Stromatolites sounds like a pious Byzantine librarian who wrote “I am offended by this!” in the margins of Neoplatonic discourses. But no …

When I visited my son in Western Australia we visited an unremarkable lagoon with active stromatolites. They don’t look like much – mounds of stuff left behind by untold generations of bacteria, like the ancient city mounds (‘tells’) that dot the middle east.

They are probably the oldest, continuously active life forms on the planet. There are stromatolite remains in Western Australia that have been dated to 3.7 billion years old.

The remarkable thing about life on this planet is how quickly it became active. For about 3 billion years bacterial lifeforms terraformed the planet, oxidising everything in sight until there was an oxygen surplus, a bizarre situation considering oxygen is just one spark away from an accident waiting to happen. We think of wood as inflammable, and petrol, and polyester nighties, but no, oxygen is the causus belli in every case. Oxygen provides the necessary free energy for centrally-organised multicellular life, with differentiated cell types.