最古老的陸地化石可以解釋地球是如何從雪球州恢復過來的

最古老的陸地化石可以解釋地球是如何從雪球州恢復過來的

Thread-like filaments, attached to hollow spheres in 635 million-year-old rocks, represent the earliest evidence we have of life on land. They may also help explain how life rebounded from “Snowball Earth”, the periods when it was so cold even much of the equator was covered in ice.

在6億3千5百萬年前的巖石中，絲狀的細絲附著在空心球體上，這是我們擁有的陸地上有生命的最早證據(jù)。它們也可能有助于解釋生命是如何從“雪球地球”中恢復過來的。在“雪球地球”時期，地球非常寒冷，甚至赤道的大部分地區(qū)都被冰雪覆蓋。

The upper parts of the Doushantuo Formation in South China have provided an abundance of fossils, but the older ones were thought to predate anything of interest. Virginia Tech PhD student Tian Gan only stumbled across a set of preserved branching filaments and hollow spheres close to the formation's base by chance. "It was an accidental discovery," Gan said in a statement.

中國南方陡山沱組的上部已經(jīng)提供了大量的化石，但更古老的化石被認為比任何有趣的東西都要早。弗吉尼亞理工大學的博士生田甘(音譯)只是在巖層底部偶然發(fā)現(xiàn)了一組保留下來的分支細絲和空心球體。甘在一份聲明中表示:“這是一個意外發(fā)現(xiàn)。”

The only thing the filaments truly resemble is modern-day fungi, and the authors think that's probably what they were. Wherever it fits on the tree of life, however, Gan thinks it may explain one of paleontology's big questions: how did life rebound so quickly after being almost wiped out by snowball Earth?

這些絲狀物唯一真正相似的是現(xiàn)代的真菌，而作者認為這可能就是它們曾經(jīng)的樣子。然而，甘認為，無論它與生命之樹的哪個位置相吻合，它都可以解釋古生物學的一個大問題:在幾乎被雪球地球毀滅的情況下，生命是如何迅速復蘇的?

Stephen Luntz

Snowball Earth was not like more recent ice ages. The ice was so thick and universal we are unsure how any life survived at all, making the sudden appearance of the Ediacaran diversity soon after the world warmed a mystery.

雪球地球不像更近的冰河時代。冰層如此之厚，如此普遍，我們不確定生命是如何存活下來的，這使得在世界變暖后不久突然出現(xiàn)的埃迪卡拉多樣性成為一個謎。

Gan's discovery may answer that. “We realized that this could be the fossil that scientists have been looking for a long time. If our interpretation is correct, it will be helpful for understanding the paleoclimate change and early life evolution," Gan said.

甘的發(fā)現(xiàn)或許可以回答這個問題。“我們意識到這可能是科學家們已經(jīng)尋找了很長時間的化石。如果我們的解釋是正確的，這將有助于理解古氣候變化和早期生命進化，”甘說。

In Nature Communications, Gan advances the theory fungi broke down rocks until the nutrients they contained washed to the sea, fertilizing the post-snowball era.

在《自然通訊》中，甘提出了真菌分解巖石的理論，直到巖石中含有的營養(yǎng)物質(zhì)被沖到海里，成為后斯諾鮑時代的肥料。

"Fungi have a mutualistic relationship with the roots of plants, which helps them mobilize minerals, such as phosphorus,” Gan explained.

“真菌與植物的根有一種互惠關(guān)系，這有助于它們調(diào)動礦物質(zhì)，如磷，”甘解釋說。

"The question used to be: 'Were there fungi in the terrestrial realm before the rise of terrestrial plants'," said co-author Professor Shuhai Xiao "And I think our study suggests yes. Our fungus-like fossil is 240 million years older than the previous record. This is, thus far, the oldest record of terrestrial fungi."

“過去的問題是:‘在陸生植物出現(xiàn)之前，陸生領(lǐng)域中是否存在真菌?’”合著者肖樹海教授說，“我認為我們的研究表明存在。”我們發(fā)現(xiàn)的類真菌化石比之前的記錄早了2.4億年。這是迄今為止最古老的陸生真菌記錄。”

Fungus or not, the fossil appears to have lived in sheet cavities in the dolostone rocks in which it was found, but Xiao acknowledged; “Little is known about how exactly they lived and how they were preserved. Why can something like fungi, which have no bones or shells, be preserved in the fossil record?" The spheres may be part of the same organism, or something else with which the fungus had a symbiotic relationship.

不管是不是真菌，這具化石似乎生活在發(fā)現(xiàn)它的白云巖的片狀洞里，但肖承認;“他們究竟是如何生活的，又是如何被保存下來的，我們知之甚少。為什么像真菌這樣既沒有骨頭也沒有殼的生物，能在化石記錄中保存下來呢?”這些球可能是同一生物體的一部分，或者是與真菌有共生關(guān)系的其他東西。

The cavities were sealed shut with natural cement 632 million years ago, which the authors believe rules out more recent colonization of the space.

這些空腔是6.32億年前用天然水泥封起來的，作者們認為這排除了最近在太空中殖民的可能性。

Molecular clocks indicate the last common ancestor of fungi and other forms of life lived 900-1,500 million years ago, but this is presumed to have been in the oceans. It's been a mystery when a descendent on the fungal line first had the bright idea of taking over the land. A few candidates for terrestrial fungi of immense age have been found, but these were in estuary sediments, and could as easily have lived on location as been washed off the land.

分子鐘表明，真菌和其他生命形式最后的共同祖先生活在9億至15億年前，但據(jù)推測，這是在海洋中。當真菌系的一個后代第一次有了接管土地的聰明想法時，這一直是個謎。人們已經(jīng)發(fā)現(xiàn)了一些年代久遠的陸生真菌的候選者，但這些真菌都存在于河口的沉積物中，它們既可以輕易地從陸地上被沖走，也可以輕易地在當?shù)厣妗?/p>