The article delves into the geological and biological landscape of Earth 2.5 billion years ago, during the Archean Eon. It highlights the key developments in the planet’s history, focusing on the origins of life and the evolution of the atmosphere. The main keyword, “What existed 2.5 billion years ago,” addresses the search intent of readers looking to understand the early conditions of Earth and the emergence of life forms during that time. The content offers detailed information about the environmental conditions, types of organisms that existed, and the significance of this era in the broader context of Earth’s history. This article would be valuable for webmasters seeking to provide educational content on Earth’s geological history and the evolution of life.