What does the allusion to Charles Darwin mean in the book Fahrenheit 451?

At the end of Fahrenheit 451 by Ray Bradbury, the main character, Montag, is being chased by the Hound as war is breaking out around him. His illicit storing of books has been revealed, and the Hound will find him and kill him unless he escapes. He eventually follows a river to a wilderness where he senses Clarisse has been before, and he finds a group of people gathered by a fire. They and their leader, Granger, welcome Montag and give him a fluid that will change his perspiration so that the Hound can no longer track him. He then sees the Hound devour an unidentifiable man (identified as Montag) on the portable viewer, so Montag knows he will no longer be tracked. 

Granger then introduces the members of this group, each of whom has memorized a book and then burnt it. Granger introduces Montag to the other members of the group: "I want you to meet Jonathan Swift, the author of that evil political book, Gulliver's Travels! And this other fellow is Charles Darwin, and this one is Schopenhauer..." (page 151). Members of the group have memorized books and become their authors. In this passage, Bradbury includes allusions, or references to several famous authors, scientists, philosophers, and others in history. 

Charles Darwin is a particularly interesting allusion because he developed the theory of evolution through natural selection, later referred to as "survival of the fittest," through his observations of birds on the Galapagos Islands. Survival of the fittest means that those individuals who are best suited to their environment survive and have offspring and pass along their advantageous traits to their offspring.

Granger and his group are the members of Montag's society who are able to survive, as a bomb is dropped that disintegrates the city in which Montag used to live. Therefore, Granger's group are those who will pass along what they have to the future world. Granger says, "We'll pass the books on to our children, by word of mouth" (page 153). Therefore, Granger, Montag, and the rest of their group will pass along their memory of books to the future, just as the creatures who have the most advantageous traits pass them along to their children as part of the "survival of the fittest" or natural selection in Darwin's work.