Sulfur Caused Early Life to Sprout

The whole land will be a burning waste of salt and sulfur—nothing planted, nothing sprouting, no vegetation growing on it.
(Deuteronomy 29:23)

Researchers made headlines recently when they announced the discovery of evidence for fossilized sulfur-metabolizing microbes.1 Although sulfur is often associated with death and destruction, this latest work indicates it played a key role in allowing life to thrive on early Earth. The data indicates that sulfur-loving organisms existed on our planet, around 3.4 billion years ago.

This work does not represent the first and only evidence for early life on Earth. A variety of geochemical and fossil markers indicate a diversity of microbes lived on our planet as far back as 3.8 billion years ago. See previous discussions for more details:

The problem is that some researchers dispute whether these markers provide unequivocal signatures for biological activity. They argue that abiotic mechanisms could have generated the same chemical fingerprints as life. They also assert that geological processes could have produced micro- and macrostructures that superficially resemble micro- and macrofossils.

This new work does represent the most comprehensive case that microstructures found in the Strelley Pool Formation of Western Australia are bioauthentic. At the same time, it rules out abiotic explanations for these features. This study follows on the heels of a report given by Frances Westall of the French National Center for Scientific Research at the Origins 2011meeting in July.2 Westall reported on microfilaments associated with aragonite, a calcium carbonate mineral. These structures were found in the Barberton Greenstone Belt of South Africa and date at 3.5 billion years old. According to Westall, this association can only be explained if photosynthetic microbes were present on early Earth.

In spite of the controversy, the evidence continues to mount that life was present on early Earth, perhaps as far back as 3.8 billion years ago. It is instructive to note that Martin Braiser, one of the chief skeptics of the claims for early life on Earth, is now one of the investigators arguing for the existence of sulfur-metabolizing microbes.

Part of the reason why some scientists are skeptical about the existence of early life on Earth has to do with the implications. The best evidence to date indicates that life could not have existed permanently on Earth prior to 3.8 billion years ago. In other words, even though Earth is 4.5 billion years old, the first 700 million years of its existence don’t matter for the origin-of-life scenario. The “clock” starts at 3.8 billion years ago. We have evidence that life was present on Earth at 3.8 billion years ago, which leaves very little time for chemical evolution to generate the origin of life.

For more details on this discovery listen to the August 22, 2011 edition of Science News Flash.

Endnotes:

  1. David Wacey et al., “Microfossils of Sulphur-Metabolizing Cells in 3.4 Billion-Year-Old Rocks of Western Australia,” Nature Geoscience (2011), published electronically August 21, 2011, doi:10.1038/NGEO1238.
  2. Katharine Sanderson, “Calcified Clue to Ancient Photosynthesis,” Nature News (2011), published online July 6, 2011, doi:10.1038/news.2011.397.

 

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