# How does evolution actually happen

Discussion in 'Biology & Genetics' started by Dudeyhed, Mar 2, 2003.

1. ### paulsamuelRegistered Senior Member

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no, Gould's not denying that evolution happens. What Gould is saying.

macroevolutionary changes (in which he includes specieation) cannot be explained by microevolutionary processes (random mutation and gradual change through selection). this is the crux of the controversy.

he's saying specifically,

natural selection resulting in evolution does not occur only at the organismal level (he propounds species and cladal selection)

not all variation is produced randomly, so, in some instances, evolution is directed.

adaptive and non-adaptive changes are not solely responsible for evolution (i.e. non-selective processes).

The Darwinian foundation is there, but the framework has changed (or been replaced) so that it's hardly recognizable as Darwinian any longer.

These are not just mathematical changes, these are revisions that could be considered major (certainly Dawkins, Maynard Smith et al. consider them major since they are so adamant and vociferous in their opposition to them)

3. ### ElectricFetusSanity going, going, goneValued Senior Member

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Are you proposing intelligent design or control here?

5. ### paulsamuelRegistered Senior Member

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i'm not proposing anything, just passing on what Gould is proposing (I think). i believe the point he's trying to make is that there are regulatory, structural and developmental constraints. As I said, I'm on the first chapter and I'll know more of his thesis when I read more.

7. ### PersolI am the great and mighty Zo.Registered Senior Member

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Originally posted by paulsamuel
Gould's not denying that evolution happens. What Gould is saying.... macroevolutionary changes... cannot be explained by microevolutionary processes... this is the crux of the controversy.
I've read articles that have said something is 'missing' in evolutionary theory, but all these articles were seemed to also be 'missing' something. This book sounds like a good read, but is it too complicated for a non-biologist?

These are not just mathematical changes, these are revisions that could be considered major (certainly Dawkins, Maynard Smith et al. consider them major since they are so adamant and vociferous in their opposition to them)

I wish I had time to become well versed on both sides

Do they have fair objections to Gould's theory, or do they just not like it?

8. ### paulsamuelRegistered Senior Member

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Gould's book is excellent! It will require some effort to read for the non-expert. if you do decide to take it on, have plenty of reference material handy, use the bibliography to support your knowledge. i promise it will be a very rewarding experience.

some of the controversy has been reduced to name-calling. Gould calls the post-synthesis Darwinists 'Ultra-darwinists,' meaning that they disallow any tampering with the basic Darwinian principles. They call Gould's theory of punctuated equilibrium (his theory of spurts and jumps to explain macroevolutionary changes) "evolution by jerks." Gould calls their gradual microevolutionary explanation of macroevolutionary changes "evolution by creeps."

the main objection to Gould's premises are their speculative nature, and Gould admits that his theories are thin on data.

9. ### PersolI am the great and mighty Zo.Registered Senior Member

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I'm debating on getting the book. As always I have too many things I want to know and not enough time to learn them.

I thought that fossil records demonstrated evolutionary spurts... Do the Dawkins/Smith's camp have a theory to explain these spurts that they think is better?

10. ### paulsamuelRegistered Senior Member

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AFAIK, they contend that the paucity and spotty nature of the fossil record is artefactual, and, given a full historical record, would show macroevolution as a consequence of gradual microevolutionary processes.

11. ### DudeyhedConformerRegistered Senior Member

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macroevolution? microevolution?

I still don't understand how radom mutations that have a minute chance of even having a positive effect can be attributed to the evolution of all life even over however many year life has been around.

And how does mutaion change the number of chromosomes an organism has?

How does a whole new species come into existance if all that happens is a mutaion in one or maybe more genes?

Even if a mutain happened in chromatin, (I could be and probably am wrong, but I think that to reproduce, two organisms need to have an equal number of chromosomes and chromosomes are made from chromatin) what are the chances of a mutation happenig in the chromatin of another organism of the same species?

The whole chicken/egg thing of this is confusing me. What are the parents of a new species?

12. ### spuriousmonkeyBannedBanned

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because it is not the random mutation that drives evolution but natural selection.

13. ### DudeyhedConformerRegistered Senior Member

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how can natural selection create new species?

14. ### spuriousmonkeyBannedBanned

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sexual selection is often quite powerful in creating new species. This can happen for instance in genetically encoded behavioral traits. If for instance certain females preferably want to mate with males that display certain behaviour and this behaviour has a genetic basis than selection can drive a subset of the population towards more and more extreme forms of this behaviour. At one point the females don't want to mate with males that behave 'normal'.

i think that there are some examples of speciation in the fruitflies and speciation thread.

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16. ### spuriousmonkeyBannedBanned

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the selection for this kind of behaviour can of course never happen if there isn't genetic variation in a population. If all individuals are the same than there is nothing to select for.

That's the function of mutations basically, although there are some other ways to create more genetic information.

how can the chromosome number change? Sometimes they duplicate too many times. This results in extra chromosomes.

how can a new gene be created?
genes are duplicated all the time. A perfect copy of an already existing gene is copied and inserted somewhere on a chromosome. Then these identical genes start changing because of mutation. One of these copies can then change so much that it gains a new function. It is very common for genes to have multiple copies that each function slightly differently. For instance, the gene 'Fibroblast growth factor' (FGF) has 22 copies!!! Some of them can mimic the function of another copy. For instance FGF3 has the same activity as FGF10. But others are totally different.
As you can see this is an excellent method to create more complexity. Complex organisms therefore usually have more genes and more copies of genes.

17. ### paulsamuelRegistered Senior Member

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If you get the book use Amazon (you can get it <$30, and I've seen it at other places for >$70).

18. ### MFrobotH43DRegistered Member

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I would also like to know how change happens on the chromosomal level. How does an organism with a new chromosome get that chromosome into the next generation?

19. ### ElectricFetusSanity going, going, goneValued Senior Member

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It depends on the nature of the chromosome and the organism. In plants for example they can actually double even quadruple their chromosome count with no ill effects… though this means they can only breed with other plants of 4n or 8n count. For example in the making of Wheat: a synthetic plant made through the breeding 3 different plants, a chromosome duplication was needed before it was breed with its final ancestor to make modern wheat (and people actually believe old fashion farming is not as fuck up as modern biotech!)

In animal for extra chromosome to become useful it must first be benign or not have any ill effects. Only 4 chromosome in humans can be duplicated with the fetus surviving to child birth… and even so only in the case of triple X in women is the duplication also benign. Also some inbreeding is need to for that copied chromosome to become double again and the count to be even. Such events are rare but had to happens since the genetic relation of chromosomes to each other has been proven.

20. ### DudeyhedConformerRegistered Senior Member

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does this mean that chromosome numbers can only increase?

I can believe the production of new genes now. It's the creation of a new species (is that what speciation is?) that I don't understand yet.

21. ### ElectricFetusSanity going, going, goneValued Senior Member

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Nope depends on the vitality of the chromosome. In fruit flies for example all males only have one sex chromosome and females have 2. The males seem to live fine with that one.

22. ### DudeyhedConformerRegistered Senior Member

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vitality of the chromosome?

Ok, so the male lives with one chromosome, but how could a chromosome drop off in a new species?

23. ### ElectricFetusSanity going, going, goneValued Senior Member

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Vitality: Webster Dirctionary discribes: "1b: capacity to live and develop"

The theory is that if the chromosome has no importance it will be lost... In most cases though this begins with section of the chromosome being lost, take the human male sex chromosome that evolved from the female sex chromosome: all that is needed is only as few key genes the rest decayed or fell off.