That’s the view taken in a new paper which departs from the consensus that modification only produced the explosion:
The Cambrian explosion was a unique animal radiation ~540 million years ago that produced the full range of body plans across bilaterians. The genetic mechanisms underlying these events are unknown, leaving a fundamental question in evolutionary biology unanswered. Using large-scale comparative genomics and advanced orthology evaluation techniques, we identified 157 bilaterian-specific genes. They include the entire Nodal pathway, a key regulator of mesoderm development and left-right axis specification; components for nervous system development, including a suite of G-protein-coupled receptors that control physiology and behaviour, the Robo-Slit midline repulsion system, and the neurotrophin signalling system; a high number of zinc finger transcription factors; and novel factors that previously escaped attention. Contradicting the current view, our study reveals that genes with bilaterian origin are robustly associated with key features in extant bilaterians, suggesting a causal relationship. – Peter Heger Is a corresponding author,
Wen Zheng, Anna Rottmann, Kristen A Panfilio, Thomas Wiehe, The genetic factors of bilaterian evolution, eLife 2020;9:e45530 DOI: 10.7554/eLife.45530
That’s pretty straightforward: “The genetic mechanisms underlying these events are unknown, leaving a fundamental question in evolutionary biology unanswered.” and “Contradicting the current view, our study reveals that genes with bilaterian origin are robustly associated with key features in extant bilaterians, suggesting a causal relationship.” = the genes originated with the bilaterians (creatures with two distinct sides).
Now here’s a question: What is the origin of new genes? We know how new ideas come into the world: People think them up. But how do new genes come into the world?