Two years ago, Foley Benson found a buried treasure.

The Santa Rosa Junior College professor was researching Mayan ruins when he stumbled across some literature with a surprising reference to a hidden community of Sephardic Jews that dated back to the discovery of the New World. Though others knew of the group's existence, "I was just stunned," Benson recalled.

Today, he's uncovering details of those ancient Jews of Mexico — and how the horrors of the Inquisition forced them to practice their faith in secret. Tracing their footsteps through the centuries, Benson has met modern descendants who still lead secret spiritual lives in the American Southwest and in Mexico.

"There are communities now that are operating covertly and all around them are people who have no understanding that these people are Jews," said Benson, an anthropologist and a trustee at Santa Rosa's Congregation Shomrei Torah.

Benson, 52, turned his accidental discovery into an ongoing research project and a personal quest. He's joined a small group of scholars called the Society for Study of Crypto Judaism. He's also giving talks to Bay Area Jewish groups on his findings, with the first set for Sunday morning, Sept. 14 at Temple Beth Hillel in Richmond.

"What I have found is an astonishing legacy of beautiful heroism and great cleverness and extreme risk," he said. "In many cases, they kept the tradition alive, risking the welfare of themselves and their families. Yet they maintained it, even today."

In travels on both sides of the U.S. border, Benson is finding evidence of secret communities and is starting to meet Jews who practice underground. In New Mexico alone, there may be 1,500 such families.

Benson has seen Jewish symbols in old Catholic churches. He's thumbed through telephone books and found surnames that are actually Hebrew phrases. And he's learned of blended religious customs that include lighting Shabbat candles while reciting the rosary.

Because of generations of fear and secrecy, Crypto-Jews don't usually divulge their life stories to strangers. But in northern Mexico, Benson befriended an accountant who is probably a direct descendant of a group of Jews who migrated from the south in the 1580s. "Both he and his wife are Jews and are hiding in their town," said Benson. "In a sense, it's not over for them."

Their Jewish background remains such a closely guarded secret that families like the accountant's don't even reveal it to their own children — until they're considered mature enough to keep the information quiet.

Fear of ostracism and attack are well founded, Benson believes. One man living in a tiny town in northern New Mexico reported that he was beaten as a child and taunted for being Jewish, even though his family considered itself Catholic. Another man in New Mexico faced such community outrage when he identified himself as being Jewish that he was forced to sell his ranch and move away.

The secrecy also stems from a legacy of fear. When Jews began pouring into the New World in search of a haven from oppression in Spain and Portugal, their oppressors followed. The inquisition actually opened branch offices in Mexico, Benson said.

If discovered, Jews would be tortured, stripped of all their belongings and forced to reveal details of their religious lives. From records of the day, Benson has learned that Mexico City in the 16th century housed at least 15 synagogues tucked away in homes, stores and warehouses.

Hoping to escape persecution, bands of Jews traveled for months to get to distant lands in the north. While some were captured, Benson said others made it safely to what is now northern Mexico, New Mexico and Arizona.

Their underground practices persist to this day. "The inquisition lasted until the 19th century," said Benson. "In a sense, even though it's officially subdued, I don't want to say it's ended."

Benson said that Crypto-Jews also face criticism from within their own ranks. Some Jews have chastised them for "not being sufficiently Jewish," said Benson. He considers such attacks "appalling."

"I think there's a lesson here for all of us," Benson said. "They kept it alive under the most adverse conditions and so should we, because what we have is just so beautiful.

"I want to share the message that I think these people have brought to me, and that is, very simply, it is worth keeping alive."