IntroductionEgenis Director Professor John Dupré heeds the call.
The Government is calling for a renewed public debate about gentically modified (GM) crops.With concern growing about world food shortages, it is surely right to reconsider the role of GM crops in the global production of food. If GM is indeed a technology with significant potential, there may be a possibility for preventing many millions of deaths from starvation and, unless there are pressing reasons to suppress the technology, there is a moral obligation to explore this potential. So are there any such pressing reasons?
Various ill consequences have been alleged as likely to follow the introduction of GM crops, generally involving harm to human health or to the environment. Yet there is no serious evidence that GM foods are harmful to our health. This is hardly surprising. Human physiology has adapted to dealing with a far greater diversity of genetic and chemical substances than is presented by GM crops. It is of course possible that a protein product of an inserted gene could be toxic. One might make some very dangerous vegetables by inserting suitable genes from Death Cap mushrooms, for instance. But there are possible health benefits as well as possible harms. Bt maize, which produces the insecticidal Bacillus thuringiensis toxin, is likely to contain fewer artificial insecticide residues (often assumed to cause harm to health), and also appears less susceptible to contamination with dangerous mycotoxins produced by fungi that attack crops at the sites of insect damage. Only detailed research can substantiate claims for health benefits or risks, research that has yet to provide any conclusive results.
Environmental impacts are even harder to assess. There has been concern that the cultivation of herbicide resistant plants or Bt plants might have adverse effects on surrounding wildlife. However, the net effect of using such crops is to provide weed and pest management options that reduce the use of herbicides and pesticides, which is likely to benefit wildlife. The question is again an empirical one, and requires specific investigation of specific patterns of use of crops and chemicals.
Other objections to GM are more abstract and address the ethical acceptability of mixing genes from organisms of different kinds. The ‘Yuk!’ factor evoked by GM is often grounded in misconceptions of biology. In particular, I suspect that it is a view of the genome as the essence of the organism, the so-called blueprint, that leads to the belief that there is something fundamentally problematic about genomic intervention. The idea that the genome has a qualitatively different status from other molecules in the cell is sometimes referred to as ‘genetic exceptionalism’. But the assumptions about genomes that underlie this exceptionalism are increasingly indefensible.
First, the picture of the genome as a blueprint is hopeless. Genomes have resources that can be deployed in many ways by different organisms. The same stretch of gene sequence can, by virtue of subsequent reorganisation of gene products, end up involved in the generation of thousands of different protein products. So even at the level of protein products, which products the cell generates depends on much more than merely the sequence of nucleotides. In fact it now appears that even the experience of the organism can affect the chemical processes in the cell. A well-studied example is the sequence of effects by which maternal care of rats leads to changes in the chemical activity of brain cells which, in turn, generate maternal behaviour in the adult pups. This illustrates the complexity of the processes by which features of an organism are transmitted to future generations and the dependence of these processes on a great deal more than merely the genome.
Against genetic exceptionalist objections to GM it is often pointed out that, whatever the ethical status of intentional manipulation of genomes may be, it has being going on for millennia through selective breeding. True, say doubters, selective breeding certainly leads to changed genomes, but the changes that occur are all confined within the bounds of a species or, at least, a closely related group of species. Surely this is a quite different matter from putting bits of a snowdrop in a strawberry, or a bacterium in a potato? This violation of the integrity of the species genome is arguably ‘unnatural’.
It is much less unnatural, however, than is widely recognised. Microbes are now known to exchange genetic material regularly, often with very distantly related organisms. Even among higher animals, and certainly among plants, hybridisation is far commoner than was once thought. Perhaps more significant still, all animals and plants, far from being isolated systems with species-specific genomes, are actually complex symbiotic systems. Some 90% of the cells that make up a functioning human are bacteria essential to the proper functioning of the whole, and these bacteria contain about 99% of the genes within the organism. There is almost certainly some gene exchange between the diverse components of this system. And perhaps most significant of all, for every cellular organism on Earth there are about 10 virus particles. Viruses are nuclease vectors, carrying RNA or DNA into cells and in many cases inserting DNA into genomes. Cells are often able to excise this alien DNA, but in many cases it stays within the host genome. It is increasingly believed that insertions of DNA have played a central role in major transitions in the trajectory of evolution of multicellular organisms. So the insertion of foreign DNA is hardly a uniquely human innovation; indeed life exists in a constant and massive flux of DNA against which individual genomes are only partially insulated.
It seems possible that a better sense of the dynamic nature of the genome and its constant changes in response to internal processes, external influences, and virus-borne DNA, might make us more sanguine about the minor human contributions to this process. Certainly we are right to be cautious about changes to the nature of the things we eat, but this caution calls for evidence about consequences rather than treating as sacrosanct particular parts of biological systems. And with starvation a very real risk to human well-being in much of the world, we have an ethical duty to consider very seriously ways in which our food supply might be significantly enhanced.