A fresh look at the fossil evidence for early Archaean cellular life
A fresh look at the fossil evidence for early Archaean cellular life
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DOI：
10.1098/rstb.2006.1835
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发表时间：
2006-06-29
影响因子：
6.3
通讯作者：
Wacey, David
中科院分区：
文献类型：
--
作者：
Brasier, Martin;McLoughlin, Nicola;Wacey, David
岩石记录为我们提供了独特的证据来测试细胞生命首次出现在地球上的时间和地点。然而，它的研究需要谨慎。如果没有对形态空间和背景进行批判性分析，使用多种现代技术，加上拒绝替代非生物（零）假设，就不应该接受年龄超过3.0 Gyr的叠层石和“微体化石”的生物起源。以前的观点认为，在古代，微体化石类物体中生物学形态和碳化学的共同出现是生物起源的一个假定指标是不够的。就像著名的火星微化石一样，我们需要问的不是“这些结构让我们想起了什么？””，而是“这些结构是什么？地球上最古老的假定“微体化石”组合在3.4-3.5 Gyr碳质硅质岩中，如Apex硅质岩，同样是自组织结构，无法通过生物成因测试。在大约2.7 Gyr之前的化石记录中存在一个解释学悖论：合适的岩石（例如同位素轻的碳质硅质岩）广泛存在，但生命信号是神秘的，难以破译。一种新的方法包括详细绘制保存完好的砂岩颗粒在约3.4 Gyr Strelley池燧石。这些可以包含显示同源性，颗粒选择性和几个层次的地球化学处理的石内微管。初步研究邀请比较一类环境包体线索推定微生物的起源和现代厌氧变形菌和火山玻璃euendoliths的活动。
The rock record provides us with unique evidence for testing models as to when and where cellular life first appeared on Earth. Its study, however, requires caution. The biogenicity of stromatolites and 'microfossils' older than 3.0 Gyr should not be accepted without critical analysis of morphospace and context, using multiple modern techniques, plus rejection of alternative non-biological (null) hypotheses. The previous view that the co-occurrence of biology-like morphology and carbonaceous chemistry in ancient, microfossil-like objects is a presumptive indicator of biogenicity is not enough. As with the famous Martian microfossils, we need to ask not 'what do these structures remind us of?', but 'what are these structures?' Earth's oldest putative 'microfossil' assemblages within 3.4-3.5 Gyr carbonaceous cherts, such as the Apex Chert, are likewise self-organizing structures that do not pass tests for biogenicity.There is a preservational paradox in the fossil record prior to ca 2.7 Gyr: suitable rocks (e.g. isotopically light carbonaceous cherts) are widely present, but signals of life are enigmatic and hard to decipher. One new approach includes detailed mapping of well-preserved sandstone grains in the ca 3.4 Gyr Strelley Pool Chert. These can contain endolithic microtubes showing syngenicity, grain selectivity and several levels of geochemical processing. Preliminary studies invite comparison with a class of ambient inclusion trails of putative microbial origin and with the activities of modern anaerobic proteobacteria and volcanic glass euendoliths.