It was Danish plant biologist Wilhelm Johannsen who called them genes. Genes, it was discovered, could mutate. This offered an explanation for the emergence of new varieties – even new species – and hence for evolutionary change. In the absence of mutation, genes were immortal, immune to somatic changes, the unmoved movers that determined all bodily functions. It was not until the 1930s that the Mendelian and Darwinian mechanisms were reconciled, in the work of mathematically minded geneticists J.B.S. Haldane and Ronald Fisher in England and Sewall Wright in the US. They brought together genetics and natural selection as the accepted mechanism for evolution, called the Modern Synthesis by Haldane and Fisher and neo-Darwinism by Wright. In this synthesis, it was genes that carried the variations within a species from generation to generation. By the 1950s the formal definition of evolution had become “a change in gene frequency within a population’. Organisms had disappeared from the account; what mattered, was not even the genome but individual genes operating independently of one another – an approach derided by Sewall Wright as ‘beanbag genetics’. Unlike the mathematicians, his real-world field studies made him more aware of complexity, and of the interaction of genes during development.
However, beanbags won out for mainstream genetics, and this privileging of genes over and above the organisms in which they are embedded has had a disastrous consequence for the life sciences. The genetic turn deprived the term ‘evolution’ of one of its original, pre-Darwinian meanings -development, the unrolling lifecycle of any living creature. Developmental biology’s starting point is the study of similarities – the biological processes that generate all living creatures, from the transitions between caterpillar and butterfly to the extraordinary uniformity in the way in which humans develop from fertilised egg through embryo, foetus, infant and into adulthood. Development thus emphasises form, pattern, wholeness and above all time, the species-typical dynamic of any organism’s lifecycle. As ethologist Patrick Bateson and molecular biologist Peter Gluckman describe it, developmental processes must be simultaneously robust – capable of withstanding environmental insults – and plastic – capable of change in response to challenge. Ignoring development enabled an inexorably reductionist genetics to become the study of differences between organisms, assumed to be coded in the genes.