As one of the last great Victorian naturalists and iconoclasts of the 20th century, Leon C. Croizat explored conceptual and methodological questions in the fields of botany, zoology, biogeography, anthropology, evolution, taxonomy, archeology, linguistics, and philosophy. Few other 20th-century biologists have had such a significant impact on the integration of evolution, systematics, and biogeography, the three principal elements of the historical sciences. Born in Turin, Italy, Croizat seemed destined for a life of jurisprudence, although his lifelong interest was in the natural sciences. During his early years, Croizat was exposed to a prominent circle of local Italian naturalists, including the early exponent of cladistic systematics Daniele Rosa.
In 1924, to escape the rise of Italian fascism, Croizat immigrated to the United States, where his formal training in Italian jurisprudence provided him with few professional opportunities, particularly during the Great Depression. He eventually became acquainted with Elmer Drew Merrill, director of the Arnold Arboretum, and was employed there as a technical assistant. Croizat availed himself of the arboretum’s extensive research library, where he was able to review the research fields necessary to write on biogeography, evolutionary theory, and botanical evolution. In 1947, Croizat’s position was terminated when Merrill lost a power struggle with the botanist Irwin Widmer Bailey, who was intolerant of Croizat’s heterodoxy. Croizat emigrated once again, this time to Venezuela at the invitation of Henri Pittier. In the 1950s, Croizat retired from teaching to devote his time to research, while his wife took up professional landscape gardening. In 1972, the Croizats moved to Coro, where they were appointed codirectors of the new Jardin Botdnico Xerdfito “Dr. Leon Croizat.” While developing the Jardin, Croizat continued his research and publishing until his death at the age of 89.
Often at radical variance with prevailing and popular views about evolution and biology, Croizat’s writings are often ignored by prominent and influential scientists. However, they have withstood the test of time, with many of his ideas either being adopted or reflected in later research. Croizat is best known for his new approach to biogeography. In the 1950s, he did what no one else had ever thought of doing before. He tested Darwin’s theory of evolution through bio-geography. In so doing, he was able to demonstrate that Darwin’s theory of centers of origin and dispersal failed to predict global patterns of distribution and their correlation with tectonics. Long before continental drift and plate tectonics became the accepted world-view for geologists and evolutionists, Croizat used animal and plant distributions to successfully predict the geological structure of regions such as North and South America and the Galapagos Islands. The subsequent corroboration of his predictions by geologists demonstrated the progressive nature of panbiogeography over the prevailing Darwinian theory.
As an alternative to Darwinism, Croizat proposed the biological synthesis known as panbiogeography. This evolutionary framework rested on the foundations of biogeographic analysis to understand species, speciation, and biological differentiation in space, time, and form as a single synthesis rather than as the disparate conglomeration of disconnected hypotheses exemplified in Darwinism. His panbiogeography also provided for a concept of biological evolution that did not require natural selection or any form of teleology to “explain” organic differentiation and speciation. Adopting the term orthogenesis, Croizat, like Rosa and other biologists before him, viewed the generation of novel variation as a process biased by the existing genetic and developmental types of organization. Adaptation was seen as a consequence of evolution rather than a cause, and his orthogenetic approach eliminated the unscientific narrative approach to evolution prevailing then, as now, in Darwinian theory that explains the origin of an adaptation by its ability to meet a future goal such as the resulting advantage or utility. Croizat’s orthogenetic framework also anticipated subsequent developments in molecular and developmental genetics.
Far less recognized are Croizat’s contributions to anthropology and archeology, particularly for bio-geographic aspects of human evolution and cultural development. He proposed a biogeographic context for the origins of modern humans along a sector ranging between South Africa, Europe, and East Asia, which contrasted to Darwinian notions of an original birthplace followed by a concerted and sequential outward dispersal. Croizat saw human evolution as a combination of migration and stabilized differentiation around two principal focal areas: what he called “Cro-Magnon” in Africa and Europe and “Austro-Melanesian” in East Asia. In the 1970s, he also produced a comprehensive analysis of the biogeographic origins of American Indians that anticipated current theories by proposing seafaring colonization (coastal theory) by people who were not modern Asians in appearance (now implicated in studies of skulls such as the Kennewick Man), and arrival before the Clovis culture (upward of 40,000 years ago that compares well with the 20,000-30,000 now predicted by some anthropologists). He also predicted the American Indians are principally derived from seafaring coastal Asian Austro-Melanesian people rather than from continental Asians.
- Craw, R. C., Grehan, J. R., & Heads, M. J. (1999). Panbiogeography. New York: Oxford University Press.
- Croizat, L. (1964). Space, time, form: The biological synthesis. Caracas, Venezuela: Author.