Re: The driving force of evolution

On Aug 9, 3:03 am, forbisga...@xxxxxxx wrote:
On Aug 8, 6:46 pm, "J.A. Legris" <jaleg...@xxxxxxxxxxxx> wrote:



On Aug 8, 4:59 pm, Wolf <ElLoboVi...@xxxxxxxxxx> wrote:

J.A. Legris wrote:

[...]

That's my point. It will make more sense once you've read the article.
It's only 8 pages long.

--
Joe

Er, Joe, how can eight page paper make sense if the thesis stated in the
abstract doesn't make sense? I mean, the final sentence of the abstract
is the paper's thesis, isn't it? Masatoshi Nei wrote:

"It appears that the driving force of phenotypic evolution is mutation,
and natural selection is of secondary importance."

It seems obvious to me that whatever mutations occur can have no effect
on the phenotype unless they confer some adaptive advantage, or unless
the owner of that new mutation has some other adaptive advantage that
permits or enables genetic drift. In either case, natural selection will
be the "driving force," by which I presume Masatoshi Nei refers to the
event(s) that initiate some more or less permanent change in a species'
phenotype.

The most charitable interpretation of Masatoshi Nei's paper is that he's
quibbling about the semantics of 'driving force.'

HTH

RTFP

I was going to but I'm not willing to spend money to do so.

This item requires a subscription to Proceedings of the National
Academy of Sciences Online.

I share the concern of others but differ slightly.
If someone asked me what drove the consumer market
the production of goods or its cosumption I'd
just look at them quizically. Consumers cannot buy
that which is not produced but production isn't
sufficient cause for consumption despite some people's
vigorous assertion of a variant of "Say's law"
that goes "production creates its own demand."


The price of the paper is the first valid criticism posted here.

Nei argues that before selection can act on phenotypes, the underlying
genetic mutations must occur, most of which have insignificant effects
on the phenotype, as indicated by the large amount of neutral genetic
variation within species. The mutations that are significant drive the
phenotype down developmental pathways that are unpredictable and
tightly restrictive on subsequent viable mutations. Natural selection
is the final arbiter of which mutations persist, but the mutations
themselves are setting the agenda. As I see it, an analogy is that of
a highly creative artist producing new works that are released into
the market. The artist must update his materials and techniques to
follow popular trends, but the selectivity of the market is secondary
to his creative output.

--
Joe

Here's a quotation from Nei's closing section:
================================================

In this article, I have examined various types of molecular data
concerning the evolution of phenotypic characters from the point of
view of the selectionism/mutationism controversy. The main conclusions
are as follows. (i) A multigene family concerned with basic
developmental processes (e.g., HOX genes) is generally highly
conserved, but the number of gene copies involved tends to increase
with increasing complexity of the organism or the character. (ii) When
a physiological character is controlled by a gene family, the number
of gene copies may vary extensively among different organisms, and
there are many pseudogenes in the genome. There are also extensive
polymorphisms of copy number within species. This high degree of copy
number variation is caused by genomic drif t as well as by
environmental factors. (iii) The evolutionar y change of physiological
and morphological characters occurs by mutational changes of the
protein-coding and regulatory regions of genes. The genes controlling
the characters expressed in the early stage of development are highly
conserved, and evolutionary changes occur primarily in the characters
expressed in
later stages of development. At the nucleotide level, the driving
force of phenotypic evolution is mutation, and there is a significant
component of neutral or nearly neutral changes. (iv) The prospective
view of evolution suggests that evolution occurs without purpose by
mutation and adaptation to new environmental conditions, and therefore
it is intrinsically unpredictable.

As mentioned in the introduction, a majority of current evolutionists
believe in neo-Darwinism. In one of the most popular textbooks on
evolution, Futuyma (ref. 20, p. 10) states that evolutionary change is
a population process in which one genotype replaces other
ones, and for this process to occur, mut ation is quite ineffective
because of its low rate of occurrence, whereas even the slightest
intensity of natural selection can bring about substantial change in a
realistic amount of time. He also states ''Natural selection can
account for both slight and great differences among species, and
adaptations are traits that have been shaped by natural selection.''
Although this type of statement is quite common in the evolutionar y
literature, it is obvious that any advantageous genotype is produced
by mutation including all kinds of genetic changes. Natural selection
occurs as a consequence of mutational production of different
genotypes, and therefore it is not the fundamental cause of
evolution.

Most molecular evolutionists are well aware of the importance of
mutation in protein evolution. Yet, many investigators are trying to
identify even the slightest trace of natural selection using various
statistical methods (99 -102). Using these methods, a number of
authors have reported that a substantial proportion of amino acid
substitutions are caused by positive Darwinian selection (103-106).
However, the statistical methods used are based on many assumptions,
which are not necessarily satisfied with actual data (18, 107, 108).
Furthermore, their estimates of selection coefficients are often of
the order of 10E-6 (100, 106) and are unlikely to affect gene function
(18). Note also that although these authors emphasized natural
selection, they are actually estimating the proportion of mutations
that are adaptive.

Historically, the word mutationism was used to refer to William
Bateson's saltationism or similar ideas, in which natural selection
plays little role. Later Morgan (109) presented a more reasonable form
of mutationism taking into account the role of natural selection. His
view was abstract and based on a few lines of speculative arguments.
However, recent molecular studies of phenotypic evolution support the
basic ideas of his view and have extended it to a more comprehensive
view presented in this article. If the new form of mutation theory
described here is right, even in its crudest form, more emphasis
should be given on the roles of mutation in the study of evolution.
Neo-Darwinians developed an impressive set of selection theories
concerning the evolution of sex (110), altruism (12), new species
(10), and others, without considering mutations that affect the
characters involved such as male and female reproductive organs. These
theories should be reexamined by studying the molecular basis of
physiological and morphological components of the characters involved.
It is also important to clarify the mechanism of formation of novel
characters by mutation whether selection is involved or not. A group
of molecular biologists are already working in this direction (111),
but participation of population biologists and genomic scientists in
this enterprise would speed up our understanding of phenotypic
evolution.

===========================================

.

Relevant Pages

  • Re: No distinction between artificial and natural selection - John
    ... can impart a direction to evolution. ... I don't know why it should be necessary because natural selection is ... I never would claim that mutation is not an important factor in ... The evolutionary mechanisms beyond selection include ...
    (talk.origins)
  • Re: No distinction between artificial and natural selection - John
    ... can impart a direction to evolution. ... I don't know why it should be necessary because natural selection is ... I never would claim that mutation is not an important factor in ... The evolutionary mechanisms beyond selection include ...
    (talk.origins)
  • Re: Seanpit, ID and complexity
    ... random mutation and I assume natural selection. ... Evolution was accepted in 1859 as a ... happened after it allegedly occurs based on various lines of evidence. ... I would define "random mutation" as the idea that "permanent changes ...
    (talk.origins)
  • Re: Seanpit, ID and complexity
    ... random mutation and I assume natural selection. ... definitions of "evolution." ... evolution within a species. ...
    (talk.origins)
  • Re: Natural selection is a false term - says Darwin in Origin Species
    ... language had any meaning at all. ... Chomsky says that natural selection can't explain where ... evolution for example are used so inter-changeably that nobody even ...
    (talk.origins)