Once again, the examples given are "microevolution" (I use that term for lack of a better one).
No, they are not. Microevolution is evolutionary changes that take place within an interbreeding population. That is, within a species.
These changes are incipient speciation so they are no longer microevolution.
It is not a limit you can point at and say "there's the final limit". It is not a limit that would be easy to define. But it is a limit nonetheless.
This limit that you can't point to and can't define sounds a bit like my invisible friend that I can't point to either. When you have a definition of it and can point to it then come back to the discussion. In the meantime you have nothing to bring to the discussion other than your own lack of knowledge about the subject and your incredulity.
Does that mean Cocker Spaniels could be bred for milllions of years and we could get a 60 foot taller one eventually? 99.9% of scientists would say no. Because there are limits.
If 99.9% of scientists would say no it is only because 60 foot tall is beyond the physical limits of what a mammalian tetrapod body plan would support. Drop the 60 foot to 20 feet and 99.9 % of scientists would then say "yes" we could get such a thing.
You are making things up and do not have any idea what you are actually talking about.
In fact, cocker spaniel sized things DID breed over millions of years into things that weighed 10+ tons.
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