The Story of Western Science

by Susan Wise Bauer

  Almost imperceptibly, DNA was being granted the power to determine who we are, rather than merely what we are. And this impulse was carried along by a field of study that existed even before the Watson-Crick model sprang into being: population genetics.

  Population genetics was intimately related to the “modern synthesis” of the 1930s and 1940s, which had attempted to reconcile cell-level research with the larger story of organic life, the history of the entire species with individual discoveries in microbiology.

  In the same decade that T. H. Morgan and his team were mapping fruit fly genes, the English biologist and statistician Ronald Fisher was examining the odds that those genes would emerge in any given generation. Fisher—a twin whose brother had died shortly after birth, a Cambridge-trained mathematician who was more interested in the life sciences than in his own field of study—is often credited, along with Julian Huxley, Ernst Mayr, the British mathematician and biologist J. B. S. Haldane, and a few others, as a creator of the modern synthesis. In the 1930s, Fisher championed the idea that the probability of certain genetic information passing from one parent to one child could be calculated, and that these calculations could be crunched into an even more basic conclusion: a number predicting which individuals might survive, and which might die.2

  This was a paradigm-shifting idea. A century earlier, the “will to live” had been simply accepted as part of what it meant to be human. It was an ineffable, incalculable factor, a survival “instinct” that could not be reduced to physical factors (actually, not so different from the present day).

  But now, Fisher was proposing a quantitative definition of the will to live—one that had a chemical basis, ungrounded in the free human psyche. The will to live (“fitness,” in Darwinian terms) had to do with body instead of spirit, organs instead of determination. It depended on a certain combination of genes, which Fisher envisioned as a bag of factors that behaved not unlike gas molecules in a chemical laboratory: randomly mixing, mating, and replicating.

  That mixture of genes might lead to a longer claw, a more powerful muscle, better camouflage coloring, or a characteristic refusal to lie down and die. But all four were the product of gene mixtures; all four could be predicted, should your mathematics be good enough. Courage, like a sharp tooth, was a genetic characteristic—not a transcendent quality. And good math meant that you could predict how often (and, very roughly, where) courage, or sharp teeth, would show up in later generations. Population genetics attempted to do just this: to calculate when genetic variants would show up as changes in appearance or behavior, and then to compare those predictions with the characteristics of a current population of plants, or animals, or (even) people.3

  Population genetics was a tricky, squeaky, infant field. Its early practitioners worked on the assumption that alleles (particular forms of a gene, located at specific places on the chromosome) could be passed from parent to child; the round shape of a pea was determined by an allele, as was an oblong and wrinkled shape. Where these characteristics might show up was mostly, although not entirely, a mathematical calculation: “At present,” J. B. S. Haldane wrote in 1938, “one may say that the mathematical theory of evolution is in a somewhat unfortunate position, too mathematical to interest most biologists and not sufficiently mathematical to interest most mathematicians. Nevertheless, it is reasonable to suppose that in the next half century it will be developed into a respectable branch of Applied Mathematics.” 4

  Haldane himself was already committed to the mathematical theory of evolution. Even before knowing exactly how genetic information was transmitted to the next generation, he had theorized that our will to survive was related to the urge to preserve our particular alleles. Famously, when asked whether he would be willing to sacrifice himself for a brother, he gave a mathematician’s answer: “No,” he reputedly replied. “Two brothers or eight cousins.” Both would preserve the same amount of genetic material.5

  After publication of the Watson-Crick model, that “genetic material” was more clearly understood: the will to survive was related to the desire to protect, and pass on, a particular arrangement of DNA. In the early 1960s the English biologist William D. Hamilton proposed that DNA preservation could explain unselfish behavior, such as self-sacrifice. His hypothesis, nicknamed “Hamilton’s Rule,” suggested that altruism is always found in closely related organisms; when one creature sacrifices itself for another, it is always because they share genes. When a mother bird leads a cat away from her nest, at risk to her own life, the real beneficiary of this self-sacrificing behavior isn’t the young birds; it is the mother’s DNA, which has already been reproduced in her babies and now must be protected.

  Hamilton pointed out that this theory explained an odd behavior in bees and ants: females in both species will sacrifice their babies to protect their sisters. Bees and ants have a particular kind of reproduction called haplodiploidy. Some of their eggs mature into adults without being fertilized by males; these eggs (oddly enough) produce male offspring. Eggs that are fertilized by mature males hatch into females. As a result, males have only one set of chromosomes, while females have two—which means that female bees and ants have more genes in common with their sisters than with their own offspring.6

  This, Hamilton concluded, was why an ant will share food with her sisters and allow her children to starve. The probability of unselfishness, and its potential beneficiaries, could be calculated from the amount of DNA that two living creatures shared: the mathematics of altruism.

  A few years later, the American chemist and geneticist George Robert Price proposed an equation that could predict such behavior: Price’s Equation, an expression of the relationship between the genetic material of a parent and the genetic material in successful offspring. The equation,

  Δ = Cov(wi,zi) + E(wi Δzi)

  where w stands for the fitness of an organism, and z for a particular attribute, can be used to predict the appearance, or absence, of any measurable trait: “an exact, complete description of evolutionary change under all conditions,” as evolutionary biologist Steven A. Frank puts it. (Right after publishing this equation, Price converted to Christianity and gave away most of his goods to the homeless and poor; five years later he killed himself.)7

  In 1976 the Oxford biologist Richard Dawkins published The Selfish Gene, a book that incorporated Hamilton’s Rule, Price’s Equation, and insights from population genetics into a macroexplanation: a comprehensive scientific explanation for all organic life, including ours. “Intelligent life on a planet comes of age when it first works out the reason for its own existence,” Dawkins begins, and the reason he has worked out is a simple one: we eat, sleep, have sex, think, write, build space vehicles and war machines, sacrifice ourselves or others, all in order to preserve our DNA. Natural selection happens at the most basic level, the molecular; our bodies have evolved to do nothing more than protect and propagate our genes, which are ruthlessly selfish molecules working to ensure their own survival.8

  It was not a comforting view of the world, and The Selfish Gene roused quite a bit of public furor. But Dawkins’s conclusions were simply the logical outworking of the implications of Darwinian natural selection, combined with insights from the previous decades of population genetics and microbiology.

  He had certainly not “invented the notion . . . that the body is merely an evolutionary vehicle for the gene” (as one science book claims), any more than Watson and Crick had “discovered” DNA. In fact, in 1975, the year before The Selfish Gene was published, the biologist E. O. Wilson had concluded (in the first chapter of his text Sociobiology) that “the organism is only DNA’s way of making more DNA.” But Dawkins was a good writer and a capable rhetorician, and The Selfish Gene managed to spell out the implications of this idea with particular clarity, accessible both to lay readers and to students of the life sciences. In the words of evolutionary biologist Andrew Read, a doctoral candidate when the book came out, “The intellectual framework had already been in t
he air, but The Selfish Gene crystallized it and made it impossible to ignore.”9

  •

  The American biologist E. O. Wilson was hard on Dawkins’s heels.

  Twenty years earlier, Wilson had earned his reputation by demonstrating that the complex and sophisticated behavior patterns of fire ants were, in fact, based on chemical signals. Entomologists had struggled to explain how fire ants managed to communicate clearly with each other (were they tapping their antennae? stroking each other’s bodies? emitting some other signal?). One possible explanation was that the ants were giving off chemical cues, but no one had identified how. Wilson, just turned thirty and fresh from his PhD, was trying all sorts of odd things with fire ants (“uncontrolled experiments,” he called them much later, “quick and sloppy . . . performed just to see if you can make something interesting happen”). He tried to turn a line of marching ants with a powerful magnet. (“The ants couldn’t care less.”) He tried chilling colonies and switching their queens to see if he could mix different species together; this actually worked. And he picked out all of the major organs in the abdomen of worker ants, most of the organs no thicker than a single thread, and tried to identify one of them as the emitter of those theoretical chemical signals.10

  One of the organs, the “almost invisible” Dufour’s gland, just above the sting, came up positive. When Wilson used the dissected gland to mark a trail, other fire ants poured out of their nest to follow it. Wilson had proved the existence of pheromones, chemical substances that have the power not merely to direct, but also to intensify, galvanize, change behavior.

  Behavior rests on chemistry: this became one of the cornerstones of Wilson’s approach to organic life. His evolving philosophy was disciplinary reductionism; insights from physics and chemistry, demonstrable through experimentation, able to be confirmed by calculation, were the bedrock of all human knowledge. Biology rests on this bedrock; biological laws are directly derived from physical and chemical principles. And the social sciences—psychology, anthropology, ethology (natural animal behavior), sociology—float above, entirely dependent upon the “hard” sciences beneath.11

  In the early 1960s, Wilson encountered Hamilton’s work on the preservation of DNA in related organisms, a theory that had now been labeled “kin selection”: “I became enchanted,” Wilson later wrote, “by the originality and promised explanatory power of kin selection.” As he continued to study insect behavior, he—like Dawkins—synthesized biochemical discoveries, population genetics, kin selection, and his own field observations into two texts that became classics. The Insect Societies (1971) argued that ant colonies behave like organisms, dividing labor, individuals sacrificing themselves for the whole, each ant less an individual than a part of the whole, a cog in the machine; the behavior of this entire society could be explained, predicted, entirely accounted for by physical and chemical factors.12

  And then, in 1975, Wilson published Sociobiology: The New Synthesis, which extended the same argument to all societies, including ours. Human behavior, no less than ant actions, resulted from nothing more transcendent than physical necessity. Even seemingly intangible feelings and motivations (hate, love, guilt, fear) are

  constrained and shaped by the emotional control centers in the hypothalamus and limbic system of the brain. . . . What, we are then compelled to ask, made the hypothalamus and limbic system? They evolved by natural selection. . . . The hypothalamus and limbic system are engineered to perpetuate DNA.13

  We are flooded with remorse, or the impulse to altruism, or despair, only because our brains (independent of our conscious knowledge) are reacting to our environment in the way that will best preserve our genes.

  “Sociobiology,” then, was the attempt to understand human society solely as a product of biological impulse. Ethics, philosophy, sociology, psychology: Wilson predicted that all would give way to real science, which, in the last analysis, boiled down to molecular biology.

  The conventional wisdom also speaks of ethology, which is the naturalistic study of whole patterns of animal behavior, and its companion enterprise, comparative psychology, as the central, unifying fields of behavioral biology. They are not; both are destined to be cannibalized by neurophysiology and sensory physiology from one end and sociobiology and behavioral ecology from the other. . . . The future, it seems clear, cannot be with the ad hoc terminology [and] crude models . . . that characterize most of contemporary ethology and comparative psychology. Whole patterns of animal behavior will inevitably be explained within the framework, first, of integrative neurophysiology, which classifies neurons and reconstructs their circuitry, and, second, of sensory physiology, which seeks to characterize the cellular transducers at the molecular level.14

  “I hope not too many scholars of ethology and psychology will be offended by this vision,” Wilson added, which was unreasonably optimistic. Social scientists, as well as a healthy number of biologists, reacted with predictable outrage. In the fall of 1975, a group of scientists that included Wilson’s Harvard colleague Stephen Jay Gould formed an opposition organization called the “Sociobiology Study Group,” and published its objections in an open letter in the New York Review of Books. Wilson’s sociobiology, they pointed out, was deterministic: it removed free will and choice from human society, making our current state seem inevitable.

  Determinist theories . . . consistently tend to provide a genetic justification of the status quo and of existing privileges for certain groups according to class, race or sex. Historically, powerful countries or ruling groups within them have drawn support for the maintenance or extension of their power from these products of the scientific community. . . . These theories provided an important basis for the enactment of sterilization laws and restrictive immigration laws by the United States between 1910 and 1930 and also for the eugenics policies which led to the establishment of gas chambers in Nazi Germany.

  Wilson’s Sociobiology, the writers protested, was simply another version of these same dangerous ideas.

  [Its] supposedly objective, scientific approach in reality conceals political assumptions. Thus, we are presented with yet another defense of the status quo as an inevitable consequence of “human nature.” . . .

  Wilson joins the long parade of biological determinists whose work has served to buttress the institutions of their society by exonerating them from responsibility for social problems. From what we have seen of the social and political impact of such theories in the past, we feel strongly that we should speak out against them.15

  Wilson’s response, which was to accuse his opponents of Marxism, didn’t advance the discussion much.

  But while the name-calling continued, other biologists, biochemists, and geneticists rallied behind Sociobiology. Over the next twenty years, Wilson’s “new discipline” would give birth to yet another science: evolutionary psychology.

  Wilson came to his own defense with On Human Nature. Published three years after Sociobiology, the book focused in, more closely, on humans. All of Sociobiology except for the last chapter had been based on animal research: “The final chapter,” Wilson later mused, “should have been a book-length exposition. . . . to address in a focused manner the main objections that had arisen and yet might arise from political ideology and religious belief. . . . [I wrote] On Human Nature in an attempt to achieve these various ends.”16

  On Human Nature did not back away from the “admittedly unappealing” conclusions of Sociobiology: “The human mind,” Wilson began, “is a device for survival and reproduction, and reason is just one of its various techniques.” He then explained how each of our most treasured attributes arise from our genes (so, for example, “The highest forms of religious practice . . . can be seen to confer biological advantage,” not to mention that “genetic diversification, the ultimate function of sex, is served by the physical pleasure of the sex act”). And he closed his screed with a paean to scientific thinking:

  [its] repeated triumphs in explaining and controlling
the physical world; its self-correcting nature open to all [who are] competent to devise and conduct the tests; its readiness to examine all subjects sacred and profane; and now the possibility of explaining traditional religion by the mechanistic models of evolutionary biology. . . . In the end . . . the evolutionary epic is probably the best myth we will ever have.17

  Like James Watson and Richard Dawkins, Wilson proved to be a talented writer, with a knack for powerful metaphors. On Human Nature was praised, excoriated, and read; it was an instant best seller, and in 1979 it won a Pulitzer Prize.

  •

  In 1981, Stephen Jay Gould struck back.

  Gould, twelve years Wilson’s junior, had already secured his place in the pantheon of evolutionary biologists by proposing (along with Niles Eldredge) a halfway place between uniformitarianism and catastrophism: punctuated equilibrium, the theory that species remain essentially the same for very long periods of time, interspersed with (relatively) fast periods of significant change. And, like Wilson, Gould was a good writer: a regular essayist for the general-interest magazine Natural History; the author of numerous professional works, as well as two highly popular science books for the general public.