When it announced that it would use ethanol in its racing fuel, NASCAR joined a wider trend in the United States. Jared C. Tilton/Getty Images for NASCAR hide caption

Wooden boats known as dhows are used in trade between Dubai and Iran. The emirate has long been an economic lifeline for Iran, despite U.N., U.S. and EU sanctions against Tehran's nuclear program. But new financial restrictions imposed on Dubai by the United Arab Emirates' capital, Abu Dhabi, have made Iran-Dubai trade more difficult. Peter Kenyon/NPR hide caption

Cotton Jones is a duo from Cumberland, Md. Courtesy of the artist hide caption

Study says it might be the ritual of taking placebos that makes them work like pills. David Sucsy/iStockphoto.com hide caption

This tooth, which was also found in Denisova Cave, has a DNA structure similar to that of a finger bone. Its shape and physical structure are, however, very different from that of Neanderthals and modern humans, leading researchers to believe that the Denisovans are a distinct group. David Reich, et al./Nature hide caption