Male widowbirds have an unusually large tail, making flight harder than it ought to be. But why evolve a tail that gets in the way? The answer is older than Methuselah: because chicks dig it. Yes, apparently for female widowbirds, at least, size matters. Back in the 1930s, a statistician named Ronald Fisher coined the term runaway selection to describe how this works. Females prefer longer tails and consequently mate with well-endowed males. As a result, their offspring have longer tails and, over generations, the trait continues to become exaggerated (until natural selection steps in, the point at which the tail prevents survival). Unwittingly, some components of Fisher's theory can aptly describe the emergence of exaggerated religious traits as well.
Take for example the recent photo snapped by a passenger of an orthodox Jewish man ensconced in a full-size plastic bag during a flight to Tel Aviv. One might reasonably question: Why would someone wear a hefty cinch-sak on an airplane (or ever, for that matter)? Turns out the man in question is a kohen, from the tribe of Jewish priests, and is forbidden to be in a cemetery as that would render him impure. Which brings us to the plastic bag. This particular kohen suspected that he would be flying over a cemetery (however one determines that) and asked his rabbi what he should do. The rabbi suggested the kohen's purity would remain intact so long as he did a convincing impression of a fruit basket while the plane sailed over the graveyard.
The logic is clear. The rays of impurity ostensibly radiate directly upward from the ground (i.e., there is no prohibition against a kohen walking a block away from a cemetery) and extend miles into the sky. These emissions apparently can penetrate the hull of the plane, continue through the cargo hold and enter into the pressurized cabin, alas, only to be repelled by someone resembling an individually wrapped Cadbury Easter Bunny.
Pity the flight attendant who had to crinkle his bag mid-flight and sheepishly ask if he had remembered to order the kosher meal. Of course, the benefit of wearing a plastic bag is that it prevents one from inadvertently groping neighboring passengers while sleeping, as allegedly happened to this individual (no wonder he has 11 children).
The rabbi who dispensed the cellophane advice informed us that we should not question what we don't understand. In an interview with an Israeli publication, he justified his reasoning: "If a person from the Zulu tribe would see me talking into a telephone, he would think I had gone mad, because he can't understand how sound waves can travel hundreds and thousands of kilometers."
Wow. Apparently this rabbi has been shouting at inconceivably high decibel levels into his phone, since the sound waves are traveling so far (the more traditional route is to have those waves converted into digital or electric signals and then reconstructed at the other end). Naturally, this small misunderstanding does not prevent the rabbi from disparaging the Zulus, who, according to Wikipedia, number roughly 10-11 million people. Assuming there remain some Zulus who don't know about telephones, I can guarantee that within 10 minutes of having used one, they'd be ordering pizza for delivery. Seriously, it is not as though we non-Zulus are privy to some innate telephone knowledge and, nonetheless, we seem to overcome any initial astonishment just fine. I'm not certain the analogy holds for the pernicious rays of impurity, which defy any logic.
So back to Fisher and his theory on runaway selection. What is the allure of these excessive acts of devotion? Like the tail of the widowbird, the plastic-bag mentality is the product of a perceived set of preferences. The notion is that there is a divine being who can be swayed and seduced by displays of stricter-than-thou observance. However, unlike male widowbirds who receive feedback in the form of survival and mating outcomes, there is, of course, no way of actually knowing when the divine presence has been sufficiently placated. Consequently, some people become even more driven to ensure they stand out from the masses. It's hard to know whether to pity the man in the plastic bag if not the rabbi who sent him, or just to be struck by the absurdity of it all. Nevertheless, there is an unmistakable allure to distilling the confusing world into a single question: Paper or plastic?