There has been quite a competition to find the oldest fossils on Earth. Many scientists have spent many years looking for them because they tell the beginnings of the story of evolution and reveal when life began on Earth. There are many impressive fossils such as the dinosaur fossils in London’s Natural History Museum but the world’s oldest fossils are nothing like those, they are so tiny that the scientists have dubbed them “micro-fossils”. They are bacteria, which lived in a very different world to the one that exists today. The oldest ones found so far were found in 2007, but news of their finding was published in 2010 in the journal Nature Geoscience after the team had properly analyzed their findings.
The fossilized microbes were found in 3.4 million year old sandstones at the remote Strelley Pool, in the Pilbara around 38 miles west of Marble Bar, in Western Australia. Their location means that there was life on Earth 3.4 million years ago. However, scientific analyses of the specimens show the bacteria lived in a world without oxygen. These creatures processed sulphur for energy and growth rather than oxygen. According to Professor Martin Brazier, of Oxford University, co-researcher on the fossils, similar bacteria are common today, living places where there is little oxygen and they can live on organic matter, for example, smelly ditches, hydrothermal vents, hot springs, and other such places.
The sandstones, which host the fossils, formed in a shallow water estuary or beach. The fossils are tiny, just a few microns across. Having subjected the fossils to the most advanced techniques probing their origins, the researchers are certain that the round and oval fossils within the rock are bacterial cells along with their protective tubes. In addition, iron pyrite or “fool’s gold” crystals found with the fossils, iron pyrite is formed from iron and sulphur, and isotopes within the crystal indicate that it was a by product of the bacteria’s sulphur based metabolism. The scientists also believe that the fact that these isotopes are light isotopes signify that they are life and that the two facts when taken together indicate that there was a sulphur eco-system in the place where they found the fossils.
According to Dr David Wacey, University of Western Australia, the microbes lived on an earth very different to earth today, with very warm temperatures with 140f – 158f sea temperatures; the sea contained few large landmasses, and a methane and carbon dioxide rich atmosphere. In these conditions, the ability to process sulphur would have an evolutionary success strategy.
Although, some researchers claim that there are fossils older than the Western Australian fossils. These scientists claim that some found in Ishua, in Greenland are 3.75 billion years old. However, some experts believe that the analysis of these fossils was selective and not as exhaustive as that done on the Western Australian fossils.
The reason why this discovery is so important is that it gives clues to those searching for life on other planets. Nili Fossae, in the Northern Hemisphere on Mars is, according to images from the three orbital probes, identical to Pilbara. Knowing about our own planet helps experts to understand other planets.
