Chapter Five is entitled, "The Roots of Religion," and in it Dawkins discusses why people hold religious beliefs and why such beliefs are so widespread.
He describes the problem in the first section of the chapter. He says that since we are the products of evolution, we need to consider why natural selection seemingly favored religious belief. It isn't an easy question to answer because religious practices and beliefs seem so inefficient and natural selection usually punishes inefficiency.
So Dawkins asks the question, since religion has such a high cost in terms of time, energy and resources what evolutionary benefit does it offer?
This is a good question. Consider Christianity as an example. Christians are called to follow the example of a man who failed to pass on his genes to the next generation. To the extent that Christians follow Jesus' example, it would seem that we are becoming less fit, in the Darwinian sense.
It is tempting to offer a religious explanation for this dilemma. One might argue that God blesses and encourages religious behavior, thus allowing religious people to continue to multiply despite their self-sacrificing behavior.
This explanation has two problems. First of all, I'm not sure that God shows his followers special favor. Instead, I would argue that God is working to bless the whole world.
Second, there are so many different religious beliefs and practices. Even if we claim that one group survives because God has favor on them, then why does a group with a contradictory set of beliefs and practices survive as well? Is God simultaneously working to support both groups?
Clearly there isn't a simple, religious explanation that works in this case.
Having said all that, I'm looking forward to this chapter. Dawkins is, first and foremost, an evolutionary biologist and in this chapter he's making an evolutionary argument. Since it's his area of expertise Dawkins is able to make a compelling case.
In the first section, Dawkins just goes over possible explanations for why human beings seem to have evolved with religious beliefs.
The first explanation comes from the theory of group selection. The idea is that religious behaviors that hurt an individual's chance of survival might help the group's chance of survival.
The second explanation is that religious behavior might not benefit our genes. Dawkins writes, "An animal's behavior tends to maximize the survival of the genes 'for' that behavior, whether or not those genes happen to be in the body of the particular animal performing it." It is possible that religious behaviors may not have evolved to benefit us, but to benefit someone or something else.
For the third explanation, Dawkins suggests that religious ideas themselves might behave in a gene like fashion. He argues that the religions themselves may have "evolved" in order to ensure the survival of the religious ideas, in much the same way that animals evolve to ensure the survival of their genes.
I look forward to reading a more detailed account of what Dawkins believes is the cause of religion.