or tongue or penis or inside the throat or other body part. All of those costly public or painful displays serve to convince other believers that one is serious in one’s commitment to their religion and will even sacrifice one’s life if necessary. Otherwise, if I merely shouted “I’m a Christian!,” I might be lying for personal advantage (as some prisoners do in the hopes of gaining parole), or to save my life. While the second and third attributes (i.e., a social movement and costly sacrifices) seem to me necessary conditions for a movement to count as a religion, they’re not sufficient conditions by themselves. There are also non-religious social movements sharing deeply held beliefs and demanding costly sacrifices of their adherents, such as patriotism.
The next-to-last attribute of religions is that belief in gods and other postulated supernatural agents has practical consequences for how people should behave. Those rules of behavior may variously take the form of laws, moral codes, taboos, or obligations, depending on the type of society. While virtually all religions have such rules of behavior, it is not the case that rules of behavior stem only from religion: modern secular state governments, countless non-religious groups, and atheistic or agnostic citizens also have their own rules.
Finally, many religions teach that supernatural agents not only reward virtuous rule-obeying people and punish evil-doers and rule-breakers, but also can be induced by prayers, donations, and sacrifices to intervene on behalf of mortal petitioners.
Thus, religion involves a constellation of five sets of attributes, which vary in strength among the world’s religions (including traditional religions). We may use this constellation to understand the differences between religion and several related phenomena that share some but not all of the attributes of religion. Patriotism and ethnic pride resemble religion in being social movements distinguishing their adherents from outsiders, demanding sacrifice (even of one’s life) as a display of one’s commitment, and celebrated in rituals and ceremonies such as (for Americans) Independence Day, Thanksgiving Day, and Memorial Day. Unlike religion, patriotism and ethnic pride do not teach belief in supernatural agents. Sports fans, like religious believers, form social groups of adherents (e.g., Boston Red Sox fans) distinct from adherents of other social groups (e.g., New York Yankee fans) but don’t espouse supernatural agents, don’t demand great sacrifices as proof of affiliation, and don’t regulate a broad range of moral behavior. Marxism, socialism, and other political movements do attract committed groups of adherents (like religions), motivate adherents to die for their ideals, and may have broad moral codes, but don’t rely on the supernatural. Magic, sorcery, superstition, and water-witching (the belief that underground water can be located by a divining rod) do involve belief in supernatural agents with consequences for everyday behavior. However, magic, superstition, and related phenomena do not serve as defining attributes of committed social groups akin to believers: there are not groups of believers in the dangers of black cats who meet every Sunday to re-affirm their separateness from non-believers in the dangers of black cats. Perhaps the grayest borderline area involves movements such as Buddhism, Confucianism, and Shintoism, about which there are varying degrees of uncertainty whether they constitute religions or else philosophies of life.
Functions and electric eels
Religion is nearly universal in humans, but nothing even remotely resembling it has been described in animals. Nevertheless, we can inquire about—indeed, we have to wonder about—the origins of religion, just as we wonder about the origins of other uniquely human traits such as art and spoken language. Six million years ago, our ancestors were apes that surely lacked religion; by the time that the first written documents appeared around 5,000 years ago, there was already religion. What happened in the intervening 5,995,000 years? What were religion’s antecedents in animals and in human ancestors, and when and why did it arise?
A method termed the functional approach has been the commonest framework adopted by scholars of religion since they began studying it scientifically almost 150 years ago. They ask: what functions does religion fulfill? They note that religion often imposes heavy costs on individuals and societies, such as impelling many people to live celibate lives and to forgo having children, to go to the effort and expense of building huge pyramids, to kill one’s valuable domestic animals and occasionally even one’s own child and oneself, and to spend much time repeating the same words over and over again. Religion must have functions and bring benefits to offset those heavy costs; otherwise, it wouldn’t have come into being and couldn’t be maintained. What human problems did the invention of religion solve? A brief summary of the functional approach might be to assert something like this: religion was invented in order to carry out certain functions and solve certain problems, such as maintaining social order, comforting anxious people, and teaching political obedience.
Another approach, emerging more recently from the field of evolutionary psychology, objects: religion surely didn’t evolve and wasn’t consciously invented for any specific purpose or to solve any specific problem. It wasn’t the case that some budding chief got a brilliant idea one day and invented religion from scratch, foreseeing that he could more easily hold his subjects in sway if he convinced them of religious reasons to build a pyramid. Nor is it likely that a psychologically attuned hunter-gatherer, concerned that his fellow tribesmen had become too depressed by a recent death to go hunting, made up a story about the afterlife in order to console them and give them new hope. Religion instead probably arose as a by-product of some other capacities of our ancestors and of their own animal ancestors, and those capacities had unforeseen consequences and gradually acquired new functions as they developed.
To an evolutionary biologist like myself, there is no contradiction between these two different approaches to the origin of religion, in effect postulating two stages. Biological evolution itself similarly proceeds in two stages. First, variation between individuals is generated by mutations and recombinations of genes. Second, because of natural selection and sexual selection there are differences among the resulting variant individuals in how they survive, reproduce, and pass on their genes to the next generation. That is, some of those variant individuals turn out to perform functions and to solve life’s problems better than do other variant individuals. A functional problem (e.g., surviving in a colder climate) isn’t solved by an animal realizing that it needs thicker fur, nor by cold climates stimulating mutations for a thicker fur. Instead, something (in the case of biological evolution, the mechanisms of molecular genetics) creates something else (in this case, an animal with thicker or thinner fur), and some life conditions or environmental problems (in this case, cold temperatures) endow some but not others of those variant animals with a useful function. Thus, gene mutations and recombinations provide the origins of biological diversity, while natural selection and sexual selection sieve that starting material by the criterion of function.
Similarly, evolutionary psychologists assert that religion is a by-product of features of the human brain that arose for reasons other than building pyramids or comforting bereaved relatives. To an evolutionary biologist, that’s plausible and unsurprising. Evolutionary history is chock-full of by-products and mutations that were initially selected for one function and then developed further and became selected to fulfill another function. For example, creationists skeptical of the reality of evolution used to point to electric eels that electrocute their prey with 600- volt shocks, and then argued that a 600-volt eel could never have arisen from a normal no-volt eel by natural selection, because the necessary intermediate stages of low-voltage eels couldn’t electrocute any prey and wouldn’t be good for anything. In fact, it turns out that 600-volt eels evolved through changes of function, as a by-product of electric field detection and electricity generation in normal fish.
Many fish have skin sense organs sensitive to electric fields in the environment. Those fields can be either of physical origin (e.g., from ocean currents or from the mixing of waters of different salinities), or else of biological origin (from the electrical triggering of animals’ muscle contractions). Fish possessing such electric-sensitive sense organs can employ them for two functions: to detect prey, and to navigate through the environment, especially in muddy water and under nighttime conditions where eyes are of little use. The prey reveal themselves to the animals’ electric field detector by having a much higher electrical conductivity than does fresh water. That detection of environmental electric fields may be termed passive electrodetection; it does not require any specialized electricity-generating organs.
But some fish species go further and generate their own low-voltage electric fields, which let them detect objects not only by an object’s own electric field, but also by its modification of the electric field set up by the fish. Organs specialized to generate electricity evolved independently in at least six separate lineages of fish. Most electrical organs are derived from the electricity-generating membranes of muscles, but one fish species develops its electric organs from nerves. The zoologist Hans Lissmann furnished the first compelling proof of such active electrodetection, after much inconclusive speculation by others. Lissmann conditioned electric fish, by food rewards, to distinguish an electrically conducting object from a non-conducting object of identical appearance, such as a
