Exploring Prehistoric Life
The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse.
How new species are created is at the core of the theory of evolution. Mammals may be a good example of how sex chromosome change drove major groups apart.
The evolutionary history of life on Earth traces the processes by which living and fossil organisms have evolved since life appeared on the planet, until the present day.
Fossils are evidence of ancient life forms or ancient habitats which have been preserved by natural processes.