Bacon might be the greasy gastronomical craze of the decade in the United States, but in the Islamic and Jewish communities of the Middle East, pork has been off the menu for centuries.

That’s in large part because certain religious writings ban dining on swine. But long before the emergence of the Old Testament and the Qur’an, people in the Middle East had largely cut the meat from their diets. But why?

As New Historian reports, Richard W. Redding, a professor of anthropology at the University of Michigan recently published a study attempting to decipher the historical origins of this cultural trend. He writes that archeological and anthropological evidence shows that between 5,000 and 2,000 B.C., the domesticated animals were common in the Fertile Crescent, likely used as “a household-based protein resource”—in other words, they were kept on hand as a tasty, nutritious food source. Then, around the 1,000 B.C., the keeping and eating of pigs sharply declined.

Pigs need a fair amount of water to survive, which makes them poor travel buddies when a family needs to move—and this could be one factor informing their disappearance from the dinner table. But Redding doesn’t think that’s the primary reason. The blame for the change, his research suggests, can be placed on chickens, which took over pork’s role as a food source.

There’s good reason an ancient Middle Easterner might pick chickens over pigs. New Historian’s Adam Steedham Thake explains:

Chickens have several advantages over pigs. First, they are a more efficient source of protein than pigs; chickens require 3,500 litres of water to produce one kilo of meat, pigs require 6,000. Secondly, chickens produce eggs, an important secondary product which pigs do not offer. Third, chickens are much smaller and can thus be consumed within 24 hours; this eliminates the problem of preserving large quantities of meat in a hot climate. Finally, chickens could be used by nomads. While neither chickens nor pigs can be herded in the same way as cattle, chickens are small enough to be transported.

And, Redding argues, it wouldn’t make sense to keep both pigs and chickens, since their food and care needs are similar. “Under these circumstances, the chicken becomes a major protein resource,” he writes, concluding that “If the pig had been integral to the subsistence system in the Middle East, it would not have been prohibited” by religious edicts.

Today, poultry and eggs are reportedly the second most-consumed group of foods in the Middle East next to red meats. But, Redding says, the pig never fully disappeared from the region. Pig husbandry continued in some woodland and marsh areas where more abundant feed options meant the animal could pig-out without challenging chickens’ survival.