When successful mating only occurs among a sub population but no longer is possible with the larger population you have a new species like the large beak finch or the donkey vs horse.
Yes, is it so unusual that time or more specifically number of generations is required? Seems clear to me.
Will dogs continue to be the same species? Or will they branch into little dogs who can no loner mate with big dogs. Anyhow, without human intervention it is very doubtful that any of today’s dogs would exist.
There must be something in the gene allele where there are two recessive traits involved for the labs.
You seem to be trying really hard to stand by an ideology that may cause a ton of discomfort if you were to acknowledge the actual science.
I suggest that you continue your journey for the truth.
Don’t be convinced by anything that some “Scientist” has told you. Find out for yourself.
I spent nearly a dozen years trying to deny Creation as the answer. I read virtually everything from both sides and explored the physics of “Humanism” which is basically, Buddhism.
If you are actually interested, and are starting from the secular nature of our culture, I would recommend Joseph Campbell. He will bring you to Buddhism, but if you are honest with yourself, you will dig deeper.