|The stromatolites in figure a are from Greenland; those in c and d are younger stromatolites from Western Australia. Figure b shows the layers created by microbes as they formed the Greenland stromatolites (blue lines). ‘Stroms’ are several overlapping stromatolites. |
How quickly did life 'take off' on Earth?
The answer to this question is probably relevant to the likelihood that life will be found on other suitable planets too because it it happened quickly on Earth this suggests the process was not the vastly unlikely event that creationists try to present it as but a process (or processes) that can happen in just a few hundred million years if not even more quickly.
Yes, I know that a few hundred million years is not a short time but, compared to the 4.5 billion years or so that Earth has been around, it is during Earth's early childhood. It also suggests that Earth was not the hot, inhospitable, volcano-strewn and desiccated ball of rock that it was once thought to be but that it settled down quite quickly to be closer to what we have today (sans life, initially, of course). It also brings the early Mars within the timescale over which life could have arisen there at a time when Mars was thought to have been suitable, complete with liquid water, atmosphere, etc.
The discover of these stromatolites in Greenland rock pushes the earliest age at which cellular life was known to exist on Earth with a fair degree of certainty back to 3.7 billion years ago from the previous earliest known evidence dated at 3.48 billion years old found in Australian rocks.
Biological activity is a major factor in Earth’s chemical cycles, including facilitating CO2 sequestration and providing climate feedbacks. Thus a key question in Earth’s evolution is when did life arise and impact hydrosphere–atmosphere–lithosphere chemical cycles? Until now, evidence for the oldest life on Earth focused on debated stable isotopic signatures of 3,800–3,700 million year (Myr)-old metamorphosed sedimentary rocks and minerals from the Isua supracrustal belt (ISB), southwest Greenland. Here we report evidence for ancient life from a newly exposed outcrop of 3,700-Myr-old metacarbonate rocks in the ISB that contain 1–4-cm-high stromatolites—macroscopically layered structures produced by microbial communities. The ISB stromatolites grew in a shallow marine environment, as indicated by seawater-like rare-earth element plus yttrium trace element signatures of the metacarbonates, and by interlayered detrital sedimentary rocks with cross-lamination and storm-wave generated breccias. The ISB stromatolites predate by 220 Myr the previous most convincing and generally accepted multidisciplinary evidence for oldest life remains in the 3,480-Myr-old Dresser Formation of the Pilbara Craton, Australia. The presence of the ISB stromatolites demonstrates the establishment of shallow marine carbonate production with biotic CO2 sequestration by 3,700 million years ago (Ma), near the start of Earth’s sedimentary record. A sophistication of life by 3,700 Ma is in accord with genetic molecular clock studies placing life’s origin in the Hadean eon (>4,000 Ma).*
*Citation links removed for clarity. See original paper for references
Allen P. Nutman, Vickie C. Bennett, Clark R. L. Friend, Martin J. Van Kranendonk & Allan R. Chivas
Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures
Nature (2016) doi:10.1038/nature19355
Copyright © 2016, Rights Managed by Nature Publishing Group. Reprinted with kind permission under licence #3940091337487.
So, refined data from several strands of evidence seems to be converging on life getting going on Earth relatively quickly, causing scientists to revise upwards any estimates of the probability of it arising at all. This also causes them to revise upwards the probability of life arising elsewhere in the Universe and even in our solar system when the conditions were right.
To any dedicated young-earth creationist or Bible literalist, this will just add to their paranoia that this is all a big conspiracy to make them think their ignorant superstition really isn't better than real, physical, testable and observable evidence, no matter how desperately frauds try to sell them the notion that it is. I wonder how they'll explain this one away.
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