A short history of nearly everything (50 page)

Linnaeus had divided the animal world into six categories: mammals, reptiles, birds, fishes, insects, and “vermes,” or worms, for everything that didn’t fit into the first five. From the outset it was evident that putting lobsters and shrimp into the same category as worms was unsatisfactory, and various new categories such asMollusca andCrustacea were created. Unfortunately these new classifications were not uniformly applied from nation to nation. In an attempt to reestablish order, the British in 1842 proclaimed a new set of rules called the Stricklandian Code, but the French saw this as highhanded, and the Société Zoologique countered with its own conflicting code. Meanwhile, the American Ornithological Society, for obscure reasons, decided to use the 1758 edition ofSystema Naturae as the basis for all its naming, rather than the 1766 edition used elsewhere, which meant that many American birds spent the nineteenth century logged in different genera from their avian cousins in Europe. Not until 1902, at an early meeting of the International Congress of Zoology, did naturalists begin at last to show a spirit of compromise and adopt a universal code.

Taxonomy is described sometimes as a science and sometimes as an art, but really it’s a battleground. Even today there is more disorder in the system than most people realize. Take the category of the phylum, the division that describes the basic body plans of all organisms. A few phyla are generally well known, such as mollusks (the home of clams and snails), arthropods (insects and crustaceans), and chordates (us and all other animals with a backbone or protobackbone), though things then move swiftly in the direction of obscurity. Among the latter we might list Gnathostomulida (marine worms), Cnidaria (jellyfish, medusae, anemones, and corals), and the delicate Priapulida (or little “penis worms”). Familiar or not, these are elemental divisions. Yet there is surprisingly little agreement on how many phyla there are or ought to be. Most biologists fix the total at about thirty, but some opt for a number in the low twenties, while Edward O. Wilson inThe Diversity of Life puts the number at a surprisingly robust eighty-nine. It depends on where you decide to make your divisions—whether you are a “lumper” or a “splitter,” as they say in the biological world.

At the more workaday level of species, the possibilities for disagreements are even greater. Whether a species of grass should be calledAegilops incurva, Aegilops incurvata, orAegilops ovata may not be a matter that would stir many nonbotanists to passion, but it can be a source of very lively heat in the right quarters. The problem is that there are five thousand species of grass and many of them look awfully alike even to people who know grass. In consequence, some species have been found and named at least twenty times, and there are hardly any, it appears, that haven’t been independently identified at least twice. The two-volumeManual of the Grasses of the United States devotes two hundred closely typeset pages to sorting out all the synonymies, as the biological world refers to its inadvertent but quite common duplications. And that is just for the grasses of a single country.

To deal with disagreements on the global stage, a body known as the International Association for Plant Taxonomy arbitrates on questions of priority and duplication. At intervals it hands down decrees, declaring thatZauschneria californica (a common plant in rock gardens) is to be known henceforth asEpilobium canum or thatAglaothamnion tenuissimum may now be regarded as conspecific withAglaothamnion byssoides , but not withAglaothamnion pseudobyssoides. Normally these are small matters of tidying up that attract little notice, but when they touch on beloved garden plants, as they sometimes do, shrieks of outrage inevitably follow. In the late 1980s the common chrysanthemum was banished (on apparently sound scientific principles) from the genus of the same name and relegated to the comparatively drab and undesirable world of the genusDendranthema .

Chrysanthemum breeders are a proud and numerous lot, and they protested to the real if improbable-sounding Committee on Spermatophyta. (There are also committees for Pteridophyta, Bryophyta, and Fungi, among others, all reporting to an executive called the Rapporteur-Général; this is truly an institution to cherish.) Although the rules of nomenclature are supposed to be rigidly applied, botanists are not indifferent to sentiment, and in 1995 the decision was reversed. Similar adjudications have saved petunias, euonymus, and a popular species of amaryllis from demotion, but not many species of geraniums, which some years ago were transferred, amid howls, to the genusPelargonium . The disputes are entertainingly surveyed in Charles Elliott’sThe Potting-Shed Papers .

Disputes and reorderings of much the same type can be found in all the other realms of the living, so keeping an overall tally is not nearly as straightforward a matter as you might suppose. In consequence, the rather amazing fact is that we don’t have the faintest idea—“not even to the nearest order of magnitude,” in the words of Edward O. Wilson—of the number of things that live on our planet. Estimates range from 3 million to 200 million. More extraordinary still, according to a report in theEconomist, as much as 97 percent of the world’s plant and animal species may still await discovery.

Of the organisms that wedo know about, more than 99 in 100 are only sketchily described—“a scientific name, a handful of specimens in a museum, and a few scraps of description in scientific journals” is how Wilson describes the state of our knowledge. InThe Diversity of Life , he estimated the number of known species of all types—plants, insects, microbes, algae, everything—at 1.4 million, but added that that was just a guess. Other authorities have put the number of known species slightly higher, at around 1.5 million to 1.8 million, but there is no central registry of these things, so nowhere to check numbers. In short, the remarkable position we find ourselves in is that we don’t actually know what we actually know.

In principle you ought to be able to go to experts in each area of specialization, ask how many species there are in their fields, then add the totals. Many people have in fact done so. The problem is that seldom do any two come up with matching figures. Some sources put the number of known types of fungi at 70,000, others at 100,000—nearly half as many again. You can find confident assertions that the number of described earthworm species is 4,000 and equally confident assertions that the figure is 12,000. For insects, the numbers run from 750,000 to 950,000 species. These are, you understand, supposedly theknown number of species. For plants, the commonly accepted numbers range from 248,000 to 265,000. That may not seem too vast a discrepancy, but it’s more than twenty times the number of flowering plants in the whole of North America.

Putting things in order is not the easiest of tasks. In the early 1960s, Colin Groves of the Australian National University began a systematic survey of the 250-plus known species of primate. Oftentimes it turned out that the same species had been described more than once—sometimes several times—without any of the discoverers realizing that they were dealing with an animal that was already known to science. It took Groves four decades to untangle everything, and that was with a comparatively small group of easily distinguished, generally noncontroversial creatures. Goodness knows what the results would be if anyone attempted a similar exercise with the planet’s estimated 20,000 types of lichens, 50,000 species of mollusk, or 400,000-plus beetles.

What is certain is that there is a great deal of life out there, though the actual quantities are necessarily estimates based on extrapolations—sometimes exceedingly expansive extrapolations. In a well-known exercise in the 1980s, Terry Erwin of the Smithsonian Institution saturated a stand of nineteen rain forest trees in Panama with an insecticide fog, then collected everything that fell into his nets from the canopy. Among his haul (actually hauls, since he repeated the experiment seasonally to make sure he caught migrant species) were 1,200 types of beetle. Based on the distribution of beetles elsewhere, the number of other tree species in the forest, the number of forests in the world, the number of other insect types, and so on up a long chain of variables, he estimated a figure of 30 million species of insects for the entire planet—a figure he later said was too conservative. Others using the same or similar data have come up with figures of 13 million, 80 million, or 100 million insect types, underlining the conclusion that however carefully arrived at, such figures inevitably owe at least as much to supposition as to science.

According to theWall Street Journal , the world has “about 10,000 active taxonomists”—not a great number when you consider how much there is to be recorded. But, theJournal adds, because of the cost (about $2,000 per species) and paperwork, only about fifteen thousand new species of all types are logged per year.

“It’s not a biodiversity crisis, it’s a taxonomist crisis!” barks Koen Maes, Belgian-born head of invertebrates at the Kenyan National Museum in Nairobi, whom I met briefly on a visit to the country in the autumn of 2002. There were no specialized taxonomists in the whole of Africa, he told me. “There was one in the Ivory Coast, but I think he has retired,” he said. It takes eight to ten years to train a taxonomist, but none are coming along in Africa. “They are the real fossils,” Maes added. He himself was to be let go at the end of the year, he said. After seven years in Kenya, his contract was not being renewed. “No funds,” Maes explained.

Writing in the journalNature last year, the British biologist G. H. Godfray noted that there is a chronic “lack of prestige and resources” for taxonomists everywhere. In consequence, “many species are being described poorly in isolated publications, with no attempt to relate a new taxon[37]to existing species and classifications.” Moreover, much of taxonomists’ time is taken up not with describing new species but simply with sorting out old ones. Many, according to Godfray, “spend most of their career trying to interpret the work of nineteenth-century systematicists: deconstructing their often inadequate published descriptions or scouring the world’s museums for type material that is often in very poor condition.” Godfray particularly stresses the absence of attention being paid to the systematizing possibilities of the Internet. The fact is that taxonomy by and large is still quaintly wedded to paper.

In an attempt to haul things into the modern age, in 2001 Kevin Kelly, cofounder ofWired magazine, launched an enterprise called the All Species Foundation with the aim of finding every living organism and recording it on a database. The cost of such an exercise has been estimated at anywhere from $2 billion to as much as $50 billion. As of the spring of 2002, the foundation had just $1.2 million in funds and four full-time employees. If, as the numbers suggest, we have perhaps 100 million species of insects yet to find, and if our rates of discovery continue at the present pace, we should have a definitive total for insects in a little over fifteen thousand years. The rest of the animal kingdom may take a little longer.

So why do we know as little as we do? There are nearly as many reasons as there are animals left to count, but here are a few of the principal causes:

Most living things are small and easily overlooked.In practical terms, this is not always a bad thing. You might not slumber quite so contentedly if you were aware that your mattress is home to perhaps two million microscopic mites, which come out in the wee hours to sup on your sebaceous oils and feast on all those lovely, crunchy flakes of skin that you shed as you doze and toss. Your pillow alone may be home to forty thousand of them. (To them your head is just one large oily bon-bon.) And don’t think a clean pillowcase will make a difference. To something on the scale of bed mites, the weave of the tightest human fabric looks like ship’s rigging. Indeed, if your pillow is six years old—which is apparently about the average age for a pillow—it has been estimated that one-tenth of its weight will be made up of “sloughed skin, living mites, dead mites and mite dung,” to quote the man who did the measuring, Dr. John Maunder of the British Medical Entomology Center. (But at least they areyourmites. Think of what you snuggle up with each time you climb into a motel bed.)[38]These mites have been with us since time immemorial, but they weren’t discovered until 1965.

If creatures as intimately associated with us as bed mites escaped our notice until the age of color television, it’s hardly surprising that most of the rest of the small-scale world is barely known to us. Go out into a woods—any woods at all—bend down and scoop up a handful of soil, and you will be holding up to 10 billion bacteria, most of them unknown to science. Your sample will also contain perhaps a million plump yeasts, some 200,000 hairy little fungi known as molds, perhaps 10,000 protozoans (of which the most familiar is the amoeba), and assorted rotifers, flatworms, roundworms, and other microscopic creatures known collectively as cryptozoa. A large portion of these will also be unknown.

The most comprehensive handbook of microorganisms,Bergey’s Manual of Systematic Bacteriology , lists about 4,000 types of bacteria. In the 1980s, a pair of Norwegian scientists, Jostein Goksøyr and Vigdis Torsvik, collected a gram of random soil from a beech forest near their lab in Bergen and carefully analyzed its bacterial content. They found that this single small sample contained between 4,000 and 5,000 separate bacterial species, more than in the whole ofBergey’s Manual . They then traveled to a coastal location a few miles away, scooped up another gram of earth, and found that it contained 4,000 to 5,000other species. As Edward O. Wilson observes: “If over 9,000 microbial types exist in two pinches of substrate from two localities in Norway, how many more await discovery in other, radically different habitats?” Well, according to one estimate, it could be as high as 400 million.

We don’t look in the right places.InThe Diversity of Life , Wilson describes how one botanist spent a few days tramping around ten hectares of jungle in Borneo and discovered a thousand new species of flowering plant—more than are found in the whole of North America. The plants weren’t hard to find. It’s just that no one had looked there before. Koen Maes of the Kenyan National Museum told me that he went to one cloud forest, as mountaintop forests are known in Kenya, and in a half hour “of not particularly dedicated looking” found four new species of millipedes, three representing new genera, and one new species of tree. “Big tree,” he added, and shaped his arms as if about to dance with a very large partner. Cloud forests are found on the tops of plateaus and have sometimes been isolated for millions of years. “They provide the ideal climate for biology and they have hardly been studied,” he said.