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  • ["The human race exaggerates everything: its heroes, its enemies, its importance." | Charles Bukowski]

  • Imagine aliens land on the planet a million years from now and look into the geologic record.

  • What will these curious searchers find of us?

  • They will find what geologists, scientists, and other experts are increasingly calling the Anthropocene or new age of mankind.

  • The impacts that we humans make have become so pervasive, profound, and permanent that some geologists argue we merit our own epoch.

  • That would be a new unit in the geologic time scale that stretches back more than 4.5 billion years, or ever since the Earth took shape.

  • Modern humans may be on a par with the glaciers behind various ice ages, or the asteroid that doomed most of the dinosaurs.

  • What is an epoch?

  • Most simply, it's a unit of geologic time.

  • There's the Pleistocene, an icy epoch that saw the evolution of modern humans.

  • Or there's the Eocene, more than 34 million years ago, a hothouse time during which the continents drifted into their present configuration.

  • Changes in climate or fossils found in the rock record help distinguish these epochs and help geologists tell deep time.

  • So what will be the record of modern people's impact on the planet?

  • It doesn't rely on the things that may seem most obvious to us today, like sprawling cities.

  • Even New York or Shanghai may prove hard to find buried in the rocks a million years from now.

  • But humans have put new things into the world that never existed on Earth before, like plutonium and plastics.

  • In fact, the geologists known as stratigraphers who determine the geologic timescale, have proposed a start date for the Anthropocene around 1950.

  • That's when people started blowing up nuclear bombs all around the world and scattering novel elements to the winds.

  • Those elements will last in the rock record, even in our bones and teeth for millions of years.

  • And in just 50 years, we've made enough plastic, at least 8 billion metric tons, to cover the whole world in a thin film.

  • People's farming, fishing, and forestry will also show up as a before and after in any such strata because it's those kinds of activities that are causing unique species of plants and animals to die out.

  • This die-off started perhaps more than 40,000 years ago as humanity spread out of Africa and reached places like Australia, kicking off the disappearance of big, likable, and edible animals.

  • This is true of Europe and Asia, think woolly mammoth, as well as North and South America, too.

  • For a species that has only roamed the planet for a few hundred thousand years, Homo sapiens has had a big impact on the future fossil record.

  • That also means that even if people were to disappear tomorrow, evolution would be driven by our choices to date.

  • We're making a new homogenous world of certain favored plants and animals, like corn and rats.

  • But it's a world that's not as resilient as the one it replaces.

  • As the fossil record shows, it's a diversity of plants and animals that allows unique pairings of flora and fauna to respond to environmental challenges, and even thrive after an apocalypse.

  • That goes for people, too.

  • If the microscopic plants of the ocean suffer as a result of too much carbon dioxide, say, we'll lose the source of as much as half of the oxygen we need to breathe.

  • Then there's the smudge in future rocks.

  • People's penchant for burning coal, oil, and natural gas has spread tiny bits of soot all over the planet.

  • That smudge corresponds with a meteoric rise in the amount of carbon dioxide in the air, now beyond 400 parts per million, or higher than any other Homo sapiens has ever breathed.

  • Similar soot can still be found in ancient rocks from volcanic fires of 66 million years ago, a record of the cataclysm touched off by an asteroid at the end of the Late Cretaceous epoch.

  • So odds are our soot will still be here 66 million years from now, easy enough to find for any aliens who care to look.

  • Of course, there's an important difference between us and an asteroid.

  • A space rock has no choice but to follow gravity.

  • We can choose to do differently.

  • And if we do, there might still be some kind of human civilization thousands or even millions of years from now.

  • Not a bad record to hope for.

  • If you're interested in learning more about the impact we're having on the planet, we recommend "The Unnatural World" by David Biello, the author of this lesson. Thanks for watching!

["The human race exaggerates everything: its heroes, its enemies, its importance." | Charles Bukowski]

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B2 US TED-Ed epoch record soot asteroid homo sapiens

How long will human impacts last? - David Biello

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    林宜悉 posted on 2021/10/17
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