics is ridiculously biased toward selectionist hypotheses. Despite the fact that scientists (i.e; Derek A. Roff, H. Allen Orr, Michael Lynch, Arlin Stoltzfus, ...) have built models to detect phenotypic evolution when selection is absent.

 

But I also think that molecular population genetics is too often dominated by obsolete neutral models. Matthew Hahn (Indiana U.) recently wrote in Evolution;

 

Some of the reluctance to move away from neutral models is

also likely to be a continued reaction to rampant pan-selectionism

and adaptationist storytelling (cf. Gould and Lewontin 1979).

 

And I agree 100% with him.

 

pionner,

 

Again, my answer is; quantitative genetics. It has methods to evaluate the proportion of variations caused by heredity, and the proportion caused by the environment (see; heritability). So it is possible to see if an increase in the average height is caused by evolution (natural selection, drift,, ...) or by the environment.

 

It might be difficult to do so in the fossil record, but in this case we have molecular genetics, which is a powerful tool to detect natural selection events in the past.