Diverse life forms may have evolved earlier than previously thought

Centimetre-size pectinate-branching and parallel-aligned filaments composed of red haematite, some with twists, tubes and different kinds of haematite spheroids - Diverse microbial life existed on Earth at least 3.75 billion years ago, suggests a new study led by UCL researchers that challenges the conventional view of when life began. For the study, published in Science Advances , the research team analysed a fist-sized rock from Quebec, Canada, estimated to be between 3.75 and 4.28 billion years old. In an earlier Nature  paper*, 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 centimetre 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. The team also provide evidence of how the bacteria got their energy in different ways.