I reckon a book that may interest you greatly would be Richard Dawkins, the selfish gene. Not so much for all the biology in it (although it is very interesting, and seems to fit the data) but it also describes how replication could have come about. He also offers up different possibilities in his other works. (You could probably come across these explainations on the internet also)
Unseul
Give a man a fire and he's warm for a day. Set a man on fire and he's warm for the rest of his life....