Charles Darwin did not come up with the idea of evolution. He was merely the first to come up with an explanation for how evolution worked.
Darwin came up with the idea of Natural Selection. This is the idea that the environment an organism resides in helps to determine which organisms outlive and produce young, and those who do not eventually die out.
When Darwin was a young man he journeyed around the world on the H.M.S. Beagle (1831-1836), a research vessel. His service was to make observations on the plants and animals found in the places where the ship came in.
While on the trip, Darwin observed many strange and new plants and animals and began to wonder how they could have come into existence. Darwin was particularly struck by the animals of the Galapagos Islands, where he ascertained that each island had a different kind of tortoise.
When he returned back to England in 1837, Darwin wrote a record of the voyage entitled "The Voyage of the Beagle," though in that book he did not try to explain his observations he discovered.
Darwin also began to work on other projects. He studied earthworms, orchids, pigeons and many other animals and plants. At the same time he was working on a lengthy essay to justify and back up his idea of Natural Selection. Soon after his return to England, Darwin became very ill. He had probably contracted a disease while on his voyage. He remained ill for the rest of his life, rarely able to work long hours or travel far from his home.
It was not until 1858 when Darwin finally published his ideas. He was moved to finally publish when he received a letter from Alfred Russell Wallace, in which Wallace outlined his ideas of Natural Selection that were alike to his own. Darwin had been working on his theories for 22 years, almost as long as Wallace had been alive.
Darwin combined his thoughts with Wallace's and presented them to a meeting of the Linnaean Society on July 1, 1858. The next year, 1859, Darwin published "The Origin of Species by Natural Selection". Darwin continued to call this book a portion of a much larger piece of work, though this "abstract" was 230 pages long.
The book was an immediate publishing success, selling out the first day it was in print. It also was the direct source of great controversy.
It took several years, but eventually the scientific community started to rally behind Darwin, who was quietly writing letters and working on his "larger book" at his home in the country. He was no longer physically powerful enough to fight a strong defense of his work required, so a friend, T. H. Huxley (often called "Darwin's Bulldog"), carried out the defense in many debates in the years following the publication of "The Origin" (as most biologists call the book).
Once starting with an idea in his head, then working slowly and patiently
to gather information to support it, and despite being confined to his
home for much of his life because of his week condition, Charles Darwin
still became the father of modern biology