20亿年前，大灭绝几乎杀死了地球上所有的生命

20亿年前，大灭绝几乎杀死了地球上所有的生命

There have been several mass extinction events during the planet’s history, including the Cretaceous–Paleogene extinction event, arguably the best known because of the death of the dinosaurs. Now, researchers may have discovered a new mass extinction event, one that happened 2.05 billion years ago and likely killed between 80 percent and 99.5 percent of all of life on Earth.

在地球历史上曾发生过几次大灭绝事件，包括白垩纪-古近纪大灭绝事件，可以说恐龙的死亡是最著名的。现在，研究人员可能已经发现了一个新的大灭绝事件，一个发生在20.5亿年前的大灭绝事件，可能造成地球上80%到99.5%的生命死亡。

In a study published in PNAS, a group of researchers looked at rocks in Hudson Bay, Canada, that formed billions of years ago and found that there was a sharp drop in life 2.05 billion years ago. This happened in conjunction with the end of the Great Oxidation Event (GOE), a period between 2.4 billion and 2 billion years ago that saw a surge and ultimately, a huge drop in oxygen levels on the planet.

在《美国国家科学院院刊》(PNAS)上发表的一项研究中，一组研究人员观察了加拿大哈德逊湾(Hudson Bay)数十亿年前形成的岩石，发现那里的生命在20.5亿年前急剧减少。这与大氧化事件(GOE)的结束同时发生，这是24亿到20亿年前的一段时间，见证了地球上氧气水平的激增，最终，氧气水平大幅下降。

“Using insights from sulfur and barium isotope measurements, combined with radiometric ages from bracketing strata, we infer that the sulfate minerals studied here record ambient sulfate in the immediate aftermath of the GOE (ca. 2,018 Ma),” the study’s abstract reads. “These sulfate minerals captured negative triple-oxygen isotope anomalies as low as ∼ −0.8‰. Such negative values occurring shortly after the GOE require a rapid reduction in primary productivity of >80%, although even larger reductions are plausible.”

该研究的摘要写道:“利用硫和钡同位素测量结果的洞见，结合包裹地层的放射性年龄，我们推断，这里研究的硫酸盐矿物记录了GOE(约2018 Ma)刚发生后的环境硫酸盐。”这些硫酸盐矿物捕获到的负三氧同位素异常低至∼0.8‰。这样的负值发生在采空区之后不久，要求初级生产力迅速降低80%，尽管更大幅度的降低是可能的。”

The abstract continues: “Given that these data imply a collapse in primary productivity rather than export efficiency, the trigger for this shift in the Earth system must reflect a change in the availability of nutrients, such as phosphorus. Cumulatively, these data highlight that Earth’s GOE is a tale of feast and famine: A geologically unprecedented reduction in the size of the biosphere occurred across the end-GOE transition.”

摘要继续说：“考虑到这些数据意味着初级生产力的崩溃，而不是效率的下降，地球系统中这种转变的触发因素必须反映出营养物质(如磷)的可用性的变化。总的来说，这些数据强调了大氧化事件是一个盛宴和饥荒的故事：在地质上，在GOE过渡期结束时，生物圈规模空前减小。”

The Great Dying Event, the largest known mass extinction event, killed 96 percent of all marine species and 73 percent of terrestrial vertebrate species.

这次大灭绝是已知的最大规模的物种灭绝事件，96%的海洋物种和73%的陆生脊椎动物在这次大灭绝中死亡。

The researchers believe that the mass extinction event may have been caused by an “oxygen overshoot,” where oxygen increased to staggering and unsustainable levels that ultimately dropped precipitously once the organisms that needed it to survive ran out of nutrients.

研究人员认为，这次大灭绝事件可能是由“氧气过量”引起的，在这种情况下，氧气增加到惊人的、不可持续的水平，最终一次急剧下降，导致对氧气赖以生存的生物营养耗尽而亡。

The study’s co-author, Peter Crockford, told Newsweek that between 200 and 100 million years before the event, there was a large amount of life on the planet.

该研究的合著者彼得·克罗克福德告诉《新闻周刊》，在大氧气事件发生前2亿到1亿年，地球上有大量生命。

“Over the 100 to 200 million years before this die-off event there was a large amount of life on the planet, but after this event a huge portion died off,” Crockford told the news outlet. “However, instead of recovering like more recent mass extinctions, the amount of life on the planet or size of the biosphere stayed small for the following billion years of Earth’s history—about two billion to one billion years ago.”

“在这次灭绝事件之前的1亿到2亿年间，地球上有大量的生命，但在这次事件之后，有很大一部分死亡了，”Crockford告诉新闻媒体。“然而，在接下来的10亿年里，地球上的生命数量或生物圈的大小并没有像最近的大规模灭绝那样恢复，而是保持在很小的范围内——大约在20亿到10亿年前。”

“While extinction is not the appropriate term for this event, given that we will likely never know what, if any, actual species went extinct, it appears there was certainly a dramatic reduction in the amount of life on the planet,” Crockford wrote in a blog post accompanying the research.

克罗克福德在与这项研究同时发表的一篇博客文章中写道:“虽然灭绝不是这个事件的恰当术语，因为我们可能永远不会知道，如果真的有任何物种灭绝了，那么地球上的生命数量肯定会大幅减少。”

Crockford told Newsweek that the potential discovery could give insight into how Earth in the distant future.

克罗克福德告诉《新闻周刊》，这一潜在的发现可以让我们洞察地球在遥远的未来是如何发展的。

“Just like two billion years ago, the biosphere today (including us) relies on the base of the food chain,” he added. “Today, that is microorganisms in the ocean and plants on land. Although oxygen levels will likely never change at a pace fast enough to a level significant enough for humans to take much notice, they could absolutely change over the next billion years.”

“就像20亿年前一样，今天的生物圈(包括我们)依赖于食物链的基础，”他补充道。今天，海洋中的微生物和陆地上的植物。尽管氧气水平可能永远不会以足够快的速度变化到足以引起人类注意的水平，但在未来10亿年内，它们绝对可能发生变化。”