CHARLES DARWIN RESEARCH STATION, Galápagos — Of all the giant tortoises on these islands, where the theory of evolution was born, only a few have received names that stuck. There was Popeye, adopted by sailors at an Ecuadorean naval base. There was Lonesome George, last of his line, who spent years shunning the females with whom he shared a pen. And there is Diego, an ancient male who is quite the