"Biologists, or rather botanists and zoologists, studied flora and fauna in exhaustive detail, in niches, in situ, penetrating the mysteries of their local habitations, measuring them, counting them, tracking cycles, writing all this down in the equivalent of field guides, and developing the ability to predict many natural phenomena, including phenomena of change: if frost falls, the bud is harmed; if the soil is enriched, growth improves, and so on. The world of life forms was a text whose meaning the biologist interpreted. But these interpretations did not explain and were not meant to explain the biological processes according to which these species could exist in the first place, or descend, or develop, or differ. To explain these more basic issues required the theory of evolution, which, once it was available, became an indispensable instrument in the professional study of local, narrowly coordinated, in situ life forms and the niches they inhabit."