In this final installment to the series, David Attenborough travels to four unique locations about the globe where an abundance of fossilized plant and animal remains have given us a detailed picture of what life could have been like in prehistoric times. Each of the sites experienced its own set of circumstances which enabled it to preserve many perfect specimens for extraction and analysis. Piecing together the collected evidence, paleontologists have been able to determine early animal hierarchies, their diets and their evolutionary paths.