[expat2]

The dilemma is the fact that evolution would appear to be way faster during the Cambrian explosion than Darwin’s theory would allow. They haven’t explained that away - only the minimal evolution before that.

[BroJoeK]

expat2: "The dilemma is the fact that evolution would appear to be way faster during the Cambrian explosion than Darwin’s theory would allow.
They haven’t explained that away - only the minimal evolution before that."

Darwin himself noted the Cambrian explosion of life, and he supposed that more fossils would be found from previous ages.
In fact, some have been found -- Precambrian life beginning around 600 million years ago, or 60 million years before the Cambrian Explosion.
But these were all soft-bodied creatures, and so left fossils only under the rarest, most ideal conditions.

Further, the Cambrian Explosion extended for another 70 million years after the Cambrian itself.
So we are really looking at an "explosion" not of just 20 million years, but of 150 million years.