Whales are held up as a model of what unguided evolution can do in a short time: in this case, just 8 million years, or perhaps even half that.
If you tried to build a pipe that had to rotate on its long axis while maintaining its angular shape, could you do better than this?
Could humanity have had its origin in a first pair, or did it have to come from a population of at least several thousand?
The subject of biomineralization also allows comparing the explanatory power of design over Darwinian evolution.
Frustrated by abrupt appearance, some evolutionists are simply declaring that there is no problem with the Cambrian explosion.