chapter  8
The Primitive Earth
Pages 8

Understanding how life may have originated necessarily involves understanding the environment of the early Earth. This statement is true even if life originated somewhere else and was transported to Earth-an idea referred to as “panspermia” Even in this, to some extreme, version of life s origin, it is of interest to know what the early environment of Earth might have been like, if only to predict how life might have adapted once it got here. For more conventional models, in which life originates somewhere on Earths surface, it is even more important to understand what that surface was like. Here, we review current thinking about the origin of the Earth, along with its atmosphere and oceans. We then discuss what is known and what is not known, about early atmospheric composition and climate. Finally, we touch briefly on the effects of early life on the atmosphere. This last topic is not directly relevant to prebiotic evolution. However, it fits in with the overall picture, as one of the best ways of investigating the origin of life is to try to work backwards from the earliest organisms and to do so we need to understand how they interacted with the world in which they lived.