First Life sees Attenborough tackle the subject of the origin of life on Earth. He investigates the evidence from the earliest fossils, which suggest that complex animals first appeared in the oceans around 500 million years ago, an event known as the Cambrian Explosion. Trace fossils of multicellular organisms from an even earlier period, the Ediacaran biota, are also examined. The naturalist travels to Canada, Morocco and Australia, using some of the latest fossil discoveries and their nearest equivalents amongst living species to reveal what life may have been like at that time. Visual effects and computer animation are used to reconstruct and animate the extinct life forms.