What evidence do scientists use to evaluate theories about the Earth's early atmosphere?

Scientists use geological evidence, such as rock formations and fossil records, along with data from gas emissions from volcanoes to evaluate theories about the Earth's early atmosphere. They also analyze isotopic ratios in ancient rocks to infer the composition of the atmosphere at that time.

A strong answer should directly address the approved learning objective to evaluate evidence and uncertainty when discussing the Earth's early atmosphere. This question belongs to The Earth's early atmosphere within The composition and evolution of the Earth's atmosphere, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to early atmosphere, and keeps the wording specific to AQA GCSE revision.