WHAT’S THE OLDEST FOSSIL EVER FOUND?

The oldest fossils found are stromatolites. It’s thought that the oldest were discovered in Australia and are nearly 3.5 billion years old. Stromatolites were formed by the activity of ancient microorganisms, primarily cyanobacteria. The photosynthetic activity of these early life forms caused a reduction in the carbon dioxide present in the surrounding water. This drop in the acidity of the water caused calcium carbonate to be deposited. Calcium carbonate and other sediments from the water were then trapped in the sticky layer of mucilage that surrounds bacterial colonies. Over time the bacterial colonies grew and layer upon layer of sediment built up, leaving behind these ancient stromatolite structures. They provide us with a valuable record of early life on Earth.