Dawkins on Kimura

in article [email hidden], Tim Tyler at [email hidden]
wrote on 2/22/04 10:56 PM:

Quoted message said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
"evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
of natural selection (e.g., populations of reproducing agents), they will look increasingly like closed-
minded zealots as time goes on. At this point, I think it is absurd and telling that Dawkins begins
his argument with such a false premise as "Darwinian selection remains the only explanation for
adaptive evolution."

Quoted message said:

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events - but
it's probably a bit player in most other places - as far as the *features* of organisms go (as
opposed to the makeup of their genes).

Is this all just a gut feeling on your part? That would be fine. I just want to know if there is any
reason your assertion should be persuasive to others.

Cheers,

Guy

Tim Tyler said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events - but
it's probably a bit player in most other places - as far as the *features* of organisms go (as
opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
old age, have different reactions to medications, have different physical abilities like being able
to run for long distances, sing very well, be really strong, and so on and so on -- these are all
the result of adaptations and natural selection?

Wow.

[email hidden]

Guy Hoelzer <[email hidden]> wrote or quoted:

Quoted message said:

in article [email hidden], Tim Tyler at [email hidden]

Quoted message said:

Quoted message said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
"evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
of natural selection (e.g., populations of reproducing agents), they will look increasingly like
closed-minded zealots as time goes on. At this point, I think it is absurd and telling that
Dawkins begins his argument with such a false premise as "Darwinian selection remains the only
explanation for adaptive evolution."

I can't really make out what you are on about here.

It seems as though you are asserting that "populations of reproducing agents" "lack the basic
ingredients for the process of natural selection".

That doesn't seem to make much sense.

Or maybe you are saying that evolution (of a sort) can occur in some systems which "lack the basic
ingredients for the process of natural selection". I guess that is true in theory - e.g. if you have
a hypothetical system - where agents all reproduce at the same rate - and have no phenotype and
can't influence their own copying rate in any way, then evolution will occur solely by drift. I'm
not sure where Dawkins' views come in, though.

Quoted message said:

Quoted message said:

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events -
but it's probably a bit player in most other places - as far as the *features* of organisms go
(as opposed to the makeup of their genes).

Is this all just a gut feeling on your part? That would be fine. I just want to know if there is
any reason your assertion should be persuasive to others.

Drift is most effective when population sizes are small. Selection is most effective when population
sizes are large. I reckon this fact (in conjunction with nature's population sizes) will often
limit's drift's usefulness as an explanation for features of organisms.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove lock to reply.

dkomo said:

Tim Tyler said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events - but
it's probably a bit player in most other places - as far as the *features* of organisms go (as
opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
old age, have different reactions to medications, have different physical abilities like being
able to run for long distances, sing very well, be really strong, and so on and so on -- these are
all the result of adaptations and natural selection?

Why not? Their ancestors have experienced different environments, so hte selective pressures will be
different. Add into the mix variation in the environment (which can help maintain polymorphism), and
disruptive selection, we have plenty of adaptive explanations for the diversity we see.

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

Bob

--
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗ Journal
of Negative Results - EEB: jnr-eeb.orgjnr-eeb.orgOpen ↗

dkomo <[email hidden]> wrote or quoted:

Quoted message said:

Tim Tyler wrote:

Quoted message said:

Quoted message said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events -
but it's probably a bit player in most other places - as far as the *features* of organisms go
(as opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
old age, have different reactions to medications, have different physical abilities like being
able to run for long distances, sing very well, be really strong, and so on and so on -- these are
all the result of adaptations and natural selection?

Drift and selecion are theories of *evolutionary change*. You are just talking about variation.

There can be as much variation in a population you like without the structure of the population
changing over time.

Also, merely pointing out the existence of variation in a trait does not demonstrate it is neutral
(or near enough neutral to be subject to drift) - since:

* there is such a thing as frequency-dependent selection;
* most of the members of the population will not be long-term ancestors - and any variation they
exhibit is of pretty low relevance;

The second point grows in force when you take a gene's eye view.

Of your examples, I would identify the best one as "eye colour".

There /may/ be a case that eye colour is the subject of drift.

***If*** so, eye colour would be one of the things I classified as a "minor feature".

However I am not convinced that eye colour is anywhere remotely *near* neutral.

existence of variation in it can be explained adaptively by the hypothesis that those with unusual
iris colours tend to be preferred mates.

Further, there is geographic variation in the trait - which suggests to me adaptation as a
sun-shield.

If eye colour is *not* significantly under the influence of selection, how come nature has chosen
bright pure pigments for the irises of the eyes of many people's in northern regions - while
ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and were
most exposed to the sun?

In summary, I think there are plenty of signs that iris colouration is strongly adaptive.

Where is the evidence that the spectrum of iris colourations observed in human populations is
due to drift?
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove lock to reply.

Tim Tyler said:

Drift is most effective when population sizes are small. Selection is most effective when
population sizes are large. I reckon this fact (in conjunction with nature's population sizes)
will often limit's drift's usefulness as an explanation for features of organisms.

What is "drift"? Genes mutate randomly, malign mutations die out, mutations that have no effect on
an organism don't really matter and beneficial mutations propagate and supplant organisms without
that mutation. This generally leads to a new species, in time. But what's "drift"?

--Jeff

--
Ho, ho, ho, hee, hee, hee and a couple of ha, ha, has; That's how we pass the day away, in the merry
old land of Oz.

Anon. <[email hidden]> wrote or quoted:

Quoted message said:

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

It may be hard to do - but should be possible in principle:

If you used a large population and "stirred" it well, the effects of drift would become very small
compared to selection.

You could similarly create circumstances that emphasised drift - small populations - with death
striking young individuals at random.

These sorts of experiments or observations should - in principle - have the power to tease out the
effects of drift and selection empirically - and distinguish between hypotheses about to what extent
the forces contribute to the forms of organisms.

In theory, drift can help populations escape local maxima that selection would leave them stuck
on. Quantifying that effect seems like an important task for the participants in the drift vs
selection debate.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove lock to reply.

On Tue, 24 Feb 2004 20:57:29 +0000 (UTC),
Tim Tyler <[email hidden]> wrote:

[snip]

Quoted message said:

Where is the evidence that the spectrum of iris colourations observed in human populations is due
to drift?

It's probably hidden in the same place as the evidence that it's due to natural selection.

Larry Moran

Anon. said:

dkomo said:

Tim Tyler wrote:

[snip]

Quoted message said:

Quoted message said:

Quoted message said:

Drift may have something to say about small populations on islands around speciation events - but
it's probably a bit player in most other places - as far as the *features* of organisms go (as
opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
old age, have different reactions to medications, have different physical abilities like being
able to run for long distances, sing very well, be really strong, and so on and so on -- these
are all the result of adaptations and natural selection?

Why not? Their ancestors have experienced different environments, so hte selective pressures will
be different. Add into the mix variation in the environment (which can help maintain
polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
diversity we see.

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

Yes. Until we can actually test the hypotheses it's wise not to *assume* that all morphological
features are adaptations, don't you think?

Tim seems to be making the default assumption that most morphological features are due to natural
selection. Dawkins certainly makes that assumption. Is this valid?

Larry Moran

in article [email hidden], Tim Tyler at [email hidden]
wrote on 2/23/04 7:53 PM:

Quoted message said:

Guy Hoelzer <[email hidden]> wrote or quoted:

Quoted message said:

in article [email hidden], Tim Tyler at [email hidden]

Quoted message said:

Quoted message said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
"evolution" in complex dynamical systems that seemingly lack the basic ingredients for the
process of natural selection (e.g., populations of reproducing agents), they will look
increasingly like closed-minded zealots as time goes on. At this point, I think it is absurd and
telling that Dawkins begins his argument with such a false premise as "Darwinian selection
remains the only explanation for adaptive evolution."

I can't really make out what you are on about here.

Sorry. My argument got drowned out by my anti-Dawkins rant.

Quoted message said:

It seems as though you are asserting that "populations of reproducing agents" "lack the basic
ingredients for the process of natural selection".

That doesn't seem to make much sense.

Nor I. It is not what I meant to say. What I meant was that natural selection is a mechanism of
adaptive evolution exhibited by "populations of reproducing agents", but no justification has ever
been offered AFAIK for the position that it is the only possible mechanism in this context. Now that
it is clear that optimizing, adaptive processes occur in all sorts of contexts, manifesting an array
of mechanisms, I think the view espoused by Dawkins above is no longer tenable.

Quoted message said:

Or maybe you are saying that evolution (of a sort) can occur in some systems which "lack the basic
ingredients for the process of natural selection".

Yes. This is part of my view.

Quoted message said:

I guess that is true in theory - e.g. if you have a hypothetical system - where agents all
reproduce at the same rate - and have no phenotype and can't influence their own copying rate
in any way, then evolution will occur solely by drift. I'm not sure where Dawkins' views come
in, though.

Right. This is all fine, but off the point and not what I meant to say. My point was that natural
selection is not the only possible adaptive process.

Quoted message said:

Quoted message said:

Quoted message said:

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events -
but it's probably a bit player in most other places - as far as the *features* of organisms go
(as opposed to the makeup of their genes).

Is this all just a gut feeling on your part? That would be fine. I just want to know if there is
any reason your assertion should be persuasive to others.

Drift is most effective when population sizes are small. Selection is most effective when
population sizes are large. I reckon this fact (in conjunction with nature's population sizes)
will often limit's drift's usefulness as an explanation for features of organisms.

You must also be making an implicit assumption about the typical strength of selection in natural
populations, because drift operates in all finite populations of any size. In other words, drift can
dominate weak selection in large populations, and even strong selection in small populations (e.g.
mutational meltdown). The balance between the influences of drift an selection was explored
explicitly in Ota's Nearly Neutral model.

So what is the basis for your expectation that selection is usually strong enough to relegate drift
to being a "bit player" in natural populations?

Cheers,

Guy

Tim Tyler said:

dkomo <[email hidden]> wrote or quoted:

Quoted message said:

Tim Tyler wrote:

Quoted message said:

Quoted message said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
(I would argue) that most if not all the evolutionary changes we actually see in the
macroscopic world (as opposed to those concealed among the molecules) are adaptive and
Darwinian.'' - A Devil's Chaplain, p.85.

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events -
but it's probably a bit player in most other places - as far as the *features* of organisms go
(as opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases
in old age, have different reactions to medications, have different physical abilities like
being able to run for long distances, sing very well, be really strong, and so on and so on --
these are all the result of adaptations and natural selection?

Drift and selecion are theories of *evolutionary change*. You are just talking about variation.

There can be as much variation in a population you like without the structure of the population
changing over time.

That's what I'm getting at. Drift and selection are not the only alternatives. It's possible to have
*no* selection and *no* drift (if the population is large). The allele frequencies will remain
constant according to the Hardy-Weinberg Law.

Quoted message said:

Also, merely pointing out the existence of variation in a trait does not demonstrate it is neutral
(or near enough neutral to be subject to drift) - since:

Neither does pointing out the existence of a trait demonstrate that it is an adaptation that
occurred in the past. People who believe that most or all features of organisms have been selected
for are known as "panadaptationists." Dawkins is certainly one. Gould certainly was not. I was under
the impression that panadaptationism is frowned upon these days by most evolutionists.

I think many of the traits I pointed out are either what Gould called "spandrels":

spandrel.comabout.htmlOpen ↗

or they are neutral mutations that have persisted within human populations for a very long time.
They are *not* adaptations to anything.

Quoted message said:

* there is such a thing as frequency-dependent selection;
* most of the members of the population will not be long-term ancestors - and any variation they
exhibit is of pretty low relevance;

The second point grows in force when you take a gene's eye view.

Of your examples, I would identify the best one as "eye colour".

There /may/ be a case that eye colour is the subject of drift.

Why does it have to be the subject of drift? It could simply be an allele which is not under
selection and whose frequency remains pretty constant in a particular human subpopulation.

Quoted message said:

***If*** so, eye colour would be one of the things I classified as a "minor feature".

However I am not convinced that eye colour is anywhere remotely *near* neutral.

Quoted message said:

existence of variation in it can be explained adaptively by the hypothesis that those with unusual
iris colours tend to be preferred mates.

Further, there is geographic variation in the trait - which suggests to me adaptation as a
sun-shield.

If eye colour is *not* significantly under the influence of selection, how come nature has chosen
bright pure pigments for the irises of the eyes of many people's in northern regions - while
ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and
were most exposed to the sun?

In summary, I think there are plenty of signs that iris colouration is strongly adaptive.

It could be. I'm not the diametric opposite of a panadaptationist, as one well known poster to this
group is, but I do insist that the burden of proof lies with those who claim that particular traits
are adaptations. You made an argument about eye color, but you don't have any empirical proof. And
this, unfortunately, is the case with most features of organisms. We simply have no direct proof
that they are in fact adaptations, even though we accept the principles of variation and selection.

Quoted message said:

Where is the evidence that the spectrum of iris colourations observed in human populations is due
to drift?

False dichotomy. It's not selection *or* drift (or even both operating at the same time). Iris
colourations could simply be neural traits that are subject to neither, being in Hardy-Weinberg
equilibrium.

[email hidden]

Anon. said:

dkomo said:

Tim Tyler said:

Another quotable bit:

``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
Devil's Chaplain, p.85.

I'm not sure about the "all" but I'm inclined to agree with the "most".

Drift may have something to say about small populations on islands around speciation events -
but it's probably a bit player in most other places - as far as the *features* of organisms go
(as opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases
in old age, have different reactions to medications, have different physical abilities like
being able to run for long distances, sing very well, be really strong, and so on and so on --
these are all the result of adaptations and natural selection?

Why not? Their ancestors have experienced different environments, so hte selective pressures will
be different. Add into the mix variation in the environment (which can help maintain
polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
diversity we see.

Bah! Sounds like panadaptationism. See my reply to Tim Tyler.

We have plenty of "just so" stories to explain each and every purported adaptation. Any amateur
evolution theorist can come up with half a dozen armchair explanations for each such trait. What we
don't have in most cases is empirical proof that a particular feature of an organisn is indeed an
adaptation to the environment.

Quoted message said:

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

It may be that many features of organisms are incidental and play no role in their evolution. That
doesn't necessarily imply that these features are subject to drift. Drift is a phenomenon of small,
isolated populations.

[email hidden]

Quoted message said:

Dawkins quote: ``Darwinian selection remains the only explanation for adaptive evolution - and it
is arguable (I would argue) that most if not all the evolutionary changes we actually see in the
macroscopic world (as opposed to those concealed among the molecules) are adaptive and
Darwinian.'' - A Devil's Chaplain, p.85.

GH:- IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
"evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
of natural selection (e.g., populations of reproducing agents), they will look increasingly like closed-
minded zealots as time goes on. At this point, I think it is absurd and telling that Dawkins begins
his argument with such a false premise as "Darwinian selection remains the only explanation for
adaptive evolution."

JE:- Darwinian selection _does_ remain the only _testable_ explanation for adaptive evolution.
However, Dawkins et al have NOT represented the Darwinian argument, they have only represented the
Hamiltonian argument which is competitive to the Darwinian argument. It is entirely incorrect to
suggest that gene centric Neo Darwinism somehow represents Darwin's original theory of evolution by
natural selection.

The Hamiltonian argument fails because empirically, genes only have a _dependent_ fitness. What are
they entirely fitness dependent on? The Darwinian _fertile_ organism level of selection. Hamilton
_artificially_ split the single Darwinian fertile organism level into two independent levels within
just an over simplified model allowing just a hypothetical gene level of selection to compete and
win against the empirical Darwinian level forcing organism fitness altruism. Hamilton's model
deleted all genetic epistasis whereas the Darwinian argument included it.

Quoted message said:

I'm not sure about the "all" but I'm inclined to agree with the "most". Drift may have something
to say about small populations on islands around speciation events - but it's probably a bit
player in most other places - as far as the *features* of organisms go (as opposed to the makeup
of their genes).

GH:- Is this all just a gut feeling on your part? That would be fine. I just want to know if there
is any reason your assertion should be persuasive to others.

JE:- Sampling error is just a random event. This being the case, it can only be validly supposed to
cause temporal variation and not evolution. Once you allow sampling error as causative to evolution
within evolutionary theory, you reduce this theory to a non testable status. The testability of
evolution by Darwinian natural selection is not removed if sampling error is regarded as either
random or non random _variation_ because variation is not causative to evolution it is just one of
many limiting factors within the Darwinian theory of evolution.

Regards,

John Edser Independent Researcher

PO Box 266 Church Pt NSW 2105 Australia

[email hidden]

in article [email hidden], Tim Tyler at [email hidden]
wrote on 25/2/04 9:57 AM:

Quoted message said:

If eye colour is *not* significantly under the influence of selection, how come nature has chosen
bright pure pigments for the irises of the eyes of many people's in northern regions - while
ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and
were most exposed to the sun?

In summary, I think there are plenty of signs that iris colouration is strongly adaptive

The genetics of eye colour are not yet well understood
athro.cominherit1.htmlOpen ↗ But even if there is selection for eye
colour. Which genes contribute to that phenotype is probably the result of a kind of genetic drift
unless the population contained all possible mutations that could contribute to to the desired
phenotype at the same time. That is, for selection of the sequence that was best at giving the brown
eye colour phenotype, to occur. The population would have to be infinite. Selection acts on
phenotype, the neutral theory applies to genotype.
--

Phillip Smith [email hidden] replace bugger with ihug applied-evolution.co.nzapplied-evolution.co.nzOpen ↗

"he who is smeared with blubber has the kindest heart" -- a Greenland Eskimo adage

dkomo <[email hidden]> wrote or quoted:

Quoted message said:

Tim Tyler said:

dkomo <[email hidden]> wrote or quoted:

Quoted message said:

Tim Tyler wrote:

Quoted message said:

Quoted message said:

Quoted message said:

> Drift may have something to say about small populations on islands around speciation events
> - but it's probably a bit player in most other places - as far as the *features* of
> organisms go (as opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat
or skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different
diseases in old age, have different reactions to medications, have different physical
abilities like being able to run for long distances, sing very well, be really strong, and so
on and so on -- these are all the result of adaptations and natural selection?

Drift and selecion are theories of *evolutionary change*. You are just talking about variation.

There can be as much variation in a population you like without the structure of the population
changing over time.

That's what I'm getting at. Drift and selection are not the only alternatives. It's possible to
have *no* selection and *no* drift (if the population is large). The allele frequencies will
remain constant according to the Hardy-Weinberg Law.

Large populations slow down - but don't eliminate - drift.

You only get no drift in an infinite population - and then it makes no sense to talk about gene
frequencies at all.

Quoted message said:

Quoted message said:

Also, merely pointing out the existence of variation in a trait does not demonstrate it is
neutral (or near enough neutral to be subject to drift) - since:

Neither does pointing out the existence of a trait demonstrate that it is an adaptation that
occurred in the past.

Of course.

Quoted message said:

People who believe that most or all features of organisms have been selected for are known as
"panadaptationists."

Genetic drift is enough to indicate than not all features of organisms have necessarily been
selected for.

Attributing "most" things to selection seems quite reasonable to me, though.

Quoted message said:

I was under the impression that panadaptationism is frowned upon these days by most evolutionists.

Adaptations are certainly all over the place.

"Panadaptationism" is - or ought to mean "adaptations everywhere" - but exactly how common that is
supposed to mean isn't clear.

The word doesn't seem to be in the dictionary - has anyone actually bothered to define it - or is it
just a term of derision?

Quoted message said:

I think many of the traits I pointed out are either what Gould called "spandrels":

spandrel.comabout.htmlOpen ↗

or they are neutral mutations that have persisted within human populations for a very long time.
They are *not* adaptations to anything.

Most of your traits were statements about the existence of variation within in a trait.

You mentioned: brown, green, or blue eyes, being short or tall, being fat or skinny, being beautiful
or ugly, having red, black or blonde hair - and so on.

I've discussed eye colour already. Height is an adaptive trait - perhaps with some frequency
dependent selection for different heights being caused by the existence of different
lifestyles. Similarly with weight. Also, a fair bit of the observed variation in both traits is
not genetic at all.

Beauty is adaptive - and being ugly is mal-adaptive - and exists through being constantly generated
- and not yet having been weeded out. Hair colour is also adaptive. Black hair protects against UV
radiation - and that's why all African types have black hair (except a few albinos who soon get
ill). Red and blond hair are (I claim) clearly the result

Quoted message said:

Quoted message said:

* there is such a thing as frequency-dependent selection;
* most of the members of the population will not be long-term ancestors - and any variation they
exhibit is of pretty low relevance;

The second point grows in force when you take a gene's eye view.

Of your examples, I would identify the best one as "eye colour".

There /may/ be a case that eye colour is the subject of drift.

Why does it have to be the subject of drift? It could simply be an allele which is not under
selection and whose frequency remains pretty constant in a particular human subpopulation.

If the population is finite, it will drift.

Quoted message said:

Quoted message said:

***If*** so, eye colour would be one of the things I classified as a "minor feature".

However I am not convinced that eye colour is anywhere remotely *near* neutral.

Quoted message said:

Quoted message said:

existence of variation in it can be explained adaptively by the hypothesis that those with
unusual iris colours tend to be preferred mates.

Further, there is geographic variation in the trait - which suggests to me adaptation as a sun-
shield.

If eye colour is *not* significantly under the influence of selection, how come nature has
chosen bright pure pigments for the irises of the eyes of many people's in northern regions -
while ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the
equator and were most exposed to the sun?

In summary, I think there are plenty of signs that iris colouration is strongly adaptive.

It could be. I'm not the diametric opposite of a panadaptationist, as one well known poster to
this group is, but I do insist that the burden of proof lies with those who claim that particular
traits are adaptations.

Hmm. It seems to me that whenever I get into a discussion there's always someone who claims that the
burden of proof lies on my side.

Nine times out of ten I can't see why that is the case - and this is one of them.

I suggest "adaptation" should *normally* be the default hypothesis - because adaptation has shown
itself to be the best, most powerful theory for accounting for the forms of organisms.

That's not to say that it's responsible for *everything* - but that - if anything - the burden of
proof ought to normally be on the drift side of the fence - since drift typically hasn't been shown
to be responsible for very much of anything.

Quoted message said:

You made an argument about eye color, but you don't have any empirical proof.

...but I could soon find some on request. The dark eyes of african populations is a well known fact
- and has no explanation under the hypothesis that iris colour is subject to drift.

eye colour being adaptive, though ;-)

Frequency-dependent selection favouring rare eye colours has been demonstrated in Drosophila
melanogaster - I believe - in:

``Minority mating advantage of certain eye color mutants of Drosophila
melanogaster. IV. Female discrimination among three genotypes.''

- calorierestriction.orgpmidOpen ↗

...but this just demonstrates that the idea is plausible - not that it is responsible for the
observed human variation.
--
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phillip smith <[email hidden]> wrote or quoted:

Quoted message said:

Tim Tyler at [email hidden] wrote on 25/2/04 9:57 AM:

Quoted message said:

Quoted message said:

If eye colour is *not* significantly under the influence of selection, how come nature has
chosen bright pure pigments for the irises of the eyes of many people's in northern regions -
while ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the
equator and were most exposed to the sun?

In summary, I think there are plenty of signs that iris colouration is strongly adaptive

The genetics of eye colour are not yet well understood
athro.cominherit1.htmlOpen ↗ But even if there is selection for eye
colour. Which genes contribute to that phenotype is probably the result of a kind of genetic drift
unless the population contained all possible mutations that could contribute to to the desired
phenotype at the same time. That is, for selection of the sequence that was best at giving the
brown eye colour phenotype, to occur. The population would have to be infinite. Selection acts on
phenotype, the neutral theory applies to genotype.

That doesn't seem to make any sense. This bit:

"for selection of the sequence that was best at giving the brown eye colour phenotype, to occur. The
population would have to be infinite.''

...and this bit:

"Which genes contribute to that phenotype is probably the result of a kind of genetic drift unless
the population contained all possible mutations that could contribute to to the desired phenotype at
the same time."

...don't add up as arguments. Can you say what you mean more clearly?
--
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|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove lock to reply.

dkomo said:

Tim Tyler wrote:

<snip>

Quoted message said:

Why does it have to be the subject of drift? It could simply be an allele which is not under
selection and whose frequency remains pretty constant in a particular human subpopulation.

<snip>

Quoted message said:

Quoted message said:

Where is the evidence that the spectrum of iris colourations observed in human populations is due
to drift?

False dichotomy. It's not selection *or* drift (or even both operating at the same time). Iris
colourations could simply be neural traits that are subject to neither, being in Hardy-Weinberg
equilibrium.

OK, hands up all those who have studied the assumptions for HWE and still believe that it's a good
model of reality?

In this particular case, the fact that the population is finite (and the sub-populations are
smaller) means that drift WILL occur. It's just a fact of life (and death). And it's difficult to
see how you can have a polymorphism without one of the two acting at some stage.

Bob

--
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗ Journal
of Negative Results - EEB: jnr-eeb.orgjnr-eeb.orgOpen ↗

Tim Tyler said:

Anon. <[email hidden]> wrote or quoted:

Quoted message said:

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

It may be hard to do - but should be possible in principle:

If you used a large population and "stirred" it well, the effects of drift would become very small
compared to selection.

You could similarly create circumstances that emphasised drift - small populations - with death
striking young individuals at random.

These sorts of experiments or observations should - in principle - have the power to tease out the
effects of drift and selection empirically - and distinguish between hypotheses about to what
extent the forces contribute to the forms of organisms.

In theory, drift can help populations escape local maxima that selection would leave them stuck
on. Quantifying that effect seems like an important task for the participants in the drift vs
selection debate.

SBT anyone? There's been a lot of discussion about this (its called the Shifting Balance Theory).
The problem is that the theory is so complex that it's difficult to show all the bits working at the
same time. My own opinion is that SBT probably isn't very important, because if it was, we would
have plenty of examples of it by now. Scientific, huh?

Bob

--
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗ Journal
of Negative Results - EEB: jnr-eeb.orgjnr-eeb.orgOpen ↗

dkomo said:

Anon. said:

dkomo said:

Tim Tyler wrote:

>Another quotable bit:
>
>``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
>(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
>world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
>Devil's Chaplain, p.85.
>
>I'm not sure about the "all" but I'm inclined to agree with the "most".
>
>Drift may have something to say about small populations on islands around speciation events -
>but it's probably a bit player in most other places - as far as the *features* of organisms go
>(as opposed to the makeup of their genes).

Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
old age, have different reactions to medications, have different physical abilities like being
able to run for long distances, sing very well, be really strong, and so on and so on -- these
are all the result of adaptations and natural selection?

Why not? Their ancestors have experienced different environments, so hte selective pressures will
be different. Add into the mix variation in the environment (which can help maintain
polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
diversity we see.

Bah! Sounds like panadaptationism. See my reply to Tim Tyler.

We have plenty of "just so" stories to explain each and every purported adaptation. Any amateur
evolution theorist can come up with half a dozen armchair explanations for each such trait. What
we don't have in most cases is empirical proof that a particular feature of an organisn is indeed
an adaptation to the environment.

Yes, so we need empirical observation to resolve this argument. My point is that we know that
spatial and temporal variation in selection pressures occurs, so we can't rule them out just because
we don't like them. Examining their effects is difficult (I've looked at both. One study needed a 60
year time seies, the other merely a crossing experiment with a couple of thousand frogs).

Quoted message said:

Quoted message said:

Of course, drift may also be an explanation, but I believe that we can only separate out the
contributions of the different causes empirically.

It may be that many features of organisms are incidental and play no role in their evolution. That
doesn't necessarily imply that these features are subject to drift. Drift is a phenomenon of
small, isolated populations.

And there are a lot of them about, even in organisms like insects.

Bob

--
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗ Journal
of Negative Results - EEB: jnr-eeb.orgjnr-eeb.orgOpen ↗