Exterminate All the Brutes 

William Bache gave an outline of Sven Lindqvist's Exterminate All The Brutes. The book is a good introduction to how European powers used Darwinian natural selection theories and scientific racism to justify slavery and their global imperial ambitions. These ideologies were successful due to advances in firepower coupled with the ability of European powers to globably project their sea-going naval forces. Their ships and gunboats were used to control coastal and river-based trade over much of the world.