To make an ugly analogy, based on cruel social practices now thankfully abandoned, but in force not long ago, I encountered both spatial and temporal modes of segregation when I began my college studies in southwestern Ohio during the late 1950s. The town movie theater placed whites in the orchestra and blacks in the balcony, while the local skating rinks and bowling alleys maintained different “white” and “Negro” nights. (Student and community activism, spurred by the nascent civil rights movement, fought and vanquished these cruelties during my watch. I remember my own wholehearted and, in retrospect, pretty inconsequential participation with pride.)
An instructive evolutionary example of this first strategy arises from a classical argument about modes of speciation, or the origin of a new species by branching from an ancestral population. Such branching may occur if a group of organisms can become isolated from the parental population and begin to breed only among themselves in a different environment that might favor the evolution of new features by natural selection. (If members of the separating group continue to interact and breed with individuals of the parental population, then favorable new features will be lost by dilution and diffusion, and the two groups will probably reamalgamate, thus precluding the origin of a new species by branching.)
The conventional theory for speciation—called allopatric, and meaning “living in another place”—holds that a population can gain the potential to form a new species only by becoming geographically isolated from the ancestral group, for only strict spatial separation can guarantee the necessary cutoff from contact with members of the parental population. Much research into the process of speciation has focused on the modes of attaining such geographic isolation—new islands rising in the sea, continents splitting, rivers changing their courses, and so on.
A contrasting idea—called sympatric speciation, or “living in the same place”—holds that new groups may speciate while continuing to inhabit the same geographic domain as the parental population. The defense of sympatric speciation faces a classic conundrum, and most research on the subject has been dedicated to finding solutions: if isolation from members of the parental population is so crucial to the formation of a new species, how can a new species arise within the geographic range of the parents?
This old issue in evolutionary theory remains far from resolution, but we should note, in the context of this essay, that proposed mechanisms usually follow the Holy Sepulchre principle of granting the new group a room of its own within the spatial boundaries of the parental realm—and that such “internal isolation” may be achieved by either the spatial or the temporal route. The best-documented cases of the spatial strategy invoke a process with the technical name of host specificity, or the restriction of a population to a highly specific site within a general area. For example, to cite an actual (although still controversial) case, flies of the genus Rhagoletis tend to inhabit only one species of tree as an exclusive site for breeding and feeding. Suppose that some individuals within a species that lives on apple trees experience a mutation that leads them to favor hawthorns. A new population, tied exclusively to hawthorns, may soon arise and may evolve into a separate species. The hawthorn flies live within the same geographic region as the apple flies, but members of the two groups never interbreed because each recognizes only a portion of the total area as a permissible home—just as the six sects of the Holy Sepulchre never transgress into one another’s territory.
The same principle may work temporally as well. Suppose that two closely related species of frogs live and reproduce in and around the same pond, but one species uses the day-lengthening cues of spring to initiate breeding, while the other waits for the day-shortening signals of fall. The two populations share the same space and may even (metaphorically) wave and wink at each other throughout the year, but they can never interbreed and can therefore remain separate as species.
In the second, and philosophically far more interesting, strategy for securing a requisite room of one’s own, species may share the same region but avoid the need for a natural equivalent of the Status Quo, because they do not perceive each other at all and therefore cannot interfere or compete—blessedly benign ignorance rather than artfully negotiated separation. This fascinating form of imperception, which can also be achieved by either spatial or temporal routes, raises one of the most illuminating issues of intellectual life and nature’s construction: the theme of scaling, or strikingly different ways of viewing the world from disparate vantage points of an observer’s size or life span, with no single way either universally “normal” or “better” than any other.
To begin with a personal story, I share my Harvard office with about a hundred thousand trilobites, all fossils at least 250 million years old, and now housed in cabinets lining the perimeter of my space. For the most part, we coexist in perfect harmony. They care little for my eye-blink of a forty-year career, and I view them with love and respect to be sure, but also as impassive, immobile pieces of rock. They cause me no trouble because I just move the appropriate drawers to an adjacent room when a visiting paleontologist needs to study a genus or two. But one week, about ten years ago, two British visitors wanted to look at all Ordovician trilobites, an endeavor that required exploratory access to all drawers. I had no choice but to abandon my office for several days—a situation made worse by the stereotypical politeness of my visitors, as they apologized almost hourly: “Oh, I do hope we’re not disturbing you too much.” I wanted to reply: “You bloody well are, but there’s nothing I can do about it,” but I just shut up instead. I relaxed when I finally figured out the larger context. My visitors, of course, had been purposely sent by the trilobites to teach me the following lesson of scaling: we will let you borrow this office for a millimoment of our existence; this situation troubles us not at all, but we do need to remind you about the room’s true ownership once every decade or so, just to keep you honest.
Species can also share an environment without conflict when each experiences life on such a different temporal scale that no competitive interaction ever occurs. A bacterial life cycle of half an hour will pass beneath my notice and understanding, unless the population grows big enough to poison or crowd out something of importance to me. And how can a fruit fly ever experience me as a growing, changing organism if I manifest such stability throughout the fly’s full life cycle of two weeks or so? The pre-Darwinian Scottish evolutionist Robert Chambers devoted a striking metaphor to this point when he wondered if the adult mayfly, during its single day of earthly life, might mistake the active metamorphosis of a tadpole into a frog for proof of the immutability of species, since no visible change would occur during the mayfly’s entire lifetime. (And so, Chambers argued by extension, we might miss the truth of evolution if the process unrolled so slowly that we could never notice any changes during the entire history of potential human observation.) Chambers wrote in 1844:
Suppose that an ephemeron [a mayfly], hovering over a pool for its one April day of life, were capable of observing the fry of the frog in the waters below. In its aged afternoon, having seen no change upon them for such a long time, it would be little qualified to conceive that the external branchiae [gills] of these creatures were to decay, and be replaced by internal lungs, that feet were to be developed, the tail erased,.and the animal then to become a denizen of the land.
Since organisms span such a wide range of size, from the invisible bacterium to the giant blue whale (or to the fungus that underlies a good part of Michigan), the second, or spatial, strategy of coexistence by imperception achieves special prominence in nature. This concept can ‘best be illustrated by an example that has become something of a cliché (by repetition for appropriateness) in intellectual life during the past decade.
To illustrate his concept of “fractals,” mathematical curves that repeat an identical configuration at successively larger or smaller scales ad infinitum, mathematician Benoit Mandelbrot asked a disarmingly simple question with a wonderfully subtle nonanswer: how
long is the coastline of Maine? The inquiry sounds simple but cannot be resolved without ambiguity, for solutions depend upon the scale of inquiry, and no scale can claim a preferred status. (In this respect, the question recalls the classic anecdote, also told about folks “down East” in Maine, of a woman who asks her neighbor, “How’s your husband?”— and receives the answer, “Compared to what?”)
If I’m holding an atlas with a page devoted to the entire state of Maine, then I may measure a coastline at the level of resolution permitted by my source. But if I use a map showing every headland in Acadia National Park, then the equally correct coastline becomes much longer. And if I try to measure the distance around every boulder in every cove of Acadia, then the length becomes ever greater (and increasingly less meaningful as tides roll and boulders move). Maine has no single correct coastline; any proper answer depends upon the scale of inquiry.
Similarly for organisms. Humans rank among the largest animals on earth, and we view our space as one might see all of Maine on a single page. A tiny organism, living in a world entirely circumscribed by a single boulder in a cove, will therefore be completely invisible at our scale. But neither of us sees “the world” any better or any more clearly. The atlas defines my appropriate world, while the boulder defines the space of the diatom or rotifer (while the rotifer then builds the complete universe of any bacterium dwelling within).
We need no Status Quo to share space with a bacterium, for we dwell in different worlds of a common territory—that is, unless we interfere or devise a way to intrude: the bacterium by generating a population large enough to incite our notice or cause us harm; Homo sapiens by inventing a microscope to penetrate the world of the invisible headland on a one-page map of the earth.
Frankly, given our aesthetic propensities, we would not always wish to perceive these smaller worlds within our domain. About 40 percent of humans house eyebrow mites, living beneath our notice at the base of hair follicles above our eyes. By ordinary human standards, and magnified to human size, these mites are outstandingly ugly and fearsome. I would just as soon let them go their way in peace, so long as they continue the favor of utter imperceptibility. And do we really want to know the details of ferocious battles between our antibodies and bacterial invaders—a process already distasteful enough to us in the macroscopic consequence of pus? (Don’t get me wrong. As a dedicated scientist, I do assert the cardinal principle that we always want to know intellectually, both to understand the world better and to protect ourselves. I am just not sure that we should always crave visceral perception of phenomena that don’t operate at our scale in any case.)
Finally, this theme of mutually invisible life at widely differing scales bears an important implication for the “culture wars” that supposedly now envelop our universities and our intellectual discourse in general (but that have, in my opinion, been grossly oversimplified and exaggerated for their perceived news-worthiness). One side of this false dichotomy features the postmodern relativists who argue that all culturally bound modes of perception must be equally valid, and that no factual truth therefore exists. The other side includes the benighted, old-fashioned realists who insist that flies truly have two wings, and that Shakespeare really did mean what he thought he was saying. The principle of scaling provides a resolution for the false parts of this silly dichotomy. Facts are facts and cannot be denied by any rational being. (Often, facts are also not at all easy to determine or specify—but this question raises different issues for another time.) Facts, however, may also be highly scale dependent—and the perceptions of one world may have no validity or expression in the domain of another. The one-page map of Maine cannot recognize the separate boulders of Acadia, but both provide equally valid representations of a factual coastline.
Why should we privilege one scale over another, especially when a fractal world can express the same form at every scale? Is my hair follicle, to an eyebrow mite, any less of a universe than our entire earth to the Lord of Hosts (who might be a local god as tiny as a mite to the great god of the whole universe—who then means absolutely nothing in return to the mite on my eyebrow)? And yet each denizen of each scale may perceive an appropriate universe with impeccable, but local, factual accuracy.
We don’t have to love or even to know about all creatures of other scales (although we have ever so much to learn by stretching our minds to encompass, however dimly and through our own dark glasses, their equally valid universes). But it is good and pleasant for brethren to dwell together in unity—each with some room of one’s own.
ILLUSTRATION CREDITS
Grateful acknowledgment is made to the following for permission to reproduce the images herein:
pages v, 14 American Museum of Natural History, photograph by Jackie Beckett
page 37 American Museum of Natural History, photograph by Stephanie Bishop
page 38 The Granger Collection, New York
page 96 Rare Book Collection, Skillman Library, Lafayette College
page 127 Courtesy of Jonathan A. Hill
page 128 Christie’s Images
page 193 American Museum of Natural History, photographs by Jackie Beckett
pages 204, 208, 212, 213, 214 All images from the Edward Arnold Collection, courtesy of the Eiffel Tower Millennial Exhibition
page 300 Corbis-Bettmann
page 309 Corbis-Bettmann
page 322 Courtesy of Joyce Pendola
pages 323, 330 (bottom images) Courtesy of Andrew Knoll
All other images appearing throughout are from the author’s collection.
INDEX
A
Aaron, Hank, (i)
Abbott, E. A., (i)
abstract concepts, gender of, (i)
Accademia dei Lincei
after Cesi’s death, (i), (ii), (iii)
and direct observation, (i), (ii)
emblem of, (i), (ii), (iii), (iv)
formation of, (i), (ii), (iii)n
and fossil wood, (i)
Galileo as member of, (i), (ii), (iii), (iv), (v), (vi), (vii), (viii), (ix)
papal government and, (i)
publications of, (i), (ii), (iii), (iv), (v), (vi)
rules and goals of, (i)
Stelluti as member of, (i), (ii), (iii), (iv), (v), (vi)
achievement, factors in, (i)
Acquasparta, mineral wood of, (i)
Adams, Frank Dawson, (i)
adaptation
diversity and, (i)
linearity vs., (i), (ii)
to local environments, (i), (ii), (iii), (iv), (v), (vi)
predation and, (i)
progressionism and, (i)
Agricola, Georgius, (i), (ii), (iii)
alchemy, (i)
algae, fossils of, (i)
Allen, Mel, (i)
allopatric speciation, (i)
amateur, meaning of word, (i)
ammonites, fake carvings of, (i)
Amundsen, Roald, (i)
Anatomy of Melancholy (Burton), (i)
animals, origins of, (i)
ankylosaurs, (i)
Anolis lizard, (i)
anthrax bacilli, (i)
Argenville, Dezallier d’, (i), (ii)
Aristotle, (i), (ii), (iii), (iv), (v)
Armstrong, Neil, (i), (ii)
Asch Building, New York, (i), (ii)
astrology, (i)
astronomy, (i)
Buffon on origin of planets, (i)
Galileo’s observations in, (i), (ii), (iii), (iv)
telescope and, (i)
Atdabanian phase, (i)
atom, forces of, (i)
authority, proof by, (i)
autosuggestion, self-improvement via, (i)
“Averroës’ Search” (Borges), (i)
Azoic era, (i)
B
Babbage, Charles, (i), (ii)
Bacon, Francis, (i), (ii), (iii), (iv)n
death of, (i)
idols of, (i), (ii), (iii), (iv), (v), (vi)
/> bacteria, evolutionary changes in, (i)
Baliani, G. B., (i)
bandes, concept of, (i)
Barber, Red, (i)
Barberini, Francesco, (i), (ii), (iii), (iv)
Barberini, Maffeo, (i), (ii)
Barghoorn, Elso, (i), (ii)
barnacles, taxonomy of, (i)
Barrington, Daines, (i)
baseball, (i), (ii), (iii)
“Battle Hymn” (Howe), (i)
Beagle voyage, (i), (ii), (iii), (iv), (v), (vi)
Beak of the Finch (Weiner), (i)
beauty, standards of, (i)
behavior, genetic determinants of, (i)
Bell, Thomas, (i)
Bell Curve, The (Murray and Herrnstein), (i)
Bengston, Stefan, (i)
Beringer, Johann Bartholomew Adam, (i)
colleagues’ views of, (i), (ii), (iii)
correction of tale about, (i)
fame sought by, (i), (ii)
fossils found by, (i), (ii)
legend of, (i), (ii)
paleontology in time of, (i), (ii), (iii), (iv)
significance of, (i), (ii)
Bertrand, Elie, (i)
biogeography, (i)
biography
power of chronology in, (i)
in science writing, (i)
synergy in, (i)
biological and chemical weapons, (i)