He argues that from early nineteenth century speculation, Charles Darwin came to suggest that natural selection drove species to "a higher stage of perfection",[1] jumping from relative to absolute progress. In this, Ruse argues, he was followed by many later biologists. Ruse interviews well-known evolutionary biologists such as Ernst Mayr, John Maynard Smith, Stephen Jay Gould, and E. O. Wilson, and both reports their views and gives his own opinion of how progressionist they were.