Billions of years ago on the young planet Earth 数十亿年前，在年轻的地球上， simple organic compounds assembled into more complex coalitions 简单的有机化合物组合 成了更复杂的结合体， that could grow and reproduce. 能够成长及繁殖。 They were the very first life on Earth, 它们是地球上最早的生命， and they gave rise to every one of the billions of species 自此之后，地球上 出现的数十亿种物种 that have inhabited our planet since. 通通都起源于它们。 At the time, Earth was almost completely devoid 在当时，地球上可说是非常缺乏 of what we’d recognize as a suitable environment for living things. 我们认为适合生物的环境。 The young planet had widespread volcanic activity 在年轻的地球上， 到处都是火山活动， and an atmosphere that created hostile conditions. 当时的大气也造成了 很不友善的条件。 So where on Earth could life begin? 所以，生命究竟起源于 地球上的何处？ To begin the search for the cradle of life, 若要开始寻找生命的摇篮， it’s important to first understand the basic necessities for any life form. 很重要的是先要了解各种生命形式有什么基本需求。 Elements and compounds essential to life include hydrogen, methane, nitrogen, 对生命来说必备的元素 和化合物包括：氢、甲烷、 carbon dioxide, phosphates, and ammonia. 氮、二氧化碳、磷酸盐、氨。 In order for these ingredients to comingle and react with each other, 若这些要素彼此之间 要能混合、产生作用， they need a liquid solvent: water. 就需要有液体的溶媒：水。 And in order to grow and reproduce, 若要成长和繁殖， all life needs a source of energy. 所有生命都需要能量来源。 Life forms are divided into two camps: 生命形式可以分成两大类： autotrophs, like plants, that generate their own energy, 自营生物，如植物， 会产生自己要用的能量， and heterotrophs, like animals, that consume other organisms for energy. 以及异营生物，如动物， 要食用其他有机体来取得能量。 The first life form wouldn’t have had other organisms to consume, of course, 当然，最早的生命形式 不会有其他有机体可以食用， so it must have been an autotroph, 所以它们一定是自营生物， generating energy either from the sun or from chemical gradients. 能量来自太阳或化学梯度。 So what locations meet these criteria? 所以，什么地点能符合这些条件？ Places on land or close to the surface of the ocean 地面上的地方，或海洋中 接近表面的地方 have the advantage of access to sunlight. 比较有取得阳光的优势。 But at the time when life began, the UV radiation on Earth’s surface 但在生命刚出现时， 地球表面上的紫外线 was likely too harsh for life to survive there. 很可能太过严酷， 让生命无法存活下来。 One setting offers protection from this radiation 有一种环境能提供 保护，阻挡紫外线， and an alternative energy source: 同时也有替代的能量来源： the hydrothermal vents that wind across the ocean floor, 在海底蜿延的海底热泉区， covered by kilometers of seawater and bathed in complete darkness. 它们被数公里的海水覆盖， 完全处在黑暗中 A hydrothermal vent is a fissure in the Earth’s crust 深海热泉区是地球地壳上的裂缝， where seawater seeps into magma chambers 在那里，海水会渗入岩浆库中， and is ejected back out at high temperatures, 接着以高温重新被喷射出来， along with a rich slurry of minerals and simple chemical compounds. 附带的泥浆中丰含 矿物质及简单的化合物。 Energy is particularly concentrated 深海热泉区的陡峭化学梯度 at the steep chemical gradients of hydrothermal vents. 有特别集中的能量。 There’s another line of evidence that points to hydrothermal vents: 还有其他证据证明 深海热泉区是生命起源： the Last Universal Common Ancestor of life, or LUCA for short. 生命的最后共同祖先（LUCA）。 LUCA wasn’t the first life form, but it’s as far back as we can trace. LUCA 并非最早的生命形式， 但它已古早到我们无法追踪。 Even so, we don’t actually know what LUCA looked like— 即便如此，我们其实不知道 LUCA 是什么样子的—— there’s no LUCA fossil, no modern-day LUCA still around— 没有 LUCA 化石， 也没有现代 LCUA 存在—— instead, scientists identified genes that are commonly found in species 不过，科学家发现，在现今仍然存在的 三大生命领域物种中 across all three domains of life that exist today. 有些共同的基因存在。 Since these genes are shared across species and domains, 因为这些基因存在于 不同的物种和领域， they must have been inherited from a common ancestor. 它们一定是来自共同的祖先。 These shared genes tell us that LUCA lived in a hot, oxygen-free place 这些共同基因告诉我们 LUCA 住在一个很热、没有氧气的地方， and harvested energy from a chemical gradient— 并从化学梯度取得能量—— like the ones at hydrothermal vents. 就像深海热泉区的化学梯度。 There are two kinds of hydrothermal vent: 有两种深海热泉区： black smokers and white smokers. 黑烟囱和白烟囱。 Black smokers release acidic, carbon-dioxide-rich water, 黑烟囱会释放富含 二氧化碳的酸性水， heated to hundreds of degrees Celsius and packed with sulphur, iron, copper, 温度高达摄氏数百度，且满是硫磺、铁、铜， and other metals essential to life. 以及其他对生命很重要的金属。 But scientists now believe that black smokers were too hot for LUCA— 但现在科学家相信， 对 LUCA 而言黑烟囱太热了—— so now the top candidates for the cradle of life are white smokers. 所以，最可能是生命摇篮的 候选地点是白烟囱。 Among the white smokers, 在各处的白烟囱当中， a field of hydrothermal vents on the Mid-Atlantic Ridge called Lost City 在大西洋中洋脊有一块 深海热泉区叫做失落城市， has become the most favored candidate for the cradle of life. 是最有可能的生命摇篮候选地点。 The seawater expelled here is highly alkaline and lacks carbon dioxide, 这里喷出的海水是高度碱性的， 且缺乏二氧化碳， but is rich in methane and offers more hospitable temperatures. 但富含甲烷，温度也比较适宜。 Adjacent black smokers may have contributed the carbon dioxide necessary 邻近的黑烟囱可能有提供 失落城市的生命在演化时 for life to evolve at Lost City, 所必需要的二氧化碳， giving it all the components to support the first organisms 补全了支持最早有机体 所必要的所有元素， that radiated into the incredible diversity of life on Earth today.
