When I was young, I remember being taught that the laws of kashrut derived from a pre-modern understanding of hygiene. Pigs were “dirty” and you took the risk of contracting trichinosis if you ate raw or undercooked pork.
Keeping kosher, as a result, was a way of staying healthier. Indeed, today even non-Jews will buy food with kosher certification because of the perception that it’s more nutritious.
As I grew older, that simplistic explanation gave way to a more Talmudic approach: there were no medical or scientific reasons why we should eat cows and carp but not pigs or kangaroos. Rather, keeping kosher was a deliberately inscrutable sign of our faith and devotion to God.
But what if that first idea was actually right? What if kashrut does have its roots in helping us avoid illness?
To go one step further, is it possible that religion in general developed in part as a pre-conscious strategy to help humans steer clear of disease?
That’s the thesis of Thomas B. Ellis, a professor in the department of philosophy and religion at Appalachian State University in Boone, North Carolina. Ellis was in Jerusalem last week to present a talk on “The Immunology of Religion” at the third “Judaism and Evolution” conference, held at the Schechter Institute of Jewish Studies.
Populations living close to the equator or closer to sea level, he told the conference attendees, tend to suffer from greater numbers of infectious diseases. Spend any time in South and Southeast Asia, for example, and you know the risk of getting sick from all manner of parasites, mosquitos and food-borne maladies.
In order to strengthen their immunity, Ellis says, humans in these areas have historically formed tight knit “collectivist” groups which strictly prohibit eating or sleeping with members of another group. The Indian caste system as it was originally conceived is perhaps the epitome of keeping people of different groups apart.
These “breeding isolates,” as Ellis calls them, block disease transmission and help those in the group boost their immunity against outside illnesses, giving them an advantage over groups from another valley, for example, that might not have developed the same resistance to local diseases. Over many generations, it can even alter DNA, Ellis adds.
The Middle East, where Judaism first developed, was in the past warmer and wetter than it is today “and thus more conducive to an infectious disease ecology,” Ellis says. It’s not surprising that a collectivist approach took hold here too.
Religious practice, Ellis asserts, developed organically on the back of this immunologically-savvy group organization. Early religious leaders weren’t aware of the public health benefits on which they were building their new spiritual systems. They hadn’t developed a science of how germs work.
But like physical evolution, the evolution of ideas doesn’t require conscious thought. Dogs learn to stay away from parasite-infected meat through natural selection. The dog doesn’t “think” about what it’s doing.
Religious customs could have evolved similarly.
Jewish Law – which has much to say about what you can eat and with whom you can sleep – is in many ways the philosophical descendent of millennia of trial and error honed first while fighting disease.
In this respect, the halacha mandating abstention from pork is not because the pig itself is inherently unhealthy or “impure.” Rather, it’s a byproduct of a bigger system that aims to strengthen physical fitness by relying on boundaries between religious groups.
Ellis presented another example of how religious customs act to inadvertently promote immunological health: the blood sacrifice.
Like many ancient societies, the Jewish Temple was awash with animals being killed as part of religious ritual. Today most of us see that as barbaric. But Ellis argues that watching the blood and guts of animal sacrifice is intrinsically stressful – and that’s a good thing.
While chronic or long-term stress has been shown to depress the immune system, “acute or short-term stress…can enhance innate and adaptive immune responses,” according to Stanford researcher Firdaus Dhabhar. Seeing blood apparently tells the body to get prepared to fight off a trauma that could be coming its way.
“Does killing a chicken actually cure people?” Ellis asked. “No. But watching a blood sacrifice is a non-pharmacological way of upregulating your immune system and the immune systems of people around you.”
It helps explain why so many religions call for some sort of blood sacrifice when someone gets sick. Among the Torah’s prescriptions for curing leprosy, for example, is sacrifice.
Ellis’s hypotheses can help us understand our past, but what about the future? We don’t need to watch an animal being slaughtered to boost our immune systems today; we have drugs and vaccines for that. Ditto on not eating or sleeping with people outside our group – science and modern hygiene have that covered too.
Has religion reached the end of its usefulness, then? Hardly.
Ellis also spoke at the conference about the value of religious practice as a technique to mitigate another classic chronic stressor: uncertainty (something we have in abundance these days). And religion, of course, has evolved to be about far more than just health.
But if we take seriously the latest understandings into the possible immunological origins of religious law and ritual, it may very well change the modern Jew’s commitment to some of the stringencies of halacha or, on the opposite end of the spectrum, lead us to generate new reasons for why we continue to do what we do in the light of science.
I first wrote about Tom Ellis and the immunology of religion at The Jerusalem Post.