Questioning the evidence for Earth's oldest fossils
Questioning the evidence for Earth's oldest fossils
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DOI：
10.1038/416076a
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发表时间：
2002-03-07
期刊：
影响因子：
64.8
通讯作者：
Grassineau, NV
中科院分区：
文献类型：
--
作者：
Brasier, MD;Green, OR;Grassineau, NV
类似保存完好的细菌和蓝藻微化石的结构类似于西澳大利亚 Warrawoona 群 34.65 亿年前的尖燧石 (1-4)，目前为地球上生命提供了最古老的形态学证据，并被用来支持产氧光合作用的早期开始 (5)。已提出十一种丝状原核生物，其形状和几何形状各异，符合真正的太古代微化石所需的标准(1-5)，并与其他因不可靠或不可再现而被驳回的微化石形成对比(1,3,6,7)。这些结构比假定的蓝藻生物标志物 (8)、蓝藻基因组论证 (9)、含氧大气 (10) 和任何相对多样化的微化石 (5) 都要早近十亿年。在这里，我们报告了关于该类型和重新收集的材料的新研究，涉及测绘、光学和电子显微镜、数字图像分析、显微拉曼光谱和其他地球化学技术。我们将所谓的微化石样结构重新解释为由多代含金属热液脉燧石和火山玻璃中的非晶石墨形成的次生文物。尽管没有对主要生物形态的支持，但推断出地球上最古老的已知热液系统之一是碳化合物的费托合成和碳同位素分馏。
Structures resembling remarkably preserved bacterial and cyanobacterial microfossils from similar to3,465-million-year-old Apex cherts of the Warrawoona Group in Western Australia(1-4) currently provide the oldest morphological evidence for life on Earth and have been taken to support an early beginning for oxygen-producing photosynthesis(5). Eleven species of filamentous prokaryote, distinguished by shape and geometry, have been put forward as meeting the criteria required of authentic Archaean microfossils(1-5), and contrast with other microfossils dismissed as either unreliable or unreproducible(1,3,6,7). These structures are nearly a billion years older than putative cyanobacterial biomarkers(8), genomic arguments for cyanobacteria(9), an oxygenic atmosphere(10) and any comparably diverse suite of microfossils(5). Here we report new research on the type and re-collected material, involving mapping, optical and electron microscopy, digital image analysis, micro-Raman spectroscopy and other geochemical techniques. We reinterpret the purported microfossil-like structure as secondary artefacts formed from amorphous graphite within multiple generations of metalliferous hydrothermal vein chert and volcanic glass. Although there is no support for primary biological morphology, a Fischer-Tropsch-type synthesis of carbon compounds and carbon isotopic fractionation is inferred for one of the oldest known hydrothermal systems on Earth.