A sculpture of St Gregory as Pope on display at The Cloisters museum in New York City. Credit:Nicole Bengiveno "None of it is even close to being true," said Greger Larson, one of the main authors of the report debunking the myth. "The whole thing is a house of cards," Larson said, acknowledging that he too has cited the story just like many other researchers. The remaining question, he said, is: "Why did we never question this? Why were we so willing to believe in this origin myth?" By "we", he means scientists, not Christians or Roman Catholics who observe Lent. A quick, unscientific survey of several products of extensive Catholic education drew blank stares when the subject of foetal rabbits came up. I myself can say that in eight years at St Justin's Grammar School, during which time eating meat on Friday was forbidden and often discussed, not one nun ever said: "But laurices, now, no problem there." I did ask some with expertise, just to be sure. Charlie Camosy, a theologian at Fordham University who writes about ethics and animals, read the paper and supplementary material from Larson's article in Trends in Ecology & Evolution. "Nothing about this is familiar to me," he emailed back. He did say that misconceptions about religious ideas on animals were common.

Larson and others took the story for granted, and the debunking started out as something else entirely. Larson researches the origins of domestic animals like dogs and pigs. He asked a graduate student in his Oxford University laboratory, Evan Irving-Pease, to use the well-accepted date of rabbit domestication, 600, as a basis for checking the accuracy of a tool that helps researchers use modern DNA to look back in time and estimate when different species diverged. Irving-Pease first did a bit of historical housekeeping and searched for the papal edict. "He comes back," Larson said, "and says, 'Small problem. It doesn't exist.'" That was only the beginning. With a tug on that one thread, the whole story unravelled. Irving-Pease went on to document a kind of historical telephone game, with an initial error embellished and extended by one writer after another. The problem began, he said, in 1936, when a German geneticist, Hans Nachtsheim, writing about domestication, said that St Gregory of Tours (not Pope Gregory, a different person altogether) had written that foetal rabbits were popular during Lent.

Actually, St Gregory merely described one person consuming foetal rabbits during Lent, and that person was sick, died shortly thereafter, and may not even have been a Christian. Nonetheless, in 1963, another writer, Frederick Zeuner, in another book on domestication, added to the mistake and said the foetal rabbits were not considered meat. "From that point on," Irving-Pease said in an email, "the story takes on a life of its own, as further small details get embellished in each retelling." In the end, he wrote, the "watery" environment of the womb made the foetal rabbits fish, "St Gregory becomes Pope Gregory and, finally, his manuscript becomes a papal edict." With that story debunked, Larson says, the whole business of rabbit domestication is unclear. It is known that domestic rabbits descended from the European rabbit, Oryctolagus cuniculus, which originated in France and Spain.

And, they were kept by humans in penned warrens and fattened for slaughter in hutches at least since the first century BC. That is not, however, the same as controlling their breeding, which is usually considered a mark of domestication. Larson and colleagues write that the earliest evidence of skeletal changes that mark a difference between domestic and wild rabbits occurs in the 18th century, around the time people began keeping rabbits as pets. At such recent times, DNA evidence is not very useful. Larson suggests that the reason for the acceptance of the foetal-rabbit story is that even scientists fall victim to the appeal of a good narrative. And, he said, it indicates an underlying and mistaken view of domestication as an event, not a process. The domestication of rabbits, he believes, involves a long interaction with humans. They were hunted for thousands of years in south-west France and the Iberian Peninsula; consumed as foetuses; kept by Romans and during mediaeval times in warrens and hutches; and most recently bred as pets. All of this is the story of their domestication. That is where Leif Andersson, of Uppsala University in Sweden, disagrees. Andersson, who was a senior author of a 2014 paper on the rabbit genome, found the debunking of the myth persuasive, but he noted in an email that he and his co-authors did not cite the story in their genome paper.

But, he said, he did not agree that all instances of domestication have been continuous processes over a long period. For rabbits in particular, he said, that conclusion was "misleading". He said there is a consensus that it happened in modern times and that his paper showed that domestic rabbits are more closely related to wild rabbits from southern France than to those from the Iberian Peninsula. Rabbits may have been domesticated around 600, he wrote, saying that he found nothing in Larson's paper to exclude the possibility that, papal edicts aside, "French monks or farmers in southern France, because they loved rabbit meat, made a specific effort during a period of 50-100 years to establish tame rabbits that became the founding population for the domestic rabbit". New York Times