be evidence of sacrilege. The degree to which we believe something now becomes a determinant of its truth value. Once again, this joins a long line of features that tends to remove all rational boundaries from religious thought, permitting any and every deceptive ploy and self-deceptive concept.
We Are Right
And here comes the critical, all-encompassing self-deception: we are the measure of what is good, we represent the best, we have the true religion, and as believers we are superior to those around us. (We have been “saved”; they have not.) Our religion is one of love and concern for the world, our God a just God, so our actions can’t be evil when they are done in God’s name.
Given the ease with which religion slides toward self-deception, what are the larger forces that might propel a religion toward more or less self-deception? One important factor is the degree to which the religion is associated with the powerful in a society. Another important force has to do with religious fragmentation. Because religions almost always preach within-religion mating, fragmentation is expected to lead to intergroup conflict over minor religious distinctions. I will argue that parasite load—average pressure on a society every generation from coevolving parasites—may be an important force fragmenting religions and thus encouraging parochial self-deception. The evidence for an association with parasite load is strong, but the evidence for a connection to self-deception not nearly so strong. First, let us turn to the positive association between religion and health.
RELIGION AND HEALTH
Religious behavior and practice appear to be positively correlated with health, a well-established fact with dozens of careful studies in support, on both sick people and well. Longitudinal studies suggest that variables such as degree of attendance at religious service are positively associated with survival years into the future.
Part of this effect may result from the tendency of religions to establish rules related to health: avoid tobacco and alcohol, pork, top predators such as sharks and lions (which tend to concentrate toxins as they move up the food chain), and generally risky or unwise behavior, such as gambling. One long-term study of US Christians showed that degree of religious attendance in 1965 predicted a change to more positive health behaviors thirty years later.
Under Islam, some behavior is prohibited, some encouraged, and some required. The forbidden (haram) tend to relate directly to health:• Gambling
• Alcohol
• Eating pigs or dogs
• Eating dead meat
• Eating meat of animals not slaughtered the Islamic way (cutting throat at aorta and bleeding animal)
• Eating predatory fish
• Eating shellfish
• Usury (charging interest on money)
• Saying oiff to parents (an expression of impatience or annoyance), or yelling at them
• Suicide
All of the prohibitions regarding eating probably reduce parasite acquisition. Predatory fish are like sharks and lions in other religions—top predators that may be forbidden because they strongly concentrate toxins. Bleeding presumably reduces exposure to blood parasites. Only avoiding usury and saying oiff may not be directly related to personal health.
It is perhaps interesting to note that of the requirements in Islam (wajeb), three have positive connections to health (among other effects):• Daily prayer (five times per day)
• Cleanliness (must be clean to pray: use only running water or sand)
• Fasting
• Alms to poor
• Pilgrimage to Mecca (if possible)
• Testifying (“there is only one God and Muhammad is his prophet”)
The latter three are clearly social: two showing off, and one helping a group member, all with unknown possible immune effects.
But the relation between religion and health goes deeper than health-related behavior. Some effects may come from the benefits of positive belief itself—for example, on immune function—as well as benefits that flow from being a member of a mutually supporting group, including musically supported activities that raise group consciousness, a very common feature of religion. As we have seen (Chapter 6), music has positive immune effects, while noise has negative ones. The exalting, positive music of so many religions is probably on the high end for positive immune effects (in contrast to, say, jazz or rap). Even confessing sins to God and disclosing trauma may have beneficial immune effects. The private confessional in the Catholic Church facilitates this, as do numerous public rituals of confession common to Amerindian religions. It seems likely that private, verbal confession in prayer has similar immune benefits, an example of a personal benefit to private religious behavior because it mimics a social interaction.
Whatever the precise causes, the links between religion and health seem strong enough on their own to select directly for religious behavior and belief. As