[nightlight7]

Adding oxygen doesn't imply or demonstrate that neo-Darwinian mechanism (random mutation + natural selection) produced the new functioning body plans.

[BroJoeK]

nightlight7: "Adding oxygen doesn't imply or demonstrate that neo-Darwinian mechanism (random mutation + natural selection) produced the new functioning body plans."

Sure, the words they use are "suggest" and "may", so what we are looking at here are: at least four new factors introduced onto the Earth just before the "Cambrian Explosion".
Those were:

1. The melting of "snowball earth" said to be caused by increased volcanic activity.
   
2. The breakup of the Gonwandaland super-continent, which changed ocean currents, transporting deep-ocean nutrients to shallower waters.
   
3. Increasing oxygen levels caused by algal blooms resulting from those increased nutrients.
   
4. Increasingly complex life forms toward the end of the pre-Cambrian: