God's Rule
Religiosity, Altruism, and Genetic Relatedness
by Charles Brack
Average highest gift to an offspring, another relative, and a non-relative
Darwin was particularly intrigued by the hymenoptera (bees, wasps, and ants), and at one time, viewed them as a major obstacle to his theory of natural selection. The problems presented by the eusocial insects were sterility in the worker castes and their extraordinarily high levels of altruism directed towards their sisters.
This did not seem to be explainable by the natural selection of inherited traits at the level of the individual organism. However, Darwin was never lacking for intuition. In the Origin of Species, he noted that the problem "disappears when it is remembered that selection may be applied to the family, as well as the individual and may thus gain the desired end". Thus, he was walking down the genetic pathway, although he did not know it.
As the science of genetics developed, it became more obvious what was behind the curtain of the puzzling behaviors of altruism and love. The giants of population genetics, Fisher, Haldane, and Wright, all dabbled with this confluence of low genetic distance and altruism, but it was William Hamilton that formally proposed the theory of kin selection, highlighted by Hamilton's rule:
rB - C > 0
For there to be an evolutionary value to altruism (as defined by increasing the individual’s relative genetic presence in the gene pool in the next generation), the coefficient of relatedness, r, times the benefit B bestowed upon the target of the altruistic act, must be greater than the cost C to the altruist. For example, in performing altruism towards a sibling, (with which 50% of genes are shared and the coefficient of relatedness = 0.5), the benefit of the altruistic act must be more than twice the associated decrease in fitness for the altruist's genes to be increased in the next generation.
Thus, the evolutionary value of altruism increases as the coefficient of relatedness increases, which explains the high levels of altruism expressed towards immediate family members, and the rapid altruistic drop off as genetic relatedness decreases. While the pristine mathematics of Hamilton's equation have been met with much fanfare, how closely does it describe real animal behavior?
While Hamilton certainly did not expect altruism to be a uniform function of relatedness, the research, so far, has supported a generally positive correlation across most species. This correlation is typically substantial in parent-offspring relationships, particularly for slowly maturing species. But altruism is much weaker in sibling-sibling relationships, and can even become spiteful, especially in environments where reproductive competition is high and opportunities for dispersal are limited.
Note that this asymmetry in parent-offspring and sibling-sibling altruism occurs even though the coefficient of relatedness is identical (0.5), and seems to be inconsistent with predicted behavior based on Hamilton's rule. Genes appear to prefer genes that are metabolically closer, that is, more directly in the line of chemical synthesis, as they are between parent and offspring.
Religiosity and altruism towards genetic relatedness
In the animal kingdom, human altruism is perhaps the most widely expressed across genetic distance of any species, although humans are certainly not uniform when it comes to investing altruism towards children, siblings, parents, and non-relatives. Even more interesting is that this altruistic expression seems to vary by political-religious disposition.
This is seen in the diagram at the top of this page, which depicts the responses to three questions in our most recent survey: What is the most amount of money you have ever spent on a gift for: 1) your child 2) other blood relative 3) non-relative (excludes spouses). This gives us an indicator of the magnitude of altruism to the various degrees of genetic relatedness.
The respondents were categorized based on their own self-described level of religiosity, which we classified into three cohorts: religious (those reporting that they were very, moderately, or a little religious); non-religious (agnostics, atheists, and those that never think about religion); and, spiritual (those reporting they are spiritual rather than religious).
The rationale for separating the spiritual from the religious comes from our proposal that the spiritual actually share more cognitive and behavioral traits with the nonreligious, although, like the religious, they tend to be more reproductive (see God, meet Darwin).
Spirituality, which is more ambiguous than religiosity, seems to be more under the influence of the right hemisphere, and interestingly, the right hemisphere (especially the lateral prefrontal cortex), seems to play a larger role in atheism and agnosticism. More ambiguous religious constructs, such as spirituality, may be more closely linked to activity in the right temporal cortex, while religiosity seems to be more related to activity in the left temporal cortex.
For our three cohorts, the religious, non-religious, and spiritual, we computed the mean monetary value of their most extravagant gift towards children, other blood relatives, and non-relatives, excluding spouses (see Table 1 below). Although we did not directly capture the relatedness of other blood relatives, we presume, in most cases, these to be siblings or parents, which like children, have a coefficient of relatedness of 0.5.
Table 1: Largest gift to various degrees of genetic relatedness
As can be seen in the above table, the magnitude of the gifts vary substantially based on not only genetic relatedness, but also by level of religiosity. Children are the greatest recipients of gifts for all cohorts, ranging from $1,916 for the spiritual, to a high of $2,645 for the religious (we did not adjust for income and family size in these statistics). Further, the wording of the survey questions allowed for multiple interpretations as to what exactly a "gift" meant.
Given these problems, we must be careful in our interpretations. But there were indeed some interesting trends. First, let's look at the gift statistics associated with the non-religious, which are heavily populated by those with liberal political dispositions, although in our survey, we had an unusually large percentage of non-liberal non-religious participants.
First, they had a mean highest gift of $2,195 devoted to a child, which was 3.89 (see Adjusted) times the mean highest gift given to a non-relative (non-spouse). The "Adjusted" statistics are simply the dollar amount of the gift divided by the dollar amount of the highest gift to the non-relative. This gives us a baseline to track how much people favor relatives over non-relatives.
And this is where it is particularly interesting for the non-religious. Their maximum gift to other blood relatives and non-relatives were almost the same ($612 and $564). In short, this statistic showed little favoritism towards non-child blood relatives compared to non-relatives, although other altruistic measures indeed show more favoritism towards other blood relatives. In any event, for the non-religious, we certainly see the above Hamiltonian equation having limited applicability towards gift giving, especially towards siblings and parents.
Looking at the religious, we see the other extreme, where there is strong favoritism towards both children and non-child blood relatives. The religious scored the mean highest gift towards both children and other blood relatives, at $2,645 and $1,145, respectively. They also had the highest Adjusted ratios of relatives versus non-relatives, at 4.11 for children and 1.78 for other blood relatives, although their mean highest gift towards non-relatives exceeded the non-religious ($643 versus $564).
Thus, for this statistic, the religious are showing a general elevation in gift giving, which favors blood relatives to a greater extent than the non-religious.
This brings us to the interesting behavior of the spiritual. The spiritual were the most egalitarian of the three cohorts, showing the lowest rate of favoritism towards children ($1,916), while the most elevated of the three cohorts when it came to gifts to non-relatives ($690). The adjusted ratio for children (2.78) was the lowest among the cohorts, while other blood relatives (1.55) fell in between the religious and the non-religious.
Altruistic preferences towards parents and siblings
If a species is to last thousands of generations, and be observed today, it must either reproduce at very high rates or disproportionately express altruism towards offspring. Altruistic investment in offspring is even more important for species with slow maturation cycles, usually associated with the development of more complicated central nervous systems. Thus the correlation between altruism and cognitive capacity.
Following the general trend of increased altruism and cognitive capacity, humans display extraordinarily long-term altruistic behavior towards offspring. As seen above, this altruistic bias occurs even though they maintain the same genetic relatedness, 0.5, with parents and siblings.
However, we have gathered some interesting, although inconclusive, evidence that humans may even be discriminating in the way they distribute altruism between parents and siblings. In our most recent survey, we asked our respondents whether or not they would donate a kidney to a sibling and to a parent. The responses are seen in the graph below.
People would rather donate a kidney to a sibling than a parent
Interestingly, the religious report the highest levels of altruism (i.e., willingness to donate a kidney) to both parents and siblings, while the non-religious and spiritual report being substantially less willing, at least in the case of the parent.
We must again be careful in our interpretation of the above results, since the stated willingness to donate a kidney does not necessarily translate into actually doing it. But this result is certainly consistent with the aforementioned statistics associated with gift giving and genetic relatedness.
Across all cohorts, there is altruistic favoritism towards siblings over parents. This makes sense from a perspective of evolution's favoring of altruism towards reproduction, since siblings would be more likely to produce offspring than parents.
Interestingly, the religious indicate the least favoritism of siblings over parents, and indeed, this elevation in altruism towards parents is substantial when compared to the non-religious and spiritual.
God's Rule
The religious aren't just religious. They are the reigning monarchs of the Darwinian game of reproductive advantage, and we have previously proposed that religious culture and the genes that promote religiosity constitute a runaway selective process, something akin to runaway sexual selection.
Behind their anthropomorphic renderings of deity lives the secret world of genetic relatedness. This is seen in the pervasive use of father, son, brother, mother, and sister in referencing not only deities, but also their relationships with each other.
It is certainly arguable that religious practice can increase the perception of genetic relatedness between church members, therefore increasing levels of altruism. It is also arguable that the religious are fundamentally more responsive to expressing altruism to genetic relatedness. These hypotheses corroborate our proposal that religiosity tends to drive the genes of the religious disproportionately into the gene pool.
However, if the definition of altruism includes the restriction of reproductive rates, then it is arguable that the non-religious are the most altruistic of the cohorts. The non-religious are typically much less reproductive than the religious, and based on the limited results presented above, much less inclined to express altruism towards non-offspring relatives. The non-religious are less inclined to drive their genetics into the gene pool.
The spiritual may present an interesting evolutionary compromise between reproductive effectiveness and altruistic expression towards genetic distance. They are more reproductive than the non-religious, and seem to express altruism across greater genetic distance than the religious.
The study of altruism by level of religiosity is highly contentious, but critical to the understanding of the impact human political-religious disposition has on population genetics. Interestingly, the religious seem to be following Hamilton's rule much better than the non-religious and the spiritual.
Charles Brack, July 2010
