God, Meet Darwin

 

Religiosity, Reproductive Advantage, and Sexual Behavior

 


How did these two adversaries end up on the same side?

 

Of the 6.5 billion humans on this planet, roughly 8% have no spiritual or religious beliefs, which poses the interesting question: what evolutionary business does this subpopulation of non-believers have with the believers? To date, the limited genetic evidence implies that the probability of inheriting your religious disposition from your parents is just about the same as inheriting your intelligence. While environmental influences weigh heavily on religious disposition, the evidence indicates that genetics, on average, is more important (see Brouchard et al. 1990).

 

But what genes? The number of genes contributing to religious (and political) disposition might number in the thousands, but given some recent evidence, those genes associated with the development and functioning of the monoamine neurotransmitter systems, in particular the dopaminergic system, seem to exert a disproportionate influence on the modulation of religiosity and political conservatism.

 

But when you talk about genetic inheritance and inter and intraspecies competition, you are talking about natural selection. This raises the question: how much has religion impacted the frequencies of certain genes, such as the dopamine D4 receptor gene (DRD4)? The impact of the so-called "adventure" DRD4 gene on human social behavior has attracted a lot of interest, as it has been connected to excessive gambling, substance abuse, elevated levels of novelty seeking, and the acceptance of spiritual transcendence. However, DRD4 studies have led to contrasting results, as the isolation of single genes to explain aggregate behaviors is a risky business.

 

But, in one of the greatest ironies in human evolutionary history, religiosity has become an active agent in the evolution of the human nervous system. In a sense, religiosity and the genes that promote it have formed a runaway selective process analogous to Fisher's runaway sexual selection. As we shall see, the religious are the most piously discerning when it comes to selecting a mate, that is, they heavily apply religious criteria towards potential mates in what we believe to be a Darwinian attempt to improve their reproductive output.

 

We suspect that the confluence of those behaviors promoted by religious doctrine combined with the genes that promote religiosity are a runaway evolutionary process. The behaviors promoted by religions tend to facilitate reproductive output, and further, provide a cultural blanket that protects the genes that promote religiosity. The most conspicuous cultural aspect of religions is morality, which we have argued to promote both reproductive output and advantage, along with behavioral inhibition of socially inappropriate reward-seeking.

 

The cultural-religious importance of morality lies in the fact that it is primarily targeted towards regulation of the behaviors associated with the dopamine system, known for its predisposition towards reward-seeking. In short, morality is a system of checks and balances for the human dopamine system. The religious do not focus on morality because they want to. They focus on it because the have to, that is, it facilitates higher reproductive output.

 

Empathy-based controls on reward-seeking are the domain of the secular liberal, and the neural substrates supporting empathy are not as dependent on the dopamine system as is morality, and are more likely to incorporate the noradrenergic system. The moral framework associated with religion provides the social controls to offset the dopaminergic nature of religious disposition. The religious do not, and can not, rely on empathy in regulating their social behavior to the extent that the secular liberals can. Indeed, religions transfer earthly reward-seeking into the afterlife, where heavenly rewards await those that inhibit their anti-social and selfish behavior on earth.

 

But the religious moral framework, combined with the dopaminergic nature of religious disposition, has led to several substantial Darwinian advantages. These are:


1. Reproductive yield
2. The survival of small breeding populations
3. Emigration to relieve population stress
4. Economic collusion

5. Welfare and income redistribution

 

All of the above advantages are interrelated. We shall briefly touch on the survival of small breeding populations and emigration, but the focus of this month's edition will be reproductive output and reproductive advantage. The evidence for elevated reproductive output by degree of religiosity is substantial. This is illustrated in the graph below.

 


2005 Population growth by percentage of non-religious
Source: World Christian Database

 

The percentage of religious in a population is highly correlated with reproductive rates. Further, reproduction is highly correlated with the degree of religiosity. So how are the religious doing it? What is the secret to their Darwinian success?

 

A, B, and C

 

Among humans, reproductive strategies are heavily integrated with social alliances, which collectively form the foundation for religious and political behavior. Due in part to the higher reproductive rates of the religious and the mounting evidence of the genetic heritability of religious disposition, natural selection has guided the human gene pool to its current religious bias.

 

In spite of the reproductive advantages of religiosity, agnosticism and atheism are still prominent tendencies, which should probably be interpreted as an evolutionary complement to religiosity. That is, a certain level of non-religiousness in a population actually improves the reproductive yield of the religious, as those with occupations in science and technology tend towards lower rates of religiosity. Humans may indeed be in an evolutionary stalemate between the genes that facilitate religiosity and reproduction, and the genes that improve technological advancement and the carrying capacity of habitats.

 

While a certain percentage of any large population is nonreligious, there is no current evidence that this percentage remains stable over time. Instability in this percentage is further promoted by environmental influences, which can rapidly modulate levels of religiosity. Further, population density and religiosity are inversely correlated variables.

 

Religious groups are a prominent fixture in the history of the colonization of new territories, and their high levels of group altruism and tight social organization provide an effective model for the survival and fertility of small populations in unfriendly habitats. In population biology, the religious most closely resemble the behavioral and reproductive characteristics of r-selected animal populations.

 

The elevation in reproductive output by the religious is executed by a diverse combination of sexual behaviors, fertility stimulants, and parenting strategies. In this light, we shall present our data in the following categories:

 

1. Desire for offspring, religious and racial tendencies in mate selection
2. Active relationships, relationship duration, numbers of different sex partners, and monogamy
3. Non-reproductive sexual behaviors
4. Male dominance, orgasmic ability, and masturbation

 

Methods and Data

 

The data represented here was collected from three separate surveys consisting of 7,488 completed question-naires administered from March 2006 through November 2007. Religious disposition in these surveys was self-rated. For correlation analysis, these religiosity cohorts were assigned a numerical religiosity variable, on a scale of 0 to 5, with atheistic = 0, agnostic = 1, spiritual = 2, little religious = 3, moderately religious = 4, and the very religious = 5.

 

All correlation coefficients are Pearson coefficients. For certain responses, which specified a range instead of a single value, we used the midpoint of that range in statistical analysis. If the top range was unbounded, (e.g. 100+ sex partners), 100 was used instead as the midpoint. This under estimates the calculation of the mean, and we have noted these statistics with an asterisk "*".

 

The data is summarized into two different schemas: religious, spiritual, and nonreligious, and, by degree of religiosity or nonreligiosity. These degrees will be atheist (AT), agnostic (AG), very religious (VR), moderately religious (MR), and a little religious (LR).

 

The religious cohort will include the very religious, moderately religious, and little religious. The nonreligious cohort will include the agnostics and atheists. The spiritual will not be aggregated into either the religious or nonreligious cohorts, although their responses are more likely to resemble the nonreligious.

 

1. Desire for Offspring, Religious and Racial Tendencies in Mate Selection

 

Mate selection is a critical element in reproductive yield, as mismatches in the number of desired children can reduce the reproductive output of the partner with the greatest desire. Since desire for offspring varies with the level of religiosity, selecting partners for religiosity has the interesting side-effect of also matching the desire for children. Indeed, this seems to be the Darwinian secret underlying the strong tendency for the religious to seek out religious partners.


Gender

Religious Disposition

N

 Mean Number of Children Desired*

N

Religious Affiliation Match with Partner

N

Racial Match with Partner

Female

Religious

250

2.6

404

54.7%

340

83.2%

 

Nonreligious

252

1.7

322

34.5%

264

85.6%

 

Spiritual

181

2.0

212

42.0%

180

80.6%

 

VR

48

3.0

135

68.2%

108

85.2%

 

MR

115

2.4

172

51.7%

146

82.9%

 

LR

87

2.5

97

41.2%

86

81.4%

 

AG

126

1.8

238

31.9%

199

85.9%

 

AT

126

1.6

84

41.7%

65

84.6%

Male

Religious

499

2.7

982

57.5%

802

84.2%

 

Nonreligious

630

1.7

791

24.3%

564

80.3%

 

Spiritual

206

2.2

311

32.8%

234

78.2%

 

VR

134

3.5

306

64.7%

250

86.8%

 

MR

226

2.5

459

58.8%

379

85.8%

 

LR

139

2.1

217

44.7%

173

76.9%

 

AG

226

1.9

500

24.8%

356

80.6%

 

AT

404

1.6

291

23.4%

208

79.8%

Table 1: Children desired, religious and racial match with current partner
(AT=Atheist, AG=Agnostic, LR=A little religious, MR=Moderately religious, VR=Very religious) (Religious=VR+MR+LR, Nonreligious=AG+AT)

 

The number of children desired is correlated with religiosity, as evident in Table 1. The very religious (VR) in both genders had the highest mean preference for offspring, with females desiring 3.0 children, and males 3.5. These averages are about twice as high as atheists (AT), with females and males desiring 1.6 children.

 

The religious, in the process of seeking mates with common religious affiliations, are effectively seeking mates that match their desire for children and their reproductive strategies in general. This is evident from the higher correlation of partner religious affiliation with the level of religiosity (r=0.29, p<0.0001). The religious affiliation options in the questionnaire included Christian, Catholic, Mormon, Judaism, Buddhism, Hinduism, Islam, Confucianism, spiritual, agnostic, atheist, and other. If the survey respondent had a partner, we only considered it a match if the partner's religious affiliation matched the respondent's (based on the aforementioned categories). For example, it would only be considered a match if an atheist had an atheist partner, and if someone was Catholic, it would not be a match if their partner was Christian.

 

The very religious (VR) had the highest rate of matching their religious affiliation with their partners (females = 68.2%, males = 64.7%). Among males, the atheists (AT) had the lowest rate of matching religious affiliation (23.4%), while among the females; the agnostics (AG) had the lowest rate of matching (31.9%).

 

Seeking partners with the same religious affiliation is most important for those with a greater desire for offspring (i.e., the very religious), as selecting a mate with a desire for fewer children would tend to reduce the probability of achieving one's reproductive goals. Indeed, the religious were more likely to have an opinion about their partner's religion, and the nonreligious were more likely to be unsure.

 

This same phenomenon is also seen in partner racial assessments. The religious are more likely to have an opinion about their partner's race, and among the males, the religious are more likely to indicate they are of the same race as their partner. We asked the survey respondents to classify themselves into one of the following racial groups: Asian, Black, Hispanic, Indian, Middle Eastern, Native American, and White. "Not sure" was also an option in defining partner race.

 

For females, there was no correlation between religiosity and racial matching. However, for males, it was correlated (r=0.13, p<0.0001), as the very religious (VR) and moderately religious (MR) males are substantially elevated when it comes to matching the race of their partner (86.8% and 85.8% respectively). Conversely, the male atheists (AT) and agnostics (AG) were the least likely to match their partner's racial group (79.8% and 80.6%).

 

The females in this survey were more likely to have an opinion about their partner's race, and to also report they were of the same race. While the female tendency towards racial sensitivity in mate selection can be attributed to the greater female investment in reproduction, what evolutionary game are the religious males playing? Perhaps it is the same game, that is, the elevated investment in reproduction corresponds with greater sensitivity to the reproductive attributes of females.


2. Active Relationships, Relationship Duration, Numbers of Different Sex Partners, and Monogamy

 

Species with lower reproductive rates tend to neutralize their reproductive deficit by enhanced parental investment strategies. As a slowly reproducing species, humans have evolved an interesting spectrum of such strategies, and religiosity is an active component. In table 2, we see four variables with overtones in parental investment and reproductive strategies in general.

 

Religiosity and the probability of being in an active relationship are correlated variables in both genders. An active relationship in this context simply means that the person indicated they currently have a partner, although we did not identify whether this relationship was heterosexual or not. Among females, having an active partner varied with the level of religiosity.


Gender

Religious Disposition

N

Percent in an active relationship

Mean length of relationship (in years)*

Mean  different sex partners*

Self-rated Monogamy

Female

Religious

250

84.8%

8.4

10.1

9.2

 

Nonreligious

252

77.4%

6.6

14.1

8.5

 

Spiritual

181

75.1%

7.5

16.2

8.7

 

VR

48

89.6%

10.3

5.6

9.6

 

MR

115

84.4%

8.1

10.3

9.4

 

LR

87

82.8%

7.6

12.4

8.6

 

AG

126

79.4%

7.2

13.3

8.7

 

AT

126

75.4%

6.1

14.9

8.3

Male

Religious

499

79.0%

11.1

13.3

8.8

 

Nonreligious

630

62.9%

7.2

14.7

8.2

 

Spiritual

206

67.5%

8.4

19.4

8.3

 

VR

134

75.4%

12.7

9.3

9.3

 

MR

226

78.8%

11.1

14.3

8.8

 

LR

139

82.7%

9.5

15.3

8.4

 

AG

226

65.9%

7.4

15.8

8.3

 

AT

404

61.1%

7.1

14.1

8.2

Table 2: Active relationships, duration, sex partners, and monogamy
(AT=Atheist, AG=Agnostic, LR=A little religious, MR=Moderately religious, VR=Very religious) (Religious=VR+MR+LR, Nonreligious=AG+AT)

 

Male religiosity was more strongly correlated with the probability of being in an active relationship (r=0.15, p<0.0001) than was female religiosity (r=0.09, p<0.02).  The little religious males reported the highest rate, at 82.7%, while the very religious females recorded the highest overall rate (89.6%). The atheist males and females reported the lowest rates of active relationships, at 61.1% and 75.4% respectively.  In this survey, females were more likely to report an active relationship, although we did not inquire as to how many active relationships the individual was currently a part of.

 

Looking solely at the people reporting an active relationship, we computed their mean relationship length. The trends are again pronounced, with the length of the active relationship varying with the level of religiosity, in both genders.  The very religious males had the longest relationship length, at 12.7 years, followed immediately by the moderately religious males at 11.1.  The atheistic males had the shortest average duration, at 7.1 years.

 

While females reported shorter relationship durations on average, they mirrored the male pattern quite well, in which length varied with strength of religiosity.  Long relationships support the reproductive investment necessary to accommodate the greater desire for offspring, facilitating a high-yield reproductive strategy. 

 

We also computed the average number of different sex partners for our religious-gender cohorts.  Among females, religiosity was negatively correlated with the number of sex partners (r=-0.12, p<0.002).  The very religious females reported the lowest number (5.6), and the moderately religious were next (10.3).  The atheistic (14.9) and agnostic (13.3) females reported higher numbers, but not nearly as high as the spiritual (16.2).

 

Among males, the negative correlation between religiosity and numbers of sex partners was weaker, (r=-0.04, p<0.16).  The outliers for the number of sex partners were the very religious (9.3) and the spiritual (19.4). Like the spiritual females, the spiritual males led their gender in numbers of different sex partners, an interesting result indeed.    

 

When it comes to reproduction, the spiritual resemble the atheists and agnostics more than they do the religious: one of the reasons we have excluded them from the religious cohort.  People that define themselves as spiritual, yet have no religious affiliation, differ substantially from the religious on a large number of cognitive and behavioral attributes.

 

Finally, monogamy was self-rated, on a scale of 1 to 10, with 10 being the highest level.  The highest ratings were among the very religious in both genders (males = 9.3, females = 9.6).  The moderately religious in both genders were next, with males averaging 8.8 and females averaging 9.4.  The agnostics and atheists in both genders had the lowest self-ratings of monogamy.  The level of religiosity and self-rated monogamy were closely correlated variables in both genders: females (r=0.18, p<0.0001), males (r=0.16, p<0.0001).

 

3. Non-reproductive Sexual Behaviors

 

One of the prominent variations between the religious and nonreligious is the stronger reproductive valence maintained by the religious in their sexual behavior.  A sample of    sexual behaviors that do not directly lead to conception are displayed in table 3, which includes self-reported arousal levels for anal sex, oral sex, pornography, and homosexual experience.

 

Arousal levels for anal and oral sex were based on a scale of 1 to 10, with 10 being the highest level of arousal one could report.  However, the questions were not framed to delineate whether one was aroused by giving or receiving oral or anal sex.  For viewing pornography, the respondent was asked to indicate one of four options available: never, rarely, sometimes, and frequently.  In table 3, only those responding sometimes and frequently were included in the statistics.  For homosexual experience, we combined the rarely, sometimes, and frequently responses in this statistic, and excluded those indicating they never had a homosexual experience.  Note that in this survey, the experience should have resulted in an orgasm to be classified as homosexual.

 

For the sexual behavior of anal sex, the females had low arousal ratings, on average.  The lowest arousal rating was reported by the very religious females, at 2.8, and the moderate females had the next lowest rating, at 4.3.

 

Gender

Religious Disposition

N

Mean arousal for anal sex

Mean arousal for oral sex

Percentage looking at pornography (frequently or sometimes)

Percent having at least one homosexual experience

Female

Religious

250

4.2

5.9

36.4%

18.8%

 

Nonreligious

252

4.9

6.1

46.0%

32.5%

 

Spiritual

181

4.7

6.3

46.4%

34.3%

 

VR

48

2.8

5.0

14.6%

10.4%

 

MR

115

4.3

6.2

39.1%

18.3%

 

LR

87

4.8

5.9

44.8%

24.1%

 

AG

126

4.6

6.1

49.2%

29.4%

 

AT

126

5.2

6.1

42.9%

35.7%

Male

Religious

499

5.4

7.2

70.7%

16.4%

 

Nonreligious

630

6.3

7.6

84.3%

23.2%

 

Spiritual

206

6.3

7.8

77.7%

23.3%

 

VR

134

5.0

7.1

49.3%

15.7%

 

MR

226

5.3

7.2

76.6%

15.9%

 

LR

139

5.9

7.4

82.0%

18.0%

 

AG

226

6.3

7.6

85.0%

22.1%

 

AT

404

6.3

7.6

83.9%

23.8%

Table 3: Arousal for anal sex, oral sex, pornography, and homosexual experience
(AT=Atheist, AG=Agnostic, LR=A little religious, MR=Moderately religious, VR=Very religious) (Religious=VR+MR+LR, Nonreligious=AG+AT)  

 

The males were more aroused by anal sex than females, but the very religious were again at the bottom of the male scale (5.0).  Similar to the female pattern, the moderately religious males were next at 5.3.  The atheists, agnostics, and spiritual males all reported the same level of arousal, at 6.3, yet another statistic where the spiritual resemble the nonreligious more than the religious.

 

Arousal for oral sex was substantially higher in both genders, and indeed there is some evidence that oral sex may help prevent preeclampsia (see Koelman et al. 2000).  But religiosity was inversely correlated with arousal for oral sex in both genders, and the very religious reported the lowest arousal scores (females = 5.0, males = 7.1).  Interestingly, the spiritual reported the highest rates of arousal in both genders (females = 6.3, males = 7.8), another indicator of the variation between the religious and the spiritual. Among females, outside of the very religious, the correlation was weak between religiosity and arousal to oral sex (r=-0.05, p<0.23). 

 

Viewing pornography was strongly elevated among males.  Again, the very religious in both genders were by far the lowest consumers of pornography (females = 14.6%, males = 49.3%), even when compared to the moderately religious (females = 39.1%, males = 76.6%).  The agnostics led both of their respective genders (females = 49.2%, males = 85.0%) in the usage of pornography.

 

Finally, religiosity was an active trait in the reporting of homosexual experiences (to the point of orgasm).  The greater the level of religiosity, the less likely one will report having a homosexual experience.  The very religious reported the lowest rates (females = 10.4%, males = 15.7%), while the spiritual (females = 34.3%, males = 23.3%) and the atheists (females = 35.7%, males = 23.8%) reported the highest rates. 

 

4.  Male Dominance, Orgasmic Ability, and Masturbation

 

In most sexually reproducing species, dominant males sire a disproportionate number of offspring.  In humans, this phenomenon also occurs, with economic criteria usually employed in resolving male dominance status.  The reproductive advantages of male dominance have made their way into the arsenal of reproductive stimulants of the religious, and according to our results, the greater the level of religiosity, the greater the level of male dominance within the male-female relationship. 

 

Males, in general, were more likely to indicate they were dominant in their relationships.  In this relationship dominance statistic, we only included those in an active relationship.  Among females, relationship dominance is negatively correlated with the level of religiosity (r=-0.05, p<0.21), while among males, it is positively correlated (r=0.09, p<0.01).  We must note that the heterosexual or homosexual nature of these relationships was not differentiated in this statistic.

 

Orgasmic ability is critical for males, as the ability to orgasm during copulation translates directly into reproductive effectiveness.  Responding to the question of whether one orgasms more easily during intercourse or masturbation, females decidedly selected masturbation. We must note that there were a number of “not sure” responses to this question.  As seen in table 4, the religious females had a slight elevation in intercourse orgasmic ability when compared to the nonreligious (24.4% to 19.8%).  But among the males, the religious were substantially elevated in their orgasmic preference for intercourse (51.3% to 37.2%).  The very religious males recorded the highest preference, at 61.9%. 

 

While the religious indicated an elevation in copulatory orgasmic ability, the nonreligious males were still effective in the ability to achieve orgasms during copulation.  90.9% of the nonreligious males always or frequently achieved orgasm during intercourse, compared to 91.2% of the religious males and 89.7% of the spiritual males.

 

But among females, the nonreligious reported a deficit in orgasmic ability, as 43.9% reported they always or frequently achieved orgasm during intercourse, compared to 50.8% of the religious and 48.5% of the spiritual.  Note that the very religious females were the most orgasmic during intercourse, at 58.7%.  The interesting elevation of female orgasmic ability among the religious (during intercourse) might be evidence for a reproductive function to the female orgasm; however, we will defer this complex and controversial topic until later, as this can actually be interpreted to support several different theories of the evolutionary function of the female orgasm, such as Symons (1979).

 

Religious Disposition

N

Percentage  indicating they are dominant in relationship

Orgasms easier with intercourse than with masturbation

Orgasm during intercourse (frequently or always)

Mean Masturbation per week*

Religious

250

23.6%

24.4%

50.8%

1.8

Nonreligious

252

26.2%

19.8%

43.9%

2.2

Spiritual

181

24.6%

20.8%

48.5%

2.3

VR

48

13.0%

25.0%

58.7%

1.6

MR

115

27.0%

21.6%

48.3%

1.7

LR

87

24.7%

27.7%

50.0%

2.1

AG

126

22.9%

20.7%

38.8%

2.2

AT

126

29.4%

19.0%

49.1%

2.2

Religious

499

39.9%

51.3%

91.2%

3.2

Nonreligious

630

34.3%

37.2%

90.9%

4.4

Spiritual

206

36.5%

41.6%

89.7%

4.2

VR

134

44.4%

61.9%

94.9%

2.9

MR

226

41.0%

49.1%

90.2%

3.2

LR

139

33.9%

45.4%

89.5%

3.7

AG

226

34.3%

39.6%

88.1%

4.3

AT

404

34.3%

36.0%

92.4%

4.5

Table 4: Dominance, orgasmic ability, and masturbation
(AT=Atheist, AG=Agnostic, LR=A little religious, MR=Moderately religious, VR=Very religious) (Religious=VR+MR+LR, Nonreligious=AG+AT)

  

Finally, masturbation is negatively correlated with religiosity in both genders (females: r=-0.09, p<0.02; males: r=-0.22, p<0.0001).  The reproductive implications for male masturbation relate primarily to semen volume, sperm count, motility, and morphology (Pellestor et al., 1994), and imply an interesting trade-off between sperm volume and sperm quality, dependent on ejaculation frequency.  The lower rates of religious male masturbation might imply that they are releasing more sperm during copulation; an advantage in fertility, especially when combined with the lowered tendency for the religious to use contraception (Studer and Thornton, 1987).

 

Discussion

 

By some accounts, Joseph Smith, the founder of Mormonism, had as many as 84 plural marriage partners (Compton, 1997), which highlights the interesting relationship between cult formation and reproductive advantage. The reproductive advantages of cult founders can be substantial (Galanter, 1989), as seen more recently with David Koresh and his preferential sexual access to females within the Waco Branch Davidian compound (C. Wilson, 2000).

 

Primate studies indicate that dominant males maintain substantial reproductive advantages over subordinate males, especially when the number of males in the group is small (Colishaw and Dunbar, 1991). As the number of males increase, the advantages of dominance are neutralized by the costs incurred to guard mates and monopolize sexual access.  However, organized cults frequently employ behavioral regulation mechanisms that maintain the reproductive advantages of cult leaders, along with emigration and colony formation to reduce the potentially disruptive influences of kin.

 

The relationship between religiosity and emigration is interesting, as there are many parallels with the definition of r-strategists in the field of population biology. r-strategists migrate to new habitats quickly, reproduce rapidly, and disperse rapidly when those habitats are depleted. They are noted by elevations in several altruistic traits, such as mutual defense, cooperative foraging, and nest building (E. Wilson, 2000)Extinctions of small colonies are highest at two points: at the beginning of colonization; and at the point the population has reached the maximum carrying capacity of its habitat.

 

Religiosity has a positive impact on colonial longevity, as documented in the Sosis and Bressler study (2003) of 19th century communes.  The religious colonies in this study had a mean longevity of 35.6 years, while the secular colonies lasted 7.7 years.  Sosis noted that intragroup conflict and economic failure were the two most common reasons for commune dissolution.  Sosis’ costly signaling theory of religion proposes that the greater the behavioral regulations placed on the members, (e.g., celibacy and fasting), the greater the longevity of the commune.  However, as Sosis noted, there was no relationship between “costly signaling” and longevity in secular communes, creating a significant issue with the theory.  Sosis also noted that religious communes were more likely to organize around a charismatic leader than were secular communes. 

 

The relationship between religiosity and successful colonization is no doubt the result of the highly coordinated social behavior and mutual altruism practiced by organized religious groups, but of the eighty-three 19th century communes studied by Sosis, only a single religious commune has remained active until today--the Hutterites. 

 

The ability of organized religious groups to withstand r-extinctions, or extinctions of new colonies, is certainly implied by the Sosis study.  A primary difference between colonies formed by cults and colonies formed by existing religious sects lies in the level of support from the parent population, either through kinship or religious ties.  Cults are more likely to isolate themselves, thereby sustaining the dominance and reproductive advantages of the cult leaders. 

 

But from a perspective of population biology, there are several factors that have a significant impact on the total reproductive output of a colony (or any population, for that matter), such as the numbers of females and males that are in an active relationship that supports reproduction.  Based on the results in table 2, the religious males have a substantial advantage over the nonreligious males, and this implies a substantial reproductive advantage.

 

This poses an interesting question: does religiosity improve the likelihood that a male will reproduce?  Across most sexually-reproducing species, the percentage of females that produce at least one offspring is greater than the percentage of males.  Religiosity in males seems to improve the percentage that sire offspring.

 

The religious also report higher levels of monogamy and longer relationship durations.  This should ordinarily work to improve reproductive yield, especially in cases where both parties desire children.  Interestingly, the desire for the religious to have religious partners, as noted in table 1, seems to be facilitating the matching of the desire for offspring, and ultimately reproductive output. 

 

The correlation between religiosity and male dominance, as noted in table 4, pertains to dominance within the male-female relationship, and is not directly associated with intrasexual, or male-male dominance.  The correlation between intrasexual male dominance, sexual dimorphism, and reproductive advantage has certainly been documented in numerous species, but how does male dominance over females impact reproductive rates?  

 

While the Gottschall study (2003) indicates that fertility rates were higher in cases of rape than with consensual sex, fertility rates pertaining to varying degrees of sexual coercion among monogamous couples is unknown.  But we can speculate that male dominance within a relationship improves sexual access by the male.  Following this line of reasoning, the very religious males, reporting the highest level of dominance within their relationships, would have greatest sexual access to their partners.  The fertility implications are significant, as they also desire more children than any other cohort.

 

This brings us to the issue of the reported elevation in orgasmic ability among the religious females.  The connection between male dominance and female orgasmic ability would certainly be an expected outcome of natural selection, and indeed, it has been documented with other species (Troisi and Carosi, 1998).  How this relates to the more submissive role played by religious females is speculative, but the Donald Symons’ hypothesis of the female orgasm as an inert embryological byproduct, like the male nipple, would be challenged by the fact that females that are more reproductive are also more likely to orgasm during intercourse.  This is not to imply that the act of female orgasm improves fertilization specifically, rather, it seems to facilitate the general process of reproduction.  The female orgasm would presumably provide a substantial reward to induce copulation, along with the neurological chain of events that promote romantic bonding, ultimately improving reproductive yield.  

 

The proposal that female orgasmic ability is an evolutionary adaptation that promotes female choice in mate selection may have some merit when applied to the religious.  However, mate selection may only be part of the orgasmic advantage, as long-term bonds seem to be facilitated by long-term copulatory orgasmic ability.  Note that the religious females reported longer average relationships, and remarkably, higher rates of copulatory orgasmic ability in those relationships.

 

But perhaps the most significant variable associated with the reproductive advantage is the desire for children.  As seen in table 1, this is strongly correlated with religiosity.  While the religious seem to be playing a very tactical game of reproductive advantage, they are, for the most part, unaware of this game.  Evolution has loaded the nervous system with simple, yet effective, sexual and nonsexual adaptations that promote reproduction. 

 

One of these adaptations is evident in the table below, where the survey respondents were asked to select a favorite odor from the following options: chocolate, coffee, vanilla, garlic, or a newborn baby. There is indeed a positive correlation between religiosity and the hedonic preference for the odor of a newborn baby in both genders, (r=0.11, p<0.0001), which could be interpreted as an evolutionary adaptation that improves reproductive yield. 

 

 

 

Gender

Religious Disposition

N

Newborn Baby

Coffee

Chocolate

 

 

Garlic

Vanilla

Female

Religious

335

17.0%

31.0%

16.7%

7.2%

28.1%

 

Nonreligious

381

8.7%

38.3%

16.5%

12.1%

24.4%

 

Spiritual

229

14.9%

29.7%

14.9%

13.1%

27.5%

 

VR

81

24.7%

24.7%

21.0%

6.2%

23.5%

 

MR

156

16.0%

30.8%

16.7%

7.1%

29.5%

 

LR

98

12.2%

36.7%

13.3%

8.2%

29.6%

 

AG

258

9.7%

38.8%

14.3%

11.6%

25.6%

 

AT

123

6.5%

37.4%

21.1%

13.0%

22.0%

Male

Religious

567

7.8%

36.9%

15.9%

10.8%

28.8%

 

Nonreligious

672

3.3%

39.7%

13.1%

11.8%

32.1%

 

Spiritual

264

7.6%

43.6%

12.9%

9.9%

26.1%

 

VR

145

13.1%

33.8%

12.4%

12.4%

28.3%

 

MR

245

6.1%

37.6%

18.0%

10.6%

27.8%

 

LR

177

5.7%

38.4%

15.8%

9.6%

30.5%

 

AG

257

3.1%

42.4%

12.8%

10.6%

31.1%

 

AT

415

3.5%

35.4%

13.6%

13.6%

33.9%

Table 5: Favorite odor 
(AT=Atheist, AG=Agnostic, LR=A little religious, MR=Moderately religious, VR=Very religious) (Religious=VR+MR+LR, Nonreligious=AG+AT)

 

However, in this response, we cannot be sure that they were solely influenced by the odor cues associated with infants, and not some other sensory feature.  The neurobiology of parent-child bonding is complex, and involves the phylogenetically ancient olfactory system.  If indeed the hedonic preference for the odor of a newborn baby is genetically modulated, it is only one of many evolutionary adaptations that improve reproduction.

 

It is also interesting to note that this preference is one of the few instances where the spiritual resemble the religious.  The spiritual, or those that have a belief in a deity, yet no religious affiliation, actually look more like the atheists and agnostics in their questionnaire responses. Perhaps this unusual cognitive alliance between the spiritual and the nonreligious is explained by hemisphericity, or the  various mechanisms employed by the brain to resolve conflicts in the alternate behaviors and cognition promoted by the lateralization of the left and right cerebral hemispheres. 

 

The brain is a paired-organ; with each half specialized in cognitive and behavioral functionality (Demaree et al., 2005).  The left cerebral hemisphere is implicated with the propensity to apply single meanings to ambiguous targets, while the right hemisphere is prone to apply alternate meanings to the same targets (Faust and Lavidor, 2003). The general mode of left hemispheric cognition seems to be the reduction of ambiguity, which has been associated with political conservatism (Jost et al., 2003), which itself is correlated with religiosity. 

 

There is an interesting convergence along several different lines of neurocognitive research with implications for a special role of the left cerebral hemisphere in religiosity and political conservatism.  The first comes from the study of belief-bias, which has identified a left temporal lobe system in belief-biased reasoning, while the right lateral prefrontal cortex is engaged when subjects inhibit a prepotent response associated with belief-bias (Goel and Dolan, 2003).    

 

The assignment of people, objects, and events into “good” or “evil” categories is a recurrent theme in religious dogma, and the neurology supporting this assignment appears to be centered in the left parietal lobe (Newberg et al., 2001).  This region is also implicated in motor planning for the redirection of body movements, which may hint that the binary categorization of “good” and “evil” has its evolutionary origins in the neurology associated with the fight-or-flight instinct.

 

Within the left temporal lobe, asymmetrically large hippocampal volumes are correlated with higher levels of religiosity and refractory epilepsy (Wuerfel, 2004), further implicating the left cerebral hemisphere’s role in religious disposition.  But perhaps the most significant neurological relationship to religiosity lies with the dopaminergic system (Previc, 2006).  Also, see last month's edition. The dopaminergic system is an anatomically distinct arrangement of neural pathways that activate cortical and sub-cortical structures to facilitate motor-control, reward-anticipation, reward-seeking, and approach.

 

The dopaminergic system, implicated in romantic bonding, sexual function, meditative states (Kjaer et al., 2002), and reward prediction, makes it a prime candidate in the behaviors associated with religiosity and political conservatism.  The reproductive rates of the religious are better supported by a higher propensity for reward-seeking; however, to date, there is no direct evidence that the religious are elevated in their propensity for reward seeking.  

 

With the reproductive advantages of religiosity, why does agnosticism and atheism persist?  This answer to this may lie in the social integration of divergent cognitive styles, that is, optimization of one’s contributions and compensations within a social group occurs when individual brains are specialized for different sets of tasks.  This phenomenon is seen in vertebrates (Vallortigara, 2000), and our data pertaining to occupation indicates that the religious and nonreligious are performing different economic tasks. The religious and nonreligious seem to have developed a rather symbiotic division of labor, forming a sort of economic glue that counteracts their tendency for social and political conflict.  

 

In the aforementioned Sosis study of 83 nineteenth century religious and secular communes, 82 failed, following the general tendency of high extinction rates for small animal populations.  Over the same time period, the survival rate of cities with populations of over one million was one-hundred percent. 

 

Extreme levels of religiosity would seem to have an evolutionary cost, as the time and effort devoted to religious behavior leaves less time for technological and economic pursuits.  Indeed, secularism and technological change are highly correlated variables, and reproductively successful religious populations must maintain some level of integration with the economics, science, and technology of dynamic secular populations, while minimizing their negative impact on fertility.

 

It is certainly arguable that secularism, via a greater tendency for cognitive diversity, specialization, and technological change, has actually improved the carrying capacity of habitats, subsequently supporting larger religious populations. Ironically, atheism and agnosticism may indeed be an evolutionary complement to religiosity, and the evolutionary trajectory of human gene pool seems to be walking the fine line between reproductive effectiveness and technological progress.

 

The strong orientation of the religions toward the afterlife, morality, male dominance, heterosexuality, fidelity, etc., when combined with the genes that promote religiosity, is fundamentally a runaway evolutionary process emulating the Fisherian model of runaway sexual selection.  God, meet Darwin.

 

 

 Charles Brack, March 2008

 

 

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