From Andy Taylor
I agree with Robert Gaines and Shanan Peters that if calcium and silica became more bio-available as unusually large amounts of rock were eroded, it could have prompted the Cambrian explosion in complex life forms (15 June, p 30).
Levels of calcium minerals would have been so high that organisms had to find ways of removing them from their biochemical systems. Useful deposits such as spines, bones or shells would surely give an advantage. A similar argument can probably be made for silica.
Additionally, could the carbon dioxide levels required to thaw out “snowball Earth” have been high enough to cause the melting that would be required for such rapid erosion?
Bristol, UK
