By Ed Stourton
BBC News, Lalesh
Christians have been in Iraq for 2,000 years, but so many have now fled due to attacks by Islamic extremists that their communities are disappearing. With other faiths also facing extinction, the character of the country could change forever.
The Yazidis claim to be the oldest religion in the world
It was childish, but I couldn't stop the salad issue bubbling up in my mind.
I was interviewing the Baba Sheik, who, in the ancient religion of the Yazidis, holds a rank equivalent to that of the Pope. While I was swotting up, I had encountered the intriguing suggestion that Yazidis are forbidden to eat lettuce.
The Baba Sheik was enthroned on a dais above me, bearded, turbaned and venerable in years. Somehow it seemed frivolous to raise the question.
Eventually I plucked up courage. "Was it true," I asked, "that some foods were haram, or forbidden?"
No, he patiently explained, ordinary Yazidis can eat what they want, but holy men like him refrain from certain vegetables because "they cause gases".
So now I know.
Emboldened, I pressed on to the other question that comes up in any discussion of the Yazidis.
"Why," I asked, "do your enemies accuse you of devil worship?" My translator froze.
"That," he hissed out of the corner of his mouth, "is the one question you never ask a Yazidi."
We moved swiftly on.
I know a little of the story of what has happened to Christians in Iraq since the 2003 invasion because I have touched on it during previous trips there, but the richness of some of Iraq's other religious traditions was a revelation.
The main Yazidi shrine has close associations with the story of Noah
The Yazidis' main shrine is high in the hills of Iraqi Kurdistan, at a place called Lalish.
It has close associations with the story of Noah. I spotted a serpent sculpted into the wall by the main entrance, and, with all the talk of devil worship in mind, enquired what it meant.
My guide explained that when the Ark sprang a leak, one of the snakes on board coiled its body into a bung to close it up.
The Yazidis claim their religion as the oldest in the world.
After trying quite hard to get to grips with its central tenets, I confess I am still pretty shaky on the matter. But the Temple at Lalish seems a place where religion is supposed to be enjoyed.
There are lengths of brightly-coloured cloth around some of the pillars - you tie a knot when you want to say a prayer.
In one chamber, there is an armchair carved out of the living rock, and you can press yourself into it to deal with back pains.
And I was invited to throw a square of satin-like material onto a rock that stood at about the height of a basketball hoop. When I scored, there was much applause and the promise that my wishes would all come true.
The Yazidis have been victims of some terrible attacks. In 2007, a co-ordinated operation involving five car bombs in a Yazidi area killed 200 and wounded another 300.
But my instinct is they will probably survive as a distinct religion because Lalish is in what is now a reasonably secure area of Iraq.
Life of Christ
Iraq's Mandaeans face an even more uncertain future. Mandaeans believe that John the Baptist was the last great prophet.
Running water is central to all their rituals, and they go for weekly river baptisms in the way Christians go to church.
In Baghdad, I met the second most senior Mandaean priest, Sheik Alaa.
The Mandaeans regard themselves as Christianity's close cousins
He looked exactly as if he had stepped out of a film about the life of Christ. Around his neck, where a Christian bishop would carry a pectoral cross, he wore a heavy, beautifully-worked silver image of a baptismal shawl draped over crossed staves.
Sheikh Alaa explained to me that the Mandaeans are pacifists, and that by tradition many of them work as silversmiths and goldsmiths.
Being a non-violent jeweller in a society where violent crime and robbery are commonplace is a rotten combination.
The Mandaeans regard themselves as Christianity's close cousins and, like Iraq's Christians, they have been targeted by Muslim extremists who erupted onto the Iraqi scene in the chaos following the invasion.
There are stories of Mandaean girls being raped for wearing jeans, and we were told of one young man who was forcibly circumcised by his fellow students. We were told that one of them read from the Koran as the others went about the task.
Iraq's tragedy has been so huge that smaller tragedies like these stories of religious violence have got lost amidst it all.
Overall it's getting safer in Iraq today, but whether the Mandaean religion will survive to see a better future is an open question.
Some 85% of Iraq's Mandaeans now live abroad - only 5,000 remain in Iraq.
Will the new generation growing up in places like Sweden continue their ancient river rituals?
The elders like Sheik Alaa fear not.
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