Worry not about when the Anthropocene began, but how it might end

It is by their beginnings that the ages of the Earth are known. Agreeing on the precise point at which each particular syllable of recorded time began is a fundamental, often fractious and frequently long-winded part of geological science. The Cretaceous period, for example, was first identified by Jean Baptiste Julien d’Omalius d’Halloy, a Belgian geologist, in 1822. But which rocks were the earliest to belong to it remains undecided. A working group of the International Subcommission on Cretaceous Stratigraphy recently spent a decade exploring the pros and cons of an outcrop in the French Alps. In the end the subcommission felt unable to accept its findings, and the group was disbanded. A reconstituted working group is now trying again. The depths of geological time teach patience.Nowadays, though, geological time has fast-flowing shallows. In 2000 Paul Crutzen, a Dutch Earth scientist, made a public plea that the role humankind now plays in shaping the Earth be made explicit; science should recognise the advent of the Anthropocene, “the recent age of man”.