Historicism versus Process in Ecology.

“One theme underlay most of his work. This theme-it seems almost a truism now, but [Robert] MacArthur himself considered it worth stating-was the search for patterns. He emphasized patterns and equilibria and ongoing processes, while de-emphasizing the sort of one-time contingent events that figure in historical explanations. Where lies the distinction between those two types of explanation, the process-oriented and the historical? A historian pays special attention to the differences between phenomena, because they shed light on historical contingency. “He may ask why the New World tropics have toucans and hummingbirds,” Macarthur wrote, “and parts of the Old World have hornbills and sunbirds.” The hornbills of Africa and Asia are large-bodied, omnivorous birds with huge beaks allowing them to fill roughly the same ecological niche as the toucans of tropical America; likewise the sunbirds of Africa and Asia are small-bodied bright-colored nectar drinkers, filling roughly the same niches as American hummingbirds. The history-minded biogeographer wonders why hummingbirds, not sunbirds, have occupied the suitable niches on a given continent. MacArthur himself was more interested in in the similarities among phenomena, because similarities reveal the workings of regular processes. He was more inclined to wonder why hummingbirds and sunbirds, despite their different ancestries and their independent histories in two different regions of the planet, are so similar. I’ve already quoted MacArthur’s statement that to do science “is to search for repeated patterns, not simply to accumulate facts,” and the patterns that particularly concerned him were the patterns of biogeography.”

David Quammen in The Song of the Dodo.. (Scribner, 2004) pp. 431-2.