Courtesy of William Holland

Cameroonians marvel over an 18th-century slave shackle that was brought to Africa for a "history lesson" by African-American businessman William Holland, at far left.

Decades after they were taken away, African ceremonial masks have been returned to the communities that venerated them, thanks to an African-American family researcher who bought them through eBay.

Georgia businessman William Holland, who has been tracing his roots in West Africa for more than a decade, carried the three masks back with him last month during his latest trek to Cameroon. That's not all he was carrying: Holland also brought relics from the mid-18th century — the time when his ancestor was taken from Cameroon, loaded onto a ship, brought to Virginia and sold into slavery.

The masks made a big impression on the hundreds of Cameroonians who gathered for Holland's show-and-tell session. But the slave chains made an even bigger impression.

"When we brought the shackles out, that's when they were about to cry," he said. "They were shocked to see an authentic item that brought so much pain along with it."

Holland's frequent trips to Cameroon's Oku and Nso regions have been a learning experience for him as well as for his long-lost cousins. It took years for Holland to narrow down his approximate place of origin, based on DNA tests as well as a study of American and African pedigrees. Along the way, Holland found out that one of his ancestors was a slave who was pressed into service in the Confederate Army, and that more distant ancestors were members of royal families in Cameroon.

During the buildup to his latest trip, Holland combed through online auction sales, looking for artifacts that could help bridge the gap between the African and American history of his family. He worked with Cameroonian contacts to identify two elephant masks that were associated with the Nso people's secret rituals, plus a wooden mask with a human visage that was used by Oku families during funerals.

The masks were sold out of Africa in the 1970s or 1980s under murky circumstances, and eventually ended up in private hands. "It's almost the same thing as the slave trade," Holland observed. "Outsiders go to a middleman and ask them to get something or someone for them. 'I'm giving you guns, I'm giving you cowrie shells, I'm giving you iron bars. Bring me the people to fill this ship, and I'll give you this.' That's what it reminded me of."

Holland spent hundreds of dollars of his own money to buy the masks, as well as other items such as throwing knives, the wrist and ankle shackles and a "monkey wrench quilt" — a type of quilt that slaves used to signal each other that it was time to wrap up their tools and get ready for an escape. Then he headed for the Cameroonian towns of Kumbo, Bamenda and Oku.

Courtesy of William Holland

The Fon of Nso, leader of one of Cameroon's tribal groups, looks on as his aides examine a Cameroonian throwing knife that was purchased on eBay. Some of the aides are looking at a photo of a statue of Ngonnso that was taken from Cameroon to Berlin before 1910. Cameroonian authorities are seeking the statue's return.

Courtesy of William Holland

William Holland, left, gets his picture taken with Cameroonian Prime Minister Philemon Yunji Yang and Emmanuel Motika, a physics teacher from the Cameroonian town of Bamenda who is an extremely distant relative of Holland.

"It's more than just bringing things back," he explained. "It's a history lesson about those who were taken away during the slave trade. The Cameroonians didn't receive this information in school."

Holland's trip caused a sensation in Cameroon: More than 1,000 townspeople turned out to see the American who was bringing their treasures back. In Cameroon's capital, Yaounde, Holland met the prime minister. Journalists clamored for interviews. "It was crazy," Holland said. "It was a media circus."

The chiefs of the Nso and Oku peoples, who are known as "fons," joined up to give Holland a title that combines two honored names: "Shufaay," a title that is typically given to the Nso noble next in line to the king; and "Bailack," which recognizes Holland's connection to a patriarch who came to Oku from Nso centuries ago. "No Nso son or daughter is allowed to shake hands with a Shufaay again, if they are not of the same status," Holland said. "This goes back to the ancient way of doing things." 

All the attention was great — but for Holland, the most important result of the trip was the restoration of pieces of African history to their rightful places. Authorities in Kumbo are building a cultural museum that will eventually house the elephant masks and other Nso artifacts. And family members in the Oku region now have the funerary mask they were missing when their loved ones passed away.

The Fon of Oku drew a lesson from Holland's round of eBay diplomacy — a lesson that's particularly timely for the month of February, recognized in the United States as Black History Month. "He was telling people not to sell these precious things from our society," Holland recalled. "This is wrong. No matter how much money they offer, do not sell."

Holland is already planning his next trip, to the Cameroonian city of Buea in May. He'll be taking over some new history lessons to his ancestral homeland, but he's also hoping to bring back some business: Holland is planning to start up a travel business to put other African-Americans in touch with their roots, and the Africa Travel Association's annual congress in Buea seems like the perfect place for networking.

"I guess you'd call it 'historical tourism,'" Holland said. "Cameroon is really an untapped market for that."

Previous chapters in the African saga:

• 2010: DNA points to royal roots in Africa
• 2011: Family roots get tangled up in Africa
• 2011: Black history saga comes full circle
• 2011: Africans visit their American cousins
• 2011: Genes tell a tale as big as Africa 
• 2012: African-American's roots revised
• 2012: Tribal treasures recovered through eBay
• African American news from theGrio 

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Christine Cox / NBC News file

Researchers say genetic genealogy databases can be leveraged to unlock more sensitive genetic information.

Researchers have shown that it's possible to link your identity to supposedly secret genetic information about your predisposition to diseases, merely by analyzing family-tree databases and other publicly available information.

"It was quite surprising," said Yaniv Erlich, a genetic researcher at the Whitehead Institute for Biomedical Research. "When we got the first family, I was surprised. ... It's as if you opened a box that for a long time was locked."

Erlich led the research team whose work is being published in this week's issue of the journal Science. The team's study already has led to a tightening of security measures for federally sponsored genetic databases.

The security-cracking trick relies on the availability of genetic information linked to surnames in a variety of public family-tree databases. DNA samples from males can be tested to look at dozens of genetic markers on the Y-chromosome that change only rarely from generation to generation. If the markers from two individuals with the same surname are a close match, that's a tip-off that the two are closely related, even if they don't know each other.

Tens of thousands of people (including yours truly) make that information public in hopes that someone else will match up with their results. The genealogical markers aren't linked to disease or other specific traits. But under the right circumstances, they could provide an opening for links with other, more sensitive genetic information.

How the secrets were revealed
Erlich and his colleagues conducted a three-step process to see how easy it'd be to use that opening. First, they analyzed anonymous Y-chromosome data from a public database for the 1000 Genomes Project, to come up with the DNA coding for markers that are used for genealogical purposes. Then they compared those markers against entries in the two largest family-tree databases, Ysearch and the Sorenson Molecular Genealogy Foundation.

The researchers said their analysis projected a success rate of 12 percent for recovering the surnames of U.S. Caucasian males. Another 5 percent would theoretically be linked up with the wrong surnames. They said upper- to middle-class Caucasian males were easier to identify, presumably because they're more likely to participate in the family-tree databases.

Once the surnames were identified, the third step was to look at other publicly available sources to go from the surname to a specific individual: Some genetic databases, for example, include information about the age and the state of residence of an anonymous participant, and even the number of children and their birth order. Those clues were added to information gleaned from other sources, ranging from public-record search engines to obituaries.

The researchers linked five specific individuals in three separate families with supposedly anonymous genetic records. The process took three to seven hours for each family pedigree, the scientists said. Then they traced those three family-tree pedigrees to find other connections between relatives and sensitive genetic data. "In total, surname inference breached the privacy of nearly 50 individuals from these three pedigrees," the researchers wrote.

"We show that if, for example, your Uncle Dave submitted his DNA to a genetic genealogy database, you could be identified," Melissa Gymrek, a member of the Erlich Lab and the Science paper's principal author, explained in a news release. "In fact, even your fourth cousin Patrick, whom you've never met, could identify you if his DNA is in the database, as long as he's paternally related to you."

What is to be done with data?
Erlich and his colleagues made a point not to reveal the identities of those individuals, and said they were not advocating a clampdown on the availability of genetic information.

"Quite the opposite," Erlich said. "We found the gene for two devastating pediatric disorders by analyzing the data in public databases. Using these databases, we gave hope to these families and to other parents. We don't want to take away these databases. ... What we really want to do here is to have this really mature conversation about privacy — to tell people we cannot completely protect the privacy, but also to tell them about the benefits."

For years, experts have worried that sensitive genetic data could be used to discriminate against patients, potential employees or would-be insurance customers. Such discrimination is illegal when it comes to employment or health insurance, but the law doesn't cover life insurance, disability insurance or long-term care insurance. Theoretically, an insurer could search through genetic records and turn you down because you have a genetic predisposition to, say, Alzheimer's disease. 

In a Science policy paper, representatives of the National Human Genome Research Institute and the National Institute of General Medical Sciences at the National Institutes of Health said it was time to "re-examine how to balance the protection of research participants ... with the societal benefits likely to be gained through the enhanced research that broad data sharing facilitates."

They said NIH "acted swiftly to mitigate future risks" by working with the NIGMS' genetic repository to shift the data about the age of study participants out of public view and into a controlled-access area of the database.

"That reduces the risk," Erlich said. "It creates another fence."

And what about the genealogical genetic data? Max Blankfeld, vice president for operations and marketing at Family Tree DNA, said his company has been dealing with privacy issues for more than a decade — and doesn't expect the latest research to lead to policy changes. Family Tree DNA has been running the Ysearch database as a free public resource for a decade, but does not force any of its more than 400,000 participants to use it.

"People voluntarily post their information in that database, and therefore it has nothing really to do with the vast majority of the people who take the test and choose to have it protected by Family Tree DNA," Blankfeld said. "This data, we don't share with anyone."

More about genetic ancestry:

• DNA takes on a family's mysteries
• Update on Irish roots: The wearin' o' the genes
• Gene-tracing project gets an upgrade

In addition to Erlich and Gymrek, the authors of "Identifying Personal Genomes by Surname Inference" include Amy McGuire, David Golan and Eran Halperin. The work was supported by the National Defense Science and Engineering Graduate Fellowship, the Edmond J. Safra Center for Bioinformatics at Tel Aviv University, and a gift from James and Cathleen Stone.

The authors of the Science policy paper, "The Complexities of Genomic Identifiability," include Laura Rodriguez, Lisa Brooks and Erick Green of NHGRI and Judith Greenberg of NIGMS.

Alan Boyle is NBCNews.com's science editor, and also the administrator of the Boyle Surname Project at Family Tree DNA.

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.