Via ScienceNews:
...While scientists can pinpoint this pivotal period as leading to life as we know it today, it is not completely understood what caused the Cambrian explosion of life. Now, researchers led by Arizona State University geologist L. Paul Knauth believe they have found the trigger for the Cambrian explosion.
It was a massive greening of the planet by non-vascular plants, or primitive ground huggers, as Knauth calls them. This period, roughly 700 million years ago virtually set the table for the later explosion of life through the development of early soil that sequestered carbon, led to the build up of oxygen and allowed higher life forms to evolve...
