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Beyond The Blueprint
Russell Powell says it’s not easy using genes to enhance humanity, even in theory.
On display in the National Portrait Gallery of London is a ‘DNA portrait’ of geneticist Sir John Sulston. The work is billed by the artist as “the most realistic portrait in the gallery” because it “carries the actual instructions that led to the creation of John. It is a portrait of his parents, and every ancestor he ever had back to the beginning of life.”
Since the discovery of the structure of DNA, the idea that the genome (the organism’s genetic code) serves as a blueprint for the adult organism, has run deep in scientific and popular consciousness. This notion that DNA contains packets of information in the form of units called ‘genes’ which provide a set of encoded instructions for assembling the human body, motivates a wide range of ethical, political and regulatory positions on genetic technologies. UNESCO’s Universal Declaration on the Human Genome and Human Rights links human nature and human dignity explicitly to the human genome. The double helix structure of DNA provides a mechanism for template-copying with such astounding fidelity that it allows organisms containing up to one hundred trillion cells (each specialized for a particular function) to be built anew with extraordinary accuracy in each generation, and the diversity of the DNA code and its associated protein products is a crucial part of any explanation of the historical diversity of life on Earth. Perhaps it is not surprising then that the ‘genetic blueprint’ metaphor for DNA has shaped the practice of biological science, science education, and even philosophical debates concerning the ethical implications of the new biosciences. Nevertheless, ‘the genetic blueprint’ is a theoretically unsupported and highly misleading metaphor, which has cultivated a general attitude of ‘genetic exceptionalism’ that has imposed a flawed structure on philosophical discussions of human genetic engineering. For instance, in medical law and ethics, genetic information is widely regarded as a special class of medical information that requires correspondingly unique levels of regulation and oversight. Few other medical technologies are treated with such legal caution and ethical trepidation. This is what I mean by ‘genetic exceptionalism’. It is undoubtedly widespread, but is it justified?
Before sketching an answer to this question, it is important to note that genetic exceptionalism seems to have infected both critics and defenders of human genetic engineering, including positions characterized by varying degrees of nuance. Both philosophers who are skeptical of the ability of genetic engineering to increase human autonomy and wellbeing (e.g., Jürgen Habermas and Francis Fukuyama), and those who are skeptical about the value of the concept of autonomy for settling the debate (e.g., Leon Kass and Michael Sandel), view genetic intervention as a special sort of intervention – one that tinkers with the essence of human nature and the fundamental building blocks of species design. On the other hand, human genetic engineering enthusiasts (e.g., Julian Savulescu, John Harris and Nick Bostrom), are quick to point out the fallacious reasoning of the aforementioned critics, such as their implicit or explicit commitment to genetic determinism – the misguided notion that the presence of a gene virtually ensures the manifestation of its associated phenotype [characteristic] in virtually every environment. Some prominent enhancement enthusiasts, such as Allen Buchanan, oppose genetic exceptionalism to the extent of arguing persuasively that the modification of genes is not different in kind from more traditional ‘environmental enhancements’, such as improvements in early childhood education or in the nutrients provided in early embryonic development. Notwithstanding the validity of these criticisms, in touting the unprecedented and nearly unlimited potential of genetic engineering technologies to advance human wellbeing, defenders of human genetic engineering are committed to a variant of genetic exceptionalism: the power of genetic technologies to improve human health and wellbeing is sensationalized, and with it, the role of the gene.
Moreover, all major parties to the genetic enhancement debate tend to assume that a ‘map’ of the human genome presents us with a blueprint of the human organism, ready for redesign if only we could figure out how to decipher it. At present we have little clue how to decode a genetic sequence to yield information about complex human characteristics, but surely the information will be revealed as our knowledge of the molecular basis of biological development increases. On this view, the difficulties we currently face in identifying and manipulating gene functions are temporary technical obstacles. Only these obstacles, along with a suite of ethical concerns of varying persuasive power, stand in the way of the radical genetic modification of complex human traits, they say. But is the ‘genetic blueprint’ metaphor even correct?
The genetic blueprint metaphor dates back to the physicist Erwin Schrödinger (1887-1961). Its popular dissemination is due in part to the pronouncements of eminent molecular and evolutionary biologists operating with an idealized approach to biological development that emulates the reductionist approach of modern physics. The metaphor now appears frequently in science journalism, with headlines such as ‘Draft of Neanderthal’s Genetic Blueprint Revealed!’, and it also often features as a marketing device geared toward prospective consumers of genetic technologies. However, the metaphor is misleading.
The genetic blueprint metaphor arises in part from a misunderstanding of the nature of biological development, and in part as a conceptual relic of obsolete notions of genetic essentialism, the idea that genes cause and explain the properties of organisms much as elementary particles cause and explain the properties of chemical elements. The blueprint metaphor has fueled an intense suspicion of genetic modification technologies among the general public, which has no equal among non-genetic medical interventions; but the very same fallacy also causes enhancement enthusiasts to underestimate the challenges confronting the genetic engineering enterprise.
Unlike logical fallacies, biological fallacies can only be exposed through careful scientific research revealing the actual causal connections within living systems. Now, it could very well have been the case that genomes, once properly deciphered, would have served as schematics describing the functional arrangement of the mature organism. This position is increasingly unsustainable, however, in the light of our current understanding of biological development. Genes are crucial developmental resources, true; but so too are numerous non-genetic factors. That is to say, detailed knowledge of the genetic sequence of a cell is useless without equally-detailed information about the complex non-genetic context. Without the legion of biomolecular agents acting within the cell, DNA is a quintessentially inert macromolecule: it remains causally powerless. These other agents include organelle machinery, mRNA processors, scores of proteins, methylation patterns, enzymes, hormones, nutrients, membranes, temperature gradients, and feed-back loops involved in transcription, translation and protein-folding – not to mention the countless post-natal factors that influence development. None of these factors are encoded in nuclear DNA, but all of them can play a substantive role in trait development. Therefore, it does not appear possible even in principle to compute complex human characteristics from a knowledge of DNA sequences alone. So the ‘genetic blueprint’ metaphor is wrong.
There’s an ongoing debate in the philosophy of science as to whether genes play a special informational role in development. However, even accounts that support the idea that genes contain a special class of information will not support a genetic exceptionalism grounded in the claim that the knowledge and manipulation of genetic sequences is qualitatively different to the knowledge and manipulation of organic development factors more broadly. Indeed, the very concept of the gene itself has come under attack by eminent philosophers of science such as Paul Griffiths, Massimo Pigliucci, Lenny Moss and Jason Robert, among others. Yet even those who defend the concept of the gene should be inclined to reject the blueprint metaphor and its associated genetic exceptionalism. The recognition that other developmental factors are in many cases comparable in significance to genes should go some way toward disabusing both academia and the public of the notion that genetic interventions are different in kind than other biomedical (or non-biomedical) interventions. The same fact also indicates that an increasing knowledge of and ability to manipulate genomes does not entail the radical control of human design that advocates of genetic engineering have often envisioned. Like the skeptics of genetic engineering, enhancement enthusiasts also suffer from simplistic views concerning the role of genes in development, and this has caused them to underestimate the engineering challenges that confront the genetic enhancement vision.
The case of medical genetics is illustrative of the wider problem. Although more than 1,800 genes have been identified as being causally associated with hereditary diseases, it is becoming increasingly clear in the light of genome-wide studies that the vast majority of human diseases (as well as normal human traits) involve the operation of many genes of individually minor effect. And because of complex interactions between genes, their protein products, and various non-genetic factors in the cellular environment, these polygenic traits do not follow simple Mendelian patterns of inheritance. As a result, our ability to personalize medical procedures based on genomic data is currently highly limited. Many claim that these limitations will be overcome as we learn more about the interaction between genes and non-genetic factors in the generation of traits, including disease states. However, recent work on large samples of identical twins has cast serious doubt on this claim, on the contrary indicating that the predictive value of genome profiles for complex diseases such as cancer, autoimmune, cardiopulmonary, gastroenterological, and neurodegenerative disorders, may never become clinically useful, due to the complexities of the relationships between genes and traits. This is not to say that the role of genes in development is unimportant – only that their causal role may be much more subtle, more complexly configured, and more contingent on non-genetic factors, than either the critics or defenders of genetic enhancement have yet taken into account.
Given these complexities of development, many authors have suggested that effective genetic manipulation of complex phenotypes such as memory, attention, intelligence, moral emotions, and so forth, may be impossible for the foreseeable future. However, and notwithstanding the weighty reasons for pessimism, work with animals suggests that the genetic alteration of complex cognitive and behavioral capacities is not implausible. This is perhaps best illustrated by transgenic ‘Doogie’ mice: otherwise normal mice with deliberate genetic alterations, resulting in enhanced memory, learning and intelligence, as demonstrated in tests involving the navigation of a water maze, the recognition of new objects, and the time to extinction of a conditioned fear response. Less often noted, however, is that the Doogies’ non-genetically-enhanced counterparts can achieve comparable levels of cognitive acuity simply by being exposed to toys, tunnels and other low-tech ‘educational enhancements’ – once again reminding us that enhancing traits by modifying non-genetic aspects of development can be as effective as biomedical modifications, and sometimes more effective.
Given the conceptual and evidential flaws in the ‘genetic blueprint’ metaphor, philosophers thinking about the ethics of enhancement should shift their focus from the modification of genes per se to the enhancement of development generally. Thinking in terms of developmental enhancement, rather than merely genetic enhancement, will help us eschew the psychologically attractive but empirically discredited notions of the genetic blueprint, genetic exceptionalism, and genetic essentialism, which have heavily tinted the philosophical lenses of opposing factions in the enhancement debate. In one case the tint is rosy, in the other case it is something darker.
© Dr Russell Powell 2012
Russell Powell is Assistant Professor of Philosophy at Boston University.