Why Religions Ban Pork and Alcohol: Understanding Costly Signalling

The Weirdness of Religion

Throughout history, religious institutions have banned absurd and seemingly arbitrary things: Christians shouldn't work on the Sabbath, Jews shouldn't eat pork, Muslims shouldn't drink alcohol, Hindus shouldn't harm cows, and Buddhists shouldn't point their feet at the Buddha.

While cultural explanations attribute these prohibitions to impurity or impiety, they fail to answer the underlying question: Why is this particular item impure? Anthropologists have therefore theorized that, for a religion to be successful, it doesn't matter what is banned as long as something is.

They propose something called “costly signalling theory” in which conformers endure a difficulty or inconvenience to communicate a message to others. Besides prohibitions, costly signals include bizarre rituals (see below) and symbolic markers of affiliation (cross, kippah, burqa, etc.).

For example, there is a tribe in Papua New Guinea where young males have their private parts forcibly lacerated by stinging nettles. Meanwhile, Hindus have a ritual that involves dragging carts attached by hooks to their skin, Mbuti pygmies have a festival that transforms a rusty old pipe into a sacred flute, and Catholics have a ritual in which bread becomes the body of the Messiah.

The most ubiquitous costly signals are badges that include special clothing, jewellery, tattoos, and grooming habits. For example, Jews wear a kippah (skull cap), Sikhs don't cut their hair, Muslim women wear burqas, Polynesians display tattoos, and Christians wear crucifixes.

For an evolutionary biologist, these badges, bans, and behaviours might appear to be a waste of time, energy, and resources (e.g., burning food on an altar). Our species needed to gather food, find shelter, and defeat enemies, so how did they evolve? One explanation is that the signals publicly demonstrate faith, commitment, affiliation, and conformity with the group. Indeed, the signals are noticeable and public, suggesting they are designed to communicate a message.

Costly Signalling Theory

Anthropologists such as Richard Sosis and Joe Bulbulia think that costly signalling theory can explain these unusual behaviours, and that it doesn't matter what specific thing is banned, worn, or performed, as long as it is:

1. Costly. It requires effort or resources to perform or maintain. It requires dedication. It is difficult for nonbelievers to fake.

2. Noticeable. It comes up in daily life (e.g., refusing to eat pork at a restaurant) or it is highly important at a particular time (e.g., an annual festival).

3. Bizarre. It can be attributed to a religious function (e.g., pleasing to a deity) and not to any mundane function.
   
   

They propose that the signals evolved to increase within-group cooperation; a benefit that outweighed the cost of the signals. Indeed, most religions include morals that promote cooperation (e.g., love thy neighbour; don't murder or steal) and a costly signal of commitment to a religion can establish trust in one's adherance to this moral code. For example, even secular New Yorkers have been found to prefer Mormon nannies.

Lack of cooperation may have been the most important problem for ancient societies to overcome, with cheaters and free-riders extracting benefits but not enduring costs. Costly signals of cooperation provided a more effective tool than spoken promises to weed out the unwilling: nonbelievers would have found the signals difficult or undesirable to fake.

Evidence for Costly Signalling Theory

Studies have tested whether groups with high membership demands (i.e., more costly signalling) enjoy the highest levels of devotion and commitment. One study found that such groups grow at a faster rate and have more committed members than groups with lower membership demands, and that religious "bizarreness" is associated with attendance at services.

Similarly, surveys have found that Muslims, Mormons, Baptists, and Seventh Day Adventists have added to their numbers quicker than more liberal Protestant churches, while the liberalization of the Catholic Church in the 1960s appears to have accelerated its decline.

Other studies have tested for more direct effects on cooperation. For example, an examination of 83 early American communes found that surviving communes were more likely to be religious and to impose costly requirements on their members (e.g., celibacy, or giving up material possessions).

A similar study found that the collapse of the “kibbutz” (commune) movement in Israel was largely limited to secular communes. Most of the religious communes survived and remained profitable after imposing costly signals on their members (e.g., not doing business on the Sabbath). Furthermore, individuals in these communes who frequently use costly signals (typically males) showed the highest levels of cooperation in a resource allocation game.

Haredi Jews are another illustrative example. They came to Israel from Russia but continued to wear thick clothing and fur hats in the desert sun. It became a costly signal of their faith: why would they suffer the heat unless they truly believed? The signal appears to have facilitated a remarkable level of cooperation. Even when complete strangers, Haredi Jews will be guests in each other's houses, lend their cars, and provide interest-free loans.

Finally, costly signalling also appears to increase when more cooperation is needed. A study found that harsh economic conditions in Indonesia led to greater religious attendance. The suggestion is that, when resources are scarce, the need to cooperate and weed out free-riders is greater. However, the results could also be explained by a greater need for comfort.

The General Features of Costly Signals

There are many types of costly signal between humans (e.g., signals of wealth, status, skill, attractiveness, emotional need, and willingness to fight) and between social animals such as elephants. The technical definition requires that these signals:

1. Communicate something that varies within a population (e.g., levels of religious commitment).

2. Benefit the receiver of the signal with reliable information (e.g., knowing who to trust and cooperate with).

3. Benefit the sender of the signal (e.g., people cooperate with them) such that others may be tempted to fake the signal if they can endure the cost of sending it.

4. Are costlier for people who lack what is being communicated (e.g., religious commitment). In the case of religion, believers may have already conformed to a lifestyle that makes sending the signal easier (e.g., giving up vices may be more difficult for sceptics).
   
   

The costly signalling theory of religion only concerns one case of costly signalling within one species, but it meets the general definition.

What is Special About Bans? Why Pork and Alcohol?

In contrast to rituals and badges, bans are only useful as signals when they are at risk of being transgressed. It follows that, the more difficult a banned item is to give up (pork, alcohol, sex, gambling, etc.) the more effective it is at weeding out nonbelievers. For believers, besides the cooperative benefits, the removal of desirable “vices” can free time for religious activities, making them a less costly strain on resources. Thus, although anything could conceivably be banned, these types of bans are the costliest signals to send.

What About Religious Beliefs and Emotions?

Religious belief may reinforce the benefits of costly signalling. For example, if you believe that performing a ritual helps you to obtain divine protection or afterlife favour, your likelihood of performing it increases, which increases its real benefits (cooperation). This is important because the real benefits are almost certainly less likely to be recognized and acknowledged than the perceived supernatural benefits.

Religious belief, such as in afterlife judgement, can bestow further cooperative benefits if people start to police their behaviour because they think it is being watched and judged by a deity. Policing behaviour in a large society also becomes easier when enforcers only need to police the public observance of costly signals.

Remarkably, signalling theory proposes that the mere performance of a costly signal can increase religious belief. It is suggested that nonbelievers who utilize a signal (e.g., going to Church for social benefits rather than to worship) experience an unpleasant state of “cognitive dissonance”—a conflict between their beliefs and their repeated, public actions,—which forces a resolution: either start believing or stop going to Church.

Studies of cults suggest that the resolution is usually to “start believing.” Cults appear to introduce new members to costly signalling (e.g., leafletting on the street, or participating in group activities) before successfully brainwashing them with the cult's idiosyncratic teachings.

Indeed, costly signalling may elicit emotions that make associated beliefs more compelling. For example, a “religious experience” can be perceived as “more real” than reality, while singing in synchrony with a group may produce positive emotions that facilitate identification with the group's beliefs. If, however, nonbelievers remain unconvinced, they cannot fake the involuntary emotions underpinning the signal’s reliability.

Closing Remarks

Although costly signalling theory can explain many features of religious practice, including why it endures, it does not explain why individuals choose to form the specific beliefs that are the basis for these behaviours.

For example, why do religious beliefs address existential questions and concerns? Why are they shaped or constrained by particular psychological biases? Cognitive and motivational explanations for religion are better placed to answer these questions.

The most that signalling theory can say is that some of these biases and motivations came to be favoured and potentially shaped by natural selection because they resulted in behaviours that helped us to cooperate.

In other words, evolutionary explanations for religion can describe why a practice endures, but not why it came to be, or how it works in the brain. Indeed, signalling theory applies to many aspects of human and animal life, and its explanation for religion can only ever be a general one.