—Ornithological Biography
Arriving in America nine years apart, Wilson and Audubon found themselves at the edge of a large, misunderstood continent. Like many of their fellow immigrants, each had come to the New World to get away from difficulties in the Old. Their ambitions, like their backgrounds, were vague. Neither of them could have been described as an artist or a naturalist; neither had aspirations as a scientist. Both would become all of these things. For the time being, they merely increased the population of interesting North American fauna by two.
Most of the country’s 5 million immigrant citizens lived along the Eastern Seaboard. The frontier lay just beyond the Blue Ridge Mountains. Thomas Jefferson’s purchase of the Louisiana Territory in 1803 had doubled the size of the young nation, pushing the border across the Mississippi River and all the way to the Rockies, but this tremendous area—some 900,000 square miles—had scarcely been visited in three hundred years of European exploration and conquest. Little was known about the interior topography of North America apart from a skeletal outline of the major waterways. Even less had been discovered about the plants and animals living in the western two-thirds of America. The same was true with respect to the uncounted tribes of American Indians living between the two oceans.
European naturalists, disinclined to let a shortage of facts get in the way of a good story, had been busily describing and cataloguing New World flora and fauna from afar for a long time. They’d made a mess of it, but then this was a confusing time for biology, especially the study of natural history. By the end of the eighteenth century, intellectuals on both sides of the Atlantic had been swept up in the Age of Reason. The movement was the product of Enlightenment philosophy, which held that traditional lines of authority—specifically the church and secular monarchies—were inferior to rational thought and the proposition of universal human liberty. These ideas had led more or less directly to the Declaration of Independence and the establishment of American democracy. Inevitably, the same principles resulted in a clash between European science and a group of American amateurs who challenged the views of the leading naturalists of the era—including one of the shining lights of the age, Carolus Linnaeus.
Linnaeus, the father of modern taxonomy, was the Swedish botanist and physician who in 1735 formalized a naming strategy for all living organisms. A man of wide interests, Linnaeus dabbled in politics and economics, and spent many years trying (unsuccessfully) to grow tropical food crops in Sweden. His lasting contribution to biology was Systema Naturae, a compendium of species names, which he expanded and revised many times. Over the course of several editions, Linnaeus devised the binomial identification system still in use today. In the Linnaean system, each plant and animal is given a two-word name, with the first a Latin term signifying the genus to which it belongs and the second a specific or “species” name. So, for example, the gyrfalcon (Falco rusticolus) and the peregrine falcon (Falco peregrinus) can be seen to be two distinct species of similar birds belonging to a single genus.
Giving names to plants and animals is, of course, as old as language itself. Sorting them into categories is likewise an ancient practice. A thousand years before Linnaeus, Aristotle wrote at length about the “history” of animals and also about their parts. He emphasized the importance of morphological characteristics in distinguishing one animal from another, as well as the fact that morphology itself could be subdivided. For example, skin is an irreducible or “uniform” part of an animal, whereas a foot is composed of skin and several other parts, like muscle and bone. A close observer of animal behavior and anatomy, Aristotle also recognized a parallel principle of organization, in which similar species could be grouped into assemblages called “genera.” Aristotle’s definition of a genus was broad. Birds and fishes are examples of Aristotelian genera, and Aristotle regarded all terrestrial quadrupeds as belonging to a single genus. But despite their many important shared characteristics there are also unmistakable differences between, say, a lion and a porcupine. This led Aristotle to insist on the supremacy of species as the fundamental unit of natural history. “[W]e must take animals species by species and discuss their peculiarities severally.” And so it has ever been.
Linnaeus also emphasized the species as the fundamental unit of life. His binomial system was intended to make it easier to keep track of plant and animal taxa—whose numbers were expanding as European explorers pushed into new places across the globe. For several decades following the publication of Systema Naturae, students and colleagues sent Linnaeus specimens, mainly plants, from all over the world. He named them based on what he saw as their intrinsic qualities, like rocks whose origins could be explored with a hammer. Linnaeus believed the identity of a species was inherent in its appearance and that he didn’t so much choose a name as diagnose one. “The thing is, that each Stone, Plant, Animal itself shall tell the ignorant its own name so that it will be understood by everyone who has learnt the language,” Linnaeus said.
Linnaeus never imagined how truly extensive this language was. Late in life he realized that there were probably so many plants in the world that it would be hard to name them all. But he believed the number of species on earth was not incomprehensible. He estimated the total at 40,000. About half that number would be plants, with the next largest group being approximately 12,000 insects. Linnaeus thought there were maybe 2,000 species of birds and perhaps 200 mammals. He was low.
It’s a testament to the diversity and abundance of life that although we know Linnaeus was off in his estimate of how many species there are, nobody today really knows how far off. There are something like 1.7 million named species. But that’s only a small fraction of what’s out there. New species are discovered continually, and we’re not going to get a handle on the total anytime soon. Current guesses put the number at anywhere from 8 million to as many as 100 million, with 30 million being a generally accepted estimate. That includes a lot of bacteria, but also 4,300 mammals and nearly 10,000 birds. Linnaeus rightly suspected that there are many species of insects, though his estimate of 12,000 is amusing in retrospect. Beetles alone make up 300,000 known species. About one out of every three living things on the planet is a bug, and thousands of insect species thrive in anonymity in tropical forests.
Just as there were many more species than Linnaeus imagined, there was a need for more genera than he created to manage them all. As new species turned up in far-flung parts of the world like America, they were made to fit into a preexisting taxonomical scheme that seemed increasingly artificial. Linnaean taxonomy relied on morphology rather than behavioral traits or reproductive compatibility—features of natural history that required study in the field. This created confusion when unrelated species with a few coincidental similarities in appearance were crowded into the same genus. But this was only one of the shortcomings of the Linnaean system.
In Linnaeus’s day, the idea that species were the “words” of the language of biology was widely shared. Naturalists thought of nature as a book. And since nature was the product of divine Creation, this book was a kind of scripture. The study of nature was thus a pious attempt to read God’s book of life. But this raised a difficult issue. If the book of nature was a bible, then it was not meant to be edited. God was presumed to have created all living things at the same time and in a state of harmony that was immutable. Simply put, the plants and animals in the world were fixed. They were all of life that ever was or ever would be. The book of nature was written in indelible ink.
For most of his life Linnaeus believed this was so. “We count so many species as there were in the beginning,” he wrote in Systema Naturae. But he gradually came to the conclusion that at least some species arose over time. Linnaeus was sure these processes were so slow that nature could be regarded as essentially stable. Like many of his contemporaries, Linnaeus was groping his way toward a concept—evolution—that would not be articulated for another century. He didn’t get there because he didn’t realize that, just as new species could develop, the reverse was also true, and even God’s creations sometimes passed out of existence. Linnaeus had no concept of extinction.
To be fair,
