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Primitive life forms may have first appeared on Earth about 3800 million years ago. These bacteria lived in the oceans and built up solid mats of calcium carbonate, also known as lime. The deposits from the bacteria are known as stromatolites. |
Stromatolites are living fossils and the oldest living lifeforms on our planet. The name derives from the Greek, stroma, meaning “mattress”, and lithos, meaning “rock”. Stromatolite literally means “layered rock”. The existence of these ancient rocks extends three-quarters of the way back to the origins of the Solar System.
With a citizen scientist’s understanding, stromatolites are stony structures built by colonies of microscopic photosynthesising organisms called cyanobacteria. As sediment layered in shallow water, bacteria grew over it, binding the sedimentary particles and building layer upon millimetre layer until the layers became mounds. Their empire-building brought with it their most important role in Earth’s history. They breathed. Using the sun to harness energy, they produced and built up the oxygen content of the Earth’s atmosphere to about 20%, giving the kiss of life to all that was to evolve.
Living stromatolites are found in only a few salty lagoons or bays on Earth. Western Australia is internationally significant for its variety of stromatolite sites, both living and fossilised. Fossils of the earliest known stromatolites, about 3.5 billion years old, are found about 1,000km north, near Marble Bar in the Pilbara region. With Earth an estimated 4.5 billion years old, it’s staggering to realise we can witness how the world looked at the dawn of time when the continents were forming. Before plants. Before dinosaurs. Before humans.
Credit: bbc.com
Picture credit: Google
