DNA studies changed some of the traditional beliefs about pre-Columbian indigenous history. In 2003 Juan Martinez Cruzado, a geneticist from the University of Puerto Rico at Mayagüez designed an island-wide DNA survey of Puerto Rico's people. According to conventional historical belief, Puerto Ricans have mainly Spanish ethnic origins, with some African ancestry, and distant and less significant indigenous ancestry. Cruzado's research revealed that 61% of all Puerto Ricans have Amerindian mitochondrial DNA, 27% have African and 12% Caucasian. According to National Geographic, "Among the surprising findings is that most of the Caribbean’s original inhabitants may have been wiped out by South American newcomers a thousand years before the Spanish invasion that began in 1492. Moreover, indigenous populations of islands like Puerto Rico and Hispaniola were likely far smaller at the time of the Spanish arrival than previously thought."