You do understand that you just presented evidence of evolutionary concepts created by DESIGN - this is an example of intelligent design. Not an example of evolution by happenstance.
How is selection pressure applied to a particular population by humans fundamentally different than any other selection pressure?
1) Typical creationist dishonesty and moving the goalpost, You set the parameters
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"we assume based on our current theories that genetic codes diverge from an ancestral code. We cannot observe this actually happening or duplicate it in the lab".
Well that's exactly what happened with the goldfish. The lab in this case was the fishtanks and ponds and we have observed over the course of ~1100 years the genetic code of goldfish diverged from their ancestral carp.
2) And what intelligent design? The Ancient Chinese did not have Genetic engineering capabilities so in order for the bubble eye and other breeds to develop they were relying on "Happenstance" mutations and because of those "Happenstance" mutations goldfish have evolved new organs, structures, Chromosome number and genes that are not found in the gibel carp.
3) The evolution of goldfish is parallel to the evolution of male birds like the peacock and birds of paradise which the females only breed with the ones they find the prettiest. The only difference between them is that humans are deciding what's prettier not female birds.
The ones that look the prettiest (well at least to the owners) live and breed and the ones that don't look pretty enough end up becoming dinner or bait, Evolution at it's simplest