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Genes on the Brain

Promethean Fire: Reflections on the Origin of Mind

by Charles J. Lumsden, by Edward O. Wilson
Harvard University Press, 216 pp., $17.50

Immodest proclamation justly accompanies great discovery; who would gainsay Archimedes shouting “Eureka” through the streets of Syracuse, or announcing that his lever would move the earth if only he could find a place to stand. More often than not, however, immodest proclamation is a cover-up, conscious or not, for failure. When conscious, the tactic can be stunning in its audacity: let us simply declare victory and get out, Senator Aiken declared in the best potential solution I ever heard for the morass of Vietnam. When unconscious, it is hollow.

Both titles of Lumsden and Wilson’s book—and its content—record unconscious failure. They have discovered, they claim, the Promethean fire of our evolution, the key to an understanding of both the origin and the subsequent history of the human mind. This key, they proclaim, is a “largely unknown evolutionary process we have called gene-culture coevolution: it is a complicated, fascinating interaction in which culture is generated and shaped by biological imperatives while biological traits are simultaneously altered by genetic evolution in response to cultural innovation.”

In responding to criticisms that human sociobiology, in its debut as the last chapter of Wilson’s Sociobiology (1975), ignored culture for a crude form of genetic determinism, Lumsden and Wilson have now discovered culture and use it as half of a positive feedback loop to explain, with genetics as the other half, all the essentials of our mental evolution. Lumsden and Wilson summarize their concept of gene-culture coevolution in the following way:

The main postulate is that certain unique and remarkable properties of the human mind result in a tight linkage between genetic evolution and cultural history. The human genes affect the way that the mind is formed—which stimuli are perceived and which missed, how information is processed, the kinds of memories most easily recalled, the emotions they are most likely to evoke, and so forth. The processes that create such effects are called the epigenetic rules. The rules are rooted in the particularities of human biology, and they influence the way culture is formed….

This translation from mind to culture is half of gene-culture co-evolution. The other half is the effect that culture has on the underlying genes. Certain epigenetic rules—that is, certain ways in which the mind develops or is most likely to develop—cause individuals to adopt cultural choices that enable them to survive and reproduce more successfully. Over many generations these rules, and also the genes prescribing them, tend to increase in the population. Hence, culture affects genetic evolution, just as the genes affect cultural evolution.

Promethean Fire is essentially a long argument that this unexceptional, and scarcely new, style of evolution can explain what may be the three most important aspects of our own history and current status (see page 84, for example):

  1. Gene-culture coevolution was the trigger for the historical origin of mind in human evolution. It propelled the evolution of increased brain size at a rate perhaps never exceeded for major events in the history of life.

  2. Many important universal aspects of human behavior have a genetic basis and set the epigenetic rules of mind that constrain culture.

  3. Differences among human cultures, though recent in origin and often deemed superficial, are not free of genetic influence and are usually shaped, or at least strongly influenced, by the efficient process of gene-culture coevolution.

Unfortunately for the exaggerated claims made by Lumsden and Wilson, the first point, while undoubtedly just, is scarcely original with them and has formed the core of speculations about the evolutionary origin of mind ever since Darwin; the second point, also uncontroversial, is trivial, at least for the examples now available; while the third, controversial and even revolutionary if it could be established, is almost surely false as a general, or even as a common phenomenon.

The Evolutionary Origin of Mind

Lumsden and Wilson begin their book by staking a claim for discovering the origin of mind:

What was the origin of mind, the essence of humankind? We will suggest that a very special form of evolution, the melding of genetic change with cultural history, both created the mind and drove the growth of the brain and the human intellect forward at a rate perhaps unprecedented for any organ in the history of life….

For the first time we also link research on gene-culture coevolution to other, primarily anatomical studies of human evolution, and use the combined information to reconstruct the actual steps of mental evolution.

The evolution of the human brain did indeed follow a peculiar pattern strongly implicating some phenomenon like gene-culture coevolution in its increase in size from ape to human level. When we first encounter our ancestors, the australopithecines, in Africa some three million to four million years ago, they had already undergone a major anatomical transformation to upright posture without a concomitant change in their brains, which remained at an ape’s characteristic size. Why did these two essential features of our evolution—upright walk and large brains—evolve in such a detached manner, and in this particular sequence? Why did the brain evolve later, after so much of essential human anatomy was already in place?

We have had empirical knowledge of this pattern since the 1920s, when australopithecines were first discovered in South Africa. But the theme of upright walk first, brains second had been correctly surmised, in a speculative way, by many thinkers about human evolution, in part by Darwin himself, but particularly—and with remarkable perspicacity—by his German champion Ernst Haeckel.

Lumsden and Wilson, in utter disregard of this history, stake their own claim for discovery: our brains enlarged and our minds took off only when we entered the positive feedback loop of their newly discovered process: gene-culture coevolution. The speed of our brain’s increase then records the accelerative power of positive feedback.

I don’t doubt that something like gene-culture coevolution was involved in the evolution of our brain. But then Darwin and Haeckel, and all other major thinkers about human evolution, have made the same argument. In fact, I don’t know that any serious theory other than gene-culture coevolution has ever been proposed to explain the sequence of upright posture first, brains later and quickly. The standard account argues that upright posture freed the hands for development of tools and weapons. This evolving culture of artifacts and their attendant institutions of hunting, food gathering, or whatever, then fed back upon our biological (genetic) evolution by setting selection pressures for an enlarged brain capable of advancing culture still further—in short, gene-culture coevolution.

Darwin put it this way in The Descent of Man (1871):

If some one man in a tribe, more sagacious than the others, invented a new snare or weapon, or other means of attack or defence, the plainest self-interest, without the assistance of much reasoning power, would prompt the other members to imitate him; and all would thus profit…. If the new invention were an important one, the tribe would increase in number, spread and supplant other tribes. In a tribe thus rendered more numerous there would always be a rather better chance of the birth of other superior and inventive members. If such men left children to inherit their mental superiority, the chance of the birth of still more ingenious members would be somewhat better, and in a very small tribe, decidedly better.

Ironically, for the man’s work is anathema to Wilson, who senses the evil influence of Marxism behind all radical criticism of his sociobiology, the best nineteenth-century case for gene-culture coevolution was probably made by Friedrich Engels in his remarkable essay of 1876 (posthumously published in the Dialectics of Nature), “The part played by labor in the transition from ape to man.”

Engels, following Haeckel’s outline as his guide, argues that upright posture must precede the brain’s enlargement because major mental improvement requires an impetus provided by evolving culture. Thus, freeing the hands for inventing tools first (“labor” in Engels’s committed terminology) came first, then selective pressures for articulate speech, since, with tools, “men in the making arrived at the point where they had something to say to one another,” and finally sufficient impetus for a notable (and genetically based) enlargement of the brain:

First labor, after it, and then with it, articulate speech—these were the two most essential stimuli under the influence of which the brain of the ape gradually changed into that of man.

An enlarging brain (biology, or genes in later parlance) then fed back upon tools and language (culture), improving them in turn and setting the basis for further growth of the brain—the positive feedback loop of gene-culture coevolution:

The reaction on labor and speech of the development of the brain and its attendant senses, of the increasing clarity of consciousness, power of abstraction and of judgment, gave an ever-renewed impulse to the further development of both labor and speech.

Those ignorant of history do, after all, repeat it—especially when there is virtually no other way to go.

Genetic Universals

In Lumsden and Wilson’s version of gene-culture coevolution, genetic predispositions common to all normal humans act in the positive feedback loop by setting epigenetic rules—or biases in learning—that constrain and channel culture. To choose their favorite example, avoidance of incest is a biological imperative of great importance, since the frequency of birth defects rises sharply with the closeness of relationship between marriage partners (and reaches a maximum for unions between siblings). Thus, any mechanism discouraging incest would be strongly favored by natural selection and should increase within populations.

Of course, genes are not conscious agents and cannot “tell” their bearers, “Don’t copulate with close relatives or you’re in for trouble.” But “epigenetic” or learning rules with a genetic base might be selected for such an effect. We might, for example, be predisposed by our biology not to develop sexual feelings toward those individuals reared with us in early childhood—familiarity breeds contempt, and all that. Since, in ancestral societies with limited mobility and tight kinship bonds, close proximity usually meant close relationship, the epigenetic rule produced its desired biological result. Of course, we could “fool” this rule today by separating siblings or, as some societies do (thus providing the shaky basis in evidence for the form of the rule itself) by raising nonrelatives together and gauging their later sexual aversion toward one another.

I am supposed to be a “nurturist” in the great “nature-nurture” debate, but I find nothing upsetting in this notion of biological influence upon human behavior. I suppose I must also emphasize once again, and for the umpteenth time as we all do, that the categories are absurd and that there is no “nature-nurture” debate as such, Margaret Mead and Derek Freeman and the pleasant alliteration of the phrase notwithstanding. Every scientist, indeed every intelligent person, knows that human social behavior is a complex and indivisible mix of biological and social influences. The issue is not whether nature or nurture determines human behavior, for they are truly inextricable, but the degree, intensity, and nature of the constraint exerted by biology upon the possible forms of social organization.

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