Punctuated equilibrium
All-seeing-I
That is the story you make up with the original story starts to fall
apart.
--
This has been another "evolution is dead" moment, with:
Adman.
Christopher Denney
I know some people have difficulty with searching, so here is a basic
start...
http://en.wikipedia.org/wiki/Punctuated_equilibrium
Mark Evans
Oh, you mean like the information you "find" in ancient manuscripts
that nobody else has found without the assistance of controlled
substances?
Mark Evans
John Harshman
> What is "Punctuated equilibrium"?
>
> That is the story you make up with the original story starts to fall
> apart.
Never ask and answer a question if you don't actually know the answer.
It just makes you look stupid.
Dave Oldridge
8737dc...@j14g2000yqm.googlegroups.com:
>What is "Punctuated equilibrium"?
>
>That is the story you make up with the original story starts to fall
>apart.
Another transparent lie from the disciple of Belial.
>This has been another "evolution is dead" moment, with:
>
>Adman.
No, it has been another "look at the brain-dead narcissist seeking
attention" moment from the Unseeing Ego.
And the dead brain is a self-inflicted injury. You sacrificed it to your
"god."
--
Dave Oldridge+
Nic
> What is "Punctuated equilibrium"?
It's a conjecture about the dynamics of evolution.
> That is the story you make up with the original story starts to fall
> apart.
No. You make up stories regardless of the original one. Science is
fun.
> �--
All-seeing-I
wrote:> 8737dc8bd...@j14g2000yqm.googlegroups.com:
>
> >What is "Punctuated equilibrium"?
>
> >That is the story you make up with the original story starts to fall
> >apart.
>
> Another transparent lie from the disciple of Belial.
>
> >This has been another "evolution is dead" moment, with:
>
> >Adman.
>
> No, it has been another "look at the brain-dead narcissist seeking
> attention" moment from the Unseeing Ego.
>
> And the dead brain is a self-inflicted injury. �You sacrificed it to your
> "god."
>
> --
> Dave Oldridge+
It is OK. You can admit it. We all know "Punctuated equilibrium" is
the cover story for all that stuff evolution says needs time, lots of
time, to evolve.
Burkhard
> What is "Punctuated equilibrium"?
A theoretical concept put forward by Eldredge and Gould, which
elaborated on ideas by Mayr. According to this model, most species
remain stable for long (in geological terms) periods of time, and
when speciation takes palce, it happens in "bursts" over mere
thousands or tens of thousands of years.
This they argue is a direct consequence of the ToE: Once a species is
adapted to a new habitat, one of the main driving forces of evolution,
natural selection, becomes a conserving force (in this situation,
change is more likely to be disadvantageous than on one where change
in the environment has led to a species becoming badly adapted). If
the population is also large, even beneficial mutations are unlikely
to get "fixed" due to interbreeding.
So rather then seeing speciation in the main population gradually
happening over time, we should expect to find it when smaller
"fringes" of that population split up into geographically isolated
areas, and in reaction to changes in external circumstances.
This emphasises an argument already made by Darwin: "The period
during which each species underwent modification, though long as
measured by years, was probably short in comparison with that during
which it remained without undergoing any change". (On The Origin Of
Species, chap.10).
One of the consequences of this model is that it predicts that we
should not normally find in the fossil record at any one site a good
record of the process of speciation - the new species is likely to be
found "somewhere else" from the mother ship, so to speak. And because
speciation tends to happen in these smaller fringe groups (and over a
relatively short period of time, geologically speaking, though still
longer than human civilisation, say,), the odds are reduced that any
of its members will be fossilized.
This explains that while we have found lots of transitional forms
between higher taxa in the fossil record, the number of transitional
fossils between_species_ is less common - this pattern is indeed
another prediction of the model.
Analogies are always dangerous, but this may work
Compare the game of basketball with that of soccer. Put a reporter
next to each and tell him to take a picture every 3 min. In the
basketball game, a large number of these pictures will show someone
scoring, simply because in basketball there are lots of scoring
events. However, for the same reason few of these will be "decisive" -
the game moves gradually to a result. The same reporter in a soccer
game will make mostly pictures of "nothing happening much", the ball
passed around in the same areas. But if he is lucky enough to get one
of the (comparatively rare) goals, it is also much more likely to be
a "decisive" goal that decides the game. The fossil record is more
similar to the photographs from the soccer game. Nothing_seems_ to
happen for a long time (but in reality, of course lots of things go
on, just nothing visible or something you could spot in the isolated
photos, just a constant build up). Especially when the game went into
extra time and the golden goal applies though, _if_ something happens
it is immediately decisive and alters the course of the game.
Similarly in evolution, while it goes on all the time (mutations
always happen), speciation only occurs in key moments that are
unlikely to get recorded, giving how many fortuitous circumstances
have to come together to create a fossil that is found by us.
>
> That is the story you make up with the original story starts to fall
> apart.
It is a refinement of the older theory, and fully in line with its
main ideas. We call it "learning". In this case, we found some
examples in the fossil record that work just like the theory predicts,
but it is still debated just how typical PE actually is for evolution.
Open research questions also concern the question if there are other
mechanisms that may preserve the morphology of a species over time,
and so to speak "unleash" them once the environment makes this
necessary. You find some of these ideas here: M�ller, G. B. and
Newman, S. A., eds. (2003) Origination of Organismal Form: Beyond the
Gene in Developmental and Evolutionary Biology. Cambridge: The MIT
Press.
My own tentative take again in the form of an analogy: Gradualist
evolution is similar to getting bald. Think of someone who looses one
hair per day. Every day, he will look pretty similar, and indeed with
bare eyes indistinguishable from the day or even the month before.
However, if you take one photograph of him at age 20, and another at
age 55, a massive difference will be visible. (based, of course, on
the famous sorites). As a basic model, that works fine. But then you
observe that at least with some people, while they too show little
change for most of the time, there are key moments where they change
more dramatically over the course of a week or so. On closer
inspection, you find that they found a way to comb the remaining hairs
over the gradually emerging bare spots and use volume increasing
shampoo.
But this of course only works for so long, and when that strategy
collapses, it collapses quickly and in a "burst" - once tere is
nothing left to comb over, all the accumulated spots become visible at
once. But how this exactly works, and how often it happens, is still
researched.
>
> �--
Antti Korhonen
Great reply. POTM :) Hadn't thought of it like that before.
John Harshman
> On Jan 7, 5:13 pm, Burkhard <b.scha...@ed.ac.uk> wrote:
>> On Jan 7, 2:22 am, All-seeing-I <ap...@email.com> wrote:
>>
>>> What is "Punctuated equilibrium"?
>> A theoretical concept put forward by Eldredge and Gould, which
>> elaborated on ideas by Mayr. According to this model, most species
>> remain stable for long (in geological terms) periods of time, and
>> when speciation takes palce, it happens in "bursts" over mere
>> thousands or tens of thousands of years.
>>
>> This they argue is a direct consequence of the ToE: Once a species is
>> adapted to a new habitat, one of the main driving forces of evolution,
>> natural selection, becomes a conserving force (in this situation,
>> change is more likely to be disadvantageous than on one where change
>> in the environment has led to a species becoming badly adapted). If
>> the population is also large, even beneficial mutations are unlikely
>> to get "fixed" due to interbreeding.
Not quite. They argue that it's a direct consequence of Ernst Mayr's
ideas about speciation, which Ernst Mayr may have equated with the ToE,
but few others would. The reason established species supposedly become
buffered against change is the supposed existence of "coadapted gene
complexes". A change in one gene bumps up against its fit to other
genes, and is selected against. To allow any change, either a lot of
genes would have to be mutated at once in a coordinated fashion (very
unlikely) or a population bottleneck would have to allow drift to
dominate, breaking up those supposed complexes. And the latter is what
Mayr (and through him, Eldredge and Gould) proposed. That's why large
populations are suposedly unable to change, and speciation and evolution
supposedly happen only in peripheral isolates.
Now population geneticists generally suppose that adaptive evolution is
actually easier in large populations, because there's a bigger gene pool
in which advantageous mutations can arise. This is somewhat balanced by
their arising in smaller frequency (1/2N, where N is the population
size), but happening more often makes up for that. And other evidence
from population genetics makes it appear unlikely that Mayr's theory is
valid, leaving PE without a rationale.
>> So rather then seeing speciation in the main population gradually
>> happening over time, we should expect to find it when smaller
>> "fringes" of that population split up into geographically isolated
>> areas, and in reaction to changes in external circumstances.
Iff evolution in large populations was unlikely.
>> This emphasises an argument already made by Darwin: "The period
>> during which each species underwent modification, though long as
>> measured by years, was probably short in comparison with that during
>> which it remained without undergoing any change". (On The Origin Of
>> Species, chap.10).
>>
>> One of the consequences of this model is that it predicts that we
>> should not normally find in the fossil record at any one site a good
>> record of the process of speciation - the new species is likely to be
>> found "somewhere else" from the mother ship, so to speak. And because
>> speciation tends to happen in these smaller fringe groups (and over a
>> relatively short period of time, geologically speaking, though still
>> longer than human civilisation, say,), the odds are reduced that any
>> of its members will be fossilized.
This would be a good place to note that we can't reliably identify
either species or speciation in the fossil record, even if we're looking
at them. Cryptic species are abundant in the world today, and there's no
reason to suppose the past was any different. What looks like a new
species could be a change in only one of a group of previously existing
sibling species.
>> This explains that while we have found lots of transitional forms
>> between higher taxa in the fossil record, the number of transitional
>> fossils between_species_ is less common - this pattern is indeed
>> another prediction of the model.
It's also a prediction of much simpler models. Just a consequence of
poor temporal and geographic sampling, the tendency of new species to be
limited in space, to expand their ranges, and our inability to
objectively recognize speciation in the fossil record.
>> Analogies are always dangerous, but this may work
>>
>> Compare the game of basketball with that of soccer. Put a reporter
>> next to each and tell him to take a picture every 3 min. In the
>> basketball game, a large number of these pictures will show someone
>> scoring, simply because in basketball there are lots of scoring
>> events. However, for the same reason few of these will be "decisive" -
>> the game moves gradually to a result. The same reporter in a soccer
>> game will make mostly pictures of "nothing happening much", the ball
>> passed around in the same areas. But if he is lucky enough to get one
>> of the (comparatively rare) goals, it is also much more likely to be
>> a "decisive" goal that decides the game. The fossil record is more
>> similar to the photographs from the soccer game. Nothing_seems_ to
>> happen for a long time (but in reality, of course lots of things go
>> on, just nothing visible or something you could spot in the isolated
>> photos, just a constant build up). Especially when the game went into
>> extra time and the golden goal applies though, _if_ something happens
>> it is immediately decisive and alters the course of the game.
>> Similarly in evolution, while it goes on all the time (mutations
>> always happen), speciation only occurs in key moments that are
>> unlikely to get recorded, giving how many fortuitous circumstances
>> have to come together to create a fossil that is found by us.
A form of this may be true. It may indeed be that recognizable
morphological change happens in brief episodes and thus is unlikely to
be sampled. But the claim that such change is either equivalent to or
coincident with speciation is highly problematic. Further, there is no
good mechanism to prevent evolution except during speciation events, or
in small populations.
>>> That is the story you make up with the original story starts to fall
>>> apart.
>> It is a refinement of the older theory, and fully in line with its
>> main ideas. We call it "learning".
Or some of us call it "wrong". PE is popular among some paleontologists,
but not among population geneticists. There may be a core of interest
there: stasis. The relative prevalence and causes of stasis bear
investigation. But the fossil record isn't adequate to show that
punctuation and speciation are coincident.
One potential bit of confusion (probably not shared by the OP, but worth
clearing up anyway): almost all evolution, including punctuations, is
gradual in ordinary terms; that is, changes happen through multiple
alleles spreading through a population, not in any sort of saltation.
Though Gould flirted with saltation at times, it was no part of PE.
Punctuations are fast on a geological timescale, but gradual on a human
time scale.
Reddfrogg
> On Jan 7, 12:13�am, Dave Oldridge <doldr...@leavethisoutshaw.ca>
> wrote:
>
>
>
> > All-seeing-I <ap...@email.com> wrote in news:3b92dc4b-4019-4455-8e7f-
> > 8737dc8bd...@j14g2000yqm.googlegroups.com:
>
> > >What is "Punctuated equilibrium"?
>
> > >That is the story you make up with the original story starts to fall
> > >apart.
>
> > Another transparent lie from the disciple of Belial.
>
> > >This has been another "evolution is dead" moment, with:
>
> > >Adman.
>
> > No, it has been another "look at the brain-dead narcissist seeking
> > attention" moment from the Unseeing Ego.
>
> > And the dead brain is a self-inflicted injury. �You sacrificed it to your
> > "god."
>
> > --
> > Dave Oldridge+
>
> It is OK. You can admit it.
Admit what? That you are ignorant of science?
>We all know
Yes, we do all know you are ignorant.
>"Punctuated equilibrium" is
> the cover story for all that stuff evolution says needs time, lots of
> time, to evolve.
"Stuff" doesn't necessarily need "lots of time" to evolve. Some
populations have much shorter generational times than others, and
selectional pressure is different under different conditions.
The idea that evolution always requires "lots of time" is just a
strawman.
DJT
John Stockwell
Punctuated equlibrium is merely a statement of observations.
Morphologies persist within observed fossils, but changes occur
to fast and in too small of a population to be readily captured in
the fossil record. Of course, the spatio-temporal resolution of
the fossil record is so coarse that it overwelmns finer scale changes.
-John
>
> Adman.
Dan Listermann
"John Stockwell" <john.1...@gmail.com> wrote in message
news:39c85169-f700-46f5...@m16g2000yqc.googlegroups.com...
>
> Punctuated equlibrium is merely a statement of observations.
> Morphologies persist within observed fossils, but changes occur
> to fast and in too small of a population to be readily captured in
> the fossil record. Of course, the spatio-temporal resolution of
> the fossil record is so coarse that it overwelmns finer scale changes.
>
.
bpuharic
<ap...@email.com> wrote:
>
>It is OK. You can admit it. We all know "Punctuated equilibrium" is
>the cover story for all that stuff evolution says needs time, lots of
>time, to evolve.
and what's creationism's excuse for 2000 years of failure?
Mark Isaak
> What is "Punctuated equilibrium"?
/e'qui-lib'ri-um/. That answer should serve for you.
--
Mark Isaak eciton (at) earthlink (dot) net
"It is certain, from experience, that the smallest grain of natural
honesty and benevolence has more effect on men's conduct, than the most
pompous views suggested by theological theories and systems." - D. Hume
Friar Broccoli
It seems to me that you nail someone for an incorrect rendering of PE
about once a year. Here you got Burkhard for improperly equating
speciation and morphological change (you must have bonked me with this
at least 10 times before it sank in) as well as for the more common
error of misidentifying the mechanisms that Gould and Eldredge
proposed as the cause of the stasis suggested by the fossil record.
I would like to ignore these peripheral points to focus on the
apparent jerkiness of morphological change seen in the fossil record.
It seems to me that you agree with Burkhard that forms that are well
adapted to their current environment are unlikely to change until
their environment changes. Then when significant change comes, it is
likely to cause a population crash creating lots of small isolated
populations, accelerated speciation and rapid adaptive change.
Assuming that you agree that this is more or less correct, we are
talking about something that probably does occur but doesn't (as far
as I know) have a name. What should we be calling this distinctly
formed process if not Punctuated Equilibrium?
rmacfarl
"Friar Broccoli" <eli...@gmail.com> wrote in message
news:d5af27d8-cac6-4cd5...@q4g2000yqm.googlegroups.com...
I would have thought that it does have a name - isn't what you're
describing the mechanism of allopatric speciation?
http://en.wikipedia.org/wiki/Allopatric_speciation
(... as opposed to sympatric speciation:
http://en.wikipedia.org/wiki/Sympatric_speciation...)
John Harshman
that has a specific meaning already, and that's not it. PE is a theory
about the relationship between morphological change and speciation, and
about stasis except during speciation.
What you propose bears some relationship to the concept of coordinated
stasis, which you might find by googling.
I don't think your assumptions are valid, though. Significant change
might cause a population crash under some conditions, but not others.
Certain types of change cause fragmentation of habitats, which is what
you're really talking about. And that might promote speciation by
increasing the number of allopatric populations, but no crash is
necessary. But there are many other ideas about what drives speciation.
Nor is fragmentation a necessary result of environmental change;
conversely, environmental change isn't a necessary result of fragmentation.
Friar Broccoli
> "Friar Broccoli" <elia...@gmail.com> wrote in message
Not for my intended purposes, since nothing restricts speciation of
this sort to the short periods following long intervals of morphologic
stasis.
Dave Oldridge
news:56efcc45-5105-41d1...@l30g2000yqb.googlegroups.com:
WE don't ALL know any such thing. Even YOUR claim to know it is a false
one, wther from delusion or a desire to deceive.
But then YOU think GOD requires you to sin, so delusion is quite
probable.
--
Dave Oldridge+
Stuart
> "John Stockwell" <john.19071...@gmail.com> wrote in message
Its worth mentioning that where the fidelity of the geologic record is
high, species-2-species transitions
can be found.
In any event, species-2-species transition are observed in nature.
Hence we don't need a fossil record of species-2-species transitions
as
evidence they occur.
Stuart
Friar Broccoli
I did. It looked to me as though "Coordinated Stasis" (CS)
was a description of the observation and "Ecological Locking"
was the theoretical model used by Baird to explain the
observation so CS at least avoids the problem of confusing the
observation with the explanation.
This, it seems to me, leaves two problems:
1) Does this capture the full range of stasis events?
(Obviously not. A general purpose expression would be nice)
2) Is this supported (at least occasionally) elsewhere in the
geological/fossil record, apart from the sample periods
in the Silurian and Devonian. Am I correct in assuming that
whatever Eldredge and Gould were trying to explain with their
theory could be covered as CS?
I assume that when Parahippus was replaced by Merychippus at
the end of the Burdigalian that a lot of other fauna also
turned over - but I don't know for sure - and to make matters
worse that is a rather clean case. (No doubt this can be cured
with further reading)
> I don't think your assumptions are valid, though. Significant change
> might cause a population crash under some conditions, but not others.
Well duhh.
> Certain types of change cause fragmentation of habitats, which is what
> you're really talking about. And that might promote speciation by
> increasing the number of allopatric populations, but no crash is
> necessary. But there are many other ideas about what drives speciation.
> Nor is fragmentation a necessary result of environmental change;
> conversely, environmental change isn't a necessary result of fragmentation.
I suppose that what I am suggesting is that the really big
extinctions like that K-T and Permian-Triassic are all going to
show a pretty clear pattern: stasis ends, and close to nothing
will come out looking like it did when it went in. So I think
this follows my
- population crash creating lots of small isolated populations
- accelerated speciation
- rapid adaptive change
model.
Lesser extinctions caused by _environmental_ changes should
then follow this model with increasing fuzziness depending on
how great and fast the change is. This, it seems to me, fits
nicely with the Coordinated Stasis model you have suggested.
Extinctions caused by things like improved predators or
parasites are obviously going to follow a very different
and, I assume, hopelessly varied pattern.
Maybe a nice general term could be [Un]Coordinated Stasis
(U?CS).
Thanks for an interesting response.
John Harshman
I haven't been paying all that much attention to the CS literature, but
I don't think so. This is however something that could be investigated.
> I assume that when Parahippus was replaced by Merychippus at
> the end of the Burdigalian that a lot of other fauna also
> turned over - but I don't know for sure - and to make matters
> worse that is a rather clean case. (No doubt this can be cured
> with further reading)
Again, I don't know.
>> I don't think your assumptions are valid, though. Significant change
>> might cause a population crash under some conditions, but not others.
>
> Well duhh.
>
>> Certain types of change cause fragmentation of habitats, which is what
>> you're really talking about. And that might promote speciation by
>> increasing the number of allopatric populations, but no crash is
>> necessary. But there are many other ideas about what drives speciation.
>> Nor is fragmentation a necessary result of environmental change;
>> conversely, environmental change isn't a necessary result of fragmentation.
>
> I suppose that what I am suggesting is that the really big
> extinctions like that K-T and Permian-Triassic are all going to
> show a pretty clear pattern: stasis ends, and close to nothing
> will come out looking like it did when it went in. So I think
> this follows my
> - population crash creating lots of small isolated populations
> - accelerated speciation
> - rapid adaptive change
> model.
Actually, I don't think so. I don't think the K/T extinction did create
lots of small isolated poulations. It may have reduced the density of
many populations by a lot. It may have caused a number of bottlenecks.
But not allopatry. The way in which the K/T would have increased
speciation is indirectly, by opening up a lot of niches, making it more
likely that if two populations did become allopatric they would then
change, and in different directions, because so many directions were
possible.
> Lesser extinctions caused by _environmental_ changes should
> then follow this model with increasing fuzziness depending on
> how great and fast the change is. This, it seems to me, fits
> nicely with the Coordinated Stasis model you have suggested.
Actually, the sort of event I could imagine as increasing allopatry are
few; essentially, those that create islands: a general drying that
reduces forests to unconnected patches; a general warming that leaves
mountain tops as islands of boreal or tundra habitat; a raising of sea
level that splits one island into several; etc.
> Extinctions caused by things like improved predators or
> parasites are obviously going to follow a very different
> and, I assume, hopelessly varied pattern.
>
> Maybe a nice general term could be [Un]Coordinated Stasis
> (U?CS).
First question: how prevalent is stasis? Second question: does
punctuation have anything at all to do with speciation? Third question:
are punctuation episodes often coordinated among taxa. I don't know the
answers to any of those questions.
Nic
I'm very interested in this. I don't know if you were thinking about
Australia, but you have certainly put me in mind of it. The phrase
adaptive radiation has been used. Is there such a macroevolutionary
process, and is the turnover of geography up to the job? If Australia
is not a good example for my question, what about the sea? Or the
air?
> > �Extinctions caused by things like improved predators or
John Harshman
My personal view/guess is that adaptive radiations are not dependent on
having an unusual ammount of allopatry but on having such allopatry as
happens be unusually likely to lead to speciation, so we accumulate a
large number of lineages, each capable of exploring a different bit of
some vacant adaptive space. And that the reason for this unusual
likelihood is the very existence of that vacant adaptive space.
All this puts me in mind of the "taxon pulse" model, in which increases
and decreases in the number of "islands" drive diversity. And I suppose
that, all things being equal, a vacant adaptive space that happens to
coincide with a taxon pulse would likely result in a bigger adaptive
radiation than one that didn't.
Friar Broccoli
If you go to this page
http://www.cbc.ca/quirks/archives/09-10/qq-2009-12-05.html
and go down to the story about "Birdfeeder Speciation" you will see a
story about Blackcap bird speciation.
Does this fit within your preferred model or would it count as an
exception?
John Harshman
It would seem to be irrelevant to my preferred model, since we weren't
talking about speciation but about adaptive radiations. Now, what's
going on there? I see two main possibilities: one, that mates are chosen
on wintering grounds; two, that assortative mating and disruptive
selection are at work. In the first case, it's potentially an odd sort
of allopatric speciation. In the second case, it's sympatric speciation.
Given the way small passerines usually operate, I'd guess the second,
absent any better information.
Ernest Major
<jhar...@pacbell.net> writes
>Friar Broccoli wrote:
>> On Jan 10, 10:03 am, John Harshman <jharsh...@pacbell.net> wrote:
>>> Nic wrote:
>>>> On 10 Jan, 03:56, John Harshman <jharsh...@pacbell.net> wrote:
>>>>> Friar Broccoli wrote:
>>>>>> On Jan 8, 12:29 am, John Harshman <jharsh...@pacbell.net> wrote:
>>>>>>> Friar Broccoli wrote:
>>>>>>>> On Jan 7, 4:04 pm, John Harshman <jharsh...@pacbell.net> wrote:
>>>>>>>>> Antti Korhonen wrote:
>>>>>>>>>> On Jan 7, 5:13 pm, Burkhard <b.scha...@ed.ac.uk> wrote:
>>>>>>>>>>> On Jan 7, 2:22 am, All-seeing-I <ap...@email.com> wrote:
>>>>>>>>>>>> What is "Punctuated equilibrium"?
>>>>>>>>>>> A theoretical concept put forward by Eldredge and Gould, which
>>>>>>>>>>> elaborated on ideas by Mayr. According to this model, most species
>>>>>>>>>>> remain stable for long (in geological terms) periods of time, and
>>>>>>>>>>> when speciation takes palce, it happens in "bursts" over mere
>>>>>>>>>>> thousands or tens of thousands of years.
>>>>>>>>>>> This they argue is a direct consequence of the ToE: Once a
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> change is more likely to be disadvantageous than on one where change
>>>>>>>>>>> in the environment has led to a species becoming badly
>>>>>>>>>>>adapted). If
>>>>>>>>>>> the population is also large, even beneficial mutations
>>>>>>>>>>> to get "fixed" due to interbreeding.
>>>>>>>>> Not quite. They argue that it's a direct consequence of Ernst Mayr's
>>>>>>>>> ideas about speciation, which Ernst Mayr may have equated with
>>>>>>>>>
>> Does this fit within your preferred model or would it count as an
>> exception?
>
>It would seem to be irrelevant to my preferred model, since we weren't
>talking about speciation but about adaptive radiations. Now, what's
>going on there? I see two main possibilities: one, that mates are
>chosen on wintering grounds; two, that assortative mating and
>disruptive selection are at work. In the first case, it's potentially
>an odd sort of allopatric speciation. In the second case, it's
>sympatric speciation. Given the way small passerines usually operate,
>I'd guess the second, absent any better information.
>
Germany first and pair up among themselves before the Spanish-wintering
population arrives. That would be the assortative mating. Hybrids
migrate to neither Britain nor Spain, and perhaps have lower wintering
success. That would be the disruptive selection.
<URL:http://migration.wordpress.com/2009/12/09/incipient-speciation-in-eu
ropean-blackcaps/>
--
alias Ernest Major
John Harshman
That's a bit of a combination, then. Temporal separation is a kind of
analog of allopatry (in time, rather than space. But that's not
assortative mating, really. Selection against hybrids is a standard
mechanism of sympatric speciation.
Ray Martinez
It's important to note that Mayr's theory exists in a state of
acceptance by mainstream evolutionary biology----and it is not based
on molecular data.
Ray
SNIP....
John Harshman
It's important to note that Ray exists in a state of having no clue
about evolutionary biology, as well as a state of arrogance in feeling
himself qualified to pronounce on the subject.
Ray Martinez
>
> - Show quoted text -
John's point is the underlying point of my note: Harshman, despite
having a "degree" in "evolutionary biology," is clueless concerning
mainstream evolutionary biology. I am one of the few here at Talk
Origins who refuses to ignore his pontificating ignorance.
Ray
Caranx latus
> having a "degree" in "evolutionary biology," is clueless concerning
> mainstream evolutionary biology.
Translation: "John and I disagree about evolutionary biology and,
since I am ignorant about evolutionary biology, he is clearly
mistaken."
> I am one of the few here at Talk
> Origins who refuses to ignore his pontificating ignorance.
Translation: "I am proudly and tenaciously ignorant about evolutionary
biology and therefore I obviously cannot allow myself to learn
anything about it from anyone."
John Harshman
> having a "degree" in "evolutionary biology," is clueless concerning
> mainstream evolutionary biology. I am one of the few here at Talk
> Origins who refuses to ignore his pontificating ignorance.
No, that wasn't my point. Very few living, mainstream biologists accept
Mayr's theory of genetic revolutions and coadapted gene complexes. I am
in fact unable to think of any. Can you, Ray?
Ray Martinez
>
> - Show quoted text -
The context was Mayr's theory of speciation, as accepted by Gould &
Eldredge (and mainstream evolutionary biology).
Ray
Ernest Major
<e9cf4395-783c-4acf...@u7g2000yqm.googlegroups.com>, Ray
Martinez <pyram...@yahoo.com> writes
genetic revolutions and coadapted gene complexes he is referring to
Mayr's theory of speciation? Or that he is correct when he indicates
that genetic revolutions and coadapted gene complexes are not generally
accepted by contemporary evolutionary biologists?
--
alias Ernest Major
John Harshman
>> The context was Mayr's theory of speciation, as accepted by Gould &
>> Eldredge (and mainstream evolutionary biology).
> Are you unaware that when John Harshman refers to Mayr's theory of
> genetic revolutions and coadapted gene complexes he is referring to
> Mayr's theory of speciation? Or that he is correct when he indicates
> that genetic revolutions and coadapted gene complexes are not generally
> accepted by contemporary evolutionary biologists?
Well, Ray may have one point there. I'm not sure of Niles Eldredge's
current views on genetic revolutions, etc., but he is living, and was a
fan in 1972. And I did challenge him to come up with a name, which he
has perhaps done, if only by accident.
Ray Martinez
> In message
> <e9cf4395-783c-4acf-8f5f-7a17adff4...@u7g2000yqm.googlegroups.com>, Ray
> Martinez <pyramid...@yahoo.com> writes
>
> - Show quoted text -
As I suspected: you are not aware that Mayr was not a gene-centrist.
He was a naturalist. In this context "naturalist" has nothing to do
with Naturalism----and his theory of speciation is an accepted
explanation.
Ray
Ernest Major
<2b7c9fbb-3323-44e0...@u7g2000yqm.googlegroups.com>, Ray
Martinez <pyram...@yahoo.com> writes
>On Jan 11, 1:36�pm, Ernest Major <{$t...@meden.demon.co.uk> wrote:
>> In message
>> <e9cf4395-783c-4acf-8f5f-7a17adff4...@u7g2000yqm.googlegroups.com>, Ray
>> Martinez <pyramid...@yahoo.com> writes
>>
>>
>>
>> >On Jan 11, 10:50�am, John Harshman <jharsh...@pacbell.net> wrote:
>> >> Ray Martinez wrote:
>> >> > On Jan 10, 5:25 pm, John Harshman <jharsh...@pacbell.net> wrote:
>> >> >> Ray Martinez wrote:
>> >> >>> On Jan 7, 1:04 pm, John Harshman <jharsh...@pacbell.net> wrote:
>> >> >>>> Antti Korhonen wrote:
>> >> >>>>> On Jan 7, 5:13 pm, Burkhard <b.scha...@ed.ac.uk> wrote:
>> >> >>>>>> On Jan 7, 2:22 am, All-seeing-I <ap...@email.com> wrote:
>> >> >>>>>>> What is "Punctuated equilibrium"?
>> >> >>>>>> A theoretical concept put forward by Eldredge and Gould, which
>> >> >>>>>> elaborated on ideas by Mayr. According to this model, �most species
>> >> >>>>>> remain stable for long (in geological terms) �periods of time, and
>> >> >>>>>> when speciation takes palce, it happens in �"bursts" �over mere
>> >> >>>>>> thousands or tens of thousands of years.
>> >> >>>>>> This they argue is a direct consequence of the ToE: Once a
>> >> >>>>>>
>> >> >>>>>>evolution,
>> >> >>>>>> natural selection, becomes a conserving force (in this situation,
>> >> >>>>>> change is more likely to be disadvantageous than on one
>> >> >>>>>>where change
>> >> >>>>>> in the environment has led to a �species becoming badly
>> >> >>>>>>adapted). �If
>> >> >>>>>> the population �is also �large, even beneficial mutations
>> >> >>>>>> to get "fixed" due to interbreeding.
>> >> >>>> Not quite. They argue that it's a direct consequence of Ernst Mayr's
>> >> >>>> ideas about speciation, which Ernst Mayr may have equated
>> >> >>>>with the ToE,
>> >> >>>> but few others would. The reason established species
>> >> >>>>supposedly become
>> >> >>>> buffered against change is the supposed existence of "coadapted gene
>> >> >>>> complexes". A change in one gene bumps up against its fit to other
>> >> >>>> genes, and is selected against. To allow any change, either a lot of
>> >> >>>> genes would have to be mutated at once in a coordinated fashion (very
>> >> >>>> unlikely) or a population bottleneck would have to allow drift to
>> >> >>>> dominate, breaking up those supposed complexes. And the
>> >> >>>>latter is what
>> >> >>>> Mayr (and through him, Eldredge and Gould) proposed. That's why large
>> >> >>>> populations are suposedly unable to change, and speciation
>> >> >>>>and evolution
>> >> >>>> supposedly happen only in peripheral isolates.
>> >> >>>> Now population geneticists generally suppose that adaptive
>> >> >>>>evolution is
>> >> >>>> actually easier in large populations, because there's a
non-sequitur, and emphasises your ignorance of the subject. Perhaps if
you were to read Mayr, E., Change of Genetic Environment and Evolution,
published in Huxley, Hardy and Ford, Evolution as a Process: 157-180 (or
183-213, depending on edition) you would realise how much egg you're
spreading on your face.
[There used to a copy up on the web, as part of a collection of 20
classic texts on evolution, but it seems to have disappeared, so it
would seem that you will have to use a library. (A second hand copy of
the 2nd edn of 1958 will cost you $25.00 - the paperback edition of 1963
for $7, if I'm correct in inferring that this is the same book.)]
--
alias Ernest Major
Ray Martinez
Yep, you didn't know that Mayr was not a gene-centrist. It is
confirmed by your 'publication mining.' Rejecting gene-centricism does
not mean rejection of the discipline. It means a person has a
different center of primary evidence. Go ask Larry Moran about Mayr,
and then wipe the egg off of your own face.
Ray
Ernest Major
<2ede9afe-fdc9-432e...@f5g2000yqh.googlegroups.com>, Ray
Martinez <pyram...@yahoo.com> writes
>On Jan 12, 10:42�am, Ernest Major <{$t...@meden.demon.co.uk> wrote:
>> In message
>> <2b7c9fbb-3323-44e0-ac4c-11e9c9ffd...@u7g2000yqm.googlegroups.com>, Ray
>> Martinez <pyramid...@yahoo.com> writes
>>
>>
>>
>> >On Jan 11, 1:36�pm, Ernest Major <{$t...@meden.demon.co.uk> wrote:
>> >> In message
>> >> <e9cf4395-783c-4acf-8f5f-7a17adff4...@u7g2000yqm.googlegroups.com>, Ray
>> >> Martinez <pyramid...@yahoo.com> writes
>>
>> >> >On Jan 11, 10:50�am, John Harshman <jharsh...@pacbell.net> wrote:
>> >> >> Ray Martinez wrote:
>> >> >> > On Jan 10, 5:25 pm, John Harshman <jharsh...@pacbell.net> wrote:
>> >> >> >> Ray Martinez wrote:
>> >> >> >>> On Jan 7, 1:04 pm, John Harshman <jharsh...@pacbell.net> wrote:
>> >> >> >>>> Antti Korhonen wrote:
>> >> >> >>>>> On Jan 7, 5:13 pm, Burkhard <b.scha...@ed.ac.uk> wrote:
>> >> >> >>>>>> On Jan 7, 2:22 am, All-seeing-I <ap...@email.com> wrote:
>> >> >> >>>>>>> What is "Punctuated equilibrium"?
>> >> >> >>>>>> A theoretical concept put forward by Eldredge and Gould, which
>> >> >> >>>>>> elaborated on ideas by Mayr. According to this model,
>> >> >> >>>>>>
>> >> >> >>>>>>time, and
>> >> >> >>>>>> when speciation takes palce, it happens in �"bursts" �over mere
>> >> >> >>>>>> thousands or tens of thousands of years.
>> >> >> >>>>>> This they argue is a direct consequence of the ToE: Once a
>>
>> >> >> >>>>>> adapted to a new habitat, one of the main driving forces of
>> >> >> >>>>>>evolution,
>> >> >> >>>>>> natural selection, becomes a conserving force (in this
>> >> >> >>>>>>
>> >> >> >>>>>>where change
>> >> >> >>>>>> in the environment has led to a �species becoming badly
>> >> >> >>>>>>adapted). �If
>> >> >> >>>>>> the population �is also �large, even beneficial mutations
>> >> >> >>>>>>unlikely
>> >> >> >>>>>> to get "fixed" due to interbreeding.
>> >> >> >>>> Not quite. They argue that it's a direct consequence of
>> >> >> >>>>
>> >> >> >>>>other evidence
>> >> >> >>>> from population genetics makes it appear unlikely that Mayr's
>> >> >> >>>>theory is
>> >> >> >>>> valid, leaving PE without a rationale.
>> >> >> >>> It's important to note that Mayr's theory exists in a state of
>> >> >> >>> acceptance by mainstream evolutionary biology----and it is
>> >> >> >>>
>> >> >> >> It's important to note that Ray exists in a state of having no clue
>> >> >> >> about evolutionary biology, as well as a state of arrogance
Mayr was not a gene-centrist but a naturalist is more or less true -
pace the implication that a naturalist cannot also be a gene-centrist -
but it is not relevant. As I said, your response was a non-sequitur.
Ernst Mayr, in his work as a naturalist, perceived a pattern of more
strongly divergent peripheral populations. From this he deduced that
more strongly divergent speciation occurs predominantly in peripheral
isolates. His next stage was to propose a mechanism for stasis in
central populations and divergence in peripheral isolates. This is what
led him to propose coadapted gene pools (to explain stasis) and genetic
revolutions (to explain their breakdown in peripheral isolates).
From the cited book chapter - "Isolating a few individuals (the
"founders") from a variable population which is situated in the midst of
the stream of genes which flows ceaselessly through every widespread
species will produce a sudden change of the genetic environment of most
loci. This change, in fact, is the most drastic genetic change (except
for polyploidy and hybridization) which may occur in a natural
population, since it may affect all loci at once. Indeed, it may have
the character of a veritable "*genetic revolution*.". (my emphasis)
On page 538 of Animal Species and Evolution (3rd printing of 1966) Mayr
writes, in a section headed "Consequences of the Genetic Revolution",
"During a genetic revolution, the population will pass from one
well-integrated and stable condition through a highly unstable period to
another period of balanced integration."
On page 615 he write "Since new characters are not produced by mutations
(as the typologists thought" but by a reorganisation of the genotype, it
may require a "genetic revolution" (Chapter 17) to break up the
perfectly buffered genotype."
The index doesn't contain the phrase "co-adapted gene pool", but I
presume that the lurkers can recognise the concept in "well-integrated
and stable condition", "balanced integration" and "perfectly buffered
genotype".
However, on page 295 he write 'The process by which genes are
accumulated in the gene pool that collaborate harmoniously is called
"integration" or "coadaptation".'
--
alias Ernest Major
Ray Martinez
It is true, not "more or less."
> pace the implication that a naturalist cannot also be a gene-centrist -
> but it is not relevant. As I said, your response was a non-sequitur.
>
Here again is what I said:
"Rejecting gene-centricism does not mean rejection of the discipline.
It means a person has a
different center of primary evidence."
It appears that you do not know what a naturalist is in this context.
In this context a naturalist is a scientist who rejects gene-
centricism and accepts the traditional evidence of evolution as his
center of primary evidence, like Darwin.
Mayr never based evolution on a change in gene frequencies. The same
was auxilliary. You, like Harshman, are forgetting that Mayr's
speciation theory is NOT based----primarily----on molecular evidence.
Ray