The first larger land animals to wander onto land were probably arthropods, such as scorpions and spiders. Many of these creatures have been found in Silurian period rock layers, usually in association with fossils of the oldest-known vascular land plants.

No one truly knows why the first animals moved from the oceans to dry land, but there are plenty of theories. One is that animals wanted to expand their territory, similar to the way many modern animals behave. Another possibility is that as more animals evolved, there would have been a higher demand for a better food source. By adapting to land life—and the “new” food sources on land—these organisms would have a better chance of survival.