Checkmate evolutionists

[pood]

And here is that debate.

 

[Elixir]

near-neutral evolution dominates at the genotyping level and often also at the phenotypic level.

Depends what you mean by "dominates". Over generations, yes. Over millennia, not so much for many species. And over millions of years, well, the so called fitness landscape tends to change, which can make some novel mutations advantageous that would have passed as neutral or even detrimental in prior eras. If neutral drift and accident dominated over billions of years, we'd still be in the fabled primordial soup. Sometimes things happen that change everything else, like the appearance of eukaryotic forms.
I think that what those guys actually dismiss is directed evolution. If they're saying checkmate evolutionists, they're out to lunch. If they're just pointing out how rare it is that a mutation that causes phenotypic or genetic changes to become fixed in a population, I would totally agree. Mutations are a dime a dozen. Truly useful ones are one in trillions - or less. But without selection none of them would matter, not even a "Superman" gene. I don't think I ever heard an evolutionary biologist or a population geneticist say selection isn't essential, and I don't see any way it could NOT be.

omfg
"Dawkins doubts that any mutation giving rise to a visible phenotype can be neutral"

I doubt that Dawkins doubts that "any mutation giving rise to a visible phenotype can be neutral".
"Visible" has shit to do with it, except insofar as a single individual with a variant phenotype that is NOT advantageous, is unlikely to pass on its genetic cause, and that phenotype is likely not to appear in the rest of the population, so it probably will never be detected.
I would tend to agree with Dawkins if he's saying that phenotype becoming fixed in a population is very very probably a sign that at some point along the way, holders of that phenotype experience or have experienced differential reproductive success. Actually I tend to agree with Dawkins, period;. But not necessarily with people trying to tell other people what Dawkins means.

I'm sorry - I have a really hard time with most material intended for general consumption. In fact, even evo-bio people strain to maintain precision while discussing among themselves, in their descriptions and conjectures of what happens or might happen as populations evolve.

 

[pood]

I think that what those guys actually dismiss is directed evolution.

If by “those guys” you mean Dawkins and Moran, of course they do. But they certainly disagree on the relative importance of selection vs. what Moran calls “evolution by accident.”

 

[Elixir]

If by “those guys” you mean Dawkins and Moran, of course they do. But they certainly disagree on the relative importance of selection vs. what Moran calls “evolution by accident.”

Sounds like a chicken/egg pointless argument.
Both are required and neither is sufficient to produce diversity. Would either D or M disagree?

 

[pood]

If by “those guys” you mean Dawkins and Moran, of course they do. But they certainly disagree on the relative importance of selection vs. what Moran calls “evolution by accident.”

Sounds like a chicken/egg pointless argument.
Both are required and neither is sufficient to produce diversity. Would either D or M disagree?

The debate is over the relative importance of each. It’s germane to this thread because Moran contends that 90 percent junk in our genome is better explained by more accidental evolution and less adaptationism.

 

[Elixir]

The debate is over the relative importance of each.

Moran has to explain how it all became fixed then.
Factors that are co-dependent to produce an effect can only be considered equal in “importance” IMHO.
But IANAEB.
There are scads of endogenous retroviruses (retrovirii?) in the human genome. Some of them might be explained through a lens of “accidental” population-wide infections of the past. Is that the sort of thing Moran uses to support his assertion?

 

[pood]

The debate is over the relative importance of each.

Moran has to explain how it all became fixed then.
Factors that are co-dependent to produce an effect can only be considered equal in “importance” IMHO.
But IANAEB.
There are scads of endogenous retroviruses (retrovirii?) in the human genome. Some of them might be explained through a lens of “accidental” population-wide infections of the past. Is that the sort of thing Moran uses to support his assertion?

Have you read the blog debate? Moran argues that most beneficial alleles are lost by drift before going to fixation, and that many deleterious traits go to fixation by drift. They also argue over certain rhinoceros horns, with Moran contending that the assumption that such horns and other phenotypic structures being the result of selection is open to question.

 

[Elixir]

deleterious traits go to fixation by drift

Can you ‘splain me how “fixation by drift” works? Without conferring any reproductive advantage? Does M provide examples?

The utility of so many mutations that HAVE become fixed, would tend to belie his assertion unless he has reams of examples, and sound reason to believe they were never advantageous.

 

[pood]

He explains his position in some depth in this essay.

 

[Elixir]

I read (skimmed) that whole thing and find it devoid of news other than who calls what “random”. I’m not sure “wrong” describes any of it. It’s more of a semantic argument than anything else. Which is not to say it’s unimportant; it’s good to discuss things using agreed upon terms and this seems like an area where people disagree on preferences for certain terms rather than on how evolution works. Moran agrees that alleles arising from accident are far more likely to become fixed in a large (>1000) population than a neutral or harmful on would be. And I’m sure Dawkins agrees that ‘most all the mutations that do become fixed arose accidentally in the first instance.

Of course the “fitness landscape” can be said fo be “dominated” by accidents. And evolutionary benefits depend on it.
There’s less of a disagreement or controversy about evolution, and more of a disagreement on how evolutionary biology should be taught.

 

[Elixir]

I asked:

Can you ‘splain me how “fixation by drift” works? Without conferring any reproductive advantage? Does M provide examples?

FWIW... from that article.
Regarding neutral mutations that have become fixed, this is the same question that I asked:

Dawkins:

"I would still like to know what those [neutral mutations that have become fixed] are, because I don't know them"

I believe that Moran is making a mountain out of a molehill in order to give himself something to say, to make himself relevant.

 

[pood]

I asked:

Can you ‘splain me how “fixation by drift” works? Without conferring any reproductive advantage? Does M provide examples?

FWIW... from that article.
Regarding neutral mutations that have become fixed, this is the same question that I asked:

Dawkins:

"I would still like to know what those [neutral mutations that have become fixed] are, because I don't know them"

I believe that Moran is making a mountain out of a molehill in order to give himself something to say, to make himself relevant.

I think you are being a bit uncharitable to Moran, who has strong academic credentials, has authored a number of books, and is an ardent foe of creationism. (These facts don’t mean he’s right, of course, just that he is not some rando off the street blabbing on a soapbox.) He contends drift is responsible for things like junk DNA, molecular phylogenies, molecular clocks, and DNA fingerprinting. He further contends — open to dispute, obviously — that many phenotypes we assume are products of selection actually got there by neutral or nearly neutral evolution, not selection.

 

[pood]

Here is Moran’s Sandwalk blog, for those interested. I find it highly informative,

 

[Elixir]

He contends drift is responsible for things like junk DNA, molecular phylogenies, molecular clocks, and DNA fingerprinting. He further contends — open to dispute, obviously — that many phenotypes we assume are products of selection actually got there by neutral or nearly neutral evolution, not selection.

B-b-but he fails in that article to specify WHAT phenotypes and by what means (mathematical model) they became fixed in a large population.

Certainly it’s possible but my understanding is that it should be vanishingly rare. Dawkins seems to agree.
Moran is a respected PhD like Dawkins, making a living writing for public consumption. I am only an untrained nobody, just interested enough to have read some stuff and met a few kind people who ‘splained some stuff to me. So I have no dog in the race. It just seems unlikely that I should reach the same conclusions for the same reasons as Dawkins if there wasn’t an element of accuracy to them.

I think Moran may have extrapolated some things from the performance of evo algorithms. Start with a population of random attributes, make random variations with every iteration, measuring the resulting proximity to a predetermined target characteristic, saving the versions that show improvement and doing it again and again and again, at blinding rates until you get something functional.
It certainly works.
However it requires a target to be specified and an algorithm to measure distance to target. It also requires so many “generations” to achieve s goal, that it would take millions of years of generational variation to naturally produce a phenotype or design that the algorithm can simulate in minutes, hours or days.
The ONLY target for a population of biological organisms is reproduction, and generations, even for microorganisms, are really long compared to computer algorithms.
Granted, billions of years have passed on this planet, but we have observed evolution producing advantageous phenotypic changes in just hundreds of years. Why the difference?
In my lay opinion, selection can explain it. Genetic drift cannot. So I wonder on what grounds Moran can claim “most evolution” when he has a zero on the board, for traits shown to have become fixed without ever having conferred any reproductive advantage.

 

[Elixir]

@pood,
Am I missing something?
When intellectual elites disagree on stuff and the right answer looks obvious to me, of course I suspect that there’s something I’m failing to understand.

 

[pood]

@pood,
Am I missing something?
When intellectual elites disagree on stuff and the right answer looks obvious to me, of course I suspect that there’s something I’m failing to understand.

The gist of it is, I think, that most biologists think neutral or near-neutral evolution dominates at the molecular level, and selection at the phenotypic level. Moran is making the case that even at the phenotypic level, a lot of what we take as adaptations may in fact be mostly or even solely due to drift.

 

[Elixir]

@pood,
Am I missing something?
When intellectual elites disagree on stuff and the right answer looks obvious to me, of course I suspect that there’s something I’m failing to understand.

The gist of it is, I think, that most biologists think neutral or near-neutral evolution dominates at the molecular level, and selection at the phenotypic level. Moran is making the case that even at the phenotypic level, a lot of what we take as adaptations may in fact be mostly or even solely due to drift.

Yeah, that’s what I took away too.
In my lay opinion Morgan’s conjecture lacks support. Maybe it’ll pan out once we learn more, but like Dawkins I’d like to see specific examples.

 

[pood]

@pood,
Am I missing something?
When intellectual elites disagree on stuff and the right answer looks obvious to me, of course I suspect that there’s something I’m failing to understand.

The gist of it is, I think, that most biologists think neutral or near-neutral evolution dominates at the molecular level, and selection at the phenotypic level. Moran is making the case that even at the phenotypic level, a lot of what we take as adaptations may in fact be mostly or even solely due to drift.

Yeah, that’s what I took away too.
In my lay opinion Morgan’s conjecture lacks support. Maybe it’ll pan out once we learn more, but like Dawkins I’d like to see specific examples.

This looks to be an interesting take on the topic of neutral evolution and phenotypes, from Oxford, though I’ve only had a chance to skim it so far.

 

[Elixir]

Lookin’ at it. Interesting.

 

[JohnG]

“Although the human germline mutation rate is higher than that in any other well-studied species, the rate is not exceptional once the effective genome size and effective population size are taken into consideration.”