No one knows how many Afro-Turks there are but, in a country that's beginning to acknowledge its great diversity, they're beginning to unearth their forgotten history.

In 1961, Ertekin Azerturk, a Turkish businessman from Istanbul, placed a long-distance call. The voice of the switchboard operator who answered - a woman's voice, sweet and crisp, like a singer's - must have made his head spin. Must have, because from that day on, Azerturk insisted on speaking to the same operator each time he picked up the phone. During one call he found the gumption to ask his mystery girl out on a date. Her reply was as surprising to him as his request was to her. "No way," Tomris, the operator, told Azerturk. "You won't like me," she explained, "because I'm dark."

But Azerturk didn't back down and Tomris eventually gave in. When they met, he was dumbstruck. He had understood Tomris was dark, but had never figured she would be black. (He had never previously met or even heard of a Turk who was.) Tomris was, like her voice, striking, and Azerturk was smitten. Over the Azerturk family's objections, the pair married.

Azerturk and Tomris didn't live long enough to see their children grow up, says Muge, the couple's daughter, retelling the story half a century later.

Orphaned, Muge and her brother went to live with Azerturk's white parents in Istanbul. Theirs wasn't an easy childhood. "They wouldn't allow us to play in the street," Muge, now 49, says of her grandparents. "Because we were dark-skinned, they were afraid we'd have problems with the other kids."

As a child, Muge could not fully grasp why her skin was the colour it was - or why it should matter. She finally learnt, and understood, the truth in her teens. She and her brother were descendants, three generations removed, of black slaves.

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According to Hakan Erdem, a Turkish historian, for the better part of the 19th century an average of 10,000 black slaves arrived in the Ottoman Empire every year, including 1,000 in what is now Turkey. Most were used as domestic workers, cooks or nannies, and although some worked on farms very few - if any - were forced into American-style gang labour.

Slavery did not disappear from Ottoman lands overnight. While an 1857 decree, issued by Sultan Abdulmecid I under pressure from the European powers, abolished the slave trade, it did not delegalise slavery as such. As a result some households, particularly in Istanbul and near the Aegean coast, were to retain black slaves until as late as the early 1900s.

The exact number of their descendants - sometimes called Afro-Turks - is anyone's guess. Erdem floats a figure of 10,000-20,000 but admits that the real number might be much higher. While emancipated slaves in villages near the Aegean and Mediterranean coast usually married within the community, he explains, their counterparts in cities like Istanbul often did not. Several generations and many mixed marriages down the line, many Turks descended from black slaves may not even realise they have African blood in their veins. This is known to have produced a few surprises. "Sometimes, all of a sudden, you have a black baby born into a Turkish family," says Erdem. "And only after intense questioning of the elders do they remember that a grandmother could have been black."

It goes to show, says Erdem, that dark-skinned Afro-Turks might be just "the tip of the iceberg". A few years ago Erdem made the same point during a conference on the subject - and immediately caught flak from a few Turkish nationalists in the audience. "And then this guy gets up," he recalls, "with curly blond hair and blue eyes and points to a [nearby] photograph of a black man, pitch-black, and says: 'That's my uncle.' I thought: 'Well, I rest my case.'"

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For decades, Turkey's leaders, from the Young Turks to Ataturk to the early inheritors of his Republic, endeavoured to shape a homogeneous nation out of the remains of the Ottoman Empire. The country's Armenian and Greek populations, though assigned minority status, were almost entirely driven out. Groups like the Laz, the Assyrians, the Kurds, and the Circassians were subjected to assimilation measures, the government going so far as to ban their languages or, as with the Kurds, deny their existence outright. Loyal citizens of the Republic - and too few to matter - Afro-Turks could hardly pose a challenge to Turkish identity. Even if they adopted all the vestiges of local culture, however, their skin colour doomed them to being different, with all the consequences this entailed. (According to a story related to me by Erdem, a black civil servant from Izmir was once handed his marching orders after Ataturk, in town for a visit, complained that "he was not what he expected from a Turk".)

In a country that was almost entirely white, matching the Turkish founding fathers' image of a model citizen was often as difficult as it was traumatic. Fitting in, for some, meant having to forget. When she was little, Alev Karakartal remembers, she would look around her family table and think, "My dad is black, my auntie's black, I'm black. Why are we different?" Knowing it would annoy her father, she rarely asked out loud. "Whenever I'd do so, he'd say, 'Forget it, we're Turkish, we're Muslim, there's nothing to talk about.'" Karakartal, now in her mid-40s, eventually found the answers to her questions, but had to do so entirely on her own. "We didn't have any photos, any souvenirs, any information," she says. "My father destroyed them all."

Whatever discrimination Afro-Turks faced wasn't a matter of state policy, however. The terms of republican Turkey's sacred covenant were clear - identify as a Turk, and you will be accepted as one. Flawed as the formula would turn out to be, it delivered some notable results, leaving no room for laws like "separate but equal." Many black Turks fought in the Turkish war of independence against Greece. In 1927, 20 years before Jackie Robinson suited up for the Brooklyn Dodgers, Vahap Özaltay became the first black man to play for Turkey's national football team. A black Turk, Esmeray, was one of the country's most popular singers in the 1970s.

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Whether they were forcefully assimilated (as Karakartal insists) or successfully integrated (as others say) into Turkish society, today next to nothing, aside from skin colour, remains of the black Turks' African past. None of the Afro-Turks I interviewed knew their ancestors' language. Most did not even know where their ancestors had come from, or how.

Lately, however, with Turkey slowly reconciling itself to its diversity and its past, and with other ethnic groups claiming a more visible place in society, some Afro-Turks have begun to reclaim part of their heritage. Many have drawn inspiration from Mustafa Olpak, a grandson of Kenyan slaves, who in 2005 published a memoir detailing his family's journey from the Horn of Africa to Turkey, via Crete.

Three years ago, Olpak, 58, tried to present a copy of his book to Barack Obama in Turkey. He made it to the airport in Istanbul by the time Air Force One touched down, he says, but never caught so much as a glimpse of the president. He is still counting on a few minutes of Obama's time, he says, "whenever the occasion presents itself."

Olpak will always remember spring 2007 as the Afro-Turks' coming out party. It was then that he and a handful of associates revived the Feast of the Calf, a holiday celebrated by black slaves in Ottoman times and subsequently banned by the Turkish authorities.

"We were three buses full of black people going to Ayvalik, where the celebrations were taking place," Olpak recalls, chuckling. "We were passing a police checkpoint. The first bus passed and the police did a double take. The second bus passed and they did another double take. When the third started to pass, they stopped all of us. They thought we were refugees," he says. "They checked all our IDs, but they couldn't find even a single foreigner. All of us were Turks, all of us with names like Ayse, Fatma, Abdurrahman."

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Earlier this year I travelled to Cirpi, a small village 30 miles south-east of Izmir, to attend Dana Bayrami, as the Feast of the Calf is known in Turkish. In Ottoman times, the holiday would have lasted several weeks and, true to its name, involved the sacrifice of a cow. The Feast's modern, blood-free edition, I was told, would feature a panel discussion and a concert. But Olpak, whom I met in the village's leafy central square - he was wearing a checked shirt, a wispy moustache, and the expression of a man who'd rather melt into a crowd than be picked out of one - had a surprise in store. In previous years, he told me, the festivities had featured a mix of local Turkish and Roma musicians. This time around, he had invited a group of Nigerian, Congolese and Sierra Leonean artists from Istanbul. It was to be the first Dana Bayrami to feature live African music. Hundreds of people from neighbouring villages turned up to watch.

The outcome was a dance riot. While some of the more risqué parts of the African dance show elicited giggles and gasps, the performance as a whole went down a storm. Less than halfway into the show, the local villagers, most of whom had never previously heard African music, much less witnessed a black man wearing face paint, a dress and a feather-topped skullcap perform an elaborate tribal dance, flooded the stage. A few black Turkish women, one of them clad in a turquoise kaba and gele, joined in a conga line; a pair of local teenagers challenged the Africans to a dance-off; and a group of bubbly Roma girls began to bump and grind with Koko, the Congolese lead performer.

Mumin and Mumune Arapi, brother and sister (he 72, she 74), had arrived here from Haskoy, a nearby village. This was their first-ever Dana Bayrami, they told me. "It's very nice to see so many people of our colour in one place," Mumin said, taking in the scene. "It's like a family feeling." Mumin pointed to a group of Nigerian exchange students who had come from Izmir to attend the festivities. "They remind me of my father," he said. His father, he explained, had grown up a slave to a Muslim family in Thrace, in Ottoman-controlled Greece. He escaped (exactly when is not clear), married a white Turkish woman and, in 1941, crossed into Turkey, bringing along his wife and two small children. "My father always wanted his kids to know who they were and where they came from," said Mumin. "He told me, 'If anyone asks, tell them my story.'"

Mumin and Mumune seldom experienced any problems on account of race, they said. It echoed what I had heard from others. In villages where Afro-Turks have lived side-by-side with ethnic Turkish families for generations, reports of prejudice are remarkably rare. Few Turkish villagers seem to question that their black neighbours are anything other than what they claim to be - fellow Turks.

For their part, most black villagers - even if they take it for granted - don't see their African heritage as a significant part of their identity. "Afro-Turk, Mafro-Turk," a young girl from Haskoy told me, poking fun at a label that, as she rightly observed, only came into being during the last decade. "We're Turkish, and that's that."

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In the cities, however, and in inland Anatolia, where few people have ever come into contact with people of a different race, ignorance and prejudice are sometimes very pronounced. It isn't so much the exaggerated interest they arouse, ranging from benign curiosity to finger-pointing and name-calling, that bothers urban Afro-Turks. It's the incredulity that a black man or woman could be Turkish.

"I'm fed up having to explain where I come from," Kivanc Dogu, a 24-year-old from Istanbul, told me as we sat on a pair of plastic chairs on the edge of Cirpi's village square. Because he was so often taken for a foreigner, Dogu said, he felt "neither Turkish nor Afro-Turk," even if he welled up whenever he heard the Turkish national anthem.

Dogu, who works as a fashion model, has probably come as close as anyone to testing the boundaries of what it means to be - or at least to look - Turkish. Those boundaries may have become more flexible, Dogu said, but they are far from gone. "If I go to 10 job interviews, three times they'll take me, and seven times they won't," he said. "People say they would hire me, if not for my skin colour. Because I don't fit the image of an average Turk."

As dusk began to fall on the square, Kivanc was joined by a friend of his, Kerem. Among dozens of black men in woollen flat caps, black women in headscarves and baggy shalvars, Kerem decidedly - and, it seemed, deliberately - stood out, wearing dark sunglasses, a silver chain, and a black T-shirt emblazoned with images of American rappers from Lil Wayne to Chuck D. (The right sleeve had been pulled all the way up to reveal a Tupac tattoo.) "I'm not Turkish," Kerem told me, "because people don't see me as Turkish." He had never felt like he belonged, he said. "Even when I was born, the doctor told my mother I was a zenci, or n****r." Still, he insisted, "there is no racism in Turkey, only ignorance".

Dogu, I saw, was nodding in agreement. When he was little, he said, other kids would sometimes call him names. But, he said, "they didn't know any better." When a group of foreigners called him a "n****r", as once happened to him in Izmir, that was something else. "They actually knew what it meant."

Later that night, I caught up with Hayri Esenerli, a Turk whom I had met a day earlier, and a few others at a cafe in Bayindir, a short drive from Cirpi. "I had never heard of black Turks until I went to college," Esenerli, who is white, confessed when I brought up Kerem's remarks. "I saw black people speaking Turkish in Izmir, but I thought they were Turks who'd been working too much in the sun," he said. "I didn't make the connection."

It was fitting, perhaps, that the girl Esenerli would fall in love with and later marry, should turn out to be Muge, the phone operator's daughter. They met in college. "I never thought she could be of black origin until she told me," Esenerli said of Muge, who has dark, slightly greying hair, brown skin and caramel eyes. The news came as a shock to Esenerli - as did the realisation that Muge was descended from slaves. "I cried the first time she first told me about slavery," he said.

Esenerli also got all choked up earlier that day, he said, when he saw Stephan, one of the African performers, sing and dance at Dana Bayrami. "When the other Afro-Turk women began to dance with him," he said, "I felt so sorry that their culture, their heritage had been destroyed."

"We are a small community," said Alev Karakartal, who had been sitting beside him, obscured by clouds of cigarette smoke. "We don't want anything from the state: no territory, no special treatment." But, she said, "we want recognition of who we are, and where we came from".

Piotr Zalewski is a freelance writer based in Istanbul.