Charles Darwin was a famous biologist and friend of the Sixth Doctor. They met whilst Darwin was on the HMS Beagle in 1835. (AUDIO: Bloodtide) He was one of many scientists kidnapped by the Rani to create the time brain. (PROSE: Time and the Rani)
The Third Doctor also claimed to have met Darwin. (PROSE: Island of Death)
The Seventh Doctor laughed at the idea that Darwin's theory of evolution was unproven. (PROSE: Human Nature)
Darwin wrote Origin of Species by Means of Natural Selection. (PROSE: The Age of Ambition)
Behind the scenes
David Tennant voiced Charles Darwin in the Aardman Animations film The Pirates! In an Adventure with Scientists!.