The Flamingo’s Smile (33 page)

Lest it seem absurd that male structures be transformed into female organs of such different appearance, I remind readers that male and female parts often have a common basis in embryology, one developing directly from the other under the influence of different hormones. The external genitalia of all mammals, for example, begin as female structures: the clitoris enlarges, folds over and fuses to form a cylinder with a central tube, the male penis; the
labia majora
expand and fuse at the midline to form a scrotal sac. In essay 11 of
Hen’s Teeth and Horse’s Toes
, I used these equivalences to argue that the remarkable male-mimicking genitalia of female spotted hyenas arise automatically from these common pathways of sexual development, because females of this species secrete unusually high levels of testosterone during growth and become both larger than males and dominant over them.

Tassel spike and corn ear are also equivalent structures and the transformation of one to the other is equally plausible. Indeed, such interchanges often occur as teratologies, or abnormalities of development, in modern corn. Male tassel spikes may grow as female ears or partial ears with male ends, for several reasons: genetic mutations and diseases that drastically shorten the central branch, for example. Iltis sent me the accompanying photograph of such a feminized tassel, sold as an ordinary ear of corn at Kohl’s supermarket in Madison, Wisconsin, for thirty-nine cents. The central axis has grown as a complete female ear. The three lateral branches are female at the bottom, grading to male at the top, with the male parts “arranged,” Iltis tells me, “exactly as in any maize or teosinte tassel branch.” Of course, such teratologies only show the interchangeability of corn tassels and corn ears, not the evolutionary derivation of corn ears from teosinte tassels. But they surely illustrate, by strong analogy, why the genealogical path from teosinte tassel to corn ear remains so reasonable, however peculiar at first hearing.

In calling his theory the “catastrophic sexual transmutation,” Iltis forcefully identifies its two outstanding and unconventional properties. First, using the positional criterion of homology as a guide, female corn ears arose by transmutation of a male teosinte tassel spike, not by gradual enlargement of a female teosinte ear. Second, the transformation occurred rapidly under the guidance of little (or even no) genetic change, despite the sudden and striking alteration of form. I shall try to epitomize Iltis’s argument in the following basic steps:

• 1. In both corn and teosinte, hormones are distributed along simple gradients in long stems, with male zones at the tops passing through a threshold to female zones below.
  
• 2. A gradient in time of differentiation during growth also accompanies this hormonal distribution. Structures at the tops of stems develop earlier than those lower down. On a lateral teosinte branch, the terminal male tassel differentiates before the female ears below.
  

A corn “monster” purchased for thirty-nine cents at a Madison, Wisconsin, supermarket by Hugh Iltis.
PHOTO COURTESY OF HUGH ILTIS
.

• 3. The nutritional needs of a male tassel are small, those of a female ear (particularly a large and polystichous ear of corn) much larger. The differentiation of a tassel at the terminal end of a branch still leaves most nutrients available for development of subsequent female structures below (see point 2).
  
• 4. If a terminal male tassel spike transmutes abruptly to a female ear, this ear would immediately become a sink for all available nutrients and might automatically suppress the development of any subsequent female structure lower down on the branch.
  
• 5. The initial step of the catastrophic sexual transmutation, given points 1 through 4 above, might therefore require nothing more than a marked shortening of a teosinte lateral branch. The shortening would move the branch’s tip from a masculine to a feminine zone (point 1). The terminal structure would then differentiate first as a female ear (points 1 and 2). This terminal ear would appropriate all nutrients and suppress the development of any structures below, including the usual female ears of teosinte (points 3 and 4).
  
• 6. Although the shortening of a branch might induce a profound and varied set of automatic consequences (point 5), the initiating change (the shortening itself) is simple and may require only a trifling genetic alteration, perhaps the mutation of a single gene. The initial change might even require no genetic modification at all, for several corn smuts and viruses, or even a simple environmental change to cooler night temperatures or shorter days, can lead to a feminization of central tassel spikes in corn.
  
• 7. Of course, the initial product of such shortening and feminization would not be a full-blown modern corn ear. This first step would probably yield a cob with a few rows of female kernels at the base and male structures above. The production of a polystichous, or many rowed, ear remains problematical. One hypothesis envisions the conjunction of several tassel segments (as the branch shortens) and their subsequent junction and twisting to form the polystichous ear. Remember, though, that the conventional theory of derivation from a two-rowed teosinte ear encounters the very same problem and proposes the same basic resolution. As Iltis points out, the teosinte tassel is a better candidate than the teosinte ear for such a hypothetical process. The teosinte ear is, as biologists say, a strongly “canalized” structure—one that develops in basically the same way in all individuals of a race, without much variation from plant to plant. It is always two rowed and few kerneled. The tassel spike, on the other hand, is far more variable and prolific in individual units (all suitable for change to kernels). By transforming a male variant with maximal rows and units, the first step might bring us far closer to an ear of corn than any initial change from a teosinte ear could accomplish.
  
• 8. The small, initial ear of the catastrophic sexual transmutation is immediately useful as human food. Farmers therefore propagate the kernels and select future generations from plants bearing the largest ears. Ordinary agricultural selection therefore builds the bigger and fuller ear from its initial, rather runty but still useful, condition.
  

As its major general feature, Iltis’s theory proposes that a small genetic change, initiating one basic modification of form (shortening of lateral branches), automatically engenders a major alteration of structure (transformation of male tassel spike to female ear) by “playing off” the inherited sexual and developmental system (hormonal gradients from male to female along a stem, and gradients in differentiation permitting terminal structures to develop first). This theory may therefore serve as a remarkable exemplar of a process long ridiculed by conventional evolutionists but, in my view, eminently plausible in certain cases—the “hopeful monster,” a “saltational” view for the origin of novel morphological structures and species (evolution by jumps). The great German geneticist Richard Goldschmidt proposed this idea in a series of works, culminating in his 1940 book,
The Material Basis of Evolution
(recently reprinted by Yale University Press with an introduction by yours truly). Goldschmidt’s hopeful monster became the whipping boy of orthodox Darwinians, with their preferences for gradual and continuous change, and his theory suffered the unkindest fate of all—to lie unread and misunderstood while being ridiculed in a caricatured version.

In their caricatured form, hopeful monsters are dismissed for three reasons. Iltis’s proposal for the origin of corn beautifully illustrates the theory in its correct and subtle form, as Goldschmidt presented it, and provides a specific antidote for all three arguments. First, detractors claim that Goldschmidt’s theory represents a surrender to ignorance, a reliance on some quirky and capricious accident, once in a great while useful by sheer happenstance. Yet don’t we know that virtually all major mutations are harmful? Goldschmidt acknowledged that most macromutants are inviable—truly hopeless monsters in his words. The hopeful few won their status precisely because they achieved their abruptly altered form within the constraints imposed by an inherited developmental system. Hopeful monsters are not any old odd change, but large-scale modifications along the established pathways of ordinary sexual and embryological development. In Iltis’s theory, inherited hormonal and developmental gradients along a branch permit the sudden transformation of tassel spike to ear. Big changes in harmony with—and produced along—ordinary pathways of development need not be inviable, for they lie within inherited possibilities of basic organization.

Second, hopeful monsters have been rejected because they supposedly propose unknown and large-scale discombobulations of genetic systems. Indeed, late in his career, Goldschmidt did unfortunately confuse his early notion of saltational change in form with a later theory of abrupt and substantial genetic change—the so-called systemic mutation. But, in Goldschmidt’s initial version, the hopeful monster arose as a consequence of small—and therefore both plausible and orthodox—genetic changes that produce large effects upon form because they alter early stages of development with cascading effects upon subsequent growth. Iltis proposes a small (or even no) genetic change as a basis for shortening the lateral branches and producing the saltation from tassel spike to ear as an automatic consequence of developmental patterns.

Third, whom shall the hopeful monster choose as mate? It is only an individual, however well endowed, and evolution requires the spreading of favorable traits through populations. The offspring of two such different forms as a normal individual and a hopeful monster will probably be sterile or at least, in their peculiarly hybrid state, no match for normals in natural selection. But Iltis’s theory avoids this problem by calling upon human aid to propagate the seeds. The catastrophically transmutated teosinte plant is still a viable creature, with a male tassel on its central spike and female ears in terminal positions on its lateral branches.

Finally, one last interesting and unusual feature of Iltis’s theory: it invokes human feedback, not only to improve the initial ear by conventional selection but also to make it a viable structure in the first place—a striking example of interaction between two disparate species in nature. The corn ear, as a natural object, may well be unworkable—for the husks, which firmly enclose the cob as a result of shortening the lateral branch so drastically, prevent any dispersal of seeds (kernels). In a state of nature, the ear would simply rot where it fell or would seed new plants so close to each other that no offspring would reach full maturity. But farmers can peel off the husks and plant the seeds—converting a hopeless to a most hopeful and useful monster.

Corn is the world’s third largest crop, not far behind wheat and rice. As the original staple of New World peoples, it built the civilizations of an entire hemisphere. Today we grow 270 million acres of corn a year, producing nearly 9 billion bushels. Most of it does not end up in tacos or corn chips, but as animal feed—the primary source for our carnivorous appetites. We need corn for a comfortable life, but corn needs us as well, simply to survive.

THE CASE
for organic integrity was stated most forcefully by a poet, not a biologist. In his romantic paean
The Tables Turned
, William Wordsworth wrote:

The whiff of anti-intellectualism that pervades this poem has always disturbed me, much as I appreciate its defense of nature’s unity. For it implies that any attempt at analysis, any striving to understand by breaking a complex system into constituent parts, is not only useless but even immoral.

Yet caricature and dismissal from the other side have been just as intense, if not usually stated with such felicity. Those scientists who study biological systems by breaking them down into ever smaller parts, until they reach the chemistry of molecules, often deride biologists who insist upon treating organisms as irreducible wholes. The two sides of this oversimplified dichotomy even have names, often invoked in a derogatory way by their opponents. The dissectors are “mechanists” who believe that life is nothing more than the physics and chemistry of its component parts. The integrationists are “vitalists” who hold that life and life alone has that “special something,” forever beyond the reach of chemistry and physics and even incompatible with “basic” science. In this reading you are, according to your adversaries, either a heartless mechanist or a mystical vitalist.

I have often been amused by our vulgar tendency to take complex issues, with solutions at neither extreme of a continuum of possibilities, and break them into dichotomies, assigning one group to one pole and the other to an opposite end, with no acknowledgment of subtleties and intermediate positions—and nearly always with moral opprobrium attached to opponents. As the wise Private Willis sings in Gilbert and Sullivan’s
Iolanthe:

The categories have changed today, but we are still either rightists or leftists, advocates of nuclear power or solar heating, pro choice or against the murder of fetuses. We are simply not allowed the subtlety of an intermediate view on intricate issues (although I suspect that the only truly important and complex debate with no possible stance in between is whether you are for or against the designated hitter rule—and I’m agin it).

Thus, the impression persists that biologists are either mechanists or vitalists, either advocates of an ultimate reduction to physics and chemistry (with no appreciation for the integrity of organisms) or supporters of a special force that gives life meaning (and modern mystics who would deny the potential unity of science). For example, a popular article on research at the Marine Biological Laboratory of Woods Hole (in the September-October 1983 issue of
Harvard Magazine
) discusses the work of a scientist with a physicist’s approach to neurological problems:

But this dichotomy is an absurd caricature of the opinions held by most biologists. Although I have known a few mechanists, as defined in this article, I don’t think that I have ever met a vitalist (although the argument did enjoy some popularity during the nineteenth century). The vast majority of biologists, including the great geneticist T.H. Morgan (who was as antivitalist as any scientist of our century), advocate a middle position. The extremes may make good copy, and a convenient (if simplistic) theme for discussion, but they are occupied by few, if any, practicing scientists. If we can understand this middle position, and grasp why it has been so persistently popular, perhaps we can begin to criticize our lamentable tendency to dichotomize complex issues in the first place. I therefore devote this essay to defining and supporting this middle way by showing how a fine American biologist, Ernest Everett Just, developed and defended it in the course of his own biological research.

The middle position holds that life, as a result of its structural and functional complexity, cannot be taken apart into chemical constituents and explained in its entirety by physical and chemical laws working at the molecular level. But the middle way denies just as strenuously that this failure of reductionism records any mystical property of life, any special “spark” that inheres in life alone. Life acquires its own principles from the hierarchical structure of nature. As levels of complexity mount along the hierarchy of atom, molecule, gene, cell, tissue, organism, and population, new properties arise as results of interactions and interconnections emerging at each new level. A higher level cannot be fully explained by taking it apart into component elements and rendering their properties in the absence of these interactions. Thus, we need new, or “emergent,” principles to encompass life’s complexity; these principles are additional to, and consistent with, the physics and chemistry of atoms and molecules.

This middle way may be designated “organizational,” or “holistic” it represents the stance adopted by most biologists and even by most physical scientists who have thought hard about biology and directly experienced its complexity. It was, for example, espoused in what may be our century’s most famous book on “what is life?”—the short masterpiece of the same title written in 1944 by Erwin Schrödinger, the great quantum physicist who turned to biological problems at the end of his career. Schrödinger wrote:

Schrödinger then presents a striking analogy. Compare the ordinary physicist to an engineer familiar only with the operation of steam engines. When this engineer encounters, for the first time, a more complicated electric motor, he will not assume that it works by intrinsically mysterious laws just because he cannot understand it with the principles appropriate to steam engines: “He will not suspect that an electric motor is driven by a ghost because it is set spinning by the turn of a switch, without boiler and steam.”

Ernest Everett Just, a thoughtful embryologist who developed a similar holistic attitude as a direct consequence of his own research, was born 100 years ago in Charleston, South Carolina.
^*
He graduated as valedictorian of Dartmouth in 1907 and did most of his research at the Marine Biological Laboratory of Woods Hole during the 1920s. He continued his work at various European biological laboratories during the 1930s, and was briefly interned by the Nazis when France fell in 1940. Repatriated to the United States, and broken in spirit, he died of pancreatic cancer in 1941 at age fifty-eight.

Just began as an experimentalist, studying problems of fertilization at the cellular level, and in the great tradition of careful, descriptive research so characteristic of the “Woods Hole school.” As this work developed, and particularly after he left for Europe, his career entered a new phase: he became fascinated with the biology of cell surfaces. This shift emerged directly from his interest in fertilization and his particular concern with an old problem: How does the sperm penetrate an egg’s outer membrane, and how does the egg’s surface then react in physical and chemical terms? At the same time, Just’s work took on a more philosophical tone (although he never abandoned his experiments), and he slowly developed a holistic, or organizational, perspective midway between the caricatured extremes of classical mechanism and vitalism. Just expounded this biological philosophy, a direct result of his growing concern with the properties of cell surfaces considered as wholes, in
The Biology of the Cell Surface
, published in 1939.

Just’s early work on fertilization was a harbinger of things to come. He was not particularly interested in how the genetic material of egg and sperm fuse and then direct the subsequent architecture of development—a classical theme of the reductionist tradition (an attempt to explain the properties of embryology in terms of genes housed in a controlling nucleus). He was more concerned with the effects that fertilization imposes upon the entire cell, particularly its surface, and on the interaction of nucleus and cytoplasm in subsequent cell division and differentiation of the embryo.

Just had an uncanny knack for devising simple and elegant experiments that spoke to the primary theoretical issues of his day. In his very first paper, for example, he showed that, for some species of marine invertebrates at least, the sperm’s point of entry determines the plane of first cleavage (the initial division of the fertilized egg into two cells). He also proved that the egg’s surface is “equipotential”—that is, the sperm has an equal probability of entering at any point. At this time, biologists were pursuing a vigorous debate (here we go with dichotomies again) between preformationists who held that an embryo’s differentiation into specialized parts and organs was already prefigured in the structure of an unfertilized egg, and epigeneticists who argued that differentiation arose during development from an egg initially able to form any subsequent structure from any of its regions.

By showing that the direction of cleavage followed the happenstance of a sperm’s penetration (and that a sperm could enter anywhere on the egg’s surface), Just supported the epigenetic alternative. This first paper already contains the basis for Just’s later and explicit holism—his concern with properties of entire organisms (the egg’s complete surface) and with interactions of organism and environment (the epigenetic character of development contrasted with the preformationist view that pathways of later development lie within the egg’s structure).

I believe that Just’s mature holism had two primary sources in his earlier experimental work on fertilization. First, Just distinguished himself at Woods Hole as the great “green thumb” of his generation. He was a stickler for proper procedure and cleanliness in the laboratory. He had an uncanny rapport with the various species of marine invertebrates that inhabit the waters about Woods Hole. He knew where to find them and he understood their habits intimately. He could extract eggs and keep them normal and healthy under laboratory conditions. He became the chief source of technical advice for hotshot young researchers who had mastered all the latest techniques of experimentation but knew little natural history.

Just therefore understood better than anyone else the importance of healthy normality in eggs used for experiments on fertilization—the integrity of whole cells in their ordinary conditions of life could not be compromised. Over and over again, he showed how many famous experiments by eminent scientists had no validity because they used moribund or abnormal cells and their results could be traced to these “unlifelike” conditions, not to the experimental intervention itself. For example, Just refuted an important set of experiments on abnormalities of development produced when eggs are fertilized by sperm of another species. He proved that the peculiar patterns of embryology must be traced, not to the foreign sperm itself, but to the moribund state of eggs produced by environmental conditions (of temperature and water chemistry) necessary to induce the abnormal fertilization, but uncongenial for the eggs’ good health.

Just derided the lack of concern for natural history shown by so many experimenters who knew all the latest about fancy physics and chemistry, but ever so little about organisms. They referred to their eggs and sperm as “material” (I have the same reaction to modern reductionists who call the living cells and organs of their experiments a “preparation”) and accepted their experimental objects in any condition because they couldn’t distinguish normality from abnormality: “If the condition of the eggs is not taken into account,” Just wrote, “the results obtained by the use of sub-normal eggs in experiments may be due wholly or in part to the poor physiological condition of the eggs.”

Second, and more important, Just’s twenty years of research on fertilization led directly, almost inexorably, to his interest in the cell’s surface and to his holistic philosophy. Since his work, as previously mentioned, centered upon the changes that cell surfaces undergo during fertilization, Just soon realized that the cell’s surface was no simple, passive boundary, but a complex and essential part of cellular organization:

Later, pursuing a common concern of holistic biology, Just emphasized that the cell surface, as the domain of communication between organism and environment, embodies the theme of interaction—an organizational complexity that cannot be reduced to chemical parts: