In a move that a Colombian Indian tribe says could mean the end of its culture and people, Colombia’s government yesterday granted Occidental Petroleum a license to explore for oil just outside a 543,000-acre reserve inhabited by the U’wa Indian nation. The company had initially sought permission to explore directly on U’wa land, but the tribe in 1997 threatened mass suicide if that were to happen and the company backed down. The U’wa are once again considering a threat of mass suicide, claiming that the land Occidental now wants to drill on was the territory of its tribal ancestors.