Genovese nobleman or Catalan pirate? Adventurous explorer or greedy tyrant? What if the Italian gentleman who discovered America was in fact a brutal torturer and slave owner? And what if he wasn't even Italian?

Schoolchildren may learn about a daring hero who proved the Earth wasn't flat, but because his biography is pocked with holes, Christopher Columbus is a figure around whom elaborate theories and enigmatic rumors have long circulated. This year, the 500th anniversary of his death, two Spanish scholars are working to clear up some of the mysteries.

José Antonio Lorente, a geneticist at the University of Granada, is attempting to resolve one of the greatest enigmas - the question of Columbus's origins. In 1927, Peruvian historian Luis Ulloa Cisneros claimed Columbus was from Catalonia - in what is today northwestern Spain - rather than from the Italian port city of Genoa.

Since then, theories have proliferated, some suggesting that Columbus was a Catalan nobleman who rebelled against King Ferdinand's father, King John II, by engaging in piracy on behalf of the French, and then hid his origins to win favor with the son. Others maintain that he was the illegitimate child of Prince Carlos de Viana, a Majorcan nobleman related to Ferdinand and Isabella. Still others suggest that Columbus was a Jew, whose family fled to Genoa to escape persecution.

A historian at the University of Seville asked Mr. Lorente (who had previously used genetic testing to determine that bones in the Cathedral of Seville belonged to Columbus's own illegitimate son), to help resolve the Catalan/Genovese issue.