Researchers analyzed a fist-sized rock from Quebec, Canada, estimated to be between 3.75 and 4.28 billion years old. In an earlier article, the team found tiny filaments, knobs and tubes in the rock which appeared to have been made by bacteria. However, not all scientists agreed that these structures — dating about 300 million years earlier than what is more commonly accepted as the first sign of ancient life — were of biological origin. Now, after extensive further analysis of the rock, the team have discovered a much larger and more complex structure — a stem with parallel branches on one side that is nearly a centimeter long — as well as hundreds of distorted spheres, or ellipsoids, alongside the tubes and filaments. The researchers say that, while some of the structures could conceivably have been created through chance chemical reactions, the ‘tree-like’ stem with parallel branches was most likely biological in origin, as no structure created via chemistry alone has been found like it.