Punctuated equilibrium [1] is one of the predominant theories of evolution so it’s not at all far fetched. In that theory population bottlenecks are one of the main mechanisms of cladogenesis.

[1] https://en.wikipedia.org/wiki/Punctuated_equilibrium

I had not heard of this before, thank you for sharing!

We "evolved" dog breeds in microseconds in evolutionary terms. As long as the selective pressure is high change can come fast.

Adaptation need not only mean genetic (slow), it could just as well be epigenetic. The latter is not well-understood enough to be taught in school textbooks yet, but has been of great interest in recent decades.

https://en.wikipedia.org/wiki/Epigenetics

Elephants are evolving to lose their tusks.

https://www.nationalgeographic.com/animals/article/wildlife-...

Both the phenotype and the genotype of a species/population can, and do change overnight. Think about nazis killing people with big noses. The average nose size for humans shrank, and the responsible genes disappeared.

Evolution (as the change of the characteristics of a species) working in million years is stupid. It doesn't even need one generation.