Deep in Colorado, a lost valley of Jews

Rumours of a secret Jewish past had been flying around the San Luis Valley for decades. Five hundred years ago, a number of Conversos - Jews who were forced to convert by the Spanish Inquisition - made their way across the Atlantic. Over the past few decades, scholars claim to have found remnants of crypto-Jewish practices in communities in south-west USA, as well as in Latin America. As the theory goes, when the Inquisition hit the shores of the New World, the crypto-Jews moved to the far flung corners of the Spanish Empire in a bid to escape the church.

Some Hispanics are even said to keep up forms of Jewish life without knowing their origin. Demetrio Valdez, a Catholic cattle farmer in the San Luis Valley, for example, grew up practising kosher slaughter without realising that the technique was Jewish.

Dr Ostrer's study was undertaken after previous studies found that a mutation for breast cancer which is usually associated with Ashkenazi Jews - 185delAG - was prevalent in New Mexican Hispanics too.

Scientists estimate that the mutation arose well over 2000 years ago among the Hebrew tribes of Israel prior to any split between Ashkenazim and Sephardim. In his new book The Wandering Gene and the Indian Princess: Race, Religion and DNA, Jeff Wheelwright explores how the mutation may have travelled from the Middle East.

"I found that people are not always who they say they are when we apply genetic criteria to them. But in the end, the identity that people claim for themselves is indeed who they are. If genetics helps someone to make or change an identity, so much the easier," said Mr Wheelwright.

Orlando Mondragon, one of the New Mexicans who took part in the study, wasn't at all surprised to hear news of his likely Jewish heritage. "He always thought so," said his wife, Viola.