In short: Studies on ‘dyslexics’ all experience the same, absolutely fundamental problem, namely the all-important selection of their sample. The question ‘who is dyslexic?’ has yet to be answered.
Saint Augustine reputedly wrote ‘For so it is, Oh Lord my God; I measure it, but what it is that I measure I do not know.’ This quote should illuminate the following discussion on the genetics of literacy. I don’t understand genetic discourse well but I insist on my right, and my duty, to remain sceptical while watching this space with a great deal of interest. Literacy attainment, or otherwise, is a very complex social and cognitive issue. Many ill-understood influences powerfully (and variably) affect it. Individual case characteristics and whole-population findings do not necessarily relate at all well. In the words of Steve Ramm ‘Splitting complex phenomena into genetic and environmental components is just about impossible and, of course, each will feed back upon the other.” (personal communication September 2007). This aspect of our debate is, regrettably, much more complicated than it looks at first.
I find the genetic ‘proof’ of dyslexia the most difficult to deal with. It is difficult for two reasons, first because it seems to me, as a biologically trained person (I am a veterinary surgeon in ‘real life’), to run directly counter to common sense, but second because it is a subject which is, perforce, mediated (and understood) through fancy mathematics as genes exert their effects by interacting among each other and with their environment in extremely complex ways we do not yet fully understand (to say the least). I have immediately to confess an inability to follow the mathematical arguments intelligently, or indeed at all. I am, therefore, not able to challenge ‘proofs’ in the mathematical arena. There are nonetheless relevant, if captious, observations which may perfectly properly be made by the sceptical but mathematically inept, such as myself. There are many papers in which genetic effects on reading, and on dyslexia, are claimed (e.g. Cardon et al 1994 [corrected 1995], DeFries 1997, Fisher et al 1999, Olson 2006, Paracchini et al 2007, Schumacher et al 2007, Williams & O’Donovan 2006) and it will be very interesting to see what the map of the human genome eventually tells us. The genetic argument is an important strand in the debate, as it seems to be saying extraordinary and potentially considerable things, and should suffer some critical analysis. Here, I describe some of the work done and display its findings in such a way, I hope, as to allow you to deduce your own responses as well as to read mine.
Every one of us is made up of zillions of cells all containing, and all controlled by, an identical set of 23 chromosomes which make us, genetically, who we are. Each chromosome consists of an immense chain of genes. Each gene is made from a complex protein called DNA (deoxyribonucleic acid) – the famous double helix. All DNA is made from a small number of amino-acids. The order in which these amino acids appear on a gene varies between genes and is the genetic code (a bit like an alphabet where each amino acid is a letter). Each gene is a unique code, its amino acids arranged in a unique order (a bit like a set of words). Our DNA is unique to us in that the arrangement of amino acids on my genes and genes on my chromosomes is mine and mine alone. Hence its forensic value - it identifies me uniquely. The process of ‘reading’ amino acid and gene sequences is mechanised today and is relatively easily done. The human genome is already being deciphered and its alteration to order may be within reach. Scarily, it might, one day, be possible to reconstruct me (maybe even create an improved me) from a sample of my DNA. More interestingly, it may be possible to reconstruct extinct creatures from bits and pieces found here and there. The dodo might yet live again.
Our genes are responsible for our inherited characteristics. Every gene encodes information (as a particular ordering of amino acids) and a gene may issue instructions within a cell by causing the cell to encode a protein with amino acids ordered in its own image. However, each gene also interacts with other genes, with our own physiology, with our own characteristics and with our environment to exert its effect. It’s a fiendishly complicated area of knowledge and is very much still in its infancy. We are our genes (up to a point) and we are our history and our environment (up to a point) - the problem in any particular instance is, up to which point? For any aspect of ourselves, in this context, the question remains - nature or nurture? The answer is very seldom clear.