BOSTON (Reuters) - A previously unknown scrap of ancient papyrus written in ancient Egyptian Coptic includes the words "Jesus said to them, my wife," -- a discovery likely to renew a fierce debate in the Christian world over whether Jesus was married.

The existence of the fourth-century fragment -- not much bigger than a business card -- was revealed at a conference in Rome on Tuesday by Karen King, Hollis Professor of Divinity at Harvard Divinity School in Cambridge, Massachusetts.

"Christian tradition has long held that Jesus was not married, even though no reliable historical evidence exists to support that claim," King said in a statement released by Harvard.

"This new gospel doesn't prove that Jesus was married, but it tells us that the whole question only came up as part of vociferous debates about sexuality and marriage."

Despite the Catholic Church's insistence that Jesus was not married, the idea resurfaces on a regular basis, notably with the 2003 publication of Dan Brown's best-seller "The Da Vinci Code," which angered many Christians because it was based on the idea that Jesus was married to Mary Magdalene and had children.

King said the fragment, unveiled at the Tenth International Congress of Coptic Studies, provided the first evidence that some early Christians believed Jesus had been married.

Roger Bagnall, director of the Institute for the Study of the Ancient World in New York, said he believed the fragment, which King has called "The Gospel of Jesus's wife," was authentic.

But further examination will be made by experts, as well as additional testing of the papyrus fragment, described as brownish-yellow and tattered. Of particular interest will be the chemical composition of the ink.

The fragment is owned by an anonymous private collector who contacted King to help translate and analyze it, and is thought to have been discovered in Egypt or perhaps Syria.

King said that it was not until around 200 A.D. that claims started to surface, via the theologian known as Clement of Alexandria, that Jesus did not marry.

"This fragment suggests that other Christians of that period were claiming that he was married" but does not provide actual evidence of a marriage, she said.

"Christian tradition preserved only those voices that claimed Jesus never married. The 'Gospel of Jesus's Wife' now shows that some Christians thought otherwise."