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科学家可能发现了地球上最古老的生命

更新时间:2017-3-2 18:39:00 来源:纽约时报中文网 作者:佚名

Scientists Say Canadian Bacteria Fossils Are Earth’s Oldest
科学家可能发现了地球上最古老的生命

They are microscopic artwork: tiny tubes and long filaments, strange squiggles etched into some of the most ancient rocks known.

它们是显微镜下的艺术品:细管、长丝和奇怪的波形曲线蚀刻在一些已知的最古老的岩石里。

On Wednesday, researchers reported that these may be the oldest fossils ever discovered, the remains of bacteria thriving on Earth not long, geologically speaking, after the very birth of the planet. If so, they offer evidence that life here got off to a very early start.

周三,研究人员宣布,这些可能是人类所发现的最为古老的化石,是地球诞生后不久——从地质学角度来说——生活在地球上的细菌的残骸。若是如此,它们为地球上的生命出现得非常早提供了证据。

But many experts in the field were skeptical of the new study — or downright unconvinced.

但该领域的很多专家对这项新研究持怀疑态度,或是完全不相信。

Martin J. Van Kranendonk, a geologist at the University of New South Wales, called the patterns in the rocks “dubiofossils” — fossil-like structures, perhaps, but without clear proof that they started out as something alive.

新南威尔士大学(University of New South Wales)的地质学专家马丁·J·范克拉嫩东克(Martin J. Van Kranendonk)称,那些岩石中的图案为“可疑化石”,即或许是类似化石的结构,但没有确凿的证据证明它们起初是有生命的东西。

Heated disputes are nothing new in the search for the earliest life on Earth.

在寻找地球最早生命的过程中,激烈的争论屡见不鲜。

In 1993 J. William Schopf, a paleontologist at the University of California, Los Angeles, and his colleagues found what that they, too, argued were the world’s oldest fossils: chainlike blobs in 3.46 billion-year-old rocks made, they said, by bacteria. Other researchers later argued that the structures were just oddly shaped minerals.

1993年,加州大学洛杉矶分校(University of California-Los Angeles)的古生物学家J·威廉·舍普夫(J. William Schopf)和同事在有34.6亿年历史的岩石中发现了链状斑纹。他们也宣称那是世界上最古老的化石,还说是细菌留下的。后来,其他一些研究人员认为,那些结构不过是形状奇怪的矿物质而已。

But additional specimens from other sites came to light over the past two decades, and many of them have withstood scrutiny. There is now solid evidence of life dating back about 3.5 billion years.

但来自其他地点的其他标本在过去20年间不断出现,其中很多都经受住了审视。目前有可靠的证据证明,生命可以追溯到35亿年前。

Earth was a billion years old by then, and scientists have long wondered if even older fossils might be found.

地球当时已经存在了10亿年,科学家们一直都在琢磨,是否可以发现年代更久远的化石。

In August, Dr. Van Kranendonk and his colleagues reported discovering fossils in Greenland dating back 3.7 billion years. The scientists argued that the organisms were once mats of bacteria that grew in shallow coastal waters.

去年8月,范克拉嫩东克博士及其同事称,在格陵兰发现了距今37亿年前的化石。他们说,这些有机体曾是生长在沿海浅水域的细菌垫。

In the new study, published in the journal Nature, Mattew S.Dodd, Dominic Papineau and their colleagues at University College London studied rocks that were either slightly older or much older than those containing the Greenland fossils.

在成果已被《自然》(Nature)期刊发表的新研究中,马修·S·多德(Mattew S.Dodd)、多米尼克·帕皮诺(Dominic Papineau)及其伦敦大学学院(University College London)的同事对一些岩石做了研究,比起蕴含格陵兰化石的那些岩石,它们的年代或是稍稍久远一点,或是久远得多。

They came from a remote geological formation in Canada called Nuvvuagittuq, which stretches across four square miles on the coast of Hudson Bay. Geologists surveyed the formation for the first time in the 1990s.

它们来自加拿大哈德逊湾海岸一个绵延4平方英里、名叫努夫亚吉图克(Nuvvuagittuq)的偏远地质构造。地质学家首次考察这一构造是在1990年代。

Researchers have variously estimated its age at 3.77 billion years or 4.22 billion years — just 340 million years after the formation of the planet.

研究人员就其年代给出了不同的估计数字:37.7亿年前或者42.2亿年前——只比地球形成晚3.4亿年。

In 2008, Dr. Papineau collected rocks from the formation and found a number of clues indicating that they had formed around hydrothermal vents on the ancient sea floor that spewed iron and other minerals.

2008年,帕皮诺从该地质构造采集了岩石,发现有许多线索表明它们是在喷出铁和其他矿物质的远古时代海底热泉喷出口周围形成的。

He also found hints that there might have been life there — tiny blobs of rock, for instance, that contained a compound called apatite, which can form from phosphorus released by dying organisms.

他还发现了或许存在生命的线索——例如,呈小圆块的岩石里含有一种名叫磷灰石的化合物,可能是由垂死生物释放的磷形成的。

The tubes and other structures in the rock that Mr. Dodd found are also reminiscent of bacteria that live today around hydrothermal vents. They grow as filaments, feeding on iron compounds and creating tube-shaped cavities in the sediment.

多德在岩石里发现的细管以及其他结构,也让人联想起今天生活在热泉喷出口周围的细菌。它们体如细丝,以铁化合物为食,会让沉积物内出现管状腔。

Similar filaments contain iron compounds in the Nuvvuagittuq rocks, Mr. Dodd and his colleagues found, and they are attached to round clumps that resemble the tiny anchors bacteria use to hold onto rock surfaces. The rocks also contain forms of organic carbon that could have been created by bacteria.

多德及其同事发现,努夫亚吉图克的岩石中的类似细丝含有铁化合物,与细丝相连的圆形块状物与细菌用来附着在岩石表面的微型锚颇为相像。这些岩石还含有可能是由细菌制造的多种有机碳。

The researchers argue that it would be unlikely for all of these features to have formed in the absence of life. “Then you’re left with one scenario — a biological origin,” Mr. Dodd said.

研究人员称,所有这些特征不可能在不存在生命的情况下形成。“因此便剩下一种情况——生物的一个起源,”多德说。

Such a discovery could have big implications for the understanding of life’s early evolution.

这一发现对于理解生命的早期进化可能具有重大意义。

If these really are fossils 3.77 billion years old, then they show that life was already diversifying by that time, thriving in both the shallow ocean in what is now Greenland and the deep ocean in today’s Canada.

如果这些真是来自37.7亿年前的化石,那么它们就能证明,生命当时便已走向多样化,在今日格陵兰所在地的浅海中以及今日加拿大所在地的深海中茁壮成长。

And if these are fossils 4.2 billion years old, then scientists will have evidence that life began quickly on Earth, not long after the oceans formed.

如果这些是来自42亿年前的化石,那么科学家就有了证据可以证明,海洋形成后不久,地球上很快就出现了生命。

Yet Frances Westall, the director of research at the CNRS-Centre de Biophysique Moléculaire in Orléans, France, isn’t convinced these are fossils at all.

不过,法国奥尔良分子生物物理研究中心(CNRS-Centre de Biophysique Moléculaire)的研究主管弗朗西丝·韦斯托尔(Frances Westall)不太相信它们是化石。

“I am frankly dubious,” she said.

“坦白说,我抱有疑虑,”她说。

For one thing, she has argued, the filaments in the Nuvvuagittuq rocks are too big. She and her colleagues have found filaments formed by bacteria in rock dating back 3.3 billion years, and these are far smaller.

她表示,首先,努夫亚吉图克的岩石中的细丝太大了。她和同事已经在33亿年前的岩石中发现了由细菌形成的细丝,它们要小得多。

On the early Earth, bacteria were forced to stay small, Dr. Westall said, because the atmosphere did not yet have enough oxygen to fuel their growth.

韦斯托尔说,在早期的地球上,细菌只能长得小小的,因为空气中没有足够多能够促进其生长的氧气。

Long after the Nuvvuagittuq rocks formed on the sea floor, they were heated to tremendous temperatures. Some experts doubted that microscopic fossils could have survived such a baking.

努夫亚吉图克的岩石在海底形成很久之后,被加热到了极高的温度。一些专家怀疑,微体化石能否捱过这样的炙烤。

“These authors built their research on pushing speculative ideas and appear totally unaware of the considerable evidence against their interpretation,” said Wouter Bleeker, of the Geological Survey of Canada.

“这些论文作者把他们的研究建立在推测性理念之上,似乎完全没注意到与其解释相悖的大量证据,”加拿大地质调查局(Geological Survey of Canada)的沃特·布勒克尔(Wouter Bleeker)说。

In response, Dr. Papineau observed that the type of rock studied, known as chert, is very hard and might have protected fossils from high temperatures.

帕皮诺回应称,他们研究的这种名叫燧石的岩石非常坚硬,或许可以保护化石不受高温的破坏。

“I think the authors have done a good job,” said David Wacey, who researches the origins and evolution of life at the University of Western Australia. With the new evidence, he said, “One comes up with a pretty convincing biological scenario” for the origins of the mysterious rock features.

“我认为论文作者们做得不错,”在西澳大学(University of Western Australia)研究生命起源和进化问题的大卫·韦西(David Wacey)说。他说,有了这些新证据,就可以针对这些不可思议的岩石特征的起源“给出相当令人信服的生物学情境”。

Dr. Wacey was not surprised that the new work had drawn criticism.

韦西对于这项新研究招致了批评并不感到奇怪。

“It may be many years before a consensus is reached,” he said. “But this is how science progresses.”

“可能要到多年以后才能达成一致,”他说。“但科学就是这样发展的。”

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