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 opposite of George.

Diego has fathered hundreds of progeny — 350 by conservative counts, some 800 by more imaginative estimates. Whatever the figure, it is welcome news for his species, Chelonoidis hoodensis, which was stumbling toward extinction in the 1970s. Barely more than a dozen of his kin were left then, most of them female.