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Comment by OrvalWintermute | Hacker News Reader

There are at least three errors in the article:

(1) This is adaptation, not evolution, but it may be merely selection of a pre-existing color variant that already widely found in nature. We have the same exact variation of melanistic toads & frogs found in the US.

(2) They really don't know how many generations this occurred over, they have a measurement, and a measurement.

(3) The baseline wasn't built before the Cherynobyl event. As a person that has caught a great number of frogs and toads, their coloration in normal areas varies greatly based on the local Flora and sun conditions. The very dark / black frogs which are already found in nature, may have just reproduced better, instead of coloring adaptation being introduced. Frogs that live near asphalt and post-wildfire conditions would be expected to have better survival characteristics due to decreased visibility.

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> it may be merely selection of a pre-existing color variant that already widely found in nature... very dark / black frogs which are already found in nature, may have just reproduced better

If this variant is being selected for preferentially, that's evolution: "Typically, we think of biological evolution as changes in gene frequency within a population over time – if, say, birds with genes that produce wide beaks went from being rare to being common over multiple generations."

https://evolution.berkeley.edu/evolution-101/mechanisms-the-...

No..

It is a population that evolves, not an individual.

Selection of a pre-existing feature that already occurs in the gene pool is exactly how evolution works. There are only two things needed for evolution: 1) generation of diversity between individuals (see sexual recombination, V(D)J recombination, etc) 2) selection of traits

The fact that black frogs already existed at some frequency does not mean that the population did not evolve in response to radiation.

But you are right that radiation is not the only thing that might select for dark frogs.

What is the distinction between adaptation and evolution here?

If following text book, this is evolution, and adaptation is used when scientists finding some character actually is functional and evolved in past.

So it would seem this gene for melanin already existed in the gene pool of these frogs - it's not like the radiation caused a mutation that led to this. So that's what makes it adaptation vs evolution? (where the latter would be an entirely new gene that arises that wasn't in the population before?)

They are not claiming that the radiation led to evolution of an entirely new gene..that would be unprecedented. You don't get "brand new genes" in that kind of evolutionary time frame.

Also, there is not single gene for melanin. Several genes are required for the ultimate effect that you observe as dark skin. A mutation in any of these genes, or in any of the transcription factors which control expression of these genes, could lead to observed differences in frog skin color.

FYI, "new genes" are usually the result of duplication of an existing gene (https://en.wikipedia.org/wiki/Gene_duplication#Mechanisms_of...). Duplicating a gene can be useful in and of itself by providing functional redundancy. However, the new copy is then also subject to its own mutations without affecting the original copy, and over time the two genes may diverge in function.

And existing variation in the melanin genes is enough! No need for mutation. The way to rapid evolution in animals is sexual reproduction. The stronger melanin genes can add up in children where the parents had only some. When the darker children are selected for, the genes that lead to less melanin become less common.

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