The claim of impending mass extinction of the Earth's species is a never-ending drama. In 1979, the biologist Norman Myers declared that a fifth of all species on the planet would be gone within two decades. In the 1990s, E. O., Wilson popularized various numbers ranging from 4,000 to 100,000 species a year being lost, and these numbers were repeated over and over again in environmental groups' fund raising literature, in congressional testimony and in speeches by Al Gore.