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

想像外星人在一百萬年後登陸地球，並仔細觀察地球的地質紀錄。

What will these curious searchers find of us?

這些好奇的探詢者會找到關於我們的什麼呢？

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

他們會找到地質學家、科學家和其他專家開始稱之為「人類世」，或是「人類新世紀」的地層。

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

我們人類所造成的影響是如此無所不在、深遠且永久，使得有些地質學家認為我們創造了自己的「世」。

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.

這會是個地質時代表上的新單位，可以回溯到超過四十五億年前，甚至是從地球成形以來 。

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

現代人可能和各種冰河時期的冰川，或造成恐龍滅絕的小行星同等重要。

What is an epoch?

到底什麼是「世」呢？

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

簡單來說，它是地質年代的一個單位。

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

有作為現代人類的進化時代，天寒地凍的「更新世」。

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

也有超過三千四百萬年前的「始新世」，一個較為溫暖、溫室效應較強的時期，同時也是各個大陸漂移到現今位置的時期。

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

岩石記錄中發現的氣候或化石變化有助於區分這些「世」，並能幫助地質學家瞭解過去發生的事。

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

所以什麼會成為現代人對地球影響的紀錄呢？

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

這不一定是現在看起來最顯眼的事物，像是不斷向外擴展的城市。

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

就算是紐約或是上海，也可能很難在一百萬年後從石堆中被發掘。

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

但是人類創造了過去從來沒有在地球上存在過的新東西，像是鈽和塑膠。

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

事實上，地層學家，也就是決定地質年代的地質學家，已經提出「人類世」 應該要從西元 1950 年左右開始的說法。

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

那就是人類開始在全世界試爆核彈，並且讓新元素四處擴散在空氣中的時期。

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

這些元素會被保存在岩石地層內，甚至保存在我們的骨頭和牙齒中數百萬年之久。

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.

而且我們在短短五十年裡，就已經製造出了極大量，至少八十億噸的塑膠，足以將整個世界以一層塑膠薄膜包裹起來。

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.

人們的農耕、捕魚以及伐木活動也將在這地層中留下不可磨滅的痕跡，因為這些活動造成了許多獨特的動植物走向滅絕。

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.

這場大滅絕或許在四萬年前人類從非洲向外遷徙時就已經開始，而人類遷徙到澳洲等地導致了許多大型、可愛與可食用的動物消失。

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

曾生活在歐洲和亞洲的猛瑪象就是如此，我們也在北美洲和南美洲造成了這種情況。

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.

作為一個僅在地球上生存了大約數十萬年的物種，現代智人已經對未來的化石紀錄造成了極大的影響。

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

這也代表就算人類明天全部都消失，我們截至目前為止所做的選擇也會決定了其他物種的演化方向。

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

我們正在創造一個新的同質世界，由像是玉米和老鼠等我們偏愛的動植物所組成。

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

但這個新世界沒有像過去那一個擁有那麼強的適應力或彈性。

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.

如同化石紀錄所顯示的，動植物的多樣性才能使得獨特的動植物群可以面對環境的挑戰，甚至在末日劫難後重新茁壯、繁衍。

That goes for people, too.

對人類來說也是同樣的道理。

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.

如果海洋裡的微小植物因為過多的二氧化碳而無法生存，我們將會失去一半可供呼吸的氧氣。

Then there's the smudge in future rocks.

再來是對未來岩層的污染。

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

人類對於燃煤、石油和天然氣的偏好已向全世界散播無數微小的煤灰粒子。

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.

這種汙染和空氣中二氧化碳濃度的急速上升有相同的惡化趨勢，而如今懸浮微粒濃度已超過 400ppm ，超過任何其他時代的人類所呼吸的空氣。

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.

相似的微粒仍可以在六千六百萬年前火山噴發時代的古代岩層中找到，而那是一場大劫難的印記： 一顆小行星的撞擊結束了「白堊紀」。

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.

所以很可能我們製造的微粒在六千六百萬年後依然存在，讓任何好奇的外星人都可以輕易地發現。

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

當然，我們和小行星有個重要差別。

A space rock has no choice but to follow gravity.

太空隕石只能順從重力的牽引。

We can choose to do differently.

但我們可以選擇做出改變。

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

如果我們能夠改變，距離現在幾千年、甚至數百萬年後，或許人類文明仍然生生不息。

Not a bad record to hope for.

這並不是一個壞結果。

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!

如果你有興趣學習更多有關我們對這顆星球所造成的衝擊，我們推薦你讀讀 David Biello，也就是本課程作者所撰寫的《不自然世界》。感謝收看！