Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 84 (8914 total)
Current session began: 
Page Loaded: 06-27-2019 4:15 AM
25 online now:
Pressie (1 member, 24 visitors)
Chatting now:  Chat room empty
Newest Member: 4petdinos
Upcoming Birthdays: ooh-child
Post Volume:
Total: 854,844 Year: 9,880/19,786 Month: 2,302/2,119 Week: 338/724 Day: 1/62 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Definition of Evolution
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 129 of 212 (419516)
09-03-2007 11:48 AM
Reply to: Message 126 by RAZD
09-02-2007 11:15 PM


Re: So what is this evolution thing, anyway?
RAZD wrote:

"Change in a population's genetic traits across generations"

Is this acceptable?

Yes - it is acceptable. There are other acceptable definitions such as 'Evolution is the change in hereditary traits within populations of species over time'.

Works for me.


Yes, it works for me, too. But the evo-devo people say evolution can happen even without the inheritance of genetic traits. Lamarck would have agreed. But I don't.

My own short definition of "this evolution thing" is simply: A population's success in fixing beneficial alleles. This definition goes a critical step beyond saying only that evolution is a "Change in a population's genetic traits across generations."

First Law : Second Law :: change in genetic traits : fixation of beneficial alleles

—HM


This message is a reply to:
 Message 126 by RAZD, posted 09-02-2007 11:15 PM RAZD has responded

Replies to this message:
 Message 130 by NosyNed, posted 09-03-2007 12:06 PM Fosdick has responded
 Message 132 by Wounded King, posted 09-03-2007 12:36 PM Fosdick has responded
 Message 139 by RAZD, posted 09-03-2007 9:26 PM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 133 of 212 (419549)
09-03-2007 1:25 PM
Reply to: Message 132 by Wounded King
09-03-2007 12:36 PM


Re: So what is this evolution thing, anyway?
WK:

But the evo-devo people say evolution can happen even without the inheritance of genetic traits.

I'd like you to clear up quite what you mean by this.

I have read Mary Jane West-Eberhard's entire "Developmental Plasticity and Evolution" (2003). She is a leading evo-devo-ist, and she argues for the role of "homoplasy" as an alternative to homology (genetic inheritance) for explaining evolution. She argues for a "homeostatic, canalizing, contraining force" coming from the environment that accounts for evolution. Well, who would deny that changes in environmental conditions will provoke adaptive responses by populations, but adaptation does not occur until the benefical alleles are fixed. That is where evolution happens, IMO.

The same criticism can be leveled at another evo-devo-ist, Simon Conway Morris, who, in his "Life's Solution/Inevitable Humans in a Lonely Universe," says:

quote:
So the beetle, no longer the butt of Haldane's jibe, is an example of the richness of a Creation...None of it presupposes, let alone proves, the existence of God, but all is congruent. For some it will remain as the pointless activity of the Blind Watchmaker...
Is there any doubt who he has in mind for this barb?

Then you ask:

Do you mean that they recognise that epigenetic factors such as methylation exist?

I don't see evo-devo-ists talking about methylation or introns or other factors relavant to evolution. But what if they did? Even those are members of a genetic complex that must be heritable or otherwise lost in a population

—HM


This message is a reply to:
 Message 132 by Wounded King, posted 09-03-2007 12:36 PM Wounded King has responded

Replies to this message:
 Message 135 by Dr Adequate, posted 09-03-2007 6:29 PM Fosdick has responded
 Message 136 by Wounded King, posted 09-03-2007 6:46 PM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 134 of 212 (419552)
09-03-2007 1:33 PM
Reply to: Message 130 by NosyNed
09-03-2007 12:06 PM


Re: Disagreeing with "beneficial"
Nosy wrote:

Evolution happens through things like drift without any "benefit" being involved.

I agree that selection is not the only way that alleles get fixed. Drift will fixed them, too. And whatever is beneficial will likely play its role when selective pressures arise.

—HM


This message is a reply to:
 Message 130 by NosyNed, posted 09-03-2007 12:06 PM NosyNed has not yet responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 137 of 212 (419616)
09-03-2007 8:27 PM
Reply to: Message 136 by Wounded King
09-03-2007 6:46 PM


Re: So what is this evolution thing, anyway?
WK wrote:

I've worked in evolutionary and developmental biology for several years. Homology is not an equivalence term for genetic heritability.

Yes, I do agree, it is not specifically about genetic heritability. But Gould is to blame for my reckless use of the term, as in his "deep homology." Consider what he says in "The Structure of Evolutuionary Theory" (2002, p. 82) he says:

quote:
Lankaster wanted to contrast homology of overt structure, or homology sensu stricto with homology of underlying generators (later called parallelism) building the same structure in two separate lineages (homoplasy, or homology sensu lato, in Lankaster's terms). Because parallelism could not be cashed out in operational terms (as science had no way, until our current revolution in evo-devo, to characterize, or even to recognize these underlying generators, proper conceptual distinctions between parallelism and convergence have generally not been made...
I'm not sold on convergence, but I can see Gould's deep homology, or parallelism, all right. Homoplasy, too, has legs, I quess, but I disagree with the evo-devo's nagging admonition that genes are not essentially and often selfishly in control of adaptation. That's all.

Two genetic sequences can as well be homplastic as any other trait. Either West-Eberhard has meade up her own definitions of some of those words or you are not accurately presenting her position. you make it sound as if she is advocating some sort of vitalist form of intelligent design or process structuralism where similar environnments cause organisms to converge ...

Read her. I can find issues with almost every page. Read Morris, too, and tell me he isn't grinding an ID axe.

Balderdash...

OK. Educated me. What is there in "development" that accomplishes the essentials of heritability? Because no embryo can escape its gametic origin (most of the time). It's a generational thing, isn't it? How do two gametes carry any more information into fertilization than genetic information (save whatever little information comes from their cytoplasm)? I've always wanted to know how "developmental information" evades or escapes its genetic limitations, as Lewontin argues in his "The Triple Helix." He's just spitting back at Dawkins for kicking his colleague's behind—Gould's, specifically.

Oh, btw, I come with no guarantee of satisfaction. I'm mostly just winging it, you know...and, boy, are my arms getting tired!

—HM


This message is a reply to:
 Message 136 by Wounded King, posted 09-03-2007 6:46 PM Wounded King has responded

Replies to this message:
 Message 141 by Wounded King, posted 09-04-2007 2:38 AM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 138 of 212 (419622)
09-03-2007 8:39 PM
Reply to: Message 135 by Dr Adequate
09-03-2007 6:29 PM


Re: So what is this evolution thing, anyway?
Dr Adequate wrote:

No, but there might be considerable confusion as to what this has to do about "evolution without the inheritance of genetic traits".

Just curious, Dr A, do you know of any evolution going on without the inheriitance of genetic traits. Some people on this forum have claimed there are "traits" that are not heritable. I have agued that a "trait" must be heritable or it is not a "trait." Otherwise, you'd have to explain the three-legged-dog "trait."

—HM


This message is a reply to:
 Message 135 by Dr Adequate, posted 09-03-2007 6:29 PM Dr Adequate has not yet responded

Replies to this message:
 Message 146 by Taz, posted 09-04-2007 3:20 PM Fosdick has not yet responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 142 of 212 (419701)
09-04-2007 10:38 AM
Reply to: Message 139 by RAZD
09-03-2007 9:26 PM


Re: Review time
RAZD asks:

Are you or are you not proposing a change to this definition?

Yes, I am. If you will notice in Message 129 I wrote:

My own short definition of "this evolution thing" is simply: A population's success in fixing beneficial alleles. This definition goes a critical step beyond saying only that evolution is a "Change in a population's genetic traits across generations."

—HM


This message is a reply to:
 Message 139 by RAZD, posted 09-03-2007 9:26 PM RAZD has responded

Replies to this message:
 Message 144 by RAZD, posted 09-04-2007 11:51 AM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 143 of 212 (419702)
09-04-2007 10:51 AM
Reply to: Message 141 by Wounded King
09-04-2007 2:38 AM


Re: So what is this evolution thing, anyway?
WK snorts:

Hoot, do you never get tired of 'winging it' which presumably means the way you just make up all sorts of shit and then use them to smear the people your talking to?

Smearing shit is not something I really care to do. But in your case...

But I would only call this the weak sort of ID that any sort of theistic evolutionist must ascribe to no more Discovery Institute ID than the fact that a theistic evolutionist believes in a divine creator would make them a 6-day creationist.

I still don't understand how you can post so much and say so little substantively.


How's that again?

—HM


This message is a reply to:
 Message 141 by Wounded King, posted 09-04-2007 2:38 AM Wounded King has responded

Replies to this message:
 Message 148 by Wounded King, posted 09-04-2007 5:24 PM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 145 of 212 (419717)
09-04-2007 12:47 PM
Reply to: Message 144 by RAZD
09-04-2007 11:51 AM


Re: Review time
RAZD, you wrote:

Define beneficial so that it can be measured.

Michael Whitlock and his colleagues at UBC have done this rather nicely in stochastic terms. I especially like these articles:

The Probability of Fixation in Populations of Changing Size and Fixation Probability of Time in Subdivided Populations.

Whitlock advances a stochastic model to define the probability of fixing new beneficial alleles:

2hs(1-FST)Ne / Ntot

“…where hs is the change in fitness of heterozygotes relative to the ancestral homozygote, FST is a weighted version of Wright’s measure of population subdivision, and Ne and Ntot are the effective and census sizes, respectively.”

So he uses this ratio to define and measure "beneficial."

—HM


This message is a reply to:
 Message 144 by RAZD, posted 09-04-2007 11:51 AM RAZD has responded

Replies to this message:
 Message 147 by RAZD, posted 09-04-2007 3:48 PM Fosdick has responded
 Message 149 by Brad McFall, posted 09-04-2007 6:49 PM Fosdick has not yet responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 150 of 212 (419784)
09-04-2007 7:29 PM
Reply to: Message 147 by RAZD
09-04-2007 3:48 PM


Re: Review time, qualified evolution
Which differs from your definition by the qualification of the evolution involved being adaptive evolution. In other words they do not make the distinction that you are making.

OK, good point. I was speaking of adaptive evolution. I also recognize drift, gene flow, and sexual selection as means of non-adaptive evolution. You are looking for a more generalized definition, I suppose.

You also did not answer the rest of my questions on your definition: Does this evolution occur when the allele is fixed or when it becomes beneficial? If the later then fixing is irrelevant, if the former then it is no different than fixing a neutral allele.

I see your point here. Good argument.

If deleterious mutations are fixed in the population, is that devolution - previous population more fit than current? What happens if later those deleterious mutations turn out to be beneficial? At what point then does it become evolution?

Then you don't have adaptation per se, you have exaptation, which is Gould's way of explaining how previously fixed alleles that were once neutral, or even deleterious, become usefully adaptive.

—HM


This message is a reply to:
 Message 147 by RAZD, posted 09-04-2007 3:48 PM RAZD has responded

Replies to this message:
 Message 152 by RAZD, posted 09-04-2007 8:11 PM Fosdick has responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 151 of 212 (419786)
09-04-2007 7:40 PM
Reply to: Message 148 by Wounded King
09-04-2007 5:24 PM


Re: So what is this evolution thing, anyway?
Have you just totally given up on having your posts make any sort of sense?

Well, no, not "just totally." Where did you pick up the Valley Girl speak in Dundee, Scotland?

You were moaning about Conway-Morris 'grinding an ID axe', I was simply pointing out that he was not neccessarily any more ID than any theistic evolutionist and certainly not a proponent of ID as it would be generally be understood on this site, i.e. the position espoused by Philip Johnson, Michael Behe, Will Dembski and promoted by the Discovery Institute. I likened this to describing a theistic evolutionist as a creationist, since the believe in a creator, which would still be quite distinct from the common usage of creationist on this site either in the young earth or old earth context.

I liken the Discovery Institute to a Christian organization out to discover nothing but evidence of God and His glory.

Are you actually going to address any of the points I made or just keep dodging and whining?

Ah, what was your point again?

—HM


This message is a reply to:
 Message 148 by Wounded King, posted 09-04-2007 5:24 PM Wounded King has responded

Replies to this message:
 Message 158 by Wounded King, posted 09-05-2007 5:26 AM Fosdick has not yet responded

    
Fosdick 
Suspended Member (Idle past 3673 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 153 of 212 (419805)
09-04-2007 8:34 PM
Reply to: Message 152 by RAZD
09-04-2007 8:11 PM


Re: Review time, qualified evolution
Are you then happy with:
"Change in a population's genetic traits across generations"
as a generalized definition?

After kicking a few tires, I think I'm ready to buy your yellow jalopy, RAZD.

Good thread.

—HM


This message is a reply to:
 Message 152 by RAZD, posted 09-04-2007 8:11 PM RAZD has acknowledged this reply

    
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019