For the most part, I have expressed age in absolute terms of millions of years rather than use the adjectival names of periods coined by classical geology.

However, it is the fully boned species that were most successful, and spread from the oceans to rivers and lakes.You are now well over a vertical kilometre below the rim, and the surrounding rocks have been dated to the immense age of 2,000 million years. They include the orangutan, the gibbon, the chimpanzee and the primate with whom Attenborough has arguably his most famous encounter, the mountain gorilla.

All these advances in knowledge and many more will be mentioned in the appropriate places in the text that follows. Homo erectus gradually spread from Africa and reached Europe some 800,000 years ago, where a drop in temperature led to him inhabiting caves. Ideas about biodiversity and mass extinctions are now prominently included, and the revelation – now textbook – that birds are dinosaurs is front and centre, having been dismissed the first time round. For billions of years, Earth was an inhospitably alien place – covered with churning seas, slowly crafting its landscape through volcanic eruptions, the atmosphere in a constant state of chemical flux.The most suitable places for fossilisation are in seas and lakes where sedimentary deposits that will become sandstones and limestones are slowly accumulating. Finally, Attenborough describes the most prolific mammals—those that originated in the Northern Hemisphere and give birth to fully formed young. Credit should be given to Matthew Cobb, who has helped Attenborough with contemporary thinking on matters such as the intense integration of genetics into evolutionary biology – a result of our ability to read genomes with ease and speed. Williams used a traditional chamber music ensemble of ( harp, flute, clarinet, strings and percussion) combined with electronic sounds.