[quote=“gbrooks9, post:5, topic:4731”]
At the risk of starting another round of virulent rhetoric… I am still hoping to see this position: “evolution is primarily driven by existing variation, not new mutation” fully explicated in a concise thread (this one thread, or a new one).[/quote]
Hello George,
I thought that we were in agreement.
[quote]Part of the underlying premises for this hypothesis is the STARTING POINT right?
“Existing Variation” suggests that a genetically diverse population as a starting point, right?[/quote]
Yes, existing variation is what we directly observe. New mutant alleles are NEITHER necessary nor sufficient to produce evolution.
[quote]We have a choice of STARTING with, say the first FISHES … or the first land-based TETRAPOD… or the first MAMMAL
Do you think your stated hypothesis is true EVEN if we start with the first FISH?[/quote]
Yes, although there was never anything we could look back on and unambiguously identify as “the first fish.” You don’t seem to be grasping the concepts of gradualism and quantitative trait loci.
Probably.
Think of it this way: mutation is a faucet slowly dripping new variations into a huge, full bathtub of existing variation. Selection doesn’t care if the variation it is acting upon is new or already existing, but it’s almost certain to act upon the latter, just because there’s so much more of it. Cheetahs, for multiple reasons, have an empty bathtub, so they are in big trouble and can’t be saved by the tiny drops of new variation.
That time frame is more than enough to go through the bathtub many, many times.
You’re sounding like a creationist now.
[quote]Didn’t unintended CHANGES to the genetic code in fact drive this kind of evolution?
[/quote]No, the genetic code has been virtually always constant.
Or perhaps by “genetic code” you don’t mean the genetic code? If so, you should make a better effort to use standard terms. You’d be a lot less confused.