Rather than requiring an immortal soul to act as the ghost driving the human machine, modern genetics can explain all the workings of the human body, and the way it has evolved, in terms of the coded message carried in the DNA in every living cell. How much easier, then, for genes to convey information coded in a quaternary system, with the luxury of a four-letter alphabet. The information is conveyed from generation to generation by the genes being copied and handed on from parent to offspring. Human beings are also all much more closely related than you might think. In fact, if most of the people you meet are likely to be quite close relations, cousins who carry copies of many of your own genes, being nice to them and helping them to survive and pass on copies of their genes to the next generation is a good thing, as far as the selfish interest of your own genes is concerned.
Genetic selfishness is a good argument in favour of the welfare state.
Dawkins packs all this and more into just 172 pages of entertaining, clear prose. It is said that one of the reasons for the phenomenal success of A Brief History of Time is its mystic, semi-religious tone. River out of Eden is better written, on a more important subject, and easy to understand. But if there is one thing it lacks, it is mysticism. There are, alas, no million-dollar prizes available for writers who show that there is no evidence that God exists.