Microscopic fossils found in Western Australia show life on earth in its most primitive form, according to a new report.
Close to three years ago, a research team from the University of Western Australia found fossils of tiny organisms in 3.4 billion-year-old sandstone in Strelley Pool in the dry Pilbara region, some 1,500 km north of Perth.
After years of extensive analysis, there is now clear evidence that fossilized bacteria fed on sulfur, and not oxygen, in order to produce energy and grow, according to the report published in Nature Geoscience journal.
“At last we have good solid evidence for life over 3.4 billion years ago,” said the report’s co-author Professor Martin Brasier from the University of Oxford Department of Earth Sciences. “It confirms there were bacteria at this time, living without oxygen.”
The earth was very hot and volatile when these organisms lived. Volcanic activity was widespread and cloudy skies kept in the heat, pushing ocean temperatures up to around 40-50 degrees.
Oxygen levels were very low and only increased millions of years later when algae and plant matter began producing the gas through respiration. But the primitive organisms whose existence was recorded in the sandstone of the oldest known beach on earth thrived in these conditions, living off sulfur found in soil and around hydrothermal vents and hot springs.
Similar bacteria still exist today.
Fossil or Fake?
The Strelley Pool fossils are some of the best preserved ever found. But it can be very difficult to distinguish between genuine organic fossils and the natural mineralization process in rock structures. And thanks to technological advances over the last decade, convincing the scientific community of evidence of fossilized life has become even more difficult.
In 2002, for example, the same Oxford department who published this latest report claimed microfossils found in the Apex cherts of the Pilbara region were not consistent with the shape and crystal structure of fossilized bacteria, despite having been widely considered so.
Years of studying these new microfossils produced crucial results that seem to confirm they are indeed biological and were not formed through any mineralization process.
Furthermore, pyrite crystals or fool’s gold associated with the imprints are very likely to have been produced as a by-product of sulfur metabolism.
Life On Mars
This research will undoubtedly be of interest to those seeking to answer the eternal question: are we alone? If life does exist outside the earth’s atmosphere, it is likely to be in the form of sulfur-eating microorganisms in low-oxygen environments.
Professor Brasier says any proposed evidence of microfossils from elsewhere in our solar system will have to pass the same chemical and physical tests as those from Strelley Pool. “Could these sorts of things exist on Mars?” he asks. “It is just about conceivable.”
Key Statistics - Fossils in Western Australia (source: Government of Western Australia)
- The world’s oldest known fossil stromatolites, or layered rock structures, are located in Marble Bar in the Pilbara region.
- The 3.54-billion-year-old stromatolites represent more geological periods throughout history than any other worldwide.
- Organisms such as those found fossilized at Strelley Pool near Marble Bar were responsible for transforming the toxic greenhouses gasses of the earth’s earliest atmosphere into breathable oxygen.