How can scientists possibly know ... ?? An open exploration thread

[Mallon]

I'm surprised about that question frankly. I think we concluded that Natural Selection does not explain new species, and that Mutations do not explain new species. So, we're now onto something that is called "genetic drift". (I suspect the next thing will be "migrations")

But here is the example you asked for:
"Picture a situation in which the 30% of the population which carry an allele are all found in a high-density area that covers only 10% of the species' total range. You only need a disaster occurring in that restricted area to wipe out that allele."

You still haven't explained why the above scenario you quoted is an example of artificial, rather than natural, selection. I get the impression that you still do not know what artificial or natural selection is.

 

[Mallon]

That's not natural selection, but artificial selection. While you may be able to picture it, it is very very remote from anything we know to have happened. It's an hypothesis, and a weak one in my view. That's evolutionism.

I figured I should stop beating around the bush and just come out and say it. Gluadys' scenario is an example of natural, not artificial, selection. Artificial selection is typically incurred by humans via selective breeding (take dogs or flowers, for example). Natural selection occurs without human intervention, and can often result from natural disasters wiping out entire populations (or parts of them).
This is high school biology we're talking about.

 

[gluadys]

That's not natural selection, but artificial selection. While you may be able to picture it, it is very very remote from anything we know to have happened. It's an hypothesis, and a weak one in my view. That's evolutionism.

This is neither artificial nor remote from experience. Take the situation of a founder's event (which has probably been how many island populations got started.) The main body of the species is found on the mainland or on another nearby island. A few individuals make it to an island previously uninhabited by that species.

This group is small enough that some alleles occurring in the general population are under-represented in the founder's group, so appear rarely in the population of this island. Furthermore, some alleles that are found in the main population could be over-represented in this group.

An allele that is found in 20% of the population as a whole could be found in 80% of this smaller subset of the population. Or vice versa.

 

[gluadys]

I'm surprised about that question frankly. I think we concluded that Natural Selection does not explain new species, and that Mutations do not explain new species.

My goodness. Where do you think we concluded that?

I believe we concluded that natural selection does not generate new alleles. That is not at all the same thing as saying it does not explain new species.

Nor do we need natural selection to generate new alleles, since they are being generated constantly by mutations.

There are always new alleles (and old ones) for natural selection to work with.

Genetic drift is another factor, but it is in addition to, not a replacement of, natural selection.