ERNST MAYR AND THE CENTRALITY OF SPECIES.

So much has happened in the last century of our waning millennium that cardinal events of the early years are already enshrined as permanent high points in our culture. In 1904, Anton Chekhov produced The Cherry Orchard (and died later that year), James Barrie published Peter Pan, Sigmund Freud wrote The Psychopathology of Everyday Life, and Giacomo Puccini's Madama Butterfly received its first performance at La Scala amid a deafening cascade of catcalls (reversed three months later in a second and triumphant showing in Brescia under the baton of Arturo Toscanini). Also in 1904, Henry Adams described the most fantastic American spectacle of the year, the greatest illumination ever attempted with the new-fangled invention of incandescent bulbs: "The world has never witnessed so marvelous a phantasm; by night Arabia's crimson sands had never returned a glow half so astonishing, as one wandered among long lines of white palaces, exquisitely lighted by thousands and thousands of electric candles, soft, rich, shadowy, palpable in their sensuous depths." Adams was describing the St. Louis World's Fair, famous for the invention of iced tea, ice cream cones, and the first Olympic Games held in America. Yet, for the illumination provided ever since to our profession of evolutionary biology, Adams might well have been celebrating our cardinal event for that year, the birth on July 5, in Kempten, Germany, of Ernst Mayr. In the three most important of his many sequential and overlapping careers-ornithologist and systematist, evolutionary theorist, and historian of biology-Ernst Mayr has rooted his intellectual vision in defending a rational and tractable science of organic wholeness against a variety of reductionisms and sterile abstractions. I shall devote this tribute to my dear friend and mentor to a discussion of Mayr's key insight on the centrality of species as evolutionary agents, and to the contribution made by this notion to developing theories of macroevolution-a great advance not achieved as simple realization from the void, but from active struggle against previously dominating views of species as arbitrary segments of evolving lineages, and as units too comprehensive, in any case, to act as fundamental agents in sciences committed to reductionistic perspectives. But I wish to record the larger and coordinating role of this integrative organismic worldview as a linchpin of Mayr's scientific life, for this philosophical consistency holds a key to the power of his thought and the extent of his influence. This antireductionism inspired him to become a systematist and field biologist in the first place; it underlies his different (and, I believe, correct) view of the Modem Synthesis as a fusion of laboratory-genetic and field-systematist traditions and not (as so often depicted) as a reduction of "descriptive" activities in natural history to "explanatory" models of population genetics; it serves as a conceptual basis for all his major ideas in evolutionary theory, including peripatric speciation, genetic revolutions, founder effects, and unity of the genotype; it informs his fundamental vision of the history of biology as a struggle over centuries between the essentialism of Platonic traditions and the "rightminded" approach that he calls "population thinking." The centerpiece of Mayr's scientific life, coming between an earlier focus on ornithological field studies and a later dedication to history and philosophy of biological science, rests on his role as a leading architect of one of the half-dozen major scientific achievements in our century: the integration of Mendelian and Darwinian traditions to form for the first time, following factional debate ever since The Origin, a unified theory of evolution called the Modem Synthesis. Mayr was, first, a founder of the synthesis in writing a key volume that integrated systematics within the growing concensus (Mayr 1942); then a practical facilitator in helping to organize the Society that publishes this journal and in serving as the first editor of Evolution (see Smocovitis 1994); then, as a grand codifier of the synthesis in writing its most synoptic compendium (Mayr 1963); and, finally, as its primary historian (Mayr and Provine 1980; Mayr 1982). If we consider the synthesis as a fusion of three equally robust disciplines-experimental genetics, population genetics, and studies of natural history expressed primarily by systematics (and