Is this the most successful animal ever? - Nigel Hughes

譯者: Lilian Chiu 審譯者: Amanda Zhu

A procession of segmented creatures moves across the sea floor.

一群節肢動物在海底移動。

Up ahead, hundreds have begun shedding their exoskeletons

前頭有數百隻已經開始 脫下牠們的甲殼，

and piling on top of one another in what appears to be... a massive orgy.

並疊到彼此身上，這場合就像是……

大型狂歡會。

But this is not some alien world.

但這可不是外星世界。

It’s Earth about 500 million years ago,

這是大約五億年前的地球，

when these creatures, called trilobites, prospered.

這種生物叫做三葉蟲， 當時地球是牠們的天下，

Prevailing for around 270 million years

在世界上存活了約兩億七千萬年，

and encompassing more than 20,000 distinct species,

包含超過兩萬種不同的物種，

trilobites are some of the most successful lifeforms in Earth’s history.

三葉蟲是地球歷史上 最成功的生命形態之一。

When they sprung into existence,

當牠們出現時，

they were among the most diverse and sophisticated organisms

牠們是最多樣化且複雜的有機體，

Earth had yet seen.

在地球上前所未見。

And, as the earliest known animals with complex eyes,

三葉蟲也是目前所知 最早具有複眼的動物，

trilobites had a unique perspective on the ancient world.

牠們對古老的世界有著獨特的視角。

For almost all of Earth’s history before the rise of the trilobites,

根據地球的歷史， 在三葉蟲興起之前，

life had mostly consisted of microscopic marine organisms.

生命幾乎都是海洋裡的顯微有機體。

But then, scientists think an increase in oxygen allowed multicellular lifeforms

但科學家認為，後來氧氣的增加

讓多細胞的生物

to extract more energy from their food and perform more complex functions.

得以從食物中取得更多能量，

進行更複雜的功能。

This then enabled the rise of carnivores,

這就促成了食肉動物的出現，

which in turn spurred a productive arms race,

牠們激起了一場繁殖力的競賽，

resulting in what’s known as the Cambrian explosion.

最後演變為我們所知的寒武紀大爆發。

Within about 20 million years,

在兩千萬年內，

life had branched out to include most of the animal groups we know today.

生命演化並分支，發展出了 現今已知的大多數動物類別。

Trilobites were an important part of this surge.

三葉蟲是這波爆增潮的重點動物。

All trilobites had three lengthwise lobes,

所有的三葉蟲都有三塊縱向葉，

but building off the same basic components,

雖然都是由同樣的基本元素組成，

they varied greatly.

牠們的變化非常多。

Species ranged in length from a few millimeters to almost one meter

不同種的身長也不同， 從幾公釐到近一公尺都有，

and some were equipped with intriguing ornaments.

有些還配有很有趣的裝飾。

As a result, they filled many distinct niches over the ages.

因此，那段時期中出現過 多種形態和習性各異的三葉蟲。

Many trilobites plowed or burrowed into the sea floor while others swam freely.

許多三葉蟲會在海底犁地或挖洞，

其他的則自在地游泳。

Certain species had spines, horns, and even protruding tridents.

某些物種有脊椎、角， 甚至突出的三叉戟。

And their social behavior was complex:

牠們的社交行為也很複雜：

they came together to search for food, find safety in numbers, migrate and mate.

牠們會一起找食物、

聚集大量同類增加安全性、

遷徙、交配。

In fact, their fossilized conga lines represent

事實上，成排的三葉蟲留下的化石

some of the first evidence of animal group behaviour.

是動物群體行為的最早證據。

就像現代的節肢動物，

Like modern arthropods,

trilobites had compound eyes composed of many tiny lenses.

三葉蟲也有由許多小晶體 組成的複眼。

But theirs were made of the mineral calcite,

但這些晶體是由方解石構成，

which also constituted their exoskeletons.

牠們的甲殼也是同樣的成分。

These lenses allowed trilobites to form sharp images

這些晶體讓三葉蟲看見銳利的影像，

and quickly sense changes in light.

並快速察覺光線的改變。

Some had long eye stalks that helped them peep above the muddy sea floor

有些三葉蟲有很長的眼柄，

讓牠們在海底挖洞時 還能看到泥濘的海床上有什麼。

as they burrowed beneath.

Others had large dragonfly-like eyes

有些三葉蟲則具有 如蜻蜓眼般的大眼睛，

that they probably used to scour the ocean bottom

可以讓牠們在昏暗的水域 顛倒著游泳時，

as they swam upside-down in dim waters.

用來搜尋海底。

And some trilobites had pillar-like eyes that may have offered 360 degree views,

有些三葉蟲的眼睛是柱狀的，

三百六十度都能看見，

along with structures that provided shade from overhead light.

還有特殊結構，能遮蔽上頭的光線。

Yet despite their dominance of the seas,

儘管三葉蟲是海洋中的強勢物種，

trilobites were vulnerable to environmental changes and predators.

牠們很容易受環境改變影響， 也很怕捕食性動物。

About 444 million years ago, Earth cooled and sea levels dropped,

大約四億四千四百萬年前，

地球冷卻下來，海平面下降，

radically changing some of their habitats.

讓牠們的一些棲息地 發生很大的改變。

This was the beginning of what would prove to be the trilobite’s long demise.

後來證實，這就是 三葉蟲漫長滅絕之路的開端。

Some 20 million years later, fish with jaws began sweeping the sea.

大約兩千萬年後，

有頜的魚類開始席捲大海。

Trilobites developed spiky ornamentation

三葉蟲發展出了有刺的裝飾，

and neat ways of locking their joints shut.

並演化出很棒的方式 將關節閉鎖起來。

Many species could curl themselves into balls,

許多物種還能把自己蜷成球形，

entirely sealing their soft parts inside their hard exoskeletons.

把柔軟的部位完全 封在堅硬的甲殼裡面。

Then, another extinction event shook the world.

接著，另一場震撼世界的 滅絕事件發生了，

Trilobite diversity dwindled, and come about 360 million years ago,

三葉蟲的多樣性減少，

到了三億六千萬年前，

only one of the 10 former trilobite orders remained.

過去所有的三葉蟲目中， 只有十目存活下來。

Finally, rapid climate change spurred

最後，快速的氣候變遷

the greatest known mass extinction event in Earth's history.

造成了地球史上 已知的最大滅絕事件。

This catastrophic period finished the trilobites off—

這段災難性的時期 讓三葉蟲完全消失，

along with approximately 96% of all marine species.

所有海洋物種中 有近 96% 也難逃此劫。

But trilobites left a remarkable record behind.

但三葉蟲留下了非凡的記錄。

Their calcite exoskeletons made for hardy fossils

牠們的方解石甲殼 形成了堅韌的化石，

that would remain intact for hundreds of millions of years to come.

在接下來的數億年都維持完好。

We’ve found trilobite fossils on every single continent—

在每一塊大陸上 都找到過找到三葉蟲化石，

many in unlikely environments that were once part of the ocean floor.

許多發現地都曾經是海底，

原以為是不太可能 有三葉蟲蹤影的地方。

Trilobites have no direct descendants,

三葉蟲沒有直系的後代，

but their evolutionary cousins are alive and well.

但牠們在演化上的表親 現在仍然活得很好。

And since arthropods make up over 80% of current animal species,

目前的動物當中 有 80% 都是節肢動物，

we might say that, although Earth may no longer be the planet of the trilobites,

我們可以說，

雖然地球可能不再是三葉蟲的星球，

their distant relatives still reign supreme.

牠們的遠親仍然在主宰稱雄。