Is nature really red in tooth and claw?

Is nature really red in tooth and claw? – importance of cooperation in nature

Anne Fausto-Sterling

Maybe it’s time to stop thinking of the world as a dog-eat-dog sort of place.

RECENTLY, WHILE FLIPPING THROUGH THE TV channels, I stumbled across an advertisement for a nature series entitled The Trials of Life. The language of the ad, which promised “uncensored, shocking, explicit footage” and scenes of a “savage and untamed realm,” made the series sound like an X-rated flick. Watching it–so claimed the ad–would make me change how I looked at myself and nature. I would find out why we call our biological kin (and presumably ourselves?) animals.

I was astounded. True, ever since Darwin, Western European and American scientists have perceived nature as fiercely competitive–“red in tooth and claw,” in the lurid words of Alfred, Lord Tennyson. Modern textbooks still like to talk of cutthroat competition, of the survival of the fittest, as the overriding force that drives evolution and determines the way species interact. Yet research in the past two decades shows that cooperation among species plays at least as big a role as violent struggle. “Symbioses are the rule rather than the exception; organisms … are always associated with other organisms,” according to Betsey Dyer, a biologist at Wheaton College in Massachusetts. Without considerable collaboration, life on Earth as we know it would not have existed, let alone flourished.

The neglect of nature’s cooperative side is all the more surprising when you consider that even the most extreme form of togetherness–the symbiotic alliance of two entirely different species–was recognized well over a century ago. (The Greek word symbiosis–meaning “to live together”–was first used in biology by the German botanist Heinrich Anton de Bary in 1879.) Yet for reasons that had less to do with science than with history, most scientists and thinkers chose to ignore the phenomenon. Strikingly, those who did appreciate the degree of cooperation going on in the natural world were often those who espoused a vision of cooperation in human society–notably the gentle nineteenth-century Russian revolutionary Pyotr Kropotkin, the German socialist Friedrich Engels, and, in the 1940s, the American Quaker Warder C. Allee. Scientists live in the real world, not in ivory towers, and their ideas develop in a social context. Perhaps that’s why a more cooperative view of life is making a comeback. The flower children of the 1960s are the working scientists of the 1990s. The cold war is over. The fragile state of our planet is uniting us in alarm. And suddenly, it seems, you can find cooperation in plants and animals wherever you look–suggesting a whole new view of evolution and interdependence among all forms of life.

Symbiosis and mutualism (for the purposes of this article, we can safely ignore the technical distinctions between them) both refer to instances in which organisms live together and help one another out. The organisms can be of vastly differing species, such as an anemone and a hermit crab, or reef-building corals and algae. Many of these arrangements are truly astonishing, and it’s tempting to dwell on the most dramatic. How can I not mention the flashlight fish, which lures luminescent bacteria into chambers inside its body and then uses the cultures to light its way through the dark ocean and signal other flashlighters about sex and danger?

But such showy examples of symbiosis are probably not as important as some of the less visible ones. The most extensive symbiotic interactions occur underground. Here one encounters a vast subterranean network of relationships between fungi and the root systems of higher plants. The technical term is mycorrhizal symbiosis (myco means fungal, and rhizal refers to the roots). Work in the past decade suggests that at least 6,000 fungal species can interact with more than 300,000 types of higher plants; indeed, at least 70 percent (and some believe 100 percent) of all trees, grasses, shrubs, and flowers thrive because of lifelong underground interactions with one or sometimes several fungi. These fungi may grow on the root surfaces or penetrate deep into the plant’s root cells. They also send fruiting bodies–which we recognize as mushrooms–up above the ground.

What do the plants give to the fungi? Green plants engage in photosynthesis: they take carbon dioxide from the air and convert it into organic carbon, the stuff of which we are all built. To carry out this rather neat trick of making food from thin air, they use structures called chloroplasts within their cells. Fungi, though, have no chloroplasts and hence cannot make their own carbon compounds. But by living in the plant’s root system they can use some of what the plant makes. Traditional ecology teaches that the mushrooms that grow on the forest floor get their carbon from decaying vegetable matter. Students of symbiosis, however, have shown that most of these fungi get their organic goodies more directly–from the roots of the living plants they inhabit.

THAT’S GREAT FOR THE FUNGI, BUT what’s in it for the plants? A plant uses its roots to take in water and nutrients, such as minerals and trace elements found in the soil that are essential to healthy growth. The larger the spread of their roots, the bigger the area they can feed off. In times of drought, for example, a plant with a widespread root system will do better than one that covers only a small area. Enter the fungi. They live underground, forming vast threadlike nets that can cover miles of territory; their association with plant roots extends the area the roots can use, improving a plant’s nutrient uptake. There are also fungi that stimulate plants by producing growth hormone. In addition, fungi protect plants by sopping up potential toxins. Some varieties even defend the root system against small roundworms, using their filament nets to trap and digest them.

Just how beneficial is this relationship? In 1990 a group headed by F.T. Last, a biologist at the University of Edinburgh, showed that conifer seedlings with few fungi in their roots grew only two inches in two years, whereas those provided with 10,000 fungi reached ten inches–a fivefold improvement.

Occasionally symbiotic relationships involve dozens of interacting organisms. Like other animals, termites can’t digest cellulose, the major component of wood. So how do they manage to digest the wood chewed out of your house or a decaying tree stump? They get by with a little help from their friends–as many as 40 different species of bacteria, spirochetes (long, mobile bacteria), and protozoa (single-celled creatures) living inside the termite gut. These bacterial and protozoan symbionts convert cellulose into sugar to feed both themselves and their termite hosts. Without their helpers, termites could chomp wood ad nauseam, but they’d starve to death.

Even more fascinating, the terminte symbionts have symbionts. One of the most prominent residents of the termite gut is a large protozoan called a polymastigote. This beast has thousands of spirochetes attached to its surface, giving it the appearance of a shaggy-dog cell. Propelled by these spirochetes, the polymastigote swims about the gut, scooping up and digesting wood fragments. Other tiny, rodlike bacteria live on the surface near the spirochete attachment points, possibly providing the chemical energy needed for all this motion, but the actual role of these and many other termite gut organisms is still speculative. The polymastigote, for example, also has bacteria and spirochetes living inside its single-celled body, but what their metabolic functions might be is anyone’s guess.

The termite system for digesting the indigestible may also shed light on the forces that shaped the insects’ social behavior. Many termintes live in large nests, in a complex colony headed by an egg-laying queen. Egg laying, however, presents a problem for them. The egg is sterile; none of the gut symbionts are inside. To avoid starvation the new larvae must get a dose of gut microorganisms by licking the anuses of their caretakers–more mature larvae destined to become soldiers, workers, and reproducers. This vital communication between colony members of different ranks may have been the starting point for all the complex behaviors that keep everyone in the group doing the right things at the right time. In other words, social behavior may have evolved because of the need to transfer essential microorganisms from one generation to the next.

The polymastigote, made hairy by its coat of many spirochetes, also hints at how the cells of higher organisms developed in the first place. The idea that our cells are colonies of microbes was first suggested in the 1920s by the American biologist Ivan Wallin. Now, largely because of the advocacy of University of Massachusetts biologist Lynn Margulis, the idea has gained a foothold in contemporary thought. (Indeed, her marshaling of the evidence transformed Wallin from scientific crank into visionary.) The story goes something like this: In the beginning there was almost no free oxygen in Earth’s atmosphere. The first bacteria to evolve were thus anaerobic–able to survive without oxygen. Next some bacteria developed photosynthesis. They used energy from sunlight to make organic carbon from gases in the atmosphere, releasing oxygen in the process. Eventually other bacteria used oxygen to breathe. The diversity and talents of bacterial species increased. Some became excellent swimmers by developing whiplike flagella, which act like propellers, while others crept around like amoebas, extending pseudopodia (“false feet”) to pull themselves along.

The future of higher plants and animals, however, depended on a major new evolutionary step. Bacteria are relatively simple cells–sometimes likened to bags of enzyme soup with genetic material floating in it–but the cells of higher organisms are far more complicated. Just as our bodies have organs such as the heart, lungs, and stomach, our cells have minuscule organelles. They include the nucleus (containing chromosomes packed full of genes), sausage-shaped mitochondria (charged with the task of respiration), and versatile, tubelike structures called centrioles. Centrioles form the templates for making the long flagella and short, undulating cilia that cells use for locomotion. And they play a vital part in a cell’s reproduction: they help chromosomes divide accurately when the cell splits in two, thus ensuring the faithful transfer of genetic information to the next generation. Plant cells have another organelle besides. This is the chloroplast, the structure mentioned earlier that carries out photosynthesis, converting atmospheric carbon to the organic building blocks on which life depends.

HOW DID THESE MORE COMPLEX cells evolve from primordial bacteria? Margulis explains it using the “serial endosymbiotic theory” of cell evolution. In the early 1970s she proposed that way back when, some oxygen-breathing bacteria might have invaded some anaerobic amoebalike bacteria and struck a deal–we’ll breathe for you if you will creep out into new high-oxygen-containing places to find food. There’s little doubt left that these oxygen-breathing bugs are the ancestors of our mitochondria.

The new hybrid then hooked up with some tubular spirochetes. Margulis thinks the friendship looked something like the one that developed between the termite polymastigote and its spirochete pals. The nimble spirochetes helped their partners navigate and find the best feeding spots and even helped gather food into their mouths. Eventually they became permanent fixtures. They helped the cell make flagella and cilia. In addition, they lost most of their own genetic material and instead helped their hosts reproduce. The original amoebalike bacterium, now composed of three organisms living in cozy symbiosis, became the cell (with a nucleus, mitochondria, and centrioles) now found in higher animals. Some of these originally single-celled creatures evolved into the multicellular organisms we know today as animals and fungi. Others acquired a photosynthetic bacterium and became algae: single-celled organisms that–like higher plants–harness the sun’s energy to make carbon.

Although some of Margulis’s ideas remain controversial, there’s mounting evidence from many laboratories that supports this symbiotic scenario. Indeed, since the mid-1970s scientific research into every aspect of mutualism and symbiosis has increased dramatically. Yet their importance is taking an astonishingly long time to sink in. The 1991 edition of a standard college biology textbook, An Introduction to Evolutionary Ecology, lists eight entries on competition in its index but only two on mutualism and none on symbiosis. A section entitled “Why are there so many species?” devotes four paragraphs to the role of competition but never mentions the idea that the acquisition of new symbionts plays a major role in the evolution of new species.

What is going on here? Why has cooperation been ignored by so many scientists for more than a century? And why has it been especially derided in the capitalist West? Has the vision of our economic and social world as a dog-eat-dog sort of place prevented us from giving mutualism its due?

History certainly suggests this is the case. During the late 1880s and early 1890s, for example, a debate between the British evolutionist T.H. Huxley and the Russian revolutionary and scientist Kropotkin spilled over into the pages of a London magazine called The Nineteenth Century. Huxley believed that competition was the driving progressive force of nature and that there was little sense in looking to nature for moral guidance. “From the point of view of the moralist,” he wrote, “the animal world is on about the same level as a gladiators’ show.” Kropotkin–in articles later gathered into a popular book called Mutual Aid–argued that Huxley was distorting Darwin’s original ideas. His keen observations of animals struggling to survive the harsh Siberian climate convinced him that mutualism was a major influence in nature: far from relentlessly competing against one another, most animals cooperated in the interest of survival. Ultimately these observations led him to reject the exploitative brand of capitalism that had brought poverty and despair to many in his beloved prerevolutionary Russia.

For Kropotkin, biology pointed to a better way of life. But Huxley’s view of biology was widely taken to mean that capitalism–whatever its inequities–was simply following nature’s law. (To be fair to Huxley, though, he himself thought humans should rise above such nasty, brutish behavior.) Among the intellectuals preoccupied with this question was the Marxist socialist Engels. “The whole Darwinian theory of the struggle for existence,” he believed, was a “transference from society to organic nature.” Once thinkers transferred the idea of struggle from capitalist culture onto nature, he felt, it was only a matter of time before they moved “these theories back again, from natural history to the history of society.” To Engels’s mind, scientific theory grew from social belief and then was used to reinforce it.

The sparring between Huxley and Kropotkin mirrored an intense social-policy debate about competition and struggle in nineteenth-century Europe. That debate was framed, of course, by the effects of the industrial revolution, which had created undeniable wealth for some but had also caused tremendous hardship for others. In general, management tended to embrace the rawest competitive view of the world. Laborers, meanwhile, responded to the upheaval by forming unions and mutual-aid societies.

By the 1940s interest in mutualism had spread to the United States. One of its chief proponents was biologist Warder C. Allee, a Quaker who wanted to use his knowledge of zoology to build a world without war, and who, in 1949, wrote the influential book Principles of Animal Ecology; in contrast to current books, this text had multiple index entries under the topics of mutualism and symbiosis. But by the mid-1950s (the era of the cold war, McCarthyism, and anticommunist witch-hunts) the tide had turned. A quite different vision of ecology had once more taken hold–one in which organisms competed for resources.

It apparently took the turmoil of the late sixties and seventies, the years of flower power, antiwar marches, and civil rights activism, to open up some intellectual space for the revival of interest in mutualism and symbiosis. A bit of research by Douglas Boucher, a biologist and historian at the University of Quebec, illuminates the progression. In 1985 he searched for publications describing a particular mathematical model of mutualistic interactions. The first, published in 1935, had no companions until two more appeared in the mid-1960s. During the 1970s there were 17 publications, and the increased pace kept up throughout the 1980s.

Even so, acceptance is not coming nearly fast enough to satisfy Brown University biologist Mark Bertness. Bertness studies the interaction between various species that inhabit New England’s salt marshes. In benign conditions, these organisms compete, but under stressful conditions, he’s found, they behave in mutually beneficial ways. To wrest a toe-hold from the sea, for example, large numbers of ribbed mussels settle in among the small marsh grasses growing on exposed coastal mud flats. The mussels use threads to attach to the marsh grasses, which in turn help anchor the soil and other less hardy grasses. In addition, they nourish the plants by defecating right above their root systems. “It’s a perfect case of mutualism,” says Bertness. The mud flats are also home to legions of fiddler crabs. Like thousands of John Deere tractors, the crabs plow through the soil, aerating it and making it easier for grass roots to establish themselves. “If you take them away,” says Bertness, “grass production drops by about 50 percent in one growing season.”

Bertness’s general message is that when the going gets tough, the tough cooperate. But his message meets with a lot of flak. His critics argue that findings about mussels, crabs, and marsh plants are not applicable to other ecological systems, such as forest and grassland. “It’s a mind-set,” says Bertness, convinced that what a scientist already believes conditions what he or she looks for. “These kinds of interactions are going to be common in forests and grasslands too,” he insists. “It’s all dependent on the physical regime–benign or harsh.”

Where does this leave us? First, a strong case can be made for viewing nature as a socialist cooperative (“green in root and flower,” as Boucher has written to counteract Tennyson’s “red in tooth and claw”). I suspect that eventually a balanced view will emerge–of organisms influenced as much by cooperation as by struggle. But it will not happen because we suddenly discover mutualism and symbiosis. We already know a lot about these processes, and it is clear that they are widespread and of great importance in ecology and evolution. Only a change in social ambience will permit these already existing ideas to be incorporated into the mainstream of biological thought.

Scientific knowledge does not, after all, grow in a vacuum. It does not simply bubble forth from the wellsprings of nature. Nor is it driven forward by the sheer force of ideas. Instead we construct it with whatever tools of thought are available in our particular culture and moment in history. Perhaps, if we ever really do become a kinder, gentler nation, mutualism and symbiosis will be given the place in scientific theory that they surely deserve.

COPYRIGHT 1993 Discover

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