An article published in the journal “Proceedings of the National Academy of Sciences” reports the discovery of fossil tunnels that suggest that multicellular organisms existed on Earth already 2.1 billion years ago. A team of researchers studied these tunnels discovered in Gabon, concluding that groups of single cells could aggregate into an organism similar to a tiny slug that could move searching for food. An organism like this would be 1.5 billion years older than the first multicellular organisms known and for this reason the research raised controversy.