I Have Landed
Page 26
Human complexity cannot be generated by thirty thousand genes under the old view of life embodied in what geneticists literally called (admittedly with a sense of whimsy) their “central dogma”: DNA makes RNA makes protein—in other words, one direction of causal flow from code to message to assembly of substance, with one item of code (a gene) ultimately making one item of substance (a protein), and the congeries of proteins making a body. Those 142,000 messages no doubt exist, as they must to build the complexity of our bodies. Our previous error may now be identified as the assumption that each message came from a distinct gene.
We may envision several kinds of solutions for generating many times more messages than genes, and future research will target this issue. In the most reasonable and widely discussed mechanism, a single gene can make several messages because genes of multicellular organisms are not discrete and inseparable sequences of instructions. Rather, genes are composed of coding segments (exons) separated by noncoding regions (introns). The resulting signal that eventually assembles the protein consists only of exons spliced together after elimination of introns. If some exons are omitted, or if the order of splicing changes, then several distinct messages can be generated by each gene.
The implications of this finding cascade across several realms. The commercial effects will be obvious, as so much biotechnology, including the rush to patent genes, has assumed the old view that “fixing” an aberrant gene would cure a specific human ailment. The social meaning may finally liberate us from the simplistic and harmful idea, false for many other reasons as well, that each aspect of our being, either physical or behavioral, may be ascribed to the action of a particular gene “for” the trait in question.
But the deepest ramifications will be scientific or philosophical in the largest sense. From its late-seventeenth-century inception in modern form, science has strongly privileged the reductionist mode of thought that breaks overt complexity into constituent parts and then tries to explain the totality by the properties of those parts and from simple interactions fully predictable from the parts. (Analysis literally means “to dissolve into basic parts.”) The reductionist method works triumphantly for simple systems—predicting eclipses or the motion of planets (but not the histories of their complex surfaces), for example. But once again—and when will we ever learn?—we fell victim to hubris, as we imagined that, in discovering how to unlock some systems, we had found the key for the conquest of all natural phenomena. Will Parsifal ever learn that only humility (and a plurality of strategies for explanation) can locate the Holy Grail?
The collapse of the doctrine of one gene for one protein, and one direction of causal flow from basic codes to elaborate totality, marks the failure of reductionism for the complex system that we call biology—and for two major reasons.
First, the key ingredient for evolving greater complexity is not more genes, but more combinations and interactions generated by fewer units of code—and many of these interactions (as emergent properties, to use the technical jargon) must be explained at the level of their appearance, for they cannot be predicted from the separate underlying parts alone. So organisms must be explained as organisms, and not as a summation of genes.
Second, the unique contingencies of history, not the laws of physics, set many properties of complex biological systems. Our thirty thousand genes make up only one percent or so of our total genome. The rest—including bacterial immigrants and other pieces that can replicate and move—originated more as accidents of history than as predictable necessities of physical laws. Moreover, these noncoding regions, disrespectfully called “junk DNA,” also build a pool of potential for future use that, more than any other factor, may establish any lineage’s capacity for further evolutionary increase in complexity.
The deflation of hubris is blessedly positive, not cynically disabling. The failure of reductionism doesn’t mark the failure of science, but only the replacement of an ultimately unworkable set of assumptions by more-appropriate styles of explanation that study complexity at its own level and respect the influences of unique histories. Yes, the task will be much harder than reductionistic science imagined. But our thirty thousand genes—in all the glorious ramifications of their irreducible interactions—have made us sufficiently complex and at least potentially adequate for the task ahead.
We may best succeed in this effort if we can heed some memorable words spoken by that other great historical figure born on February 12—on the very same day as Darwin, in 1809. Abraham Lincoln, in his first inaugural address, urged us to heal division and seek unity by marshaling the “better angels of our nature”—yet another irreducible and emergent property of our historically unique mentality, but inherent and invokable all the same, even though not resident within, say, gene 26 on chromosome number 12.
16
Darwin’s Cultural Degree
WE CAN EMBRACE POETICAL REMINDERS OF OUR CONNECtion to the natural world, whether expressed as romantic effusions about oneness, or in the classical meter of Alexander Pope’s heroic couplet:
All are but parts of one stupendous whole
Whose body Nature is, and God the soul.
Yet, when we look into the eyes of an ape, our perception of undeniable affinity evokes an eerie fascination that we usually express as laughter or as fear. Our discomfort then increases when we confront the loss of former confidence in our separate and exalted creation “a little lower than the angels . . . crowned . . . with glory and honor” (Psalm 8), and must own the evolutionary alternative, with a key implication stated by Darwin himself (in The Descent of Man): “The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind.”
We have generally tried to unite our intellectual duty to accept the established fact of evolutionary continuity with our continuing psychological need to see ourselves as separate and superior, by invoking one of our worst and oldest mental habits: dichotomization, or division into two opposite categories, usually with attributions of value expressed as good and bad, or higher and lower. We therefore try to define a “golden barrier,” a firm criterion to mark an unbridgeable gap between the mentality and behavior of humans and all other creatures. We may have evolved from them, but at some point in our advance, we crossed a Rubicon that brooks no passage by any other species.
Thus, throughout the history of anthropology, we have proposed many varied criteria—and rejected them, one by one. We tried behavior—the use of tools, and, after the failure of this broad standard, the use of tools explicitly fashioned for particular tasks. (Chimps broke this barrier when we discovered their ability to strip leaves off twigs, and then use the naked sticks for extracting termites from nests.) And we considered distinctive mental attributes—the existence of a moral sense, or the ability to form abstractions. All proposed criteria have failed as absolutes of human uniqueness (while a complex debate continues to surround the meaning and spread of language and its potential rudiments).
The development of “culture”—defined as distinct and complex behavior originating in local populations and clearly passed by learning, rather than by genetic predisposition—has persisted as a favored candidate for a “golden barrier” to separate humans from animals, but must now be rejected as well. A study published in a recent issue of the journal Nature proves the existence of complex cultures in chimpanzees. This research demonstrates that chimpanzees learn behaviors through observation and imitation and then teach these traits to other chimpanzees. The study represents a cooperative effort of all major research groups engaged in the long-term study of particular groups of chimpanzees in the wild (with Jane Goodall’s nearly forty-year study of the Gombe chimps as the flagship of these efforts).
Isolated examples of cultural transmission have long been recognized—with local “dialects” of songbirds and the potato-washing of macaques on a small Japanese island as classical cases. But such rudimentary examples scarcely qualified as arguments against a meaningful b
arrier between humans and animals. However, the chimpanzee study, summarizing 151 years of observation at seven field sites, found culturally determined, and often quite complex, differences among the sites for thirty-nine behavioral patterns that must have originated in local groups and then spread by learning.
To cite just one example, contrasting the two most intensively studied sites (Goodall’s at Gombe and Toshisada Nishida’s in the Mahale Mountains 170 kilometers away, with no recorded contact between the groups), the Mahale chimps clap two hands together over their heads as part of the grooming ritual, while no Gombe chimp has ever so behaved (at least while under human observation. Grooming itself may be genetically enjoined, but such capricious variations in explicit style must be culturally invented and transmitted). In a commentary accompanying the Nature article, Frans de Waal of the Yerkes Regional Primate Research Center in Atlanta summarizes the entire study by writing, “The evidence is overwhelming that chimpanzees have a remarkable ability to invent new customs and technologies, and that they pass these on socially rather than genetically.”
The conventional commentary on such a conclusion would end here, leaving a far more important issue unaddressed. Why are we so surprised by such a finding? The new documentation may be rich and decisive—but why would anyone have doubted the existence of culture in chimps, given well-documented examples in other animals and our expanding knowledge of the far more sophisticated mental lives of chimpanzees?
Our surprise may teach us as much about ourselves as the new findings reveal about chimpanzees. For starters, the basic formulation of them versus us, and the resulting search for a “golden barrier,” represents a deep fallacy of human thought. We need not fear Darwin’s correct conclusion that we differ from other animals only in degree. A sufficient difference in quantity translates to what we call difference in quality ipso facto. A frozen pond is not the same object as a boiling pool—and New York City does not represent a mere extension of the tree nests at Gombe.
In addition, evolution does provide a legitimate criterion of genuine and principled separation between Homo sapiens and any other species. But the true basis of distinction lies in topology and genealogy, not in any functional attribute marking our superiority. We are linked to chimpanzees (and more distantly to any other species) by complete chains of intermediate forms that proceed backward from our current state into the fossil record until the two lineages meet in a common ancestor. But all these intermediate forms have become extinct, and the evolutionary gap between modern humans and chimps therefore stands as absolute and inviolate. In this crucial genealogical sense, all humans share equal fellowship as members of Homo sapiens. In biological terms, with species defined by historical and genealogical connection, the most mentally deficient person on earth remains as fully human as Einstein.
If we grasped this fundamental truth of evolution, we might finally make our peace with Alexander Pope’s location of human nature on an “isthmus of a middle state”—that is, between bestiality and mental transcendence.
We might also become comfortable with his incisive characterization of our peculiar status as “the glory, jest, and riddle of the world.”
17
The Without and Within of Smart Mice
EVERY AGE MUST DEVELOP ITS OWN VERSION OF THE unobtainable and chimerical quick fix: the right abracadabra to select the winning lottery number, the proper prayer to initiate the blessed millennium, the correct formula to construct the philosopher’s stone. In a technological age, we seek the transforming gene to elicit immediate salvation from within.
An excellent and provocative study of Joe Tsien and his colleagues will, one may safely predict, be widely misread in the false light of this age-old hope—combined with some equally age-old fallacies of human reasoning.
These scientists bred strains of mice with extra copies of a gene coded for a protein that can facilitate communication between neurons. Since one popular theory of memory relates this primary mental capacity to an organism’s ability to make associations—say, between the buzz of a bee and the pain of its bite—this enhanced communication might promote a recording of associations within the brain, thus creating memories.
Pundits in our age of rapid misinformation will surely transmit the story as a claim that the gene for intelligence has been cloned and that a human smart pill for routine production of kiddie geniuses lies just around the millennial corner.12 None of this punditry, however, will bear any relationship to current realities or to reasonable prospects for the short-term future. Even so, the mice studied by Tsien and his colleagues could help us to correct two common errors in our thinking about genetics and intelligence:
1. The labeling fallacy. Complex organisms cannot be construed as the sum of their genes, nor do genes alone build particular items of anatomy or behavior by themselves (see essay 15). Most genes influence several aspects of anatomy and behavior—as they operate through complex interactions with other genes and their products, and with environmental factors both within and outside the developing organism. We fall into a deep error, not just a harmless oversimplification, when we speak of genes “for” particular items of anatomy or behavior.
No single gene determines even the most concrete aspect of my physical being, say the length of my right thumb. The very notion of a gene “for” something as complex as “intelligence” lapses into absurdity. We use the word intelligence to describe an array of largely independent and socially defined mental attributes, not a quantity of a single something, secreted by one gene, measurable as one number, and capable of arranging human diversity into one line ordered by relative mental worth.
To cite an example of this fallacy, in 1996 scientists reported the discovery of a gene for novelty-seeking behavior—generally regarded as a good thing. In 1997 another study detected a linkage between the same gene and a propensity for heroin addiction. Did the “good” gene for enhanced exploration become the “bad” gene for addictive tendencies? The biochemistry may be constant, but context and background matter.
2. The compositional fallacy. Just as each gene doesn’t make a separate piece of an organism, the entire organism cannot be regarded as a simple summation of relevant building codes and their action (a skeleton cannot be generated by a head gene added to a neck gene added to a rib gene, etc.). The fact that complex systems like human mentality or anatomy can be disrupted easily by deficiencies in single factors does not validate the opposite claim that enhancement of the same factors will boost the system in a harmonious and beneficial manner. The potential “fixing” of specific abnormalities—the realistic hope of certain gene therapies for the near future—does not imply that we will be able to bioengineer superathletes or superscholars. The remedy for a specific deficiency does not become an elixir for general superiority. I can save a drowning man’s mind if I hold his head above water, but I can’t make him a genius by continually adding more oxygen to his ordinary surroundings.
Ironically, Tsien’s mice disprove these two fallacies of genetic determinism from within. By identifying their gene and charting the biochemical basis of its action, Tsien has demonstrated the value and necessity of environmental enrichment for yielding a beneficial effect. This gene doesn’t make a mouse “smart” all by its biochemical self. Rather, the gene’s action allows adult mice to retain a neural openness for learning that young mice naturally possess but then lose in aging.
Even if Tsien’s gene exists, and maintains the same basic function in humans (a realistic possibility), we will need an extensive regimen of learning to potentiate any benefit from its enhanced action. In fact, we try very hard—often without success, in part because false beliefs in genetic determinism discourage our efforts—to institute just such a regimen during a human lifetime. We call this regimen “education.” Perhaps Jesus expressed a good biological insight when he stated (Matthew 18:3), “Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven.”
VI
DEFINING AND BEGINNING
18
What Does the Dreaded “E” Word Mean Anyway?
EVOLUTION POSED NO TERRORS IN THE LIBERAL CONstituency of New York City when I studied biology at Jamaica High School in 1956. But our textbooks didn’t utter the word either—a legacy of the statutes that had brought William Jennings Bryan and Clarence Darrow to legal blows at Tennessee’s trial of John Scopes in 1925. The subject remained doubly hidden within my textbook—covered only in chapter 63 of sixty-six, and described in euphemism as “the hypothesis of racial development.”
The anti-evolution laws of the Scopes era, passed during the early 1920s in several Southern states, remained on the books until 1968, when the Supreme Court declared them unconstitutional. The laws were never strictly enforced, but their existence cast a pall over American education, as textbook publishers capitulated to produce “least common denominator” versions acceptable in all states—so schoolkids in New York got short shrift because the statutes of some distant states had labeled evolution as dangerous and unteachable.
Ironically, at the very end of the millennium (I wrote this essay in late November 1999), demotions, warnings, and anathemas have again come into vogue in several regions of our nation. The Kansas school board has reduced evolution, the central and unifying concept of the life sciences, to an optional subject within the state’s biology curriculum (an educational ruling akin to stating that English will still be taught, but grammar may henceforth be regarded as a peripheral frill, permitted but not mandated as a classroom subject).13 Two states now require that warning labels be pasted (literally) into all biology textbooks, alerting students that they might wish to consider alternatives to evolution (although no other well-documented scientific concept evokes similar caution). Finally, at least two states have retained their Darwinian material in official pamphlets and curricula, but have replaced the dreaded “E” word with a circumlocution, thus reviving the old strategy of my high school text.