As we approach 2009, there are up to 50 books celebrating the 200th Darwin anniversary and the 150th anniversary of the publication of The Origin of Species. Already the preliminary jostling about Darwin's legacy is beginning.
In today's Guardian, there is an excellent article by Madeleine Bunting, who argues that it is unfortunate that Darwin has been hijacked by ideological atheists such as Richard Dawkins, who have attempted to use Darwin's name for their own ends. Darwin himself was far more ambivalent about religion, was highly considerate and respectful of the deeply religious views of his wife, and did not go much further than describing himself as agnostic.
Bunting's voice is one of welcome calm and reason, and I personally hope she will be prominent in arguing for religious neutrality where discussions of Darwin are concerned. In what will no doubt develop into a heartfelt debate, I also hope that the contribution of my own forthcoming book A Silent Gene Theory of Evolution will play its own part in clarifying Darwin's remarkable legacy.
In any serious discussion of Darwin, certain basic points should be recognised as historical facts. The first is that Darwin was very far from inventing or generating the concept of evolution by natural means. Historical records confirm that it was a popular salon idea for the best part of a century before Darwin was born. In Darwin's introduction to the first edition of The Origin of Species it is significant that he acknowledged no less than 32 antecedents, including his own grandfather, Dr Erasmus Darwin. Several lines from Erasmus Darwin's poem, The Temple of Nature, leave the reader in no doubt that Darwin's grandfather fully grasped the concept of evolution by natural means.
Organic life beneath the shoreless waves
Was born and nursed in Ocean's pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the water mass;
These, as successive generations bloom,
New powers acquire, and larger limbs assume...
First tiny micro-organisms appear, which are too small to be seen by "spheric glass" (the lenses of microscopes), which then slowly "acquire" "new powers" and "larger limbs assume". This is as perfect a brief evocation of evolution as we are likely to read, and it was both written and published (1803) before Charles Darwin was born (1809). Yet biographies still suggest that Darwin invented the concept of evolution by natural means, and the quasi-religious mythology that the notion of evolution by natural means first occurred to Darwin as if by divine inspiration after his voyage in the Beagle will no doubt continue to be perpetuated.
What Darwin in fact proposed was that evolution is driven by natural selection of heritable variations. It was a more complex and difficult concept than at first appears, not least because at the time little was known of the mechanism of inheritance. Lacking any knowledge of genetics (Mendel's experimental findings on the inheritance of fixed characters had been first aired in 1865 but were largely ignored for several decades thereafter) Darwin assumed (correctly) that inherited random variations were generated by natural means and proposed that selection acted on these inherited variations to adapt populations of organisms over time.
This leads to a second distinction which, if followed, would obviate a great deal of unnecessary evolutionary argument. There is a vast array of evidence from the fossil record, and increasingly from genetics, which suggests that evolution occurs by natural means. Against this, the assertion that natural selection drives evolution is a theory. It is a great and inspiring theory, but it is a theory nonetheless, and in certain respects, quite a tenuous one.
In A Silent Gene Theory of Evolution I have argued that this theory needs thorough overhaul in the light of twenty-first century genetics. Darwin himself recognised the problem, and wrote in The Origin of Species that "... unless profitable variations do occur, natural selection can do nothing." Natural selection cannot drive evolution because in certain key respects it does the opposite of what is claimed. Instead of increasing variation within species, natural selection constantly reduces variation in favour of an optimum. If you have variants A, B, C, and D, one of them is likely to have a slight advantage over the others, and will gradually displace less fit variants.
If variation is consumed by the process of natural selection, what are the processes which generate variation against the current of natural selection? I struggled with this problem for 25 years, until finally, in 2000, I proposed that if significant numbers of silent or inert genes (that is to say, genes which do not code for physical characteristics) existed in the genome, they could mutate gradually over time without harming the host organism, while being reproduced in the normal way alongside the active or coding genes. In due course the silent genes could be switched on by random processes. Despite the exoticism of the theory, it was found that my definition of an inert gene corresponded precisely with what were known as the junk genes, whose function until then had proved mysterious. As the theory predicted, the junk genes were present in vast quantities -- in all multicellular animals they constitute the large majority of the genome.
In 2000 silent gene theory was resisted by my former tutor the great evolutionary theorist Professor John Maynard Smith on the grounds that he knew of no example of a silent gene becoming a coding gene. Before a year had passed there were four known examples of silent genes becoming coding genes, and the flood of further examples has continued to grow.
More recent evidence, culled from sequencing the genomes of an increasingly broad array of species, has given further powerful support to silent gene over natural selection as the main driver of evolution. If classical natural selection is correct, and the coding genes occupy a central place in evolution, then we would expect there to be a strong relation between the number of coding genes and the complexity of species. In practice, this correlation has been found to be surprisingly weak, and full of striking anomalies. For example, primitive nematode worms with only about 1000 cells have more coding genes than insects, which have billions of cells; and rice (to give another example) has more coding genes than Homo sapiens.
Against this, when the ratio of coding genes in the genome is plotted against species complexity, we find an almost perfect correlation across the whole gamut of evolutionary species. Relatively simple prokaryote bacteria have between 4-24% of silent genes. More complex unicellular organisms have between 26-52% of silent genes. Complex multicellular organisms start at 64% of silent genes and range upwards through reptiles and mammals to Homo sapiens at 98.5%. In 85 sequenced species the correlation between the ratio of silent genes and species complexity is almost perfect.
The testing of the two grand theories of evolution will take place over many years, and will charge the evolutionary debate in what I hope is a highly constructive manner. Darwin's great theory that natural selection drives evolution has held sway, entirely justifiably, for 150 years. For the first time it has a genuine rival. And for the first time we will begin to see it tested, thoroughly and rigourously, against another grand evolutionary theory.
