And sometimes, an event occurs causing changes so drastic that most species are completely wiped out within a short period of time.

有時候，一個事件的發生造成了劇烈改變，導致大部分物種在短時間內完全滅亡

So here are the 5 most incredible mass extinctions ever to occur,

現在要介紹史上五次令人無法置信的大滅絕

and a look at whether the 6th might be happening right now.

並且來看看第六次大滅絕是否即將發生

440 million years ago was the The Ordovician extinction.

四億四千萬年前是奧陶紀的滅絕

At that time, most creatures swam or crawled in shallow seas.

那時候大部分生物在淺海中游動或爬行

As newly created volcanic rock was worn down by water and wind, it reacted with carbon dioxide and absorbed it.

新形成的火山岩受風雨侵蝕，和二氧化碳作用並將它吸收

As a result, carbon dioxide levels dropped, temperatures fell and water got locked away as ice.

因此，二氧化碳程度下降，溫度也下降，水結成冰

This caused ocean levels to drop and shallow seas to drain

導致海平面下降，淺海乾涸

and after several cycles of growing and shrinking glaciers, about 86 percent of species were lost forever.

在冰河結冰、退冰數次循環後，約86%的物種永遠消失

Then over millions of years the oceans slowly repopulated with fish and the land was colonized by early plants.

而後數百萬年間，海洋中漸漸出現了許多魚群，而陸地上則出現原始植物

These plants were then eaten by the first crawling and flying insects.

最早出現的爬行、飛行類昆蟲以這些植物為食

Then 374 million years ago these new plants contributed to the next mass extinction.

三億七千四百萬年前，這些植物造成了下一次大滅絕

The plants absorbed enough carbon dioxide to create another round of global cooling.

這些植物吸收足夠的二氧化碳，導致全球再次降溫

They changed soil causing nutrients to wash into the ocean creating enormous amounts of algae which sucked up oxygen.

它們改變土壤狀況，將養分沖進海洋，導致吸收氧氣的藻類茂密增生

More than half of ocean species essentially choked to death.

超過一半的海洋物種基本上是因窒息而死

Although somewhere in the world, a small family of fish with foot-like fins and lungs managed to scrape by.

雖然在世上某處，一群有著如腳般的鰭和肺的魚，勉強存活了下來

Over the next 100 million years, these creatures would evolve into amphibians, reptiles and nearly all modern land animals.

在接下來的一億年間，這些生物演化成兩棲動物、爬蟲類，和幾乎全部的現代陸地動物

250 million years ago is the Permian extinction.

兩億五千萬年前是二疊紀的滅亡

The single worst mass extinction in history, 70 percent of life on land and over 95 percent of life in the oceans was wiped out.

歷史上最慘的一次大滅絕，70%的陸地生命和95%的海洋生命全被消滅

Billions of tonnes of volcanic gases destroyed the ozone layer and the average ocean temperature hit 40 degrees Celsius, which is hotter than most hot tubs.

數十億噸的火山氣體破壞臭氧層，海水平均溫度高達攝氏40度，比大部分熱水澡盆還燙

Acid rain fell all over the planet, devastating life on land.

酸雨下遍了整個地球，摧毀陸地上的生命

Life had only 50 million years to recover until the fourth mass extinction came.

在第四次大滅亡來臨之前，只有五千年的時間再次孕育生命

At this time early small dinosaurs roamed the land.

當時原始的小恐龍在陸地上遊走

A huge volcanic rift opened in the middle of the planet; eventually splitting the Americas from Europe and Africa, and forming the Atlantic Ocean.

一個巨大的火山裂縫在地球中間產生，最後將美洲從歐洲和非洲裡分開，形成大西洋

The volcanoes spewed out carbon dioxide, increasing temperatures and killing about 80 percent of the species around at the time.

火山噴發出二氧化碳，使氣溫升高，在那時造成了80%的物種死亡

Yet in this newly emptied world dinosaurs did extremely well and during the next 135 million years, they grew to become some of the largest land animals the world had ever seen.

然而在這剛變得荒蕪的世界，恐龍存活了下來。在接下來的一億三千五百萬年間，牠們成為世界有史以來最大型的陸地生物之一

But all good things must come to an end.

但天下無不散之筵席

Many scientists believe that the extinction of dinosaurs was caused by an asteroid the size of a small town crashing into what is now Mexico’s Yucatan peninsula.

很多科學家認為恐龍的滅亡，是由一顆與小鎮一樣大的行星，撞擊現在的墨西哥猶加敦半島地區而導致的

The impact shot millions of tons of dust into the atmosphere,

這個撞擊將數百萬噸的塵土捲入空氣中

blocking out sunlight and spelling an end to all large dinosaurs, the small ones that survived evolved into birds.

遮蔽了陽光，為大型恐龍的生命畫下了句點 (存活下來的小恐龍演化成鳥類)

The world was now primed for a small, scuffling, rat-like creature, the ancestor of all modern mammals.

世界這時由用腳走路、像老鼠一樣的小型生物所主宰，而這些生物是現代哺乳類動物的祖先

Within 50 million years, its descendants - from wildebeest and whales to horses and us humans

在五千萬年內，牠們的後裔，從牛羚、鯨魚到馬和我們人類，

have diversified and grown to dominate nearly every available environment on earth.

多樣化發展，並且逐漸在地球上幾近所有的可生長環境中都佔有一席之地

So where does that leave us now, 65 million years later?

所以在六千五百萬年後的今天，那留給我們什麼？

Well, human dominance of earth has led to big changes too, except the changes of today are happening over decades, not millennia.

人類主宰地球也造成了很大的改變，只不過今天的改變是發生在數十年間，而非數千年

Carbon dioxide levels, implicated in so many of the past extinctions, have climbed at least 25 percent in just the last 50 years, almost no time in geological terms.

與過去幾次大滅絕有著相當關係的二氧化碳濃度，在近50年間，這段在地質學上還稱不上是個時期的時間，已攀升了至少25%

In addition to climate change, we’ve exterminated hundreds of species by hunting, fishing, habitat destruction and pollution.

除了氣候變遷外，我們從事打獵、捕魚，破壞棲息地，製造空氣汙染，導致數以百計的物種滅絕

It’s been estimated that current species extinction rates are between 100 and 1000 times higher than the natural background rate,

據估計，現有物種的滅亡率，比自然滅亡率還要高出100至1000倍

and that if all the species that are currently threatened by declining populations actually do go extinct, we may reach the level of a true mass extinction in just a few hundred years.

如果現在瀕臨絕種的動物真的消失了，幾百年後，我們可能就真的面臨大滅亡時期了

And while all the mass extinctions of the past have had some survivors, it’s worth remembering that the creatures at the top of the food chain are usually hit the hardest.

雖然在過去所有的大滅亡中，都有一些倖存者，值得記得的是在食物鏈最頂端的生物，通常都是最難熬的

We may be setting the stage for history to repeat itself, and for some small, unexpected organism to replace us as the planet’s dominant form of life.

我們也許會為歷史重演作好準備，讓小型、令人意想不到的生物取代我們，成為地球上最主要的生物

Curious about the coolest animals that existed during these mass extinctions? Check out our

對在這些大滅絕當中曾存活的最酷動物感到好奇嗎？來看看我們

new video “5 Insane Creatures We Wish Still Existed” over on our AsapTHOUGHT channel

的新影片「5個我們希望還存在的瘋狂生物」，到我們的AsapTHOUGHT頻道

which explores some of the neatest and most absurd creatures through history that are

探索一些歷史上最棒、最荒謬，但已不存在的生物

no longer with us. There's a Link in the description for that video.

在簡介欄位那邊有影片的連結

And subscribe for more weekly science videos!

歡迎訂閱我們的每週影片！