Charles Darwin was a geologist and naturalist, fascinated by rocks, plants and animals. He left England on the ship, the Beagle, in 1831. The journey gave him the chance (study) various living things in their natural environments. He noticed that some species of animals were very similar each other.
At that time, people believed that all species had appeared on Earth at the same time, and (change) since. But Darwin began to think differently.
When the ship reached the Galapagos Islands in 1835, it (be) the birds that interested him the most. He suspected that the different (finch) had evolved from a common ancestor, had arrived on the islands a long time before.
It was a (complete) new idea—a theory of evolution. Darwin explained this theory in his book, On the Origin of Species. Many people refused to believe that living things, (include) humans, had evolved from lower forms of life. But Darwin's scientific studies were so convincing more and more people started to believe his theory.
Today, the book is regarded as one of the most important works ever (write)．
