Darwin’s theory of evolution has met with repeated episodes of its conspicuous rejection, from the celebrated 1860 debate between Bishop Samuel Wilberforce and Thomas Henry Huxley, to the sensational Scopes “Monkey Trial” in Dayton, Tennessee, in 1925, to court cases at the turn of the 21st century when certain American locales sought to require the teaching of either Intelligent Design or the putative controversy about human origins. Such ostentatious disavowals of Darwin’s theory and the development and success of institutions such as the Creation Museum and Ark Encounter (with well over 750,000 visitors a year) indicate that the intellectual turmoil is ongoing.
A second connection between evolutionary thinking and religions has emerged over the past few decades, which have witnessed a proliferation of evolutionary theories about religions and religiosity. Evolutionary thinkers of various stripes have set their sights on a variety of religious matters as the objects of their explanatory proposals.
Religions as Products of Natural Selection
Many theorists maintain that natural selection favors either religions or individuals’ religiosity. They construe them as adaptations that enhance the fitness either of those religious groups, or of those groups’ members, or of religious individuals. So, for example, at the level of groups, religions tend to foster in-group cooperation, helping to ensure the group’s continuation (and, perhaps, its propagation). Correspondingly, members of religious groups tend to identify with, cooperate with, and aid one another, resulting in an increase in those members’ average fitness. Behavioral ecologists argue that religions often supply particularly effective solutions to complex environmental problems, such as the management of scarce water resources. Even more straightforwardly (i.e., without introducing the controversies surrounding the question of whether groups can serve as the units of selection), evolutionary theorists simply point to the numerous studies indicating that religious individuals enjoy better physical and mental health compared with the nonreligious.
Such appeals to natural selection, however, do not remotely exhaust the range of evolutionary proposals about religions. To bring some order to this wealth of evolutionary theories addressing religious matters, it will be worthwhile to distinguish selective mechanisms. Arguably, all forms of selection are examples of natural selection in the broadest sense of that term, but evolutionary theorists, including Darwin himself, have seen fit to distinguish some selective mechanisms for separate treatment.
Religions as Products of Sexual or Cultural Selection
Some theorists addressing religious phenomena have looked to either of two of these marked selective mechanisms. The first is sexual selection, to which Darwin appealed to explain persisting maladaptive traits. Such traits (peacocks’ lavish tails, Irish elks’ gigantic antlers) might detract from some individual’s probability of surviving but might, nonetheless, increase that individual’s probability of reproducing, either because of those tails’ attractiveness to peahens or because of those antlers’ contributions to warding off other males competing for access to females. Sexual selectionists suggest that religiosity functions similarly as signals, in a female, of her faithfulness as a mate and, in a male, of not just sexual fidelity but of his trustworthiness as a provider for his partner and their offspring.
The second selective mechanism that various theorists invoke is cultural selection. Although Darwin did not employ the term, he certainly recognized the possibility of cultural traits increasing the probabilities of, again, the persistence (or even the propagation) of a group and its members. Cultural selectionist accounts have thrived for the past 40 years, but it is only in the last 15 years that some have focused on religions. Like the natural selectionists, they have stressed the roles that religions play in boosting in-group solidarity and cooperation as adaptations.
A Final Point About Such Theories’ Logical Relations
It is perfectly possible for all of these evolutionary hypotheses, the controversial status of some notwithstanding, first, not only to be consistent with one another but, second, to all be true. Note that is not the same as saying either that, in fact, they are all consistent with one another or that they are all true. The point is simply that nothing in principle renders them inconsistent with one another. That could be because each explains a portion of the variance that the others do not, or because each explains different features of religions, or because various phenomena may result from multiple evolved arrangements and are, thus, either causally complex, causally overdetermined, or both. All of them could be delivering a piece of the right story about religious phenomena—except, of course, when positive evidence for either of two hypotheses out to explain the same thing counts as negative evidence for the other.