In 1667, a Danish scientist finally concluded that certain mysterious stones prized for their supposed medicinal powers, hadn’t fallen from the sky during lunar eclipses and weren’t serpent tongues. In fact, they were fossilized teeth— many belonging to a prehistoric species that would come to be called megalodon, the biggest shark to ever live. So what was it like when megalodon ruled the seas? And what brought this formidable predator to extinction?
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 并非在月食期间从天而降, 也不是巨蛇的舌头。 事实上,它们是牙齿化石—— 其中许多属于一类史前物种, 后来被命名为巨齿鲨, 有史以来最大的鲨鱼。 那么当巨齿鲨称霸海洋时是怎么样的? 是什么致使这个凶猛的捕食者灭绝?
Because their skeletons were cartilaginous, what remains of megalodons are mostly scattered clues, like some isolated vertebrae and lots of their enamel-protected teeth. Like many sharks, megalodons could shed and replace thousands of teeth over the course of their lives. Interestingly, some fossil sites harbor especially high numbers of small megalodon teeth. Experts believe these were nurseries that supported countless generations of budding megalodons. They grew up in sheltered and food-packed shallow waters before becoming unrivaled adult marine hunters.
因为它们的骨架由软骨所组成, 巨齿鲨的残骸主要是零星的线索, 像落单的脊椎骨和大量釉质保护的牙齿。 像许多鲨鱼一样,巨齿鲨在一生中 会脱落并更换数千颗牙齿。 有趣的是,一些化石地点 发现了极高数量的 小型巨齿鲨牙齿。 专家认为那是养育 无数代新生巨齿鲨的 “育儿园”。 它们在相对安全、食物充沛的 浅水地带长大, 直到成为不可比拟的 成年海洋猎手。
Looking at the similarities with great white shark teeth, scientists estimate that megalodons might have stretched up to 20 meters— three times longer than great whites. And during their reign, which began around 20 million years ago, megalodons lived just about everywhere, with individuals also potentially undertaking transoceanic migrations.
根据与大白鲨牙齿的相似性, 科学家估计巨齿鲨 可能体长 20 米多—— 这是大白鲨的三倍。 在大约始于两千万年前的巨齿鲨统治期, 巨齿鲨几乎无处不在, 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. Otters and dugongs thrived in newly formed kelp forests, and baleen whales were at their most diverse. Megalodons had no shortage of high-energy, edible options. And it seems they were ambitious eaters. Generally, as carnivores consume protein-rich meat, certain nitrogen isotopes accumulate in their tissues— including the enamel of their teeth. Analyzing megalodon teeth, scientists confirmed they were apex predators that not only ate large prey species— but also other predators, perhaps even each other.
世界更为温暖, 海洋中充满着生命。 海獭和儒艮在新形成的 海带林中蓬勃生长, 须鲸也是最为多样的。 巨齿鲨并不缺乏高热量的食用选项, 而且它们似乎是野心熊熊的捕猎者。 一般地,当肉食者摄入 高蛋白的肉类, 一些氮同位素会聚集在其组织中, 包括牙齿的釉质。 通过分析巨齿鲨牙齿, 科学家们证实它们是顶尖猎手, 不仅捕食大型猎物, 还捕食他掠食者,甚至会自相残杀。
In addition to megalodon’s teeth, researchers have access to one exceptionally well-preserved spinal column that comprises 141 vertebrae of a 46-year-old megalodon. A 3D model of the megalodon’s body suggests that its stomach could reach volumes of almost 10,000 liters— big enough to fit an entire orca. Reconstructing their jaws, researchers think megalodons could eat a now-extinct 7-meter sperm whale in as few as four bites. And the fossilized bones of ancient cetaceans do indeed show evidence of megalodon bite marks— including some that healed over, confirming that megalodons pursued live prey.
在巨齿鲨的牙齿之外, 研究人员获得了一具 保存绝佳完好的脊椎, 由一头 46 岁巨齿鲨的 141 个脊椎骨所组成。 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—— 足以装下一整头虎鲸。 重建它们的颚骨之后, 研究者认为,只需四口 巨齿鲨就能吞下一头 现已灭绝的 7 米长抹香鲸。 古鲸类骨骼化石确实显示出 巨齿鲨咬痕的证据, 包括一些已经愈合的咬痕, 证实了巨齿鲨追踪活的猎物。
But if megalodons were so powerful, why did they go extinct? It seems there were a few contributing factors. By the time they disappeared around 3.5 million years ago, the global climate had cooled, causing more glaciers to form and the sea level to drop. This dried up many coastal habitats, meaning some of the world’s most resource-rich marine sites were lost. About a third of all marine megafauna eventually went extinct, so fewer prey species were available. And megalodons already faced high energetic demands because of their size and the mechanism they likely used to regulate their body temperature, which allowed them to navigate cold waters and attack prey with bursts of speed. Environmental changes may have made megalodons vulnerable and increasingly put them in competition with other predators, including the great white shark, a relative newcomer.
但如果巨齿鲨这么强大, 它们为什么走向灭绝? 似乎有几个因素。 在差不多 350 万年前它们消失时, 全球气候变冷, 导致更多冰川形成、海平面下降。 这使得许多沿海栖息地干涸, 意味着世界上资源富集的海洋区域消失。 约三分之一的海洋巨型动物最终灭绝, 因此可供捕食的猎物种类减少。 而巨齿鲨因为它们的体型 和可能用来调节体温的机制 使其能游经寒冷水域并快速攻击猎物, 所以能量需求较高。 环境变化也许使得巨齿鲨更加脆弱, 并使它们更多地与其他捕食者竞争, 包括大白鲨,相对较新的捕食者。
Because megalodons were highly mobile predators, their extinction had global consequences. The end of their long-distance travels probably disrupted nutrient transport between different ecosystems. And many animals were suddenly released from the immense predatory pressure of their bite. Interestingly, some marine mammals dramatically increased in size afterwards, which was perhaps partially afforded because they were no longer dealing with such a mega-existential threat. Knowing that the decline of apex predators can destabilize entire ecosystems, conservationists are working to prevent today’s sharks from facing a similar fate— this time, because of humans. And meanwhile, the megalodon remains a colossal testament to ecological interdependence and millions of years of bones well-bitten and waters well-wandered.
因为巨齿鲨是高度灵活的捕猎者, 它们的灭绝有着全球性的影响。 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。 许多动物突然不再承受 巨大的捕食压力。 有趣的是,一些海洋哺乳动物 在后来体型显著增大, 也许是因为 它们不再面对如此庞大的威胁。 由于知道顶级掠食者的减少 会颠覆整个生态系统, 保护主义者在尝试避免 今天的鲨鱼走向类似的结局—— 这回是因为人类。 同时,巨齿鲨仍然是 生态相互依存的重大见证, 是其数百万年前咬碎猎物、 漫游海洋的重大见证。