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,丹麥科學家 判定一顆神秘的石頭 —據說可以治病,因而受到重視— 不是月蝕期間從天上掉下來的, 也不是蛇的舌頭, 而是牙齒的化石— 屬於生存在史前時代的巨齒鯊, 有史以來最大隻的鯊魚。 那麼,巨齒鯊稱霸海洋時, 水面下的生活是什麼樣子呢? 巨齒鯊為什麼滅絕了呢?
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.
因為巨齒鯊的骨骼是軟骨, 所以巨齒鯊死後留下的化石相當零碎, 像是一塊塊的脊椎骨, 和許多被琺瑯質保護的牙齒。 和其他鯊魚一樣, 巨齒鯊在牠們的一生中 換下數以千計的牙齒。 有趣的是,有些化石挖掘地 藏有特別多小顆的巨齒鯊牙齒。 專家認為這些地方是巨齒鯊的育嬰場所, 養育無數幼小的巨齒鯊們成長茁壯。 牠們在糧食充足、環境安全 的淺水區域長大, 之後長大成為所向無敵的 成年水生狩獵者。
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.
觀察巨齒鯊牙齒 和大白鯊牙齒的相似處後, 科學家估計巨齒鯊身長 可能長達 20 公尺, 整整是大白鯊的三倍。 距今兩千萬年前是巨齒鯊的全盛時期, 那時隨處可見牠們的蹤影, 有些個體可能正在跨洋遷徙的半路上。
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.
那時全球氣溫較溫暖, 海洋裡的生命欣欣向榮, 水獺和儒艮在新形成的 巨藻林裡繁衍生息, 鬚鯨在當時則擁有最多樣化的基因。 巨齒鯊不缺高營養價值的可食獵物, 而且似乎牠們的食慾相當旺盛。 食肉動物吃下富含蛋白質的獵物時, 有幾種氮同位素會累積在體內組織裡, 包括牙齒琺瑯質裡。 分析完巨齒鯊的牙齒後,科學家確認 巨齒鯊是當時的頂級掠食者, 牠們不僅只吃大型獵物, 還可能吃下其他掠食者,甚至彼此。
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.
除了牙齒之外, 科學家還經手研究了一條 保存狀態極好的脊椎骨, 有 141 節椎骨, 主人是 46 歲的巨齒鯊。 巨齒鯊身體的 3D 模型表明 巨齒鯊的胃容量高達接近一萬公升, 裝得下一整隻虎鯨。 重建巨齒鯊的上下顎之後,學者認為 牠們或許可以只用四口就吃下 已滅絕的 7 公尺長抹香鯨。 古老鯨豚類動物的化石上 也看得到巨齒鯊的咬痕, 有些咬痕已經癒合, 因此證實巨齒鯊會獵食活的獵物。
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.
既然巨齒鯊那麼強悍, 那到底為什麼會滅絕? 有幾個因素。 牠們滅絕時,也就是 距今 350 萬年前, 全球氣溫下降, 冰河擴大,導致海平面下降, 讓許多淺灘生態區乾涸, 也就代表牠們失去許多 提供牠們豐富營養來源的地點。 約三分之一的巨型水生生物走向滅絕, 所以能捕食的獵物數量銳減。 巨齒鯊本身又需要大量能量, 因為牠們體型龐大, 控制體溫的機制也消耗許多熱量, 牠們才能在低溫水體中活動自如, 在轉眼間捕捉到獵物。 環境條件變化可能威脅到巨齒鯊的生存, 讓巨齒鯊跟其他掠食者的競爭更加激烈, 其中包括大白鯊,相對較晚出現的對手。
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.
巨齒鯊掠食範圍廣大, 所以牠們的滅絕會影響到全世界。 沒了巨齒鯊長距離的移動, 很可能讓不同生態系統間的 營養傳輸鏈斷裂, 使得許多動物突然從 被巨齒鯊咬噬的壓力中解放。 有趣的是,有些水生哺乳類的 身體尺寸在巨齒鯊滅絕後變大, 部分原因可能是 牠們再也不用面對 如此重大的存亡危機。 因知頂級掠食者的稀缺 會撼動整個生態系統, 所以現在環境保育家們著手保護 海裡的鯊魚,以免重蹈覆徹, 這次是從人類手中保護牠們。 巨齒鯊成為生態系統內 生物互相依附而生存的鐵證, 以及百萬年來攪亂水流、 咬食獵物的風雲動物。