Greetings Ladies (private):
Bertvan wrote: "Darwin's contribution to biology was the notion that the
diversity of nature can be accounted for by 'random mutation and natural
selection'."
I'm sure both of you are familiar with the idea that a civil law has both a
spirit and a literal written word component, such that an action may be
legal under the letter of the law, but can still violate the spirit of that
law? Well, the same thing can be said of claims like the above. The
spirit of what Bertvan said is correct, but the wording of the claim itself
is factually incorrect.
First of all, Darwin's contribution was two-fold: he established that
evolution was a fact of natural history and he proposed natural selection
as the explanation for this fact. Secondly, Darwin did not coin the word
mutation; in fact, the index of _Origin of Species_ does not contain that
word at all. The term was not invented until the early 1900's, well after
Darwin's death, and was based on the then knowledge of Mendelian genetics,
genes and chromosomes. So, Darwin could not have spoken of mutation;
instead, what he referred to was variation. Thirdly, Darwin never really
referred to variation being due to chance; instead he referred to it as
"unsolicited".
That may sound like nit-picking, but it isn't. Natural selection was based
on three assumptions: 1) nature has and continues to change, and so life
on earth must also change to survive; 2) nature provides an unlimited
supply of unsolicited, fortuitous, hereditary novelties; and 3) the
fertility of nature leads to a struggle for existence. Based on these
assumptions, Darwin concluded that, in the struggle for survival,
individuals who possess favorable novelties would survive while those who
did not would perish. He also concluded that, while each novelty in and of
itself was negligible, the steady accumulation of these novelties from one
generation to the next would produce changes which are far from negligible.
Darwin referred to his conclusion as "natural selection" and called such
novelties "variation". He did believed that these novelties appeared and
were acquired by random chance events (or as we say today, through
contingent events), but Darwin did not refer to these novelties as "random
novelties". Instead, his use of the term "unsolicited" indicates that he
saw these novelties as appearing independently of the actions and/or
desires of nature or the organism. (Whether Darwin believed that they were
also independent of the action and/or desire of God is in my opinion
uncertain.) In other words, I believe that to say that the novelties
appeared without purpose or plan is to say that a purpose or plan is
unnecessary, not that it does not exist. So to be accurate, as well as
fair, Bertvan's comment should be "unsolicited fortuitous variation and
natural selection."
The reason why this is not nit-picking is because, in Darwin's time, no one
knew how heredity worked. As such, while Darwin was convinced that
fortuitous variation in the form of unsolicited novelties was a reality, he
couldn't explain what caused them. In essence, Darwin's use of the term
variation was actually a description of what he saw in nature, not a
mechanism he proposed to explain where novelty came from. Darwin also
wanted to use a term that would indicate that evolution had occurred like
any other natural phenomenon: not as the result of some specific plan or
with a specific purpose, but independently of these anthropomorphic
considerations. At the very least he did not want to make the mistaken
impression that nature or living organisms were directly the cause of
evolution by their own actions and/or desires, so he used the term
unsolicited to describe variation.
"He stated that if this process were shown to be impossible by small,
gradual, incremental steps, his theory would collapse."
Here Bertvan seems to be suggesting that Darwin claimed that his theory
could be falsified by demonstrating that evolution occurred by "small,
gradual, incremental steps." Since in fact Darwin's theory is *based* on
this assumption, it cannot be used to refute it, so Bertvan may have worded
her claim incorrectly. What Darwin actually stated was that his theory
would be falsified if it could be shown that evolution did not occur by the
slow accumulation of unsolicited fortuitous novelties. Unfortunately,
Darwin's inability to explain where these novelties came from was a major
weakness for natural selection, and in fact Darwin originally toyed with
the idea that organisms could produce their own novelty, as suggested by
Lamarck. In the first five editions of his book, Darwin largely abandoned
this idea for his theory of unsolicited fortuitous novelties and natural
selection, but he also recognized that such a mechanism would require a
great length of time to allow for enough accumulation to account for the
diversity seen in the modern world, as well as the fact that these
accumulations would have to become permanent, two factors that Darwin could
not be certain about.
As such, when Lord Kelvin critiqued Darwin's theory by claiming that the
earth wasn't old enough to accumulate novelties slowly, and when Fleeming
Jenkin critiqued Darwin's theory by claiming that any novelty would become
diluted as it dispersed itself throughout a population (based on the then
popular notion that inheritance was based on a blending of traits), Darwin
had no ready answers. He secretly assumed that Kelvin was wrong, but he
nonetheless began to loose confidence in his own theories. He eventually
decided that there must be another mechanism in place that would hurry
evolutionary change in a purposive direction, so in the sixth and last
edition of his book he introduced the Lamarckian ideas that novelties could
be created by the environment and by the habits of the organism. He then
created the theory of pangenesis to explain how this would work. The
theory claimed that the cells responsible for reproduction acquired
characteristics from all the organs, structures and tissues of the body in
the form of particles called "gemmules" that would then instruct the sex
cells on how to create a new body. As such, any changes that occurred in
any organ, structure or tissue due to environment or habit would be passed
on to the next generation. We now know that this theory isn't true, but at
the time (circa 1870) it was able to explain the twin mysteries of
inheritance and ontogeny while at the same time explaining how evolution
could produce fortuitous novelties that brought about purposive change.
"As it was about to collapse, a bunch of biologists held a conference and
invented neo-Darwinism."
Unfortunately, this is simply not true. First of all, "Darwinism" as
Bertvan means it had collapsed before Darwin was even dead, and it was
Darwin more than anyone who caused the collapse. Darwin's theory of pan
genesis largely started the Lamarckian revival that gained momentum during
the 1870's and became dominant after his death.
Secondly, neo-Darwinism was invented by August Weismann in the late 1880's,
with the help of Alfred Russell Wallace. Both remained staunch
selectionists while the rest of their colleagues abandoned natural
selection in favor of acquired characteristics. Weismann was able to
demonstrate that there was no case of any successive generation inheriting
the acquired characteristics of the previous generation. In fact, if
anything, he established that the next generation invariably reverted to
type, regardless of the changes that occurred in the previous generation.
He explained this by pointing out that the only cells inherited by the
next generation from the previous generation were the sex cells. As such,
any changes that occurred in the body cells perished with the body, and so
they could not bequeath their changes to the next generation. And since
sex cells are isolated from the rest of the body early in their
development, they would be unaffected by changes that occur in the body
cells. As such, Weismann was claiming that inheritance was one-way: that
sex cells produced body cells, but body cells could not produce or even
influence sex cells. (This idea would be vindicated by the discovery of
DNA and the protein transcription/translation system, that effectively
prevents changes in proteins from being transmitted back into the DNA.)
Weismann also identified the nucleus as the carrier of inherited
information, and postulated based on breeding experiments and analysis of
fertilization that characteristics were inherited as separate particles
that did not blend or diffuse. This idea would be vindicated by the
discovery of chromosomes and the rediscovery of Mendel's work.
Thirdly, what Bertvan refers to as "neo-Darwinism" was not an attempt to
rescue Darwinian theory from falsification, but an attempt to explain
Darwinian theory using Mendelian genetics. Interestingly, Mendelian
genetics initially led to a further decline of Darwinism because
geneticists became convinced that evolution occurred by mutations that
replaced one gene with another, thereby causing change in abrupt, rapid
leaps rather than by slow accumulation. However, this was based on the
then assumption that each phenotypical trait was directly and solely
controlled by a single gene. We now know that many traits are created by
combinations of genes, some working cooperatively, some working in
opposition. Even those traits that can be traced back to a single gene are
influenced by other genes. It is now no longer possible to say
definitively that any one trait is directly and solely controlled by any
one gene. (In fact, once it was discovered that genes made proteins, the
rule was changed from one gene-one trait to one gene-one protein, with the
understanding that the trait in question may be influenced by many
proteins.)
On top of that, people like Fisher and Haldane were able to mathematically
demonstrate that the large mutations required for Mendelian evolution would
be rare and most likely deleterious. Instead, they demonstrated that
inconspicuous novelties that had even just the slightest selective
advantage would rapidly spread throughout a population and become
permanently established. This led to the recognition that natural
selection was a more powerful force than was generally believed.
What Bertvan calls "neo-Darwinism" is actually referred to among biologists
as the New Synthesis. It grew out of all the previous research done since
Darwin and it was a combination of fact and theory that recognized that
Mendelian and Darwinian evolution were not mutually exclusive, but could be
"synthesized" into a powerful new paradigm. The inheritance of acquired
characteristics was rejected, largely due to the work of Weismann.
Mutation was recognized as the source of Darwin's fortuitous novelties.
The apparent random nature of mutations reinforced Darwin's claim that
these novelties were unsolicited; that they occur independently of both
nature and organism (but not necessarily of God). The fact that small
mutations were more selectively advantageous than big mutations reinforced
Darwin's claim of slow accumulation of individually negligible novelties.
And the separate, particulate nature of genetic inheritance validated the
role that natural selection played in evolution. And each of these ideas
has been strengthened by what we have learned about DNA and molecular
biology. In other words, the New Synthesis was a reaffirmation of the
power and correctness of Darwin's original theories (made even more
powerful by Mendelian genetics) instead of a desperate attempt to rescue
"Darwinism" from falsification.
"The belief that 'natural selection' is the designer of biological novelty,
and that it is a gradual process, is the principle belief of
neo-Darwinism."
Here Bertvan is implying that Darwin did not originally make these claims.
It is certainly true that Darwin did not claim that natural selection was
the designer of biological novelty, but then neither did Weismann, nor does
the New Synthesis. Darwin's use of the term "unsolicited" indicates that
evolution is not driven by a designer, at least not a natural designer;
therefore, Darwin would not have made natural selection into a designer.
All natural selection does is weed out those organisms without fortuitous
novelties, leaving those that have them. Darwin had no explanation for
what produced biological novelty, except that he believed that nature was
the ultimate cause. We now know that mutations produce biological novelty,
but since the New Synthesis recognizes that mutations are also unsolicited,
they too occur independently of any designer, or at least any natural
designer.
Meanwhile, Darwin's original claim was that each novelty was almost
negligible, so they had to be accumulated to create significant change.
This implies a gradual process. Darwin never actually abandoned this
idea; he simply created another mechanism that could produce evolutionary
change faster than natural selection. When this mechanism was later
falsified and the mechanism of slow accumulation was validated, the New
Synthesis simply reaffirmed Darwin's original idea.
"If you 'prefer' chance to design, fine."
Again, Darwin's use of the term "unsolicited" is simply meant to indicate
that there is no apparent design, plan or purpose to evolution on the part
of nature or the organism. Though some (possibly even Darwin himself) take
this to mean that there is no design, period, I believe this is an
unwarranted extrapolation of a simple observation. Nor do I believe that
it serves as a foundation for modern science. It does, however, force me
to recognize that if evolution is following a divine plan, it does so in a
way that closely mimics what you would expect to see if there was no divine
plan directing evolution.
And again I would remind you that contingency simply means that events
occur independently of any direct action and/or desire on the part of
nature or living organisms.
"What one 'prefers' is not supposed to be relevant to science."
Exactly, which is why your rejection of "neo-Darwinian" evolution without
apparent cause is so puzzling.
Kevin L. O'Brien
"Good God, consider yourselves fortunate that you have John Adams to abuse,
for no sane man would tolerate it!" William Daniels, _1776_