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Life's Last Bow

Ask Science is back with a miniseries from author Henry Gee. Based on his new book, A (Very) Short History of Life on Earth, this miniseries will take you through 4.6 billion years of history with infectious enthusiasm and intellectual rigor.

By
Henry Gee
2-minute read
Episode #402
The Quick And Dirty

Subscribe to Ask Science for more episodes from this special miniseries, and make sure to read Henry Gee's A (Very) Short History of Life on Earth for more planetary history.

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On the largest scale, the tale of life on Earth, is governed by just two things. One of them is a slow decline in the amount of carbon dioxide in the atmosphere. The other is the steady increase in the brightness of the Sun.

Why is carbon dioxide becoming so scarce? In a word—weathering. New rock thrust up to become mountains is swiftly eroded. Erosion sucks carbon dioxide out of the atmosphere. The rocks are ground to dust which is, eventually, buried on the seafloor.

In the earliest days of the Earth, the entire surface of the planet was covered with ocean. There was little or no land to erode. Over time, however, the proportion of land has increased, and, with it, the potential for weathering. Slowly, the amount of carbon dioxide removed from the atmosphere has increased, relative to the rate of its replenishment through, say, volcanic eruptions.

One of life’s first challenges occurred during the Great Oxidation Event, between 2.4 and 2.1 billion years ago. A spike in tectonic activity led to a sharp increase in the burial of carbon. The world, no longer benefiting from the greenhouse effect, was tipped into an ice age that lasted 300 million years—its first and greatest ‘Snowball Earth’ episode. The severity was exacerbated by the fact that the Sun produced less heat than it does nowadays.

Life responded by an increase in complexity. Individual bacteria, living in loose associations, pooled their resources, each individual concentrating on the one aspect of life it did best. The result was the eukaryotic cell.

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Please note that archive episodes of this podcast may include references to Ask Science. Rights of Albert Einstein are used with permission of The Hebrew University of Jerusalem. Represented exclusively by Greenlight.

About the Author

Henry Gee Ask Science

Henry Gee is a senior editor at Nature and the author of several books, including Jacob’s Ladder, In Search of Deep Time, The Science of Middle-earth, and The Accidental Species. He has appeared on BBC television and radio and NPR's All Things Considered, and has written for The Guardian, The Times, and BBC Science Focus. He lives in Cromer, Norfolk, England, with his family and numerous pets.