Crossing Over: Where Art and Science Meetby Stephen Jay Gould
Crossing Over, the latest of three collaborations between scholar Stephen Jay Gould and artist Rosamond Wolff Purcell, brings together thought-provoking essays and uncannily beautiful photographs to disprove the popular notion that art and science exist in an antagonistic relationship. The essays and photographs collected here present art and science in/i>… See more details below
Crossing Over, the latest of three collaborations between scholar Stephen Jay Gould and artist Rosamond Wolff Purcell, brings together thought-provoking essays and uncannily beautiful photographs to disprove the popular notion that art and science exist in an antagonistic relationship. The essays and photographs collected here present art and science in conversation, rather than in opposition. As Gould writes in his preface, although the two disciplines may usually communicate in different dialects, when juxtaposed they strikingly reflect upon and enhance one another. Working together, Purcell's photographs and Gould's scientific musings speak to us about ourselves and our world in a hybrid language richer than either could command on its own.
In an essay on individuality, for instance, Gould looks through the lens of evolutionary theory to address the controversial issue of cloning and the often misguided fears it evokes. As a society that exalts the concept of the individual, Gould argues, we sometimes fail to recognize that clones walk among us. Identical twins represent "the greatest of all challenges to our concept of individuality." Rosamond Purcell's photograph depicting the famous Siamese conjoined twins Eng and Chang conveys an eerie feeling that cannot be captured in words.
Through its unique combination of words and photographs, Crossing Over prompts us to ponder not only the basis of the false dichotomy between art and science, but also the distinction of mind and nature, and of all humanly imposed categories of order. Gould and Purcell's work convinces the reader that a provocative interplay between art and science is not only possible, butinevitable and necessary as well.
- Crown Publishing Group
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Read an Excerpt
I FORGIVE THE SLIGHT SPIN OF SLOGANEERING CONVEYED by the motto so frequently cited by proponents of a cosmos chock-full of organisms: "Life will find a way." Life is resilient and quite capable (especially in bacterial form) of living in the most damnably improbable places from nearly boiling ponds in Yellowstone National Park to tiny pores in rocks as deep as two miles below the earth's surface. But even this degree of resilience must work within limits; if life ever evolved on the Martian surface during its initial billion years with running water, the planet's later desiccation probably extinguished our solar system's second experiment in advanced carbon chemistry.
The intriguing subject of life's resiliency features two quite separate themes. First, and foremost, naturalists extol the penetration of life into extreme or downright bizarre environments the hottest, the coldest, the driest, the most noxious pond, the tightest squeeze, the most peculiar and precarious place. But second, and all too rarely considered, we should also emphasize life's internal resiliency its flexibility to explore the limits of form and structure, not only to inhabit extremes of external environments. To the mite on my eyebrow, the tardigrade encysted for decades of dryness, and the nearly boiling bacterium (exemplars of the first theme of extreme places), I would compare the ant with only one chromosome, the blue whale at an upper limit of size, and the tapeworm at absurd dimensions of twenty feet in length and one-sixteenth inch in thickness (champions of the second theme, stretching the envelopes of possible and workable designs).
Yet just as life can penetrate to most places, but not everywhere (the first theme of resiliency), so too can the anatomies of organisms be tweaked only so far (the second theme of internal flexibility). The realized designs of life do not spread out evenly over the landscape of imaginable form. Rather, islands (often large and crowded but sometimes tiny and isolated) rise into a domain of predominant emptiness. Half a million described species crowd the island of beetles, but think of the vast uninhabited spaces along the trajectory from beetle to bacterium, or beetle to buffalo.
What do these inhabited places represent? Do they specify the designs that cannot work in Darwin's tough world of competition and survival of the fittest the one-legged mammal that could never outrun the lion? Or do they denote the regions that organisms cannot reach because physical limits upon the structure of matter bar entry the tree that cannot rise to heaven, or the bird that cannot grow as big as a whale and still stay aloft? Or do they simply mark the domains that organisms have not yet reached because the number of potentially workable designs so greatly exceeds the possibilities for exploration, even given the generosity of geological time? Imagine the conscious octopus that might have evolved (and ruled the world) in different but sensible replay of life's history.
These three possibilities the "can't work well" of Darwinian limits; the "can't work at all" of physical constraint; and the "just haven't been there yet" of restricted historical time bear markedly different implications for our concepts of life and evolution. If the third theme rules, then the order of life's taxonomy primarily records the accidents of a few roads actually taken among myriads potentially available. If the first two themes prevail, then the mechanics of good design and the physics of structural limitation decree a fairly predictable order. I believe that all three themes weave a complex tapestry of rich and conflicting reasons for life's amazing yet ordered variety.
However, one common phenomenon offers a set of best examples for people who wish to deemphasize historical accident, and view life's strikingly discontinuous occupation of potential anatomical space as a predictable combination of physical principles in good design and life's protean capacity to assume, by Darwinian processes, a wide range of form. Life seems able to seize any ecological opportunity, even by altering standard designs to very peculiar purposes.
These photographs present four striking cases of flexibility in this structural sense. All these examples illustrate groups with "standard" and well-known anatomies expressed in so many thousands of species that one might suspect an intrinsic limit to flexibility imposed by key features of design the mechanical or adaptive impossibility of modifying a key trait, for example. Nonetheless, in each case a few species have evolved radical departures from the standard.
These departures cannot be viewed as either random or capricious. Rather, they bring the oddball creature into a design space usually associated with an entirely different group of organisms an evolutionary phenomenon called convergence. If a group so firmly associated with one staid form can occasionally transgress into the territory of another, after an extensive journey through the intervening space of organic design, then even the most apparently hidebound anatomies maintain surprising flexibility for opportunistic change and life will find a way in this internal sense as well.
The first two cases of radical departure present coral- and oyster-like species among the brachiopods. The bivalved brachiopods no longer play a major role in marine ecosystems, but they dominated the early fossil record of animals. Brachiopods persisted as thousands upon thousands of species, usually viewed as pretty "boring" by all but the few paleontologists (including me) who love them all because they appear to represent so much of a muchness. Most brachiopod species seem to express only limited variations upon a simple theme: two valves, one bigger than the other, and a fleshy stalk, called the pedicle, that extends through a hole at the top of the larger valve and attaches the animal to the substrate.
Yet, in the two odd Permian species shown in these photographs, both belonging to a group with the promising name of Productacea, these traditions have been abandoned for a remarkable mimicry of the forms and lifestyles of distant taxonomic groups. One species extends one valve into a long cone, reduces the other to a cap and looks for all the world like a horn coral (and did indeed grow in reef environments). In the photograph on the left we peer directly into the top of the cup, with the cone of the enlarged valve extending invisibly behind.
In the second species one valve becomes irregular, elongated, and cemented to the substrate, while the other grows as a minimal, meandering cover protecting the equally wavy feeding apparatus, called the lophophore, within. These odd brachiopods of the genus Leptodus live like cemented oysters and have evolved a striking resemblance to the anomalous form of oysters as well. (Such an "anomalous" design works superbly for cemented creatures that must be flexible enough to grow over and around impediments.)
Fish gotta swim and birds gotta fly. Our third case of departure from the norm violates the usual imperative for birds. The capacity of this large group (represented today by about 8,000 species, most in the category of small aerial tweeters) to evolve flightless terrestrial runners of substantial size his been exploited again and again (see essay 6 for more details and a different take on this subject): the ostrich in Africa, the rhea in South America, the emu and cassowary in Australia, and the extinct moa of New Zealand. In this photograph we see bones of the largest bird of all, the extinct Aepyornis, or "elephant bird" of Madagascar compared with a local species at the upper limits of size for more conventional flying forms, but positively dwarfed by weighty parts of the past.
Our fourth case, the Mesozoic ichthyosaurs, evolved from reptiles of terrestrial design, but became so fishlike on their return to a distantly ancestral marine habitat that they even reevolved (from no antecedent structures at all in their terrestrial forebears!) a tail fin with two equal lobes, and a dorsal fin similar in form and placement to the corresponding feature of ordinary fishes. This tail fin has been judged optimal by modern engineers as a stabilizing device for preventing the animal from rolling as it swims forward.
And yet, to end by affirming the complexity of yin's opportunism in combination with yang's constraints, ichthyosaurs did not and could not become fishes again. The imprint of reptilian history could not be completely expunged. But such genealogical baggage may be viewed more as a set of opportunities than an array of brakes. The extended, graceful fins of ichthyosaurs cannot be built, as in modern fishes, of long, slender rays attached to a horizontal base. Ichthyosaurs are stuck with long bones (humerus, femur, and so forth) and fingers. So, instead of growing only three pbalanges per finger (as we maintain in all our digits except the thumb, which bears but two), ichthyosaurs evolved fins with twenty or more phalanges per digit. Thus they converted a squat and stubby projection (that, in other vertebrate manifestations, runs on the ground, scratches an enemy, or types this essay) into a long strut, looking for all the world like a fin ray, and permitting a creature from terra firma to find a way back into its own ancestral ocean.
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