The Astoria section of Queens, New York, is one of the most ethnically diverse communities on Earth. At the 30th Avenue Street Festival in July 2008, people of all heritages and complexions mingled among booths offering up Thai charms and Peruvian sweaters, Mexican corn and Italian zeppole. The sun was hot, the mood merrily multicultural. Through the crowd walked a tall, blond man with pale skin rapidly turning red. He stopped occasionally to talk to people, and if he found them obliging, asked if they could spare a few cells from the inside of their cheeks.