The Cause Of The Cambrian Explosion?
I've hypothesized that the ability to lock cells into somatic roles, through epigenetic changes activated during embryogenesis, was the trigger of the Cambrian Explosion. When highly branched network structures (e.g. vascular) can be reliable, and highly ramified cellular structures can be maintained without constant signaling, then body types can get a lot more complex.
-- Mo Costandi
Quoted on Wed Jun 22nd, 2011