Why did Megalodon go extinct? - Jack Cooper and Catalina Pimiento

翻译人员: Jacky He 校对人员: Gia Hwang

In 1667, a Danish scientist finally concluded that certain mysterious stones

1667 年一位丹麦科学家得出结论，

某些被认为具有药用功效的神秘石头

prized for their supposed medicinal powers,

hadn’t fallen from the sky during lunar eclipses

并非在月食期间从天而降，

and weren’t serpent tongues.

也不是巨蛇的舌头。

In fact, they were fossilized teeth—

事实上，它们是牙齿化石——

many belonging to a prehistoric species that would come to be called megalodon,

其中许多属于一类史前物种， 后来被命名为巨齿鲨，

the biggest shark to ever live.

有史以来最大的鲨鱼。

So what was it like when megalodon ruled the seas?

那么当巨齿鲨称霸海洋时是怎么样的？

And what brought this formidable predator to extinction?

是什么致使这个凶猛的捕食者灭绝？

Because their skeletons were cartilaginous,

因为它们的骨架由软骨所组成，

what remains of megalodons are mostly scattered clues,

巨齿鲨的残骸主要是零星的线索，

like some isolated vertebrae and lots of their enamel-protected teeth.

像落单的脊椎骨和大量釉质保护的牙齿。

Like many sharks, megalodons could shed and replace thousands of teeth

像许多鲨鱼一样，巨齿鲨在一生中

over the course of their lives.

会脱落并更换数千颗牙齿。

Interestingly, some fossil sites harbor especially high numbers

有趣的是，一些化石地点 发现了极高数量的

of small megalodon teeth.

小型巨齿鲨牙齿。

Experts believe these were nurseries that supported countless generations

专家认为那是养育 无数代新生巨齿鲨的

of budding megalodons.

“育儿园”。

They grew up in sheltered and food-packed shallow waters

它们在相对安全、食物充沛的 浅水地带长大，

before becoming unrivaled adult marine hunters.

直到成为不可比拟的 成年海洋猎手。

Looking at the similarities with great white shark teeth,

根据与大白鲨牙齿的相似性，

scientists estimate that megalodons might have stretched up to 20 meters—

科学家估计巨齿鲨 可能体长 20 米多——

three times longer than great whites.

这是大白鲨的三倍。

And during their reign, which began around 20 million years ago,

在大约始于两千万年前的巨齿鲨统治期，

megalodons lived just about everywhere,

巨齿鲨几乎无处不在，

with individuals also potentially undertaking transoceanic migrations.

个别巨齿鲨还可能进行跨洋迁徙。

The world was warmer and the ocean was brimming with life.

世界更为温暖， 海洋中充满着生命。

Otters and dugongs thrived in newly formed kelp forests,

海獭和儒艮在新形成的 海带林中蓬勃生长，

and baleen whales were at their most diverse.

须鲸也是最为多样的。

Megalodons had no shortage of high-energy, edible options.

巨齿鲨并不缺乏高热量的食用选项，

And it seems they were ambitious eaters.

而且它们似乎是野心熊熊的捕猎者。

Generally, as carnivores consume protein-rich meat,

一般地，当肉食者摄入 高蛋白的肉类，

certain nitrogen isotopes accumulate in their tissues—

一些氮同位素会聚集在其组织中，

including the enamel of their teeth.

包括牙齿的釉质。

Analyzing megalodon teeth, scientists confirmed they were apex predators

通过分析巨齿鲨牙齿， 科学家们证实它们是顶尖猎手，

that not only ate large prey species—

不仅捕食大型猎物，

but also other predators, perhaps even each other.

还捕食他掠食者，甚至会自相残杀。

In addition to megalodon’s teeth,

在巨齿鲨的牙齿之外，

researchers have access to one exceptionally well-preserved spinal column

研究人员获得了一具 保存绝佳完好的脊椎，

that comprises 141 vertebrae of a 46-year-old megalodon.

由一头 46 岁巨齿鲨的 141 个脊椎骨所组成。

A 3D model of the megalodon’s body suggests that its stomach

巨齿鲨身体的三维模型显示，

它的胃可达到近乎一万升的容量——

could reach volumes of almost 10,000 liters—

big enough to fit an entire orca.

足以装下一整头虎鲸。

Reconstructing their jaws, researchers think megalodons could eat

重建它们的颚骨之后， 研究者认为，只需四口

a now-extinct 7-meter sperm whale in as few as four bites.

巨齿鲨就能吞下一头 现已灭绝的 7 米长抹香鲸。

And the fossilized bones of ancient cetaceans do indeed show evidence

古鲸类骨骼化石确实显示出 巨齿鲨咬痕的证据，

of megalodon bite marks— including some that healed over,

包括一些已经愈合的咬痕，

confirming that megalodons pursued live prey.

证实了巨齿鲨追踪活的猎物。

But if megalodons were so powerful, why did they go extinct?

但如果巨齿鲨这么强大， 它们为什么走向灭绝？

It seems there were a few contributing factors.

似乎有几个因素。

By the time they disappeared around 3.5 million years ago,

在差不多 350 万年前它们消失时，

the global climate had cooled,

全球气候变冷，

causing more glaciers to form and the sea level to drop.

导致更多冰川形成、海平面下降。

This dried up many coastal habitats,

这使得许多沿海栖息地干涸，

meaning some of the world’s most resource-rich marine sites were lost.

意味着世界上资源富集的海洋区域消失。

About a third of all marine megafauna eventually went extinct,

约三分之一的海洋巨型动物最终灭绝，

so fewer prey species were available.

因此可供捕食的猎物种类减少。

And megalodons already faced high energetic demands because of their size

而巨齿鲨因为它们的体型

和可能用来调节体温的机制

and the mechanism they likely used to regulate their body temperature,

which allowed them to navigate cold waters

使其能游经寒冷水域并快速攻击猎物，

and attack prey with bursts of speed.

所以能量需求较高。

Environmental changes may have made megalodons vulnerable

环境变化也许使得巨齿鲨更加脆弱，

and increasingly put them in competition with other predators,

并使它们更多地与其他捕食者竞争，

including the great white shark, a relative newcomer.

包括大白鲨，相对较新的捕食者。

Because megalodons were highly mobile predators,

因为巨齿鲨是高度灵活的捕猎者，

their extinction had global consequences.

它们的灭绝有着全球性的影响。

The end of their long-distance travels probably disrupted nutrient transport

它们长距离迁徙的结束，很可能破坏了

不同生态系统之间的营养物质运输。

between different ecosystems.

And many animals were suddenly released

许多动物突然不再承受

from the immense predatory pressure of their bite.

巨大的捕食压力。

Interestingly, some marine mammals dramatically increased in size afterwards,

有趣的是，一些海洋哺乳动物 在后来体型显著增大，

which was perhaps partially afforded

也许是因为

because they were no longer dealing with such a mega-existential threat.

它们不再面对如此庞大的威胁。

Knowing that the decline of apex predators can destabilize entire ecosystems,

由于知道顶级掠食者的减少 会颠覆整个生态系统，

conservationists are working to prevent today’s sharks from facing a similar fate—

保护主义者在尝试避免 今天的鲨鱼走向类似的结局——

this time, because of humans.

这回是因为人类。

And meanwhile, the megalodon remains a colossal testament

同时，巨齿鲨仍然是

to ecological interdependence

生态相互依存的重大见证，

and millions of years of bones well-bitten and waters well-wandered.

是其数百万年前咬碎猎物、 漫游海洋的重大见证。