Tom Dickins, a Professor of Behavioural Science, has written a new book which explains how popular theories on evolutionary biology have changed in modern times
The Modern Synthesis was a long period of theoretical development in evolutionary biology that began with the invention of population genetics in the 1900s. A key innovation was Fisher’s analogical use of the ideal gas laws to envisage a population of particles, or genes, randomly bumping into one another. Just as with atoms these genes would remain in equilibrium until some external force changed that – natural selection was such a force. This analogy enabled a statistical synthesis between Mendel’s views of particulate inheritance and Darwin’s theory of gradual evolution whilst reinterpreting evolution as changes in gene frequencies within a population.
The Modern Synthesis also saw the removal of some older evolutionary ideas including those from Lamarck. Lamarck argued that developmental processes could be induced within an individual as a response to the environment. Development could lead to new and useful forms that would be inherited and would thus persist. Darwin had replaced this definition of evolution with one where successful trait variants were retained at the population level because more individuals with those variants survived and reproduced. Unsuccessful variants were removed. But Darwin did allow a role for transformation in the generation of new variation. Population genetics removed Lamarckian transformation entirely relying instead upon genetic variation and the outcome of selection. During the Synthesis additional processes were included, such as genetic drift, but all reorganized the constitution of the population without reliance upon a theory of development.
The role of developmental biology
The removal of Lamarck and the redefinition of evolution as a population level process meant that evolutionary biology was no longer a theory of form. This change has not gone unnoticed, and contemporary scholars have begun to look again at the role of developmental biology in evolution. Some have explicitly called for an Extended Evolutionary Synthesis that will incorporate mechanistic theories of form. In doing this these scholars are arguing both for new models of the emergence of useful variation and for new types of inheritance, most especially through developmentally induced transgenerational epigenetic effects.
A central argument of the Extended Evolutionary Synthesis is directed toward what is referred to as gene-centrism. During the latter stages of the Synthesis, in the 1960s, biologists began to model genes as agents whose goal is to replicate across the generations. To achieve this goal, genes contribute to traits that enable the survival and reproduction of the organisms they find themselves in. Genes, as replicators, can span many, many generations. Bodies, as vehicles for those genes, are mortal. This heuristic captured sophisticated mathematical modelling that allowed biologists to address central questions about the emergence of social behaviour, leading to the development of inclusive fitness theory. The replicator-vehicle view saw genes as packets of information, transmitted across generations, and conveying instructions for a developmental program. For many critics this view was taken as preformationist, as an assertion that the gene contained everything and should be privileged in causal models of form.
In my book The Modern Synthesis: Evolution and the Organization of Information (pictured above) I give a detailed history of the Synthesis. I argue that the use of information concepts during this period, and since, has been informal and that this informality has enable a reified view of information to emerge. By this I mean that in colloquial terms scientists have talked as if information is something to be harvested and to be transmitted, and this in turn has allowed a view that information can have causal powers. This has much to do with misinterpretations of Shannon’s 1948 mathematical theory of communication, a theory that emerged just prior to information concepts in biology. Shannon’s work is often treated as a theory of information when in fact it was really a theory of data that enabled the quantification of information. I give the detail of this position and offer what I consider to be a more appropriate interpretation where information is seen as a functional outcome of the relationship between data (as input) and a context (or system) into which it is inputted.
Genes are data
Taking this contextual view of information, I then show how genes, or more precisely DNA codons, are to be seen as data that plays a role in protein synthesis contexts. I show how this view is inherent in the writings of the Modern Synthesis, but also how it enables us to make sense of development within evolutionary biology. Genes are causally prior in developmental sequences, but not conceptually central. Claims that the late-stage Modern Synthesis was gene-centric with respect to development are thus shown to be overwrought. More technically, I then spend several chapters investigating key aspects of the developmental challenge to the Modern Synthesis, showing how each mechanistic theory is entirely compatible with the Synthesis under a correct view of information.
The central claim of my book is that evolutionary processes enable the organization of information by selecting for data-context relationships. Life is fundamentally informational. But the book is also a defence of the Modern Synthesis, and I close by discussing how such large scale, framework theories act to corral and constrain multiple bespoke theories. Developmental biology is in the business of explaining the development of multiple different systems. It is unlikely that all these theories will cohere under one developmental framework, but as complex data processing systems they can all be made sense of in terms of evolution. In this way evolutionary theory provides an account not of specific forms but instead of the kinds of form that development must deliver.