Re: An introduction


In article <wLBRf.38567$_S7.36212@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
John Harshman <jharshman.diespamdie@xxxxxxxxxxx> wrote:

forcythe@xxxxxxx wrote:

In article <JbnRf.56362$Jd.7221@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
John Harshman <jharshman.diespamdie@xxxxxxxxxxx> wrote:


forcythe@xxxxxxx wrote:


Scientifically why is evolutionary theory treated almost exclusively as
Darwinism or Neo-Darwinism and its unyielding focus on natural
selection and an oversimplified concept of mutation via genetic
mutation? Both sides of the debate are often guilty of this error, and
it makes the whole discussion pretty useless.

Agreed for the first part. But it only makes a part of the discussion
useless.


Clearly natural
selection is very important as the "bottom line" so to speak,
determining in the end the differential advancement of existing
variation, but it speaks little to the source of variation.

Of course. It speaks nothing to the source of variation, which is mutation.

Genetic mutation is the "raw source" of variation, but alone is not a
strong enough force to explain the variation required for the evolution
we observe. Means for that genetic variation to spread and affect the
variety of phenotypic variation it may cause within populations is
necessary, and itself is a stronger force of evolution than mutation.
Here I'm thinking primarily of drift (and to a lesser extent
migration), too often ignored and necessary for the model to stand.

I don't actually think that drift is necessary to produce much of the
interesting (in an adaptive sense) variation we observe. It obviously
has big effects on the total variation. But in the complete absence of
drift we would still see most of the same diversity of phenotypes
between species, and most of the adaptive evolution. Drift is clearly an
important player, though, since most variation is neutral. There may be
some confusion about what "source of variation" means.


I'm happy I've got at least one point on which to respond to you here
unsullied by my more egregious slips in terminology. Unfortunately
there doesn't seem to be much to grab on to here except to say I'm not
sure I agree.

My understanding of evolution has a heavy component of population
genetics, and my understanding of population genetics has drift as a
major player in shaping the variability of a population to give
selection something to act upon. As a quick example (these seems to
get me in trouble), it's for this reason that I don't expect to see any
major movement in human evolution as long as we've got this global
population of 6 billion with few if any small isolated groups.
Furthermore, it accounts for much of my understanding of existing human
variability established previous to the rise of globalism. Without
such a population component, I don't understand how mutation alone
could have its necessary effect.


Let's not
forget the other forces of evolution that are at play. Phenotypic
mutation is not due to genetic mutation alone.

Phenotypic mutation is not a technical term, to my knowledge. Phenotypic
differences may or may not be related to genetic differences. But those
that aren't related to genetic differences can only rarely have any
significance to evolution.

Perhaps I was speaking a bit too casually there. I was trying to
distinguish between the sort of mutation that Darwin was able to
observe, referring to it as phenotypic mutation, and the genetic
mutations that the Neo-Darwinian synthesis draws upon to account for
it.

Genetic material is obviously the medium for inheritance and selection,
but mutation is not the only way that significant phenotype-altering
changes occur within the genome.

I'm waiting for you to explain the significant phenotype-altering
changes within the genome that are not mutation. Recombination accounts
for a bit, but not, I think, all that much. I don't think I would
consider additive genetic variance to be change "within the genome", either.

In other response to you in this thread, I came to the conclusion that
a source of confusion distracting from the point I was trying to make
was that I was using the term genome too broadly. You have made a
number of very valid points about what does and does not change genomes
based upon its proper definition, and I am now attempting to unravel my
point from that poor choice in terms. Unfortunately, that distinction
between the individual and population level that I blurred in my
terminology also seems to confound the deeper point about which I think
we may disagree.

So, given the words above, I defer completely to your point. And
rather than "genome-changing," I need a better term for that which
affects the genome that one inherits.

My understanding is that we see much more change as a result of new
combinations of existing genes than from the individual mutation within
a single genome. Mutation may keep feeding into the possible new
combinations of genes, but, hypothetically speaking, we have plenty of
variability stored up to continue evolution without mutation for quite
some time.


I see that Dr. Wilkes has elaborated further on additional types of
interaction between phenotypic change and genetic change that goes
beyond my area of intimate familiarity. Part of why I'm here is to
dust off my evolutionary theory and avoid its atrophy into something "I
once kept up with."

That's "Wilkins". Non-genetic inheritance is one of his current
enthusiasms. I'm not so excited about it. But you were talking
specifically about "within the genome", which leaves out all that stuff.
What exactly did you mean?

Terminology withdrawn as pointed out above, and apparently without any
specific relation to this point. I'm not sure if this notion of
non-genetic inheritance has come into vogue since I last caught up with
the literature or if it's uniquely "Wilkins," but it seems an
interesting point.


There are much stronger
forces at work to change genomes than mutation.

If there are, I don't know about them, or any evidence for their
existence. Can you explain?

For example, the ability for drift along with your basic meiosis to
shift the frequency and combination of genes in a population has a much
stronger and swifter effect than the introduction of new genes through
genetic mutation alone. New genes via mutation are necessary, but not
sufficient.

Again, I think they are sufficient to account for the sorts of changes
we usually find interesting, and the sorts of changes that Darwin was
looking at. I study neutral evolution quite a bit, but almost none of
that would have been visible to Darwin.

Well, if we can get past this first round if miscommunications that
I've fueled, I think this topic is where I would enjoy picking up.


Also, you seem to be confusing changes "within the genome" with changes
within the population. Drift of course influences the latter.

This same poor choice of words pointed out again, and again I defer to
your correction.


Well, if this doesn't get my urge to post off my chest, I hope to take
part in the conversations to come. I look forward to the assaults from
all sides that typify this debate.

You will not be disappointed, though you might not get any replies from
creationists.

That has been another beef as I've lurked and watched the debate, but
not one that I figured I could affect in any significant way :(

The problem is that most of the creationists we get here are barely
literate, much less scientifically literate. And many of them are just
crazy. That doesn't leave many who read, think, and make considered
replies. I don't know if the creationist population of TO is
representative of the creationist population as a whole, or whether they
are self-selected.

Based on my encounters in the "real world" as contrasted to those here,
I have to think that they're self selected.

.

Relevant Pages

  • Re: Uncommondescent on "Darwins theory"
    ... Darwin never said "random mutatoins" anywhere in his book OoS ... what Darwin called "variation" ... Can you point me to where he used the word "mutation" to refer to ... about genetics? ...
    (talk.origins)
  • Re: Is the complexity of evolutionary change explainable?
    ... area of genetics and those that are questioning that the alhorithm is ... And does it put the mutation rate ... And of course we need to know the genes and mutations involved ...
    (talk.origins)
  • Re: The driving force of evolution
    ... genetic drift) cannot compete and win against non random selection. ... genetics account for all the heritable differences between say, ... where a single mutation in a single protein alters the way an entire cell ... The answer that makes most sense is that when a single amino acid ...
    (sci.bio.evolution)
  • Re: Was the hebrew bible written by Romans?
    ... mutation PLUS zero or more additional mutations. ... those who confuse genetics with the German Socialist Nutcase Party can ... these provide the actual founder ... both descendants of the founder for R. The haplogroup founders for Q ...
    (soc.history.ancient)
  • Re: Was the hebrew bible written by Romans?
    ... mutation PLUS zero or more additional mutations. ... those who confuse genetics with the German Socialist Nutcase Party can ... these provide the actual founder ... both descendants of the founder for R. The haplogroup founders for Q ...
    (soc.history.ancient)