--- In email@example.com, "hibbsa" wrote:
> Jim/Don - I think in the context of Evolution the words 'mutation' and
> 'random' increasingly have a much more generic meaning than possibly
> they did in the past.
JK: The problem is that the basic principles of biology and levels of biological organization clearly state that you, and others who think like that, are wrong.
> A mutation = any change in DNA (human caused excepted)
> Random = with respect to the selective benefit
1. Williams: ...
random mutations CAN AND DO account for some pretty difficult-to-answer
2. James Gray: It actually seems like a good idea to support the role of random gene
mutation in biological evolution from time to time on this list.
3. Feierman: Random gene mutation is the variance
generator upon which natural selection operates.4. JK: Random gene mutation is not the variance generator upon which natural selection operates.
Which one of the four statements above (with my emphasis) represents biological facts? Which of the statements above and below represents theoretical nonsense?
> A mutation doesn't have to be a mutation in the common understanding of
> the word. It can occur as part of an ordered mechanism. There is no
> rational or logical problem with this. Mutation just means, we don't
> know what the cause is. In fact, what it really means is that, for the
> purposes the word is being used, at the level of abstraction it is being
> used, it doesn't *matter* what the cause is, only that it happens.
JK: If it doesn't "matter" what causes the mutation, the cause can be random. Therefore, the unknown cause of the random mutation causes adaptive evolution. Is that what he just said? Watch how DWZ attempts to clarify it.
DWZ: It is my understanding that mutations arise from a great variety of different causes and that a large proportion of them can reasonably be called "random." For example, consider radiation from space striking DNA. I can't think of anything more random.
JK: I think it would be more random if you were lost in space at the time your DNA was struck by the radiation, after formation of your DNA randomly occurred via random processes that defy the second law of thermodynamics (i.e., entropy).
DWZ: On the other hand, a human being could receive excess radiation because of too many chest X-rays or X-rays in the dentist's office. That might be considered less "random" in the sense that it is predictable and could possibly be avoided by choice. But it has a random component in the sense that various individuals may not be aware of the risks of too much radiation, that toothaches and trips to the dentist may occur randomly, and so on. It is similar for any chemically-induced mutation.
JK: I missed the similarity between excess radiation-induced mutations and a chemically-induced "mutation." Are you saying that the similarity is because, in theory, radiation and chemically-induced mutations are caused by similar things? How similar is radiation to chemistry in the context of biologically based cause and effect?
DWZ: Correct me if I am wrong,....
JK: I've been doing that for years!
DWZ: ....but I thought everybody agreed that mutations drive evolution by natural selection and that the process is regarded as random at the level of populations of organisms.
JK: There is no biologically based scientific evidence that natural selection for mutations occurs at the level of populations of organisms. That's what the pigeon study we're discussing clarifies. Regarding the process as random makes anyone who agrees "that mutations drive evolution by natural selection and that the process is regarded as random" appear to be unable to think critically. Does the article on the pigeons tell us that the population level selection is for a random mutation? Correct me if I am wrong, but I think it tells us that Darwin was just slightly confused by his observations, which led to much more confusion even after others learned
about genetics, and then learned about molecular epigenetics.
DWZ: An implication seems to be that, at any given place on the "tree of life," evolution can "go anywhere," (unpredictably from the perspective of an observer in space), within constraints imposed by the structure of organisms up to that point and the structure of the environment.
JK: Thank you for once again exemplifying the lack of critical thinking among theorists. Evolution cannot go anywhere if organisms are undernourished or if their social environment is not constrained by the availability of nutrients. The finches beaks adaptively evolved as part of their ecological niche construction, not because different beaks were somehow naturally selected at the population level.
Nutrients enable the epigenetic landscape to become the physical landscape that establishes the structure of organisms via the effect of nutrients on stochastic gene expression.
The metabolism of nutrients to species-specific pheromones controls nutrient-dependent adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction. Telling others that " at any given place on the "tree of life," evolution can "go anywhere," eliminates the constraints of biological facts that ensure adaptive evolution is nutrient-dependent and pheromone-controlled (i.e., directional from the bottom up to its top down control in my model that links gene activation to behavior and back).
The pigeon studies and all other current studies, other than those using
only statistical analyses of population genetics, clearly show that
random gene mutation is not the variance
generator upon which natural selection operates. If the take home
message from what Jay has since added (below) indicates anything else, he is
still wrong. The difference is simply being wrong with obfuscation.
Remember: this is what he first said: Random gene mutation is the variance
generator upon which natural selection operates.
Hello Jim (Gray),
The confusion or lack of
understanding has to do with the word "driven," which implies to me an
important and controlling or rate limiting, cause and effect
relationship on the outcome of natural selection, which is adaptive
changes in gene frequencies in a population over time in a specific
environment. Given that meaning of the word, "Driving natural selection"
is not the role or function or effect of random genetic mutations in a
I like to argue (or teach in my earlier days) by
analogy, so I'll give an analogous situation having to do with enzymes
in biochemistry and the biosynthesis of the neurotransmitter serotonin
from the amino acid tryptophan. To talk about "mutation driven natural
selection" would be analogous to talking about "dietary tryptophan
driven serotonin biosynthesis." Except in the rare cases of dietary
tryptophan deficiency (like a corn based diet not supplemented by
beans), the rate limiting step for serotonin biosynthesis in a human
having a normal balanced diet is not the amount of tryptophan consumed
in the diet. Rather, it is the amount or activity of tryptophan
hydroxylase enzyme that is present in tissue at a particular time. The
amount of serotonin in any particular tissue of the body, such as a part
of the brain, is a function of the amount of or activity of (i.e., the
"Km value of") tryptophan hydroxylase present in the tissue at a
particular time, which is why tryptophan hydroxylase is called "the rate
limiting enzyme" in the biosynthesis of serotonin from the dietary
amino acid, tryptophan.
Both random genetic mutations and the amino acid
tryptophan (taken in by diet) are the substrates, random mutations
figuratively and tryptophan literally. Neither are rate limiting under
normal or natural circumstances. One can't speed up the process of
natural selection or change its direction in a population over time by
just increasing the mutation rate of genes in a population from say 1 in
20,000 cell divisions to 1 in 10,00 cell divisions. The effect on
adaptively changing gene frequencies in a population in a specific
environment from just speeding up the mutation rate would be negligible
compared to the other much more important factors in natural selection
itself, such as strong directional selection.
I hope this helps clear up the confusion.
I think it simply shows that Feierman is among the most confused of those involved in discussions that incorporate the basic principles of biology and levels of biological organization required to link sensory cause to behavioral affect. DWZ is a close second, but much less offensive because he is attempting to understand the biological basis of evolution. He does not appear to be deliberately using obfuscation in an attempt to convince others that he knows what he is talking about. Kudos to DWZ and to hibbsa for that.
James V. Kohl
Medical laboratory scientist (ASCP)
Kohl, J.V. (2012) Human pheromones and food odors:
epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338.