Evolution: time for some change?

What is evolution?

the standard answer we seem to be getting over the forum seems to be the change in gene frequency in a population over time.

This is a very unsatisfactory basis for the concept of evolution, mainly because it is just the dogma of restricted biological discipline: population biology.

If we look back in history then we see that at some point developmental biologists and population biologists started to disagree on the question if evolution could be satisfactory explained. The developmental biologist saw that there was currently something missing. The population biologist did amazing work with Drosophila and such and saw no problem.

But the time seems right that there should be a union of both disciplines in this respect. From a developmental viewpoint the dogma of change in gene frequency is pointless. They are not interested in studying the change as such. They study how an individual is made, which is only partly based on genetics. In developmental biology it is the 'arrival' of the fittest that counts, not the 'survival'. An individual is not the content of its genome, rather it is a life cycle, which is governed partly by the genome. At all stages during its life the individual must be able to survive. From a single cell, to a blastula, a gastrula, an intermediate larval stage to the adult, to the aging adult, all are different stages with different requirements. None is more important than the other. All need to be survived.


any thoughts on this matter, or are we all happy with the current viewpoints?

 

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Can you explain why "change in gene frequency in a population over time." is not a satisfactory definition of evolution… not that I disagree with your argument but I don’t think you have explained what is wrong here in detail.

 

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spurious

Whoa! Excellent topic, which will generate a lot of heat. This touches on a large difference of opinion between strict Neo-Darwinists, like Mayr, and inconoclasts like Gould. The definition, which I agree may be out-dated in this new age of evo-devo, is predicated upon the presumption that evolution proceeds gradually and that small differences in gene frequencies between populations of species add up over time to eventual speciation and further differentiation.

Gould, in his book Ontogeny and Phylogeny, as well as papers published with Eldridge (punctuated equilibrium), reject this gradualistic view of evolution and speciation.

The 2 views of evolution and speciation are not mutually exclusive, therefore, I agree the current definition is not sufficient. However, even new 'arrivals,' in addition to 'survivals' can be measured using measurements of gene frequency (I apologise for the awkward wording).

Do you have alternatives in mind for definitions?

 

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Random genetic drift leaning towards creatures that survive and breed better in the situation they are in. After all, dead creatures can't breed.

 

One argument:


genetic changes do not always mean phenotypocal changes.


This is a developmental phenomenon. The nature of developmental processes is that they are to a high degree 'buffered'. There can be an accumulation of many mutations without any phenotypical (which means visible in the organism) change. But after some time of accumulation or under different conditions there can be selection for these genetic changes.

 

Would it be more true to say that genetic changes very, very rarely mean phenotypical changes?

It may sound daft, but one question I can't figure out is why anything cares about surviving. There doesn't seem to be a appropriate mechanism. I've never seen this problem addressed except by Stuart Kaufman in relation to organised complex systems, when he wonders what it is that explains why dynamic systems are dynamic in the first place. Is there an answer?

I hope that isn't a silly question. You guys seem to know what you're talking about.

 

Of course some stages are more important than others. When an organism reaches sexual development and passes on its genes, it doesn't need to be around any more. Once it can no longer do this, it has no function within the population and has no impact on evolution of the species. Organisms that cannot reproduce are not needed by the population.

 

reply

one needs to be careful not to invoke group selection. post reproductive characteristics are blind to natural selection (old age and diseases associated with it) however this is not because they aren't needed by the 'population.'

illustration of what i mean, say there's a deleterious gene that only expresses itself in old age (post reproductive age), natural selection can never weed it out because it doesn't affect offspring till post reproductive stage, i.e. the fitness of those with the gene is equal to the fitness of those without it. it's maintained in the population indefinately.

 

very true, and a good point.

can't say I understand your question unless it's about the obvious fitness advantage of passing genes on to the next generation.

 

Re: reply

I don't disagree. But you can't say that post-reproductive organsims are as important to the population as those that can reproduce. Your example didn't really address this. I can't think of an example where a non- or post-reproductive organism is as important to the evolution of the population as one that can pass on its genes.

 

Yeah, it's a very naive question in a way. I'm asking why entities use their fitness advantage, why they bother. It's not meant as a trick question, it's something I can't figure out. Evolutionary theory seems to take it for granted that things compete for survival but there must be a reason.

Even in the best computer models of evolutionary competition the software entities have to be programmed to compete, their competitive 'instinct' doesn't evolve in any way. I'm wondering what drives that competition in real life.

 

Why would they need to be programmed to compete? A creature swimming around in a pool sees a bit of food or a potential mate and it goes right up to get it without thinking about anything else. When you have too creatures going after one piece of food you have instant competition. One who happens to be faster will be more likely get the food or the mate so it will have more children and now you have instant evolution.

 

would phenotypic plasticity be relevant to this topic?
for instance..

Dr. Stan Boutin, from the Department of Biological Sciences at the University of Alberta in Edmonton, has been studying a North American red squirrel population in Canada's southwest Yukon for almost 15 years. The squirrels, faced with increasing spring temperatures and food supply, have advanced the timing of breeding by 18 days over the last 10 years—six days for each generation. His findings appear on First Cite and will appear in the journal Proceedings of the Royal Society London B next month.

if that aint evolution what is?

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oh
i forgot to mention..lamarck rules!

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Yes but why do they bother? In software models of competition the virtual entities have to be told to compete. They don't do it naturally.

 

very true. However, would you agree that there is even less systematic (ie repeatable through generations and multiple offspring in the same generation) phenotypocal change without an associated genetic change?

I think that the reason for the drive to survive is clear enough: those who don't have a strong desire to survive won't fight as hard to do so, and will therefore be less likely to survive. therefore, will be less likely to pass on their genes.

 

I'll suggest that the squirells are genetically evolved to breed when the conditions are right (as are all living things). The breeding date have been moving up not for evolutionary or phenotypic plastical reasons, but because theur environment is changing. They are sticking to their plan- "screw when there's enough food int he fridge, and the lawn is warm" it's those two "when's" that are driving the change. lengthen the winter, and reduce the food supply, and the breeding season will shift back to its original time frame.

 

you answered your own question.

Even the most intricate software models cannot begin to simulate the 'real world' with 100% accuracy.

The entities in the virtual world has no 'limbic system' , these virtual entities have no 'urges' to procreate and to survive.

They will exhibit none of these attributes until we program them to do so.

 

So computer models are false. There's something else at work. Or is it just an infinite regression of genetic programming?

 

Computer models have to be told everything, they don't do anything naturally.

Competition is a behaviour we can observe. It is genetically selected for from the moment that ONE organism happens to have a competetive behaviour. Those that do not have it will loose and disappear. The competitive trait is bound to appear anywhere several creatures are sharing a limited ressource.

This also fits observations: The dodo, alone without competition on an isolated island with plenty of food ressources, was unable to cope when "competition" arrived, in this case in the shape of attrition from hunting. Had humans not killed off the dodos, they might have died out due to animal species introduced in their environment by humans (rats, cats, crows, parasites).

Hans