Final answer:
The Fayum site in Egypt wasn't always a desert; fossil evidence of marine life and multilayered rock structures indicate a history of significant ecological changes, supported by archaeological and historical records.
Step-by-step explanation:
The Fayum site in Egypt may currently be a desert, but we know it wasn't always that way primarily because of fossil evidence of marine life. These fossils suggest that the land, which is now arid and desert-like, was once covered by oceans. This is further supported by the presence of multiple rock layers, which help trace the Earth's geological and biological history, indicating significant changes over time including wet periods where the environment was rich enough to support early human settlements.
Other evidence such as archaeological findings, historical records, and modern techniques like satellite imagery and geological studies have allowed us to understand the climate and geographical changes that have occurred in this region. Evidence from ancient Egyptian scribes also contributes to our knowledge, indicating a diverse past far removed from the desert landscape we see today. The study of sites like Fayum provides insight into the ecological history and the human cultures that thrived in these once fertile areas.