Story highlights A slave owner goes on to co-found an organization called SOS Slaves

That abolitionist group fights to liberate slaves in Mauritania

The West African country was last in the world to abolish slavery

Experts say 10% to 20% of Mauritanians live in slavery today

As a member of Mauritania's slave-owning class, Abdel Nasser Ould Ethmane could have had anything he wanted as a present for his circumcision ceremony: a toy, money, a camel, or, as his brother would choose, a bicycle.

But the 7-year-old wanted something more sinister.

He chose Yebawa Ould Keihel, a young boy with skin the color of coal. At that moment, Abdel became a slave master.

It's an experience that's common here in Mauritania, a vast country in West Africa's Sahara Desert where activists and the United Nations estimate 10% to 20% of people are enslaved -- usually dark-skinned people who have lighter-skinned masters.

For the owners of slaves, a group of Arab people called the White Moors who raided sub-Saharan Africa for slaves centuries ago, this is no big deal.

"It was as if I were picking out a toy," Abdel, now 47, said of choosing Yebawa as his slave. "For me, it was as if he were a thing -- a thing that pleased me. This idea came to me because there were all these stories about him which made me laugh -- that he talked in his sleep, that he was a bit chubby and a bit clumsy, that he was always losing the animals he was supposed to be watching over and was then always getting punished for this. So for me, he was an interesting and comic figure.

"It's normal that I chose him."

Sadder still, Yebawa didn't consider himself human either -- at least not in the way Abdel was. Mauritania's slaves are very often brainwashed by their masters into thinking they are less than human and that their place is at the bottom of a rigid and still-enforced caste system that allows them only to serve their masters without pay or free will.

Yebawa Ould Keihel grew up as a slave in central Mauritania.

But there's a surprising twist in Abdel's story.

It's one that shows how far Mauritanians have come in their effort to combat slavery.

And how very much more must be done before the hundreds of thousands of slaves and former slaves here can truly be set free.

The young slave owner

They were raised on the same breast milk.

Yebawa's mother nursed both her son and the man who would become his master, giving Yebawa and Abdel a bond from birth.

"That does indeed create a relationship between me and them," Yebawa said.

When the two children were very young, Abdel recalled, they behaved like brothers.

But after the circumcision ceremony, everything quickly changed. The two boys could not be seen together without being scolded by their family members. Stay with your own kind, their parents said.

They had to exist in separate but intersecting worlds.

Abdel, like the rest of his light-skinned family, lived in a large camel-skin tent. Yebawa and other slaves lived in tattered tents of cloth on the periphery of their nomadic camp, which shifted locations to follow the few plants able to grow in the Sahara.

Noble families keep slaves both as servants and status symbols. Abdel's family had hundreds of slaves, he said, and their labor was divided among aunts, uncles, cousins and other relatives.

"When you divvy up slaves, either you send a slave to go serve a certain branch of the family or if you have just one slave, you divide him up in chunks of time: three months here, four or five there," he said. "That's how you share a human being."

Slaves in Mauritania typically are attached to one family from the time they are born. They can be given away as gifts for special occasions, but usually aren't bought and sold.

Because of their darker skin and lowest-caste status, slaves are treated as inferior.

Abdel's family never beat its slaves, he said, but did regard them as subhuman.

When it rained on the Tagant plateau, in central Mauritania, slaves like Yebawa picked up the edges of the tent and held them in the air all night long to prevent their masters from getting wet. Abdel recalls hearing the slaves' teeth chattering all through the cold desert nights -- and mocking this "teeth music" with his slave-owning friends.

"Here they were standing up, protecting us, and we were completely unconscious (and) ignorant," he said. "This was actually quite innocent because, for us, slavery was really a natural state. One must really have in mind that when one is born into a certain environment, it is considered the right one -- just and fair."

Free and equal

Abdel never questioned slavery as a child.

Yebawa and other slaves were required to tend to the family's goat herds, wash clothes, serve tea, cook food, and entertain a master if he was bored.

But when Abdel was about 12, his parents sent him to Nouakchott, the country's sprawling seaside capital, where he could get a better education than he could receive while living the life of a nomad. There, Abdel met a European tutor, a bizarre character, as he recalls, with a frizzy Afro and chunky glasses. This oddball teacher was Abdel's tour guide into new worlds.

After school, the tutor sent Abdel to the French Cultural Center, a library of sorts in the quarter of Nouakchott that houses foreign residents and embassies. Hesitant at first, Abdel soon dove into every book he could find. He started with French comic books like "Asterix." And while he was reading he noticed something:

None of the characters owned slaves.

Or if they did, slavery was treated as an artifact of the ancient past.

He read on, thinking nothing of it at first.

Soon he was picking up volumes about the French Revolution.

In a book pulled from the library's shelves almost at random, Abdel found the sentence that would eventually alter his life:

Men are born and remain free and equal in rights.

He read it again and again.

Men are born and remain free and equal in rights.

Slow transition

It would take years for that idea to register fully, but from the moment he read the sentence, a question started to burrow deep in Abdel's brain: What if slavery actually is wrong?

Either the books were wrong or his family was, Abdel thought.

Was his entire life a lie?

"I started to ask myself if lies were coming out of this book," he said in an interview conducted in French, "or if they were rather coming out of my very own culture."

Abdel took this idea to his father who, surprisingly, agreed with him. He had tried to free the family's slaves before, he told his son, but they didn't want to leave, so he didn't argue with them, keeping the practice in place against his own conscience.

His mother, however, was dismissive. Slavery is the natural order, she told her son. Don't question it.

"It was what God had given us, and these people who were our slaves loved us -- they wanted to stay with us and serve us," he recalls her saying. "It's not our fault if they loved us and wanted to serve us."

Soon Abdel was taking the conversation outside the family. He organized a salon of sorts, where young people who questioned life as it had always been in Mauritania could meet in secret to discuss their experiences. To have these conversations about slavery in public in Mauritania would have meant arrest.

"There were sand dunes where we would sit under the moonlight and we would discuss everything and nothing. That's where the first conversations about slavery took place."

In those discussions, Abdel finally came to see Mauritania in context -- the aberration in a world that had abolished slavery decades or centuries before.

He denounced slavery as inhumane.

With his mind made up against the practice, Abdel began to adjust to a new reality: He didn't know how to do the most basic things for himself.

Away at graduate school in Bordeaux, France, Abdel found the school cafeteria closed one day and decided to make an omelet. He put eggs, salt and pepper in a pan with oil.

But he didn't crack the eggs, he said, and the whole concoction "exploded."

He wasn't any better at laundry.

"I could not wash my socks. When they were dirty, I would throw them away in the trash and buy new socks."

He needed to go through a new education of his own -- to learn to work with his hands.

Since then, he's been working to teach other slave owners to do the same.

Mauritania's abolitionists

They met in secret on a rooftop in the dark of night, the desert stars watching over them: Abdel, the reformed slave owner, and a man named Boubacar Messaoud, who grew up in a family of slaves in southern Mauritania, near the border with Senegal.

Together they would form SOS Slaves, a group fighting to end slavery in Mauritania.

In that first conversation, they pulled a rug over their heads to muffle their voices. The year was 1995. Such discussions were not safe in Mauritania -- and still aren't.

The power of these men from different worlds coming together would shape the future of their country, which still lives in slavery's shadow.

"If we fail to convince a maximum number of whites and a maximum number of blacks" that slavery is wrong, "then slavery will not go away," Boubacar says.

Though slavery was formally abolished by Mauritania in 1981, it was the last country in the world to do so, and outsiders regarded the move as a public relations stunt more than anything else.

Both Boubacar and Abdel would be arrested and beaten several times for their activities. Mauritania's rulers denounced their group as illegal and divisive. Abdel's brother, a fellow activist named Sidi Mohammed Soueid Ahmed Elyessa, went on a nine-day hunger strike in jail. The only thing that kept him alive, he said, was a sympathetic prison guard who slipped him thimbles full of tea with extra sugar in it for sustenance.

They have continued their efforts just the same.

SOS Slaves' first push was to make the slaves' stories public. They took testimonies from slaves who had escaped, wrote them up and posted them around the Mauritanian capital in pamphlets and fliers. These men and women typically had risked their lives to escape from their masters and been forced to leave their families behind. SOS took on the work of finding and freeing those family members.

Their actions started to have impact.

They denounced the Mauritanian government's inaction on slavery, lobbying for legislation that would criminalize the practice. The law passed unanimously in 2007, making it a crime to own another person and force him or her to work.

Only one case has been successfully prosecuted, but the law is still cause for much hope among anti-slavery activists in the country.

Despite some successes, one story in particular has haunted Abdel's conscience:

That of his personal slave, Yebawa.

What is freedom?

In December, CNN arranged to reunite Abdel and Yebawa in Nouakchott. The two men -- master and slave -- hadn't seen each other in more than a decade.

In that time, much had changed. Yebawa, chubby as a child, had grown to be rail thin. Abdel had moved to the Ivory Coast out of fear he would be arrested in Mauritania for being the country's most prominent activist from the slave-owning class to now campaign against slavery.

Most importantly: Abdel's family had granted Yebawa freedom.

The two men hugged and shook hands, their skin tones -- one tan, one midnight black -- creating a noticeable contrast as they embraced.

"Look, he isn't fat (anymore)," Abdel said with a smile.

Yebawa smiled back.

The power of the situation, however, was in what they left unsaid.

Abdel and Yebawa sat side by side on an embroidered green sofa as Abdel talked about how his family had granted Yebawa his freedom many years ago. Yebawa didn't react -- his eyes stared off into the distance.

Later in the week, in a second interview, Yebawa said he was confused by the encounter: He never truly realized that he was free.

"It did not matter much," he said.

It was more important for his parents, he said, although he had not discussed it with them.

Abdel later said he could have predicted this response.

He insists his family did tell Yebawa he was free, that the idea simply never sunk in.

"He's my slave -- he'd say nothing different even today," he said. "So, with Yebawa, I failed. Yes, it was a failure. I had success with others, but not with Yebawa."

He hoped Yebawa would do something more with his life.

"It is a catastrophe," he added. "These are people in their lifetime that are obligated to do difficult manual labor. They can't live any other way. Like Yebawa, if he gets paid a salary, he can't count to see if he was paid right or not."

Last year, SOS opened a school for escaped slaves and their children in Nouakchott. It only serves about 30 people, but it's the beginning of efforts to deal with slavery's social impact -- by giving slaves job skills, an education, the tools to create a viable life if and when they escape from their masters.

Ignorance is under assault.

But the fight against ignorance cannot include slaves alone. Slave masters, too, need a dose of education -- a spark from the outside -- to pull themselves out of an insular world where slave ownership is an accepted part of life, Abdel said.

"I am not really excusing" the slave owner, he says, "just saying that he only becomes a villain when he becomes conscious" of what he's doing.

"When he sees the possibility of freeing his slaves, there starts the problem. If he is unaware of the problem, he continues to believe that this is normal.

"But today all slave owners are people who are very condemnable, because slavery has been abolished in Mauritania, many times."

The slave master-turned-abolitionist made that journey from ignorance to enlightenment. And his organization, born under the stars of the Sahara, continues its work into its second decade.

Abdel is certain others can follow.