20億年前，大滅絕幾乎殺死了地球上所有的生命

20億年前，大滅絕幾乎殺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.

在地球歷史上曾發(fā)生過幾次大滅絕事件，包括白堊紀(jì)-古近紀(jì)大滅絕事件，可以說恐龍的死亡是最著名的。現(xiàn)在，研究人員可能已經(jīng)發(fā)現(xiàn)了一個新的大滅絕事件，一個發(fā)生在20.5億年前的大滅絕事件，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《美國國家科學(xué)院院刊》(PNAS)上發(fā)表的一項研究中，一組研究人員觀察了加拿大哈德遜灣(Hudson Bay)數(shù)十億年前形成的巖石，發(fā)現(xiàn)那里的生命在20.5億年前急劇減少。這與大氧化事件(GOE)的結(jié)束同時發(fā)生，這是24億到20億年前的一段時間，見證了地球上氧氣水平的激增，最終，氧氣水平大幅下降。

“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.”

該研究的摘要寫道:“利用硫和鋇同位素測量結(jié)果的洞見，結(jié)合包裹地層的放射性年齡，我們推斷，這里研究的硫酸鹽礦物記錄了GOE(約2018 Ma)剛發(fā)生后的環(huán)境硫酸鹽。”這些硫酸鹽礦物捕獲到的負(fù)三氧同位素異常低至∼0.8‰。這樣的負(fù)值發(fā)生在采空區(qū)之后不久，要求初級生產(chǎn)力迅速降低80%，盡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.”

摘要繼續(xù)說：“考慮到這些數(shù)據(jù)意味著初級生產(chǎn)力的崩潰，而不是效率的下降，地球系統(tǒng)中這種轉(zhuǎn)變的觸發(fā)因素必須反映出營養(yǎng)物質(zhì)(如磷)的可用性的變化?？偟膩碚f，這些數(shù)據(jù)強調(diào)了大氧化事件是一個盛宴和饑荒的故事：在地質(zhì)上，在GOE過渡期結(jié)束時，生物圈規(guī)?？涨皽p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.

這次大滅絕是已知的最大規(guī)模的物種滅絕事件，96%的海洋物種和73%的陸生脊椎動物在這次大滅絕中死亡。

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.

研究人員認(rèn)為，這次大滅絕事件可能是由“氧氣過量”引起的，在這種情況下，氧氣增加到驚人的、不可持續(xù)的水平，最終一次急劇下降，導(dǎo)致對氧氣賴以生存的生物營養(yǎng)耗盡而亡。

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.

該研究的合著者彼得·克羅克福德告訴《新聞周刊》，在大氧氣事件發(fā)生前2億到1億年，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.”

“在這次滅絕事件之前的1億到2億年間，地球上有大量的生命，但在這次事件之后，有很大一部分死亡了，”Crockford告訴新聞媒體。“然而，在接下來的10億年里，地球上的生命數(shù)量或生物圈的大小并沒有像最近的大規(guī)模滅絕那樣恢復(fù)，而是保持在很小的范圍內(nèi)——大約在20億到10億年前。”

“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.

克羅克福德在與這項研究同時發(fā)表的一篇博客文章中寫道:“雖然滅絕不是這個事件的恰當(dāng)術(shù)語，因為我們可能永遠(yuǎn)不會知道，如果真的有任何物種滅絕了，那么地球上的生命數(shù)量肯定會大幅減少。”

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

克羅克福德告訴《新聞周刊》，這一潛在的發(fā)現(xiàn)可以讓我們洞察地球在遙遠(yuǎn)的未來是如何發(fā)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20億年前一樣，今天的生物圈(包括我們)依賴于食物鏈的基礎(chǔ)，”他補充道。今天，海洋中的微生物和陸地上的植物。盡管氧氣水平可能永遠(yuǎn)不會以足夠快的速度變化到足以引起人類注意的水平，但在未來10億年內(nèi)，它們絕對可能發(fā)生變化。”