In our day, the political and colonizing expansion of Europe has fallen back to what appear to be defensible, long-term limits. In general, the tropics have been yielded to their old inhabitants or new mixtures; temperate lands are firmly occupied by descendants of European stock, who have established nation-states on the European model, raise livestock and crops mostly of Old World origin, and, in short, are Neo-Europeans. The previous inhabitants of the temperate lands, plants and animals included, and of some of the tropical lands, have receded or disappeared before the Eurasian and African invaders. Alfred Crosby’s brilliant volume sketches a panorama and advances an explanation.
As the primordial land mass, Pangyaea, split into the present continents and islands, Eurasia held the bulk of the life forms and so fostered wider competition. Other continents and islands with more limited endowment to fill ecological niches could seldom develop diseases, plants, or herbivores and carnivores with comparable success. Humans, of course, evolved in the Old World and relatively quickly came to dominate both temperate zone and tropics. As hunters and gatherers, they assisted in rendering many gigantic species of herbivores extinct whereupon the larger nonhuman carnivores dependent on them obligingly vanished as well. The Neolithic Revolution increased human interference with nature and added animals and plants as ready servants.
In Western Europe by 900 there arose an unusually effective complex of human organization, technology, and utilization of temperate zone biota. When the technology for deep sea navigation, relatively capacious ships, and the knowledge of currents and winds were developed, the Europeans spread throughout the globe. They carried with them, wittingly or unwittingly, the plants, animals, pests, and diseases of the Old World. Their first years in a new land might be spent living on foods native to the area, but within a few years Eurasian grasses and animals substantially reduced or drove out native species, so that the European settlers soon found themselves in replicas of the environment they were accustomed to at home, in a word, Neo-Europes. The humans who had preceded them over land bridges or by difficult migrations in dugout, as to New Zealand, conveniently succumbed to Old World invaders in the form of diseases, ferociously lethal in a virgin environment.
European settlement has been most successful in temperate zones and distinctly less so in the tropics. Siberia, though part of the Eurasian land mass, has been partially emptied by diseases from the west and constitutes a Neo-Europe because of Russian settlement. As a case studied in some detail, Crosby devotes a chapter to New Zealand, where imported species now far outnumber native ones, and the Maori survive only after massive losses within an English-speaking commonwealth.
Crosby lays out a masterly web of hypothesis and broad interdisciplinary study. The result is stimulating and provocative. It raises many questions and attempts, through a unified theory, to give some answers.