The location of fossils in sedimentary rock is indicative of their relative age.
This means that one fossil can be classified as older than another based on their relative position in the sedimentary rock.
Fossils are divided into age groups according to a geological time scale, whereby explosions of life or mass extinctions mark the general age of Earth.
For example, layers of rock bearing evidence of the origin of most modern animal phyla would be classified as belonging to the Cambrian period in the Paleozoic era. Layers of rock bearing fossils suggest a rapid diversification of reptiles that belong to the Permian period in the Paleozoic era.
In an event often referred to as the "Big Bang," the universe arose in a relatively brief moment in time and matter was flung outward from this central origin.
Matter has been hurling through space, undergoing a number of changes as it traverses the cosmos.
Macroevolution and major events that lead to speciation was discussed here.