Leonardo’s Mountain of Clams and the Diet of Worms
Page 9
But Mendes da Costa’s own requests mostly record his concern for completion and order. He asks a Jewish friend in Bath to collect as may kinds of fossils as possible, and to send them to his local coffeehouse—a striking example of different services rendered by public places before the days of home mail delivery:
In regard to fossils, see if you could get me any ammonitae, or snake-stones, as they are vulgarly called, as also impressions of plants on a kind of coal slate, which abound in the collieries. At Lincomb and Walcot are stone quarries which afford very fine petrifactions of shells, etc. Could you procure any of these things, and send me a box full directed to the Bank Coffee-house, I shall cheerfully repay all charges whatsoever.
Mr. Schomberg, presumably a German Jew by name, knew what he wanted in return: “Send me a small pot (of about three or four pounds) of sour-crout, . . . and take care it is well secured, so as not to be broke.”
Over and over again, Mendes da Costa begs his correspondents to pack carefully and label properly:
Of whatever is collected, let each specimen be carefully wrapped up and numbered, and a catalogue made with answerable numbers to each specimen, wherein specify what it is, what is vulgarly called, where found, whether in plenty or rare, at what depths, among what other fossil bodies, and all the other curious particulars you can be informed of to elucidate the natural history of them. I beg pardon for troubling you thus, but I am greatly obliged to you for this great piece of friendship.
Mendes da Costa’s most assiduous correspondence dates from the 1740s and 1750s as he collects, and beseeches friends to procure, as many “fossils” as possible for his forthcoming comprehensive treatise The Natural History of Fossils. Following contemporary custom, Mendes da Costa secured subscriptions to this book before publication (a favored fund-raising device for expensive works). His substantial list, published after the preface to his work, includes six bishops and five lords, further testifying to his acceptability among the Anglican upper classes. (Mr. Joseph Harris, “assay master of the Tower,” also signed on for a copy.)
Mendes da Costa published a first substantial volume of his treatise in 1757, but never proceeded any further. This work is, nonetheless, his masterpiece—and a superb example of the passion for fully comprehensive order that so motivated eighteenth-century natural history. In Mendes da Costa’s time, “fossil” (from the past tense of the Latin fodere, to dig up) referred to any natural object taken from the earth, not only to the remains of organisms. In fact, rocks and minerals were the quintessential “fossils” of eighteenth-century terminology, since they belong to the mineral kingdom—as natural products of the earth—whereas remains of ancient plants and animals must be introduced into rocks from the animal and vegetable kingdoms. Thus, the bones, shells, and leaves, now exclusively honored with the term fossil, were called “extraneous fossils” in the eighteenth century—while rocks and minerals represented essential fossils. Mendes da Costa therefore intended to cover all products of geology in his treatise—rocks, minerals, and remains of ancient organisms. But his first and only volume did not proceed beyond rocks and earths. (If he had completed the full design, and had followed the usual classifications of his time, he would probably have written a second volume, on minerals and crystals, and a third, on remains of organisms.)
Mendes da Costa may have been disgusted at Linnaeus’s sexual terminology for clams, but the great Swedish naturalist still reigned as the prince of order. We know that Linnaeus’s binomial system persists in largely unaltered form as the basis for giving scientific names to organisms today. This system has served us so well (despite recognized limitations) that we forget the fallacies of its original overextended application—an amnesia also abetted by our tendency to view the history of science as a list of growing successes, with errors buried into a conventional metaphor: “the ash-heap of history.”
But Linnaeus’s original application of binomial nomenclature suffered under the common eighteenth-century fallacy of grandiosity in attempting to encompass all possible kinds of natural diversity in one system of classification. For Linnaeus didn’t apply his binomial system only to plants and animals (where the procedure has always worked well, for reasons discussed below), but also, in essentially unaltered form, to minerals, and even, in his Genera morborum of 1763, to diseases, which he grouped by their symptoms into classes, orders, and genera.
The Linnaean system implies a definite geometry for the ordering of objects, and therefore only works when the causes of order produce results conforming with this geometry. Consider two essential properties: First, the Linnaean system is hierarchical. The basic units (species) are grouped into genera, genera into families, families into orders, and so on. This scheme implies a treelike topology with the largest unit (say, the kingdom Animalia) as a single trunk; middle units as large boughs attached to the trunk (phyla like Arthropoda and Chordata); smaller units as branches emerging from the boughs (classes like Mammalia and Aves joined to the chordate bough); and, finally, basic units as twigs growing from the branches (species like Homo sapiens and Gorilla gorilla attached to the primate branch of the mammalian bough of the animal trunk). This topology correctly represents a system of objects produced by branching evolution, with continuous divergence and no suturing together of separately formed branches. Since the history of life operates by this geometry, the Linnaean system works splendidly for classifying organisms.
Second, basic units must be discrete and definable, not smoothly intergrading and constantly joining. Since organic species are independent and stable units (after the brief geological moment of their branching origin), the Linnaean system also functions ideally for complex, sexually reproducing organisms.
But the same reasons that allow the Linnaean system to classify fossil organisms so well also guarantee an inapplicability in principle to the two categories of the mineral kingdom that Mendes da Costa’s age also called “fossils”—minerals and rocks. Minerals and their crystals have definite chemical formulae, and aggregate by simple physical rules. Their relative similarities are not genealogical, and their order cannot therefore be expressed by a treelike geometry. Moreover, mineral “species” are not discrete entities composed of genealogically related individuals in historical continuity. Cambrian quartz, at half a billion years of age, does not differ from Pleistocene quartz separately made in a geological yesterday.
Rocks and soils, composed of mineral grains and the products of their erosion, fail the Linnaean requirements for an even more fundamental reason. Rocks and soils form a broad continuum of fully intergrading compositions. We cannot identify discrete species of granites, marbles, or chalks. Granites, for example, are composed of quartz, two kinds of feldspar, and a dark mineral like biotite or hornblende—and all these constituents can be mixed and matched like house paint into any desired composition.
Nonetheless, Mendes da Costa, as a devotee of the classical passion for order, struggled to do as the master Linnaeus had enjoined—to make every object of nature fit the binomial system, thereby bringing all phenomena into one grand style of order. Thus, in The Natural History of Fossils, Mendes da Costa presents a Linnaean classification of earths and stones into species, genera, and other categories now used only for organisms. His great treatise has a wonderfully archaic ring today because he seems to treat objects of the mineral kingdom as a collection of organisms, and sets, as his highest goal for this branch of geology, a grouping of rocks to match a listing of beetles. I am particularly fond of his Natural History of Fossils because this treatise, more than any other work written in English, records a short episode expressing one of the grand false starts in the history of natural science—and nothing can be quite so informative and instructive as a truly juicy mistake.
Consider Mendes da Costa’s classification of earths and stones. He does not use Linnaeus’s own names for categories, but he follows the same basic procedure. Linnaeus’s hierarchy included four levels (we have since added several more): class, order,
genus, species. Mendes da Costa uses six: series, chapter, genus, section, member, and species. At the highest level, he divides his geological objects into two series: earths and stones. Following the Linnaean principle (and a long history of Western thought traceable to Aristotle), he provides a definition of categories based on a fundamentum divisionis, or basic criterion of difference. Earths are “fossils not inflammable, but divisible and diffusible, tho’ not soluble in water”—whereas stones have the same properties, but are not divisible and diffusible.
He separates the first series, earths, into seven genera within three chapters. Chapter 1, defined as “naturally moist, of a firm texture and which have a smoothness like that of unctuous bodies,” includes three genera—boles (Bolus), clays (Argilla), and marles (Marga). Chapter 2 (“naturally dry or harsh, rough to the touch and of a looser texture”) encompasses two genera—chalks (Creta) and ochres (Ochra). Finally, Chapter 3 (“naturally and essentially compound, and never found in the state of pure earth”) also includes two genera—loams (Terra miscella) and molds (Humus).
The second series, stones, includes nine genera in four chapters, based on interesting criteria that we would now regard as partly superficial and partly on the mark for wrong reasons. The four chapters comprise (1) stratified rocks made of grit (basically sandstones, divided by Mendes da Costa into two genera for finely stratified with many horizonal bedding planes versus massive and blocky); (2) stratified rocks without grit and homogeneous (divided into two genera—basically limestones and slates in modern parlance—by the same criterion of massive versus thinly bedded); (3) marbles (separated as much for their importance to human arts as for any other reason); and (4) crystalline rocks, divided largely by the size of mineral grains into basalts and other finely crystalline rocks, granites, and porphyries.
Mendes da Costa presents an interesting rationale—though ultimately flawed—for why a system that has worked so well for organisms should render equal service to inorganic geology. “It has been by pursuing such natural and simple methods as these, that botany has so eminently raised her head above her sister sciences,” he writes, acknowledging Linnaeus’s greatest success.
Mendes da Costa recognizes the differences in formation between organic and inorganic objects, but he follows a common scientific conceit in thinking that a uniform system of classification will nonetheless suffice for all: he will engage only in humble and accurate description, not in fanciful theorizing. Differences in causality cease to matter when we cite only the pristine factuality of objective appearances: “I have been very cautious not to indulge a speculative fancy in forming hypotheses or systems, the bodies being simply described, according to the appearances which they exhibit to the senses.”
Mendes da Costa then declares success because he has managed to balance, in a single system of compromises, all the competing schemes of his contemporaries. Such a “golden mean” must yield optimality. Mendes da Costa argues that he has achieved two great balances in his system—first, by finding the “right” number of basic species as a compromise between “splitters” who love to make fine distinctions, and “lumpers” who search for essences and tend to unite objects in their quest for fundamental properties. (The terminology of splitting and lumping belongs to the twentieth century, and the implied dichotomy cannot express all subtleties of this contrast, but the struggle between joiners and dividers has pervaded the history of taxonomy.) Mendes da Costa writes: “I have endeavored to reduce this study, hitherto deficient in respect of method, to a regular science, and in the attempt have been careful neither to multiply the species, nor lessen their number, unnecessarily.”
In a second balance, Mendes da Costa tries to unify the two disparate criteria then used to form systems for rocks and minerals—the efforts of his British compatriot John Woodward to base distinctions on observation of overt properties, both exterior and interior (“a method of arrangement founded on the growth, structure, and texture of fossils”); and continental systems based on “essential” properties discovered by chemical experiment (for example, a threefold division according to various changes produced by fire into calcarii, for rocks calcined, or turned to lime [limestones and marbles, for example], apyri for those unaffected [asbestos and others], and vitrificentes for those vitrified to glass [quartz and other silicates]). Mendes da Costa tries to bring all systems together by making primary divisions with observable properties (Woodward’s system), and then applying experimental and chemical results for refinements:
I have attentively examined the Woodwardian and Wallerian [continental] systems, and, finding them defective, have presumed to form a new one from the principles of both. I have endeavored to arrange fossils, not only according to their growth, texture, and structure, but also their principles and qualities, as discovered by fire, and acid menstrua, etc. And in this way, I am confident that all the known fossils may be accurately distinguished; whereas, to attempt it by any one system hitherto followed, must occasion a strange confusion.
But Mendes da Costa’s efforts had to fail in principle because the causes and properties of rocks violate the requirements of Linnaean geometry. Following the two central fallacies discussed earlier in this essay, Mendes da Costa could neither identify clear species, nor form distinct categories in a world of complete intergradation. Biological species are natural populations, distinct by historical continuity and current interaction, and unable to interbreed with others. Rock “species” are nondiscrete and intergrading. Ultimately, Mendes da Costa just joined specimens that looked “enough alike”—a sure formula for endless bickering among specialists, for no two will ever agree. For example, he castigates his two great masters, Linnaeus and Wallerius, for designating too few species in the genus Marmor (marbles):
Wallerius, in his Mineralogy, and Linnaeus, in his Systema Naturae, are extremely confused in regard to this genus of fossils; the former had divided all the marbles into only three species; viz. of uniform, variegated, and what he calls figured marbles . . . the latter has even made them all only varieties of one species; on which I cannot but make this observation, that it is a pity the learned should apply their studies rather to perplex science, than to elucidate it, and instruct mankind.
(I am no Freudian, but one certainly glimpses Oepidal feelings in Mendes da Costa’s complex attitude toward Linnaeus—basing his life’s work on the taxonomic system of his intellectual father, but then losing no opportunity to razz the master for moral turpitude on a range of issues from the terminology of clams to the number of species of marbles.)
But Mendes da Costa cannot claim final certainty for his own divisions of Marmor. He designates eighty-one species, far more than for any other genus of rocks, and clearly to recognize the human utility of different colors and patterns, not because nature has fabricated discrete and discoverable “basic kinds.”
Equal difficulty and frustration dogged Mendes da Costa’s effort to establish the higher divisions of rocks and earths—for he encountered complete intergradation between his genera as often as tolerable separation. For example, he frankly states his difficulty in dividing boles from clays, finally admitting that only convention dictates the separation:
Several authors do not make a distinct genus of the boles, but rank them among the clays; indeed very essential characteristics are wanting to make them different genera, for only the extreme fineness of the particles of the boles is the cause of their being not so ductile or viscid as the clays, insomuch that speaking with propriety, they are only to be accounted very fine clays; I have, however, made them separate genera, as custom hath authorized it.
The human mind, with arrogance and fragility intermixed, loves to construct grand and overarching theories—a fault perhaps encountered more often in our theological than in our scientific endeavors. But solutions often require the humbler, superficially less noble, and effectively opposite task of making proper divisions into different categories of meaning and causation. For only then can we build toward gen
erality on a firmer substrate, and without feet sculpted of the genus Argilla. Mendes da Costa, following Linnaeus, tried to bring all nature into one grand system of classification, but principles appropriate for the branching of organisms do not suit the continuities of rocks and earths. How ironic, ultimately, that a system doomed by too much togetherness should embody the best work of Emmanuel Mendes da Costa, the only Jewish naturalist of note in eighteenth-century Britain—a man from a culture then defined by separation from a majority committed to the parochial notion that Anglican theology represented the one true and only way.
To heap irony upon irony, and to end with a return to the beginning, Mendes da Costa did understand the general principle that now leads us, with such confidence and justice, to classify rocks differently from organisms. I omitted one line in his critique of Linnaeus’s sexual terminology for bivalves (as indicated by the ellipses on page 81), for these words cite a technical objection, rather than the moral argument then under discussion. In this line, now restored, Mendes da Costa rejects Linnaeus’s bivalve names “not only for their licentiousness, but also that they are in no ways the parts expressed.” How simple, and how correct! The top of a clam is not the bottom of a person—and supposed visual similarities can only be misleading. Different terms should be used, lest people be lulled into false suppositions about meaningful or causal likeness. Similarly, rocks and organisms require different systems of classification to acknowledge their disparate modes of production—by timeless chemistry versus singular genealogy, by laws of nature versus contingencies of history.
But all human beings belong to a single fragile species, a biological unity too much divided by the worst emotional traits of our common nature. Separate the stones from the snakes, but let Emmanuel Mendes da Costa, a Jewish stranger in a strange land, shake hands with his Mad King George—for then, perhaps, “they shall not hurt nor destroy in all my holy mountain,” made, no doubt, of the genus Granita, from the Italian for grain, to signify all the bits and pieces of diverse minerals that come together to form this hard rock of unity.