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Are we in the Holocene or the Anthropocene?

January 14, 2015

Yesterday I came across a new word: Anthropocene. It was in Elizabeth Kolbert’s book, The Sixth Extinction. Let me explain. The geological epoch we are currently in is named the Holocene. It means the epoch since the last Ice Age, when temperatures have risen and human civilization has appeared. I’ve loved the word Holocene ever since I first learned it: it suggests to me warmth and spring and fertility, and also the epic sweep of human history which is, in the context of geological time, fleeting. Anyway the theory, proposed by the Dutch Nobel-prize-winning chemist Paul Crutzen, is that we are no longer in the Holocene. We are now in the Anthropocene, an epoch which will be recognisable to geologists of the distant future (if there are any) by the fossil record, which will contain evidence of the vast number of species that went extinct thanks to human activity.

Reading Kolbert’s book has improved my vocabulary in another way. For a long time I’ve been vaguely familiar with geological terms for past epochs and eras and eons, but without knowing exactly what they meant or when they occurred. Now I have a rough picture. The longest of geological time divisions is an eon. There have been four of these – Hadean, Archeozoic, Proterozoic (during which primitive life first appeared) and Phanerozoic (from half a billion years ago until now, and we’re still in it).

Eons are then divided into eras, which last for hundreds of millions of years, rather than the billions of the eons. The first era of the Phanerozoic was the Paleozoic, followed by the Mesozoic and then the Ceonozoic, which we are still in.

Then the eras are divided into periods, which last for tens of millions of years. The first period of the Paleozoic was the Cambrian period, during which life forms proliferated explosively. (I had always enjoyed JBD Haldane’s remark that evolution could be disproved by the discovery of fossil rabbits in the pre-Cambrian, without ever knowing exactly when the pre-Cambrian was; now I know, and enjoy the remark more.) The Mesozoic is divided into the three familiar periods of Triassic, Jurassic and Cretaceous, when dinosaurs ‘roamed the Earth’, as the saying is. Our period of the Cenozoic is called the Quaternary; it began 1.8 million years ago, and Homo Sapiens appeared around the beginning of it.

Periods are then divided into epochs, which are mere thousands or tens of thousands of years long. We may still be in the Holocene epoch; or, if Crutzen is right, we’re already out of it. The International Commission on Stratigraphy is to look into Crutzen’s proposed new term, and vote on it in 2016: so next year we’ll know whether we are in the Anthropocene or not, and if we are my spell-check will stop putting a squiggly red line under it.

PS My review of Kolbert’s book appears in the Independent on Sunday on February 1st.

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One Comment
  1. It’s “When dinosaurs ruled the Earth”, according to the banner that falls down while the T-Rex is roaring in probably the coolest movie shot ever filmed.

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