A planetary takeover by ocean-dwelling algae 650 million years ago was the kick that transformed life on Earth.
Cambridge University palaeontologist Nick Butterfield has said the period "was arguably the most revolutionary in Earth history", and not just because of the rapid biological changes. There were violent swings in climate, too, that experts have long suspected are intertwined.
Algae, more complex than bacteria but still single-celled, had themselves had been around for over a billion years (the "boring billion" some palaeontologists call it), but without making much of an ecological impact.
The episode ended after 50 million years, when the build-up of volcanic CO2 in the atmosphere created a supergreenhouse that melted the ice in a second cataclysm.
This post was first published on BBC