The Cambrian explosion as a Black Box: a qualitative appreciation

The sequence of cause and effect responsible for the Cambrian Explosion, however defined, remains elusive. But there was a ‘before’ and an ‘after’ and between the two, commencing c.650 Ma, was the collision of East Gondwana with West Gondwana. The collision produced a Himalayan-style ‘supermountain’ on which rooted vegetation was absent. Extreme erosion enriched the seas with phosphorus, a key nutrient, as well as bicarbonate ions, oxygen, and calcium, the last two of which are toxic to anaerobic eukaryotes. Extracellular detoxification products prominently included sticky molecules of the ‘oxygen-expensive’ collagen family, present in all metazoans and essential to metazoan life, as well as calcium carbonate (aragonite and calcite). The first metazoans, the first shells, and the first metazoan hardparts appear to have emerged from this context.