Revolutions that Made the Earth

Today, nearly four billion years after life first appeared on Earth, the planet hosts an abundance of complex life. Very recently, a new development – intelligence – has arisen. The varied and complex life on the planet today both maintains, and is supported by, fertile land and oceans and an oxygen-rich atmosphere. Life and the global environment have co-evolved such that neither would exist in its present form without the other.

I will trace the critical ‘revolutions’ in Earth history that have brought the planet to this point. They can be briefly summarised as:(1) The ‘Inception’, involving the origin of life ~3.7 billion years ago and the establishment of recycling ecosystems fuelled by anoxygenic photosynthesis; (2) The ‘Oxygen’ revolution, started by the origin of oxygenic photosynthesis ~2.7 billion years ago and culminating in the Great Oxidation of the Earth’s atmosphere;(3) The ‘Complexity’ revolution, starting with the origin of eukaryotes and culminating in extreme glaciations and a Lesser Oxidation ~0.8-0.6 billion years ago.

Our planet is now in the midst of what might be a new revolution. A single species, namely our own, is in the process of transforming the planet. But for the first time in the history of the Earth the agents of planetary change have a dawning collective awareness that they are changing the world. We can’t be sure if this will come to rank alongside the great revolutions that made the present Earth, not least because it is very much still underway. But the main preconditions for an Earth system revolution appear to be in place. The talk will address the question; what will it take for this to be a successful revolution?


Tim Lenton is an Earth System scientist, and Professor in Climate Change at the University of Exeter. He is a winner of The Times Higher Education Award for Research Project of the Year, and The Royal Society Wolfson Research Merit Award.

Since 2004 he has been working on key events in the coupled evolution of life and the planet, including human-induced global change. He recently published a book on this Revolutions that made the Earth (OUP, 2011). He is currently developing an evolutionary model of the marine ecosystem, and on early warning of climate tipping points.

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