Most recent interest in religion as a biological phenomenon has centred on selective evolution favouring the survival of believers. The person walking in the forest who believes that the rustling in the undergrowth is because there are evil spirits abroad is less likely to get eaten than the person who thinks it is only the wind.
I don’t think this argument holds much water. Animals subject to predation have developed a sophisticated mechanism of detecting, interpreting and responding to external stimuli. Many animals that live in groups, including the primates, use alarm calls. Mammals and birds which have a prolonged period of infancy also use behavioural strategies learned from their parents, siblings and the group. Our species developed advanced aural communication, probably as a result of an aquatic phase in our evolution (since sound carries better in water than light). It would have been easier to simply tell the offspring, “Be careful if you go down to the woods today and listen out for any strange noises. Your Uncle Jim was eaten by a sabre-tooth last month.”
Now it is true that religion favours strategies which promote reproductive success and our species has been enormously successful reproductively. Successful reproduction of the human genome is not necessarily the same as the successful survival of individuals: the former takes precedence. Religion certainly does seem to favour the survival of the species over that of the survival and wellbeing of individuals.
The reproductive success our species has enjoyed has been at enormous cost to its host environment. In many ways it is similar to the growth of a malignant tumour in an organism. It is a toxic success which will, if left unchecked, destroy its host and itself with it. Jonas Salk said, “If all the insects were to disappear from the earth, within 50 years all life on Earth would end. If all human beings disappeared from the earth, within 50 years all forms of life would flourish.”
There are two questions which arise: “How did religion originate?” and, “What can we do about the toxic reproduction of our species?”