Evolution of Earth timeline. Computer illustration of a timeline showing the evolution of Earth, from its creation (far left) to the emergence of modern humans (far right), and how the emergence of more complex lifeforms coincided with a sharp increase in the Earth's atmospheric oxygen level (blue). From left to right: the Big Bang, formation of the Moon, formation of the oceans, emergence of sulphate-reducing bacteria, emergence of oxygen producing bacteria, first eukaryotes, emergence of exoskeleton animals, dinosaurs and humans.