The book Darwin Devolves

[lee_merrill]

Source: Lehigh

Behe falsely equates the prevalence of loss‐of‐function mutations to the inevitable degradation of biological systems and the impossibility of evolution to produce novelty.

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Well, that's an overstatement, Behe shows that evolution usually selects mutations that break or degrade a gene.

Actually, that is Behe's claim, which as we can see by the polar bear example is poorly backed by cherry-picked evidence and misrepresentation.

Where then does Behe make the claim that it is impossible for evolution to produce novelty?

Blessings,
Lee

[lee_merrill]

No, it's not all they can say in reply, or even all that they do say in reply. The argument can be found in the very next sentence:

Source: ibid

]"Behe attempts to argue from analogy, equating proteins with machines and convincing us that machines cannot evolve. Calling a flagellum an outboard motor may have some merit as a teaching tool, but it is not reality. Showing that a hammer cannot evolve into a fishing rod tells us nothing about real constraints on protein evolution."

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Why didn't you quote that sentence, Dory?

Because that is not showing how a flagellum can evolve.

Further expansion on the argument can be found later in the article:

Source: ibid

Proteins are promiscuous. They moonlight, by chance interacting with other cellular components to effect phenotype outside their traditionally ascribed roles. These adventitious functions can be strengthened by selection, allowing a protein to assume a new or a dual role. This topic was raised in a recent review of Darwin Devolves in Science, where the authors highlight a study that employed experimental evolution to strengthen the weak nascent ability of a protein in the histidine biosynthesis pathway to act on a similar substrate in tryptophan biosynthesis. For multifunctional proteins, gene duplication and divergence can parse specific functions into separate proteins, each now free to specialize to its own task.

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But that is very far from evolution of a flagellum.

Source: ibid

perform multiple functions and, therefore, evolutionary paths that seem unlikely when considering only one function may be realized through a series of stepwise improvements on another function.

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But this does not (I must repeat) demonstrate the origin of the flagellum, either.

They probably read the paper:

Source: ibid

the signature of strong purifying selection against high-confidence LoF variants as a class, and the discovery of numerous known and predicted severe recessive disease alleles, indicates that many LoF alleles with large effects on human fitness exist at low frequency in the human population.

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But this is not what Behe is working with, LoF alleles with large effects on human fitness may indeed be rare, but evolution nonetheless does usually pick mutations that break or degrade genes, for increased survival value.

Blessings,
Lee

[lee_merrill]

Well, that's an overstatement, Behe shows that evolution usually selects mutations that break or degrade a gene.

That's kind of the whole point: he doesn't show that, because it's not true. The review cites extensive data showing that's only likely to be true in lab-based long term evolution experiments.

Well, it is true, because mutations that break or degrade a gene occur much more often than mutations that improve function, and degrading mutations can often be selected for survival advantage, under high selection pressure.

Blessings,
Lee

[rogue06]

Well, it is true, because mutations that break or degrade a gene occur much more often than mutations that improve function, and degrading mutations can often be selected for survival advantage, under high selection pressure.

Blessings,
Lee

As already noted the vast majority are neutral, neither beneficial or detrimental. And as also already pointed out while there may be more detrimental mutations than beneficial ones this hardly matters since the former tend to be weeded out whereas the latter get selected for.

[TheLurch]

As already noted the vast majority are neutral, neither beneficial or detrimental. And as also already pointed out while there may be more detrimental mutations than beneficial ones this hardly matters since the former tend to be weeded out whereas the latter get selected for.

Exactly this. If you track mutations as they happen, you'll find that breaking genes is the second most common class after neutral. But if you look at populations that have undergone evolution, the data show that their prevalence drops dramatically.

Focusing on the spectrum of mutations that we can observe being generated doesn't tell us much about evolution, specifically because evolution hasn't taken place at that point.

[shunyadragon]

Exactly this. If you track mutations as they happen, you'll find that breaking genes is the second most common class after neutral. But if you look at populations that have undergone evolution, the data show that their prevalence drops dramatically.

Focusing on the spectrum of mutations that we can observe being generated doesn't tell us much about evolution, specifically because evolution hasn't taken place at that point.

Many of the mutations relevant to evolution begin with combinations of neutral mutations, and doubling of gene sequences as with the evolution of the eye. The mutations Behe refers to is a side show and not even involved in evolution.

One of the best way to observe evolution and the genetics involved is in the tropical rain forests, and study the diverse populations of related varieties, subspecies, and species of birds reptiles and plants.

[lee_merrill]

Exactly this. If you track mutations as they happen, you'll find that breaking genes is the second most common class after neutral. But if you look at populations that have undergone evolution, the data show that their prevalence drops dramatically.

Well, do mutations that break genes still predominate, as far as what is selected? That is Behe's argument.

Focusing on the spectrum of mutations that we can observe being generated doesn't tell us much about evolution, specifically because evolution hasn't taken place at that point.

Yes, what is selected is what is important.

Blessings,
Lee

[shunyadragon]

Well, do mutations that break genes still predominate, as far as what is selected? That is Behe's argument.

No neutral mutations dominate. Mutations that break genes have absolutely no relevance to the mutations that are relevant to evolution

Yes, what is selected is what is important.

What is selected is based on mutations that are relevant such as multiple neutral mutations, mutations that lead to genetic diversity, and doubling of gene sequences and the selection pressure of the environment.

[TheLurch]

Well, do mutations that break genes still predominate, as far as what is selected? That is Behe's argument.

No, they do not - as you'd see if you read the most recent review that was linked here. It has extensive references back to the academic literature if you want to read further.

[lee_merrill]

No, they do not - as you'd see if you read the most recent review that was linked here. It has extensive references back to the academic literature if you want to read further.

I read the review, and looked into the MacArthur paper they referenced, and made comments, glad to continue that discussion...

Blessings,
Lee

[lee_merrill]

No neutral mutations dominate. Mutations that break genes have absolutely no relevance to the mutations that are relevant to evolution

Neutral mutations by definition are not selected. And mutations that break or degrade genes are indeed relevant to evolution, as in sickle-cell anemia.

Blessings,
Lee

[shunyadragon]

[QUOTE=lee_merrill;620365]Neutral mutations by definition are not selected. [quote]

Neutral mutations can be selected later in combinations with beneficial mutations, and contribute to the forming of a new phenotype.

And mutations that break or degrade genes are indeed relevant to evolution, as in sickle-cell anemia.

Sickle Cell Anemia is not a mutation that degrades nor breaks genes. It changed the gene it did not break it. It was a mutation that had positive effect: protects against Malaria, and a negative effect: reducing the life span. This was an advantage in Africa but not elsewhere without Malaria.

Source: https://evolution.berkeley.edu/evolibrary/article/mutations_06

But in many cases, evolutionary change is based on the accumulation of many mutations, each having a small effect. Whether the mutations are large or small, however, the same chain of causation applies: changes at the DNA level propagate up to the phenotype.

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[shunyadragon]

Neutral mutations by definition are not selected. And mutations that break or degrade genes are indeed relevant to evolution, as in sickle-cell anemia.

Blessings,
Lee

Source: https://study.com/academy/lesson/beneficial-mutations-examples-effects.html

These beneficial mutations include things like lactose tolerance, rich color vision and, in some, a resistance to HIV. Beneficial mutations can confer an advantage to the organism possessing them and, over time, these mutations can spread throughout a population.

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[rogue06]

Neutral mutations can be selected later in combinations with beneficial mutations, and contribute to the forming of a new phenotype.


Sickle Cell Anemia is not a mutation that degrades nor breaks genes. It changed the gene it did not break it. It was a mutation that had positive effect: protects against Malaria, and a negative effect: reducing the life span. This was an advantage in Africa but not elsewhere without Malaria.

This brings up the point that the environment can have a lot to do with whether a mutation is viewed as detrimental or beneficial. For instance, a mutation that causes fur to grow in thicker can be an asset in colder climates but might be a liability in warmer ones.

[lee_merrill]

This brings up the point that the environment can have a lot to do with whether a mutation is viewed as detrimental or beneficial. For instance, a mutation that causes fur to grow in thicker can be an asset in colder climates but might be a liability in warmer ones.

Yes, so the question then becomes, how often do mutations that are an asset break or degrade genes?

Blessings,
Lee