The promise of integrative biology: resurrection of the naturalist.

Integrative biology has been practiced for a very long time; it is in our roots. Before agriculture, our ancestors depended on a fully integrated knowledge of their world to successfully hunt and gather. The development of agriculture was a natural consequence of such knowledge. Democritus and Aristotle championed observation and synthesis to provide an integrated world view that subsequently was subverted and mystified for nearly 2000 years. The giants who lead us through and out of the European renaissance—da Vinci, Gesner, Harvey, Ray, Malpighi, Leeuwenhoek, Hooke, Buffon, Linnaeus, Trembly, Lamarck, Cuvier, von Baer, and of course, Wallace and Darwin and their supporters, Huxley and Haeckel—all were integrative biologists, or in the terminology of the time, naturalists. By the end of the 19th century, integrative biology, and indeed science and rational thinking, carried great promise for the 20th century. Many of us who grew up in biology in the mid 20th century also were trained to practice integrative biology, although we rarely, if ever, identified it as such. Our interest grew out of childhood curiosity and fascination with organisms, as seen all around us, in parks, forests, deserts, and seashores, and as displayed in zoos and museums. Our training, usually in biology departments, or if broken apart, in botany and zoology departments, included all aspects of biology, from cells to populations, across taxa, and including multiple disciplines, from physiology and cell biology to ecology and evolution. Many of us developed careers teaching and doing research in biology that grew out of that broad training, and we worked comfortably with a variety of organisms using multiple approaches. And as demonstrated so well by the papers from this symposium, such an approach can result in elegant, comprehensive biology of wide application. Sex is among the most perplexing and puzzling topics in biology, and if it is ever to be understood, it will only be through integrative approaches such as those presented by Hoshi et al. (2003). The evolution of multicellularity and complex life cycles is, well, complex, and demands careful dissection in an integrative manner to understand, as demonstrated so well by Kirk (2003). Biogeography is another huge topic that has fascinated biologists for centuries, and it is now yielding to the integrative techniques of phylogenetics, using both morphological and molecular data, as pre-