“Here then I had at last got a theory by which to work,” Darwin wrote in his Autobiography.40 He finally had his how, which he called natural selection.‡ His disciple Herbert Spencer coined a more portentous phrase for it, survival of the fittest, although survival of the adaptable would have been more accurate. Those who can adapt to the current environment, whether we’re talking turtles or wheatgrass or people, live to propagate and continue the species. Those who can’t, won’t.
