Evidence for evolution - fossils

Fossils of ammonites - sea creatures that became extinct about 65 million years ago

Most of the evidence for evolution comes from the fossil record. Fossils show how much, or how little, organisms have changed over time. One of the problems with the fossil record is that it contains gaps. Not all organisms fossilise well, and there will be many fossils that have been destroyed by the movements of the Earth, or simply not yet been discovered.

The horse

One of the few animals for which we have a fairly complete evolutionary record is the horse. All the main stages of the evolution of the horse have been preserved in fossil form.

Over 60 million years, the horse evolved from a dog-sized creature that lived in rainforests into an animal adapted to living on the plains and standing up to 2 metres high.

In the process its multi-toed feet, that were adapted for walking across the forest floor, evolved into single-toed hooves more suited for running over open country.

The evolution of the horse

	time period	height
Modern horse	1 million years ago	1.6 metres
Pliohippus	10 million years ago	1.0 metres
Merychippus	30 million years ago	1.0 metres
Mesohippus	40 million years ago	0.6 metres
Eohippus	60 million years ago	0.4 metres