Behe vindicated, again!

[Mercer (John Mercer)]

@Giltil

@Giltil

If suppression of melanin production is adaptive in polar bear, it is likely that some other genes on which depend melanin production have also accumulated degrading mutations in that species.

Not if those genes serve multiple functions.

And they almost all do, my own work being an example:
https://www.nature.com/articles/349709a0

Gil, mammals share the same dozens of coat-color genes. Synthesizing and distributing melanins within and between cells is a complex process, with many components performing the same functions in the nervous system, which makes perfect evolutionary sense since pigment cells are are derived from the neural crest.

IOW, the fact that homozygous deletions of the dilute (now Myo5a) gene cause neurological lethality in mice and people is perfectly consistent with physiology and evolutionary biology.

Another example is shown in Fig 1 of this paper:
https://www.pnas.org/content/pnas/88/23/10885.full.pdf

[Mercer (John Mercer)]

@jorronet

I asked a specific question for a specific paper, I read the abstracts only because I’m not going to pay for a paper that I don’t need,

Do you define “don’t need” as “supporting evolutionary theory”?

@jorronet

…and as you saw the abstract was misleading , that is why it is better to read the whole paper.

I didn’t see that the abstract was misleading. It is better to read the whole paper. Would you like a PDF?

@jorronet

But you didn’t explain it to me, another person had to do it…

But I did answer your question.

[jorronet]

No, you didn’t. But it is ok , thanks.

[Giltil (Gilbert Thill)]

@NLENTS

For anyone reading, this statement is 100% false. In fact, when someone performs a genetic technique called a “complementation screen,” s/he will typically have to sort through lots of spontaneous revertants as false positives in their screen. I’ve had this (dis)pleasure myself.

Can you tell on which species you worked for your complementation screening?

[Roy (30-year veteran)]

@Rumraket

The bright moth allele persisted at a low population frequency in the peppered moth population during the industrial revolution(it wasn’t wiped out), and when eventually measures were taken against pollution and the environment changed, the bright allele became beneficial again.

IIRC it wasn’t that low a frequency, because the dark allele is dominant.

[Roy (30-year veteran)]

@Giltil

@T_aquaticus

That doesn’t change the fact that reversion mutations can happen.

For big animals like polar bears …

Goal-post moving. The original claim you made wasn’t only about big animals like polar bears, it was about the reversal of any degenerative mutation.

If you can only support your claim w.r.t. large mammals, then your original claim is wrong.

[NLENTS (Nathan H. Lents)]

I’ve been involved in these kinds of screens three different times. I’ve used two different kinds of yeast cells (S. cerevisiae and S. Pombe) in screens for cell cycle kinases. And I assisted a colleague using human L-cells to screen for enzymes involved in phospholipid synthesis.

[T_aquaticus]

@Mercer

And they almost all do, my own work being an example:
https://www.nature.com/articles/349709a0

There is also the fact that polar bear skin is a deep black, presumably due to high levels of melanin production in the skin. This allows the polar bear to soak up what little heat there is. The mechanisms for melanin production are not only present, but selected for. All that would be needed is for melanin production to be turned on in the cells that make hair.

[Mercer (John Mercer)]

@T_aquaticus

There is also the fact that polar bear skin is a deep black, presumably due to high levels of melanin production in the skin.

I hadn’t known that.

@T_aquaticus

This allows the polar bear to soak up what little heat there is.

It’s hard to see how that would be useful in the Arctic summer. Others have hypothesized that it might be a way for the bear to navigate by sun position in low winter visibility.

@T_aquaticus

The mechanisms for melanin production are not only present, but selected for. All that would be needed is for melanin production to be turned on in the cells that make hair.

Or just as likely, melanin is still being made, but just not transferred to the hair; for dilute, the coat-color dilution is not associated with any reduction in melanin synthesis, just transfer in larger blobs. Last time I checked, the precise mechanism of the transfer was still unknown:
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-0854.2006.00425.x

[T_aquaticus]

@Mercer

It’s hard to see how that would be useful in the Arctic summer. Others have hypothesized that it might be a way for the bear to navigate by sun position in low winter visibility.

In the larger scheme, we should all be careful when drawing conclusions about the potential adaptive properties of any feature. Otherwise, Gould’s spirit will haunt us until we say “Spandrels!” three times.

@Mercer

Or just as likely, melanin is still being made, but just not transferred to the hair; for dilute, the coat-color dilution is not associated with any reduction in melanin synthesis, just transfer in larger blobs. Last time I checked, the precise mechanism of the transfer was still unknown:
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-0854.2006.00425.x

Very good point.