In the modern world, we rely on governments, courts and the
police to deter and punish those who would otherwise undermine social
cooperation. But how did human societies achieve and sustain cooperation
before these institutions existed? One possibility is religion: under
the watchful gaze of supernatural agents, people modify their behaviour
in an effort to avoid the wrath of the gods. In this issue, Purzycki et al.1 (page 327)
report a cross-cultural field-study finding that people are
consistently more willing to give money to strangers of the same
religion if the donor believes in a god that is moralizing (concerned
about good and bad behaviour), knowledgeable (aware of one's thoughts
and actions) and punishing (able to exact harm).
Pioneering anthropologists, such as Émile Durkheim and Bronisław
Malinowski in the early twentieth century, have long argued that
supernatural beliefs offer a powerful way to build materially
cooperative societies. But in the thriving new field of evolutionary
religious studies, researchers are drawing on evolutionary theory to
explore how religious beliefs can bring adaptive advantages — that is,
contribute to an individual's survival or reproductive success. Although
major debates remain2, one theory that has gathered momentum is that a belief in supernatural punishment for violating social norms may be adaptive3(Fig. 1).
Figure 1: Weighing of the heart.
This papyrus manuscript, a detail from the ancient Egyptian 'Book of the Dead' called Papyrus of Ani,
depicts a scene in which the dead Ani's heart is weighed against a
feather, representing Maat, goddess of truth and justice. At the top of
the scene are the great Egyptian gods, ready to pronounce judgment on
whether Ani should be granted entrance to the afterlife or banished to
the underworld.
How could this idea apply to cooperation? Deterring oneself from the
pursuit of self-interest because of the risk of punishment from a
watchful supernatural eye would seem to reduce an individual's
evolutionary fitness, and should thus be eliminated by natural
selection. However, even if such beliefs are false and costly, they may
have generated net benefits: to individuals, by steering them away from
selfish behaviour that risked retaliation in increasingly transparent
and gossiping human societies; and/or to groups, by increasing the
performance of the group as a whole in competition with other groups4, 5.
But
what evidence do we have for such a theory? Empirical evidence that
supernatural beliefs promote cooperation is mounting, but has tended to
rely on qualitative, society-level or proxy measures of beliefs. Study
participants have also typically been university students in developed
nations, thus omitting the small-scale societies most relevant to the
evolutionary problem at hand: how human groups achieved cooperation and
made the transition from small to large societies in the first place.
Perhaps the most important lacuna is that previous studies have not
rigorously addressed whether the beliefs of the recipients of
cooperative acts changes people's generosity towards them.
Purzycki
and colleagues' study addresses many of these issues by using
controlled experimental games among participants from eight small-scale
societies around the world and tying the results to explicit measures of
individuals' beliefs. Participants played a simple but clever game
(designed to subtly reveal preferences), in which they allocated coins
between a distant co-religionist (people who were members of the same
religion, but who lived geographically far away) and either themselves
or a local co-religionist. The researchers found that the more subjects
rated their god as moralistic, knowledgeable and punishing, the more
money they gave to distant strangers adhering to the same religion.
Notably, belief in rewards from the god could not account for the
results — supernatural punishment seemed responsible.
Because the
study is correlational, one worry is that some unexamined variable could
account for the results — perhaps certain people are disposed to both
kindness to strangers and belief in punitive gods, for example. However,
Purzycki et al. show that allocations increased for moralistic
gods that were punishing and knowledgeable, but not for more locally
relevant supernatural agents that were also punishing and knowledgeable.
Hence, general conceptions of supernatural agents cannot alone explain
the results. Rather, it is moralistic, 'big' gods that seem to stimulate
generosity towards distant co-religionists6.
The
authors did not conduct experiments to assess allocations to oneself
versus a local co-religionist, nor experiments involving non-religious
recipients, so we don't know whether local supernatural agents might
promote cooperation between individuals within the local community, as
other work has found7, or whether any kind of god promotes cooperation with strangers of another, or no, religion. Purzycki et al.
focused on cooperation with co-religionists beyond the local community,
and thus the expansion of human society from small to large groups. But
future studies of the role of local gods are needed to improve our
understanding of the evolutionary origins of religion (before there were
big groups or big gods), and of whether and how religion brings
adaptive advantages to individuals8.
It
is worth emphasizing that the subjects in this experiment were not
cooperative with random strangers, only with strangers that shared the
same god. We therefore still face the challenge of understanding the
promotion of cooperation and trust among members of different religions.
Purzycki and colleagues' finding that sharing the same god is key to
cooperation suggests that this may be an even harder nut to crack. In
fact, one of the most compelling explanations for why individuals may
help the group at their own expense is that it aids survival in an
environment of inter-group competition. Whenever the threat of
exploitation or warfare is present, the best protection is larger and
more-cohesive societies, which are better able to deter or defeat
rivals. Religion's positive role in reducing self-interest and promoting
cooperation may therefore reflect the costs of competition as much as
the benefits of generosity9.
Religion
is arguably the most powerful mechanism that societies have found to
bind people together in common purpose. From ancient civilizations, to
the spread of Christianity, to today's Islamist terrorist groups,
religion has motivated not only the subordination of self-interest for
the wider group, but even martyrdom in the name of a god. We are still
grappling to understand, from a scientific perspective, why and under
what circumstances humans sacrifice their own welfare for the benefit of
distant others10.
But there is little doubt about the power of religion to promote
allegiance to one's god and group. Purzycki and colleagues' study offers
the most explicit evidence yet that belief in supernatural punishment
has been instrumental in boosting cooperation in human societies. A
large part of the success of human civilizations may have lain in the
hands of the gods, whether or not they are real.
Since the origins of agriculture, the scale of human cooperation and societal complexity has dramatically expanded1, 2.
This fact challenges standard evolutionary explanations of prosociality
because well-studied mechanisms of cooperation based on genetic
relatedness, reciprocity and partner choice falter as people
increasingly engage in fleeting transactions with genetically unrelated
strangers in large anonymous groups. To explain this rapid expansion of
prosociality, researchers have proposed several mechanisms3, 4.
Here we focus on one key hypothesis: cognitive representations of gods
as increasingly knowledgeable and punitive, and who sanction violators
of interpersonal social norms, foster and sustain the expansion of
cooperation, trust and fairness towards co-religionist strangers5, 6, 7, 8.
We tested this hypothesis using extensive ethnographic interviews and
two behavioural games designed to measure impartial rule-following among
people (n = 591, observations = 35,400) from eight diverse
communities from around the world: (1) inland Tanna, Vanuatu; (2)
coastal Tanna, Vanuatu; (3) Yasawa, Fiji; (4) Lovu, Fiji; (5) Pesqueiro,
Brazil; (6) Pointe aux Piments, Mauritius; (7) the Tyva Republic
(Siberia), Russia; and (8) Hadzaland, Tanzania. Participants reported
adherence to a wide array of world religious traditions including
Christianity, Hinduism and Buddhism, as well as notably diverse local
traditions, including animism and ancestor worship. Holding a range of
relevant variables constant, the higher participants rated their
moralistic gods as punitive and knowledgeable about human thoughts and
actions, the more coins they allocated to geographically distant
co-religionist strangers relative to both themselves and local
co-religionists. Our results support the hypothesis that beliefs in
moralistic, punitive and knowing gods increase impartial behaviour
towards distant co-religionists, and therefore can contribute to the
expansion of prosociality.
Among the other factors2, 3, 4, 7
that influence the emergence of human ultrasociality and complex
societies, the diffusion of explicit beliefs in increasingly moralistic,
punitive and knowledgeable gods may have played a crucial role6, 7.
People may trust in, cooperate with and interact fairly within wider
social circles, partly because they believe that knowing gods will
punish them if they do not. Additionally, through increased frequency
and consistency in belief and behaviour sets, commitments to the same
gods coordinate people’s expectations about social interactions5, 6, 7, 8, 9.
Moreover, the social radius within which people are willing to engage
in behaviours that benefit others at a cost to themselves may enlarge as
gods’ powers to monitor and punish increase10.
To account for the emergence of these patterns, some evolutionary
approaches to religion have theorized that cultural evolution may have
harnessed and exploited aspects of our evolved psychology, such as
mentalizing abilities, dualistic tendencies and sensitivity to norm
compliance, to gradually assemble configurations of supernatural beliefs
that promote greater cooperation and trust within expanding groups,
leading to greater success in intergroup competition. Of course, given
that cultural evolution can produce self-reinforcing stable patterns of
beliefs and practices, these supernatural agent concepts may also have
been individually favoured within groups due to mechanisms related to
signalling, reputation and punishment5, 6, 7, 8, 9, 11, 12.
Over time, these deities spread culturally and came to dominate the
modern world religions like Christianity, Islam and Hinduism. Such
traditions eventually came to account for a large proportion of the
world’s population6, 7, 13, 14 (see Supplementary Information section S1).
Here we directly test one specific hypothesis: conceptions of
moralistic and punitive gods that know people’s thoughts and behaviours
promote impartiality towards distant co-religionists, and as a result
contribute to the expansion of sociality.
At the societal level,
several lines of converging evidence are consistent with this
hypothesis. For example, after controlling for key correlates, analyses
of cross-cultural data sets show that larger and more politically
complex societies tend to have more supernatural punishment and
moralistic deities5, 15,
and historical analyses in one geographic region show that precursors
to supernatural punishment beliefs precede social complexity16.
However, this data derives from qualitative ethnographies of entire
societies; a more focused, direct and systematic cross-cultural
assessment of what individuals think their gods care about, and whether
or not people explicitly or implicitly view their gods as concerned with
norms of interpersonal social behaviour (termed here as ‘morality’17, 18; see Supplementary Information section S4.2) has only recently begun18, 19, 20.
Analyses of cross-national databases (for example, the World Values
Survey) reveal positive relationships between beliefs in hell, beliefs
in gods’ power to punish, and various self-reported prosocial behaviours21, 22.
Although valuable, these lines of research primarily rely on survey
questions not specifically designed to address the research question we
are interested in. Moreover, they rely on samples drawn broadly from
nation states, thus excluding small-scale societies that are crucial for
assessing questions about the expansion of prosociality.
At the
individual level, two types of behavioural studies are also consistent
with this hypothesis, but each has crucial limitations. First,
laboratory experiments show that exposure to religious reminders
increases generosity and decreases cheating among religious believers23, 24, 25.
However, as is the case for most psychological experiments, the vast
majority of these studies rely on Western, Christian-majority samples,
limiting their generalizability26. Second, in one field study27
across 15 diverse societies of foragers, pastoralists and
horticulturalists, adherence to Christianity or Islam predicted greater
fairness in economic games relative to adherence to local/traditional
religions. This study, however, lacked precise measures for our
theoretically important components of beliefs about gods’
minds—punishment, knowledge and moralism. Moreover, these studies did
not consider the religious affiliation of the anonymous recipients of
players’ monetary decisions. It is therefore unclear whether these
findings explain the expansion of prosociality specifically towards
geographically distant co-religionists.
Addressing these
limitations, we combined two behavioural experiments with detailed
ethnographic interviews to assess whether participants who report that
their moralistic gods are punishing and more knowledgeable about human
thought and behaviour are more likely to impartially allocate money to
anonymous, geographically distant co-religionists over both themselves
and their local community6, 7.
In five of the sites, we also tested whether religious priming
associated with moralistic gods had effects on gameplay, but these had
no overall effect (see Supplementary Information sections S2.2.2 and S6.2.
We tested these predictions with a sample of 591 participants (310 females; observations = 35,400; Table 1 and Extended Data Fig. 1)
from eight diverse communities, including hunter-gatherers,
horticulturalists, herders and farmers, as well as fully
market-integrated populations engaged in wage labour or operating small
businesses. The participants adhere to a variety of world religious
traditions including Christianity, Hinduism and Buddhism, and report
beliefs in an immense range of local supernatural agents, including
spirit-masters, saints, ancestors, animistic beings, anthropomorphic
celestial deities, garden spirits, and ghosts (Supplementary Information section S3).
To measure favouritism towards oneself and local community under
maximally anonymous conditions, we modified the random allocation game9, 28, 29. In this game (Fig. 1),
participants play in private with 30 coins, two cups and a fair die
with three sides of one colour and three sides of another colour. In the
experiment, the participant’s job is to allocate each coin to one of
the two cups. First, they mentally choose one of the cups and then roll
the die. If one coloured side comes up, players are instructed to put
the coin into the cup they mentally chose. If the die comes up the other
colour, people are instructed to put the coin into the opposite cup
from the one they chose. Of course, as cup selection occurs only
mentally, participants can overrule the die in favour of one of the cups
without anyone else observing their decision. If people play by the
rules and thereby allocate the coins impartially, the mean number of
coins in each cup should be 15, and the distribution around this average
will be binomial. This allows us to test for systematic deviations from
this distribution (Supplementary Information section S2.2).
Figure 1: The random allocation game.
a, b, Generic game setup (a) and variants used in present work (b).
Participants played two counterbalanced games for a total of 60 coin allocations per person (Fig. 1).
In one game, the local co-religionist game, participants chose between a
cup assigned to an unspecified anonymous co-religionist from their
local community and a cup assigned to an anonymous co-religionist living
in a geographically distant community that does not regularly interact
with the player’s community. In the other game, the self game,
participants chose between a cup for themselves and a cup for another
anonymous distant co-religionist. In order to control for any effects of
ethnicity30 and nationality, both local and distant co-religionists were of the same ethnic group and nationality as the participant.
Participants
understood that money put into the cups would be given to the people
they represented, including themselves, and we actually distributed
allocations to participants and randomly selected people described by
the cups (that is, there was no deception). After gameplay, we asked
each participant a battery of questions, including a series of
counterbalanced questions about two locally relevant deities (Supplementary Information section S2).
To
assess the gods’ relative moral concern, we conducted preliminary
ethnographic interviews in each site to identify the most moralistic
deities (that is, ‘moralistic gods’), as well as locally salient,
relatively less moralistic, ‘local gods’ or spirits. We verified the
degree to which gods care about morality with a free-list task asking
about gods’ concerns19
and scales created to measure how important participants claim
punishing theft, murder and deceit are to these supernatural beings. We
measured gods’ punishment and knowledge, using the mean of two,
two-item, easy-to-understand scales with dichotomous responses. The
target gods associated with games were rated significantly more
moralistic, knowledgeable and punitive than local gods (see Extended Data Figs 2 and 3; Supplementary Information section S4).
We also aggregated gods’ punishment and knowledge scores by averaging
all four dichotomous responses, labelled ‘punishment–knowledge combined’
in Table 2. These measures are our key theoretical predictors for game allocations.
Table 2: Log odds ratios for predicting allocations to distant
co-religionists with 95% confidence intervals from our main binomial
logistic regression models
Figure 2
displays the effect of punishment for moralizing gods, without any
controls, and reveals the impact of “I don’t know” answers which were
otherwise excluded from our analyses below. When people report not
knowing if a god punishes, they put considerably fewer coins in the cups
for distant co-religionists in both games (local co-religionist game: M = 12.97, s.d. = 4.33; self game: M = 12.50, s.d. = 4.15) than those who consistently report that their god punishes (local co-religionist game: M = 14.58, s.d. = 3.24; self game: M
= 14.53, s.d. = 3.31). One way to estimate the magnitude of these
effects is to calculate the quotient of deviations from the ideal
impartial allocation of 15. Compared to those who don’t know, claiming
the moralizing god punishes increases allocations towards distant
co-religionists in the self game by a factor of 4.8 and in the local
co-religionist game by a factor of 5.3. Extended Data Figs 4 and 5 detail the overall allocation distributions for both games.
Figure 2: Allocations to distant co-religionists increase as a function of moralistic gods’ punishment.
Punishment indices are mean values of a two-item scale (see Supplementary Information section S2.3.2).
Error bars represent bootstrapped (1,000 replications) 95% confidence
intervals of the mean. Histogram labels are sample sizes per category.
Note that among the 32 individuals who responded “I don’t know” to the
questions pertaining to moralistic gods’ punishment, 17 were Hadza and
15 were inland Tannese.
We explored this relationship in more detail by regressing the
number of coins allocated to the distant co-religionist cup on a host of
variables for each game in a large set of binomial regressions (Extended Data Table 1 and Supplementary Information section S6). Table 2
shows a subset of the key predictors for the models with the largest
set of control variables, including a number of economic and demographic
variables such as education, material insecurity, number of children
and field site fixed effects. Using sites as fixed effects allows us to
remove the variation between our sites, so the results in Table 2 only capture the differences among individuals within sites. Based on previous work9, 29,
we suspected that material insecurity and number of children would
increase self and local favouritism, and therefore we include both in
our model (Supplementary Information section S2.3.1).
To affirm the robustness of these analyses, we estimated many
alternative models, formulated mixed models, and used both alternative
standard error estimates and different approaches to modelling the error
(Supplementary Information section S5.4).
Across a wide range of specifications and models including a host of
variables (for example, divine rewards, emotional closeness to distant
co-religionists, among others), both moralistic gods’ punishment and
knowledge, as well as our aggregate punishment–knowledge variable, are
reliably associated with less bias against distant co-religionists (Supplementary Tables S5–S9).
We checked whether the effects of moralistic gods’ punishment and
knowledge were indeed specific to powerful, moralizing gods. We added
local gods’ punishment and knowledge to the models presented in Table 2. Figure 3
shows the odds ratios and confidence intervals for these coefficients.
Although neither the punishing powers nor knowledge of these local
deities had any association with the allocations, the odds ratios for
our key predictors pertaining to moralistic gods actually increased.
These overall findings are correlational and should be interpreted with
caution and in combination with other evidence, also considering that
religious priming did not reveal consistent effects. However, these
patterns reduce concerns that omitted third variables might account for
the correlations we observe. A third variable, in addition to
correlating with allocations, would have to correlate only with the
punishing and knowing character of moralistic and knowledgeable gods,
but not with those same attributes in local gods or with the tendency of
either type of deity to reward people.
Figure 3: Log odds ratios with 95% confidence interval plots
of the influence of key variables on the odds that a coin goes into the
cup for the distant co-religionist.
≤ 0.001, **P ≤ 0.01; *P ≤ 0.05; ‡P ≤ 0.15). The x axis is on a logarithmic scale. Both models include other controls (n
= 390). Local co-religionist and self results include sites as fixed
effects. Note that Indo-Fijians are not included in these models due to
the lack of data for local gods. See Supplementary Tables S5 and S6 for full models (models 2FE are presented here).
These results build on previous findings and have important
implications for understanding the evolution of the wide-ranging
cooperation found in large-scale societies. Moreover, when people are
more inclined to behave impartially towards others, they are more likely
to share beliefs and behaviours that foster the development of
larger-scale cooperative institutions, trade, markets and alliances with
strangers. This helps to partly explain two phenomena: the evolution of
large and complex human societies and the religious features of
societies with greater social complexity that are heavily populated by
such gods6, 7.
In addition to some forms of religious rituals and non-religious norms
and institutions, such as courts, markets and police, the present
results point to the role that commitment to knowledgeable, moralistic
and punitive gods plays in solidifying the social bonds that create
broader imagined communities11, 12, 31.
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