Early Terrestrial Animals, Evolution, and Uncertainty

Early terrestrial ecosystems record a fascinating transition in the history of life. Animals and plants had previously lived only in the oceans, but, starting approximately 470 million years ago, began to colonize the previously barren continents. This paper provides an introduction to this period in life’s history, first presenting background information, before focusing on one animal group, the arthropods. It gives examples of the organisms living in early terrestrial communities and then outlines a suite of adaptations necessary for survival in harsh terrestrial environments. Emphasis is placed on the role of uncertainty in science; this is an integral part of the scientific process, yet is often seized upon by god-of-the-gaps creationist arguments. We hope to illustrate the importance of both uncertainty and scientists’ freedom to express doubt while a consensus is being built.