Complex sentence: The Cosmic Pathway concludes with the Age of Dinosaurs, which became extinct 66 million years ago, less than two feet from the end of the Pathway; and the duration of recorded human history, portrayed as the thickness of a human hair.
Split into simpler sentences: The Cosmic Pathway concludes with the Age of Dinosaurs, which became extinct 66 million years ago, less than from the end of the Pathway. The duration of recorded human history is portrayed, by contrast, as comparable to the thickness of a human hair.