This incredible picture of the Grand Canyon shows why it’s one of the wonders of the natural world. It’s also a key to the past. You can take a trail to the bottom of the canyon. With each step down, you take a step back in time. Lower rock layers were formed longer ago. Rocks at the bottom of the canyon are 2 billion years old. The rock layers contain fossils. They represent the living things that made the canyon home at different times over the past 2 billion years.
Charles Darwin never visited the Grand Canyon. However, he saw rock layers and fossils in other parts of the world. They were a major inspiration for his theory of evolution. Darwin’s theory is one of the most important theories in life science. You’ll see why when you read this chapter.