During my early years of graduate school, I was wrestling with the question of whether I was an unintended accident of nature or the product of a Creator.
Frustrated by abrupt appearance, some evolutionists are simply declaring that there is no problem with the Cambrian explosion.
This line of argumentation only appears compelling to those who assume from that start that the core assumptions of the standard evolutionary model are true.
The bump was originally discovered by the celebrated British sculptor Thomas Woolner, who informed Charles Darwin about it.
If one insists on and is committed to naturalism, then naturalistic, evolutionary, explanations are what you will find.