Is this the most successful animal ever? - Nigel Hughes

翻译人员: Yue Zhang 校对人员: Yanyan Hong

A procession of segmented creatures moves across the sea floor.

一队节肢动物正在海底爬行，

Up ahead, hundreds have begun shedding their exoskeletons

前方，上百个节肢动物 已经开始蜕去它们的外骨骼，

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

堆在彼此身上，就像是—— 一场大型狂欢会。

But this is not some alien world.

但这可不是外星世界，

It’s Earth about 500 million years ago,

而是 5 亿年前的地球。

when these creatures, called trilobites, prospered.

那时，这些叫三叶虫的动物处于繁盛期。

Prevailing for around 270 million years

三叶虫在地球上 存在了大概 2.7 亿年，

and encompassing more than 20,000 distinct species,

包含 2 万多个不同的物种，

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

是地球史上最成功的生物之一。

When they sprung into existence,

自它们诞生起，

they were among the most diverse and sophisticated organisms

它们是地球上迄今为止所见过的

Earth had yet seen.

最多样、最复杂的生物之一。

And, as the earliest known animals with complex eyes,

同时，作为已知最早的有复眼的动物，

trilobites had a unique perspective on the ancient world.

三叶虫看古世界有着独特的视角。

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

三叶虫兴起之前，地球历史上

life had mostly consisted of microscopic marine organisms.

绝大部分生命体由海洋微生物构成。

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

但之后，科学家认为 氧气的增加使多细胞生物

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

从食物中吸取更多的能量， 并执行更复杂的功能。

This then enabled the rise of carnivores,

这使食肉动物得以兴起，

which in turn spurred a productive arms race,

反过来又刺激了一场生产性的军备竞赛，

resulting in what’s known as the Cambrian explosion.

造成了人们所称的寒武纪生命大爆发 （Cambrian Explosion）。

Within about 20 million years,

约在 2000 万年内，

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

生命进行扩展，已囊括 我们如今所知的大多数动物群体。

Trilobites were an important part of this surge.

在这次激增中，三叶虫十分重要。

All trilobites had three lengthwise lobes,

所有的三叶虫都有三块纵向叶片，

but building off the same basic components,

但建立在相同的基本组件上，

they varied greatly.

三叶虫的种类大相径庭。

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

不同种的长度区间为几毫米到近一米，

and some were equipped with intriguing ornaments.

有的身上还带有有趣的装饰。

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

所以它们在那些年代里 填充了许多不同的生态龛。

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

许多三叶虫犁入或钻进海底， 其他三叶虫则自由游动。

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

某些品种有刺、角， 甚至突出的三叉戟。

And their social behavior was complex:

它们的社交会行为也很复杂：

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

大量聚集在一起觅食、 寻找安全的地方、迁移并繁衍。

In fact, their fossilized conga lines represent

实际上，三叶虫的化石康加线 （conga lines）体现了

some of the first evidence of animal group behaviour.

动物存在集体行为的最早证据。

Like modern arthropods,

像现代的节肢动物一样，

trilobites had compound eyes composed of many tiny lenses.

三叶虫的复眼 由许多小型的晶状体组成。

But theirs were made of the mineral calcite,

但它们的复眼是 由矿物方解石制构成的，

which also constituted their exoskeletons.

同时构成三叶虫外骨骼的物质。

These lenses allowed trilobites to form sharp images

通过晶状体， 三叶虫得以看到清晰的图像，

and quickly sense changes in light.

迅速感知到光的变化。

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

有些三叶虫有长长的眼柄 帮助它们在钻进泥泞海底的时候

as they burrowed beneath.

探视海床上方。

Others had large dragonfly-like eyes

另一些则有蜻蜓般的大眼睛，

that they probably used to scour the ocean bottom

这样在昏暗的水域中倒立游动时，

as they swam upside-down in dim waters.

它们或许能用眼睛来搜索海底。

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

有的三叶虫眼睛则呈柱状， 能提供 360 度的视野，

along with structures that provided shade from overhead light.

它们还具有遮挡头顶光线的结构。

Yet despite their dominance of the seas,

但即便在海洋中占主导地位，

trilobites were vulnerable to environmental changes and predators.

三叶虫容易受环境变化影响， 且易被捕食者抓获。

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

约 4.44 亿年前， 地球降温，海平面下降，

radically changing some of their habitats.

三叶虫的栖息地遭到急剧变化。

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

这也被证实是三叶虫长期消亡的起点。

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

大概 2000 万年后， 海里开始充满长有下颚的鱼类。

Trilobites developed spiky ornamentation

三叶虫的装饰部位长出尖刺，

and neat ways of locking their joints shut.

用妙招让鱼的下颚紧闭。

Many species could curl themselves into balls,

许多种类可以将自己卷成球状，

entirely sealing their soft parts inside their hard exoskeletons.

外骨骼完全封住柔软部位。

Then, another extinction event shook the world.

接下来，另一灭绝事件震惊了世界。

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

三叶虫的多样性逐渐减少， 先前三叶虫等级有十个，

only one of the 10 former trilobite orders remained.

而在约 3.6 亿年前，仅剩一个。

Finally, rapid climate change spurred

最终，快速的气候变化刺激了

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

地球史上已知的最大规模灭绝事件。

This catastrophic period finished the trilobites off—

这个灾难性时期导致了三叶虫——

along with approximately 96% of all marine species.

以及约 96% 海洋物种的灭亡。

But trilobites left a remarkable record behind.

但三叶虫留下了非凡的记录。

Their calcite exoskeletons made for hardy fossils

它们的方解石外骨骼变成坚硬的化石，

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

在未来数亿年内可完好无损地保存。

We’ve found trilobite fossils on every single continent—

我们在每片大陆上都发现了三叶虫化石，

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

曾经属于海底但不太可能 存在化石的环境中也找到了许多。

Trilobites have no direct descendants,

三叶虫没有直系后代，

but their evolutionary cousins are alive and well.

但它们进化的表亲生存得很好。

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

既然在目前动物物种中， 节肢动物的占比高于 80%，

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

我们可以说， 尽管地球或许不再是三叶虫的星球，

their distant relatives still reign supreme.

但它们的远亲仍享有至高的地位。