Review

February 2009

	Bert Hölldobler and Edward O. Wilson. Click their portraits to see what these men are made of. Images created by Steven R. Black

Could an Ant Colony Read This Book?

By Robert R. Dunn

The Superorganism: The Beauty, Elegance,
and Strangeness of Insect Societies
by Bert Hölldobler and Edward O. Wilson
(W.W. Norton, 2008; $55.00)

IN BIOLOGY one can spend a lifetime studying an obscure sliver of life—be it fish ovaries, flea legs, or the mites that live in the nostrils of birds. It’s often that obsessive focus that makes broader truths come clear. Edward O. Wilson and Bert Hölldobler exemplify that peculiar truism. They met in 1969 when Wilson was a forty-year-old professor at Harvard University and Hölldobler, thirty-three, had come from Frankfurt, Germany, to stay a year as a visiting scholar. Wilson was already well known for his studies of chemical communication and biogeography. Hölldobler was just beginning his work as a behavioral ecologist. They did not know it, but they were about to forge an enduring collaboration, “built” (in Wilson’s words) “upon a close friendship and a common lifelong commitment to the study of ants.” Together they would write tens of papers and three books, among them a Pulitzer Prize winner: their epic 700-page treatise, The Ants (1990).

	Click book covers for ordering information.

That said, the two have led very different lives as scientists. Hölldobler has remained doggedly focused on ants, nearly always experimentally. He has revealed the intricacies of ant communication and how that communication—whether by scent, touch, or sound—underlies cooperative behavior.

Wilson, instead, has used a worldview developed from his study of ants to do foundational and often controversial work in broader areas. He popularized the term sociobiology and literally wrote the book on the evolution of human social behavior (two books, in fact: Sociobiology: The New Synthesis, 1975, and On Human Nature, 1978—the latter also a Pulitzer Prize winner). At the time, the idea that genes controlled our actions sparked outrage. In his 1984 book Biophilia, Wilson refined and built on the hypothesis that we humans have an inherent fondness for nature, rooted in our genes. But with advancing age, Wilson too has come back to the ants: he even has a novel forthcoming that features them.

Now Hölldobler and Wilson have coauthored another major book, The Superorganism, which breathes new life into a notion that intrigued scientists before World War I: that a colony of social insects is analogous to an individual. The concept of the superorganism—which compares a colony’s members to a body’s cells and sometimes its nest to the body’s skeleton—fell out of favor as research increasingly focused on the genes of individuals. Hölldobler and Wilson, building on new insights into the evolution and workings of insect societies, seek to bring it back. To them, “superorganism” is more than a metaphor; it is a unit in the hierarchy of biological organization, falling somewhere between an ecosystem and an individual. And, they argue, it is the most useful level of biological organization at which to examine how pieces are assembled to make a whole—be it an association of bacteria, a single creature, or a whole society—as well as to understand what holds all organisms together, even when the pieces struggle toward independent goals.

In the history of life, there have been only a few occasions when separate individuals have come together to cooperate and, in doing so, have become so well integrated that we now recognize them as a single organism. Those include the origin of cells with mitochondria, from an early symbiosis between two different species of bacteria; plant cells, which arose when a eukaryotic cell (a cell with a nucleus) incorporated a photosynthetic bacterium, the grandmama of all chloroplasts; and multicellular creatures in general, which have arisen multiple times. To those, Hölldobler and Wilson would add the more sophisticated colonies of social insects (leaf-cutter ants, some termites, honeybees, and the like).

THE AUTHORS BEGIN THEIR new book by considering the origins of societies. In doing so they set out to explain why the workers of many species of ants, bees, wasps, and termites give up reproduction, either partially or completely, to work for their overbearing mother. The simplest model of natural selection is that genes are carried by individual organisms, and that heritable genes belonging to the individuals that are more successful at surviving and reproducing will proliferate. But when the costs of going it alone are great and individuals living or working together are related, a model referred to as “kin selection” comes into play. If success in evolution revolves around passing on your genes, you should be willing to die for, maybe not one, but two brothers, because, on average, each shares half your genes.

That is the traditional view of how sociality has evolved. But both Hölldobler and Wilson argue that group selection (in addition to individual selection) is a crucial component of evolution in insect societies. In group-selection models, evolution favors the groups whose members cooperate more effectively, regardless of whether such cooperation helps a given individual (or that individual’s kin) reproduce. The two colleagues, however, hold somewhat different views.

Hölldobler sees the evolution of insect societies as proceeding along stepping stones. In a paper written jointly with the evolutionary biologist Hudson Kern Reeve, of Cornell University, he has stated that individual insects in nascent societies only cooperate with their closest relatives, while still competing with other group members for the right to pass on the most genes. As societies grow larger and more complex, however, competition among colonies grows fiercer, and as a consequence, group selection begins to act. It is at this stage that Hölldobler sees insect societies as making the transition to superorganisms: conflict among individuals is restricted, workers never reproduce, and a colony begins to seem more and more like a body. Wilson, taking a more extreme position, has proposed a model that emphasizes group selection even for nascent colonies.

Such group selection models are controversial. Scientists who focus on genes—most vocal among them Richard Dawkins, author of The Selfish Gene—argue that selection on the gene is the real driving force behind selection on the individual, let alone the group. This clash of views is inherently compelling, perhaps in part because the question of why individuals cooperate seems so central to our own daily struggles.

Hölldobler and Wilson took five years to write The Superorganism—in part, one suspects, because they have attempted, as far as possible, to reconcile their differing opinions and to present a united front. Crucially, they agree that once societies reach a sufficient level of sophistication, they operate like organisms, becoming the primary targets on which selection acts, with the individual ants almost as limited in their autonomy as a body’s cells.

Time will tell whether the broader community of scientists agrees with the views expressed in The Superoganism. Perhaps Hölldobler and Wilson’s greater contribution, though, is their survey of the many ways that component individuals make highly evolved societies work efficiently, through simple behaviors governed by a hierarchy of rules—and the genes regulating those rules. How, in practice, does a superorganism function, when it depends upon “the combined operation of tiny and short-lived minds”?

Much of what prevents individual social insects from going their merry ways, and enables the most sophisticated societies to be so well integrated, involves communication and the division of labor. Within families such as that of the ants, Formicidae, social insects vary relatively little in their morphologies (that is why any three-year-old can learn to identify “an ant”). And much of the diversity in life histories, the basic ways of living, among species can be attributed simply to differences in chemical communication, caste systems, and perhaps also mutualisms—insect societies’ interdependencies with other partner species.

Although their book’s thesis potentially pertains to all social organisms, not just insects, Hölldobler and Wilson focus on ants, with bees relegated to a supporting role and only an occasional cameo by a wasp or termite. Some of the stories are already familiar, yet it is clear that dramatically more is now known about ants, particularly about variation among species, than when The Ants was published. Twenty years ago it would have been reasonable to talk about a typical ant colony in which a single queen mates once and produces eggs, the colony competes against all neighbors, and the fertile offspring fly to mate and start new colonies. No more. We now know of parthenogenetic ant species (in which males are unnecessary for reproduction); ant species that have no territorial boundaries among colonies; ant species in which all of the workers lay eggs; ant species in which many tens of queens but no workers lay eggs; species that have no workers at all; and species whose queens mate many times. Using the same basic parts, ants do it many ways.

In showing how much we have learned about the diversity of ant societies, Hölldobler and

	Robert R. Dunn is an ecologist in the Depart- ment of Biology at North Carolina State University in Raleigh. His first book, Every Living Thing: Man’s Obsessive Quest to Cata- log Life, from Nanobac- teria to New Monkeys, was recently published by Harper Collins/ Smithsonian.

Wilson also, inadvertently, show something else: how much we owe to their research. It is easy to think, for example, that the fact that ants lay pheromone trails to attract each other to food has always been common knowledge. But it was worked out in large part by Hölldobler and Wilson, as was a great deal else. Like their subjects, the two communicated, “grubbing around and talking back and forth.” They used division of labor (Hölldobler chasing down the mechanisms, Wilson thinking more broadly, integrating). Their successes are also due to their mutual respect as friends, and even to a bond of kinship. Wilson has called Hölldobler the younger brother he never had. They share no genes, but have done much for each other—and for the rest of us.

Bookshelf

February 2009

By Laurence A. Marschall

Six-Legged Soldiers: Using Insects as Weapons of War
by Jeffrey A. Lockwood (Oxford University Press, 2009; $27.95)

Humans, according to Aristotle, are the only political animals, but that hasn’t stopped insects from fighting alongside us in military conflicts worldwide since the dawn of civilization. The ancient Mayans, more than 4,500 years ago, filled gourds with stinging insects to harass would-be attackers. In a.d. 908 defenders of Chester, England, collected all available beehives and tossed them into tunnels dug by invaders, successfully repulsing a hostile army of Danes and Norwegians.

According to entomologist and science writer Jeffrey A. Lockwood of the University of Wyoming, who has combed the literature of ancient and modern warfare, military leaders have ignored insects at their own peril. Some infestations were relatively passive: mosquitoes carrying yellow fever successfully defended North America against Napoleonic incursions; during the Russian Revolution, typhus-bearing lice killed millions of civilians and combatants, prompting Vladimir Lenin to declare that “either socialism will defeat the louse, or the louse will defeat socialism.”

By the mid-twentieth century, the louse had lost. For that matter, the impact of all diseases on troops in the field lessened as the sciences of epidemiology and entomology were incorporated into the practice of military hygiene. But Lockwood’s arch-villain is General Ishii Shiro, who headed a vast Japanese biological-warfare effort called Unit 731 during World War II. General Ishii’s agency found numerous ways to infest opposing populations with disease-carrying insects. For instance, bombs and crop-duster planes filled with plague-infected fleas were tested “successfully” in China.

Undoubtedly many world super-powers, especially the United States and its former rival the Soviet Union, have mounted vigorous research in the use of insects as vectors for both human and agricultural disease. Documentation of modern military entomology, however, is hard to come by. Thus much of the second half of this book is rife with claims and counterclaims. Did the United States deploy plague-bearing insects in Korea or drop citrus-killing aphids on Castro’s Cuba? Regardless of whether any of these charges are provable, it’s clear from this chilling account that insect warfare is, even more than in the past, a formidable danger. “The proboscis,” as Lockwood grimly quips, is still “mightier than the sword.”

Eating the Sun: How Plants Power the Planet
By Oliver Morton (Harper Collins, 2008; $28.95)

All hail the chloroplasts! Oliver Morton loves those tiny organelles, and so should we, for our lives and our livelihoods depend on their diligent work in taking sunlight and turning it into chemical energy. The first third of this often poetic study of photosynthesis by journalist Morton is a “science procedural,” in the spirit of John McPhee’s Basin and Range, focusing on the investigators who have unlocked the secrets of photosynthesis.

As early as the late 1700s, English minister and teacher Joseph Priestley had advanced the idea that plants took something from the air (which we now know as carbon dioxide) and put something else back into the atmosphere that animals needed to live (oxygen); his Dutch contemporary Jan Ingenhousz figured out that they could do so only in sunlight. In 1804, Swiss scientist Nicolas-Théodore de Saussure grasped that plants were making food in the process. But the precise mechanism of that transformation wasn’t uncovered until the twentieth century, when, using newly discovered radioisotopes, scientists were first able to tag and trace atoms of carbon as they shuttled through the metabolic pathways of plants.

Readers outside the biochemical community are unlikely to recognize the names of the scientists who carried out this research— Andrew Benson, Robin Hill,

	Laurence A. Marschall is W.K.T. Sahm Professor of Physics at Gettysburg College in Pennsylvania, and coauthor, with Stephen P. Maran, of Galileo’s New Universe: The Revolution in Our Understanding of the Cosmos, published by BenBella Books.

and Martin Kamen, to name a few. But, as Morton makes clear through accounts of intellectual wrangling, their insights were as significant to our understanding of the wellsprings of life as the discovery of the structure of DNA. If Watson and Crick are better known to the public,perhaps it is because photosynthesis can’t be summarized as iconically as the double helix.

Plants are, of course, the reason why ours is the only planet in the solar system with an oxygen-rich atmosphere. Morton takes us back a couple of billion years to when photosynthetic bacteria opened the way for the profusion of life today. He convinces us that chloroplasts may be small, but as major consumers of sunlight and carbon dioxide, they play a crucial role in Earth’s energy balance. As we face the challenges of global warming and dwindling fossil-fuel reserves, an understanding of those green organelles may be the key to a sunny future for us all.

Copyright © Natural History Magazine, Inc., 2009