Coat color evolution--is there evidence for new mutations?

[Mercer (John Mercer)]

@T_aquaticus

The paper says that there is gene flow between the mice on the black basalt and the mice in the adjacent light colored desert. In fact, I cited that evidence in an earlier post.

I know. That fact alone should have been sufficient for you to pause, reconsider, and retract your claim.

@T_aquaticus

I don’t think the Pinacate locale is isolated from the Avra Valley and Portal populations, but given your propensity for wanting exact language I didn’t leap to that conclusion.

I don’t want language, I want evidence. It’s a science thang.

@T_aquaticus

If the desert has been around much longer than the black basalt lava flows, would you agree that this is good evidence?

Are there no dark regions in the desert?

@T_aquaticus

It suggests independent mutations in separate geographic locations that weren’t able to spread through the population, even though there appears to be a lack of reproductive isolation.

Why not multiple alleles in the ancestral population?

@T_aquaticus

Given the young age of the lava flows, it suggests new mutations at each of these sites.

I don’t see how the young age of the lava flows suggests new mutations instead of selection for existing alleles. Can you explain?

@T_aquaticus

I never said that mutations happen after selection. Where did you get that from?

@T_aquaticus

A new mutation resulting in black fur allowed the mice to take up a new niche in environments dominated by black basalt rocks.

I’m saying that you have zero evidence that allows you to distinguish between that and:

An allele already present in the ancestral population resulting in black fur allowed the mice to take up a new niche in environments dominated by black basalt rocks.

@T_aquaticus

What I am saying is that the mutations causing black fur emerged in the light colored population surrounding the black basalt flows.

“Emerged” is a weasel word.

What you said is that they are new. I’m saying that you have no evidence that demonstrates that they weren’t present in the ancestral population and then “emerged.” There are terms in genetics that are more accurate, ya know.

@T_aquaticus

Normally, those alleles would be quickly eliminated from the population.

Only if there was no flow between that population and others that live in darker habitats AND there were no dark habitats before the lava flows existed.

Those seem like two mighty big assumptions to me.