Move to the EES

This blog covers the core concepts and arguments typically involved. Integrating Development and Inheritance: The Epigenetic System, Evo-Devo, and the Case for an Extended Evolutionary Synthesis The theory of evolution, as solidified in the 20th century's Modern Synthesis (MS), provided a framework centered on genes as the primary unit of inheritance and variation. Natural selection, genetic drift, mutation, and gene flow acting on randomly generated genetic variation were seen as the principal engines of evolutionary change. However, accumulating evidence from diverse fields, particularly developmental biology and epigenetics, has prompted a call by researchers for an 'Extended Evolutionary Synthesis' (EES). This proposed extension seeks to integrate phenomena inadequately addressed or conceptualized by the MS, arguing that factors like developmental processes and non-genetic inheritance play crucial causal roles in evolution. The interc...

For decades, the neo-Darwinian synthesis has provided the dominant framework for understanding evolution. It posits that evolution occurs through the gradual accumulation of random genetic mutations within a population, with natural selection acting upon the resulting phenotypic variations. Inheritance, in this view, is almost exclusively mediated by the DNA sequence passed from parents to offspring. This process operates on long timescales, with significant evolutionary change typically unfolding over many generations. However, the burgeoning field of epigenetics is introducing a profound challenge this picture, revealing inheritance mechanisms that operate on potentially much shorter timescales and challenging some core assumptions of the traditional model. The Long Timescale: Genetic InheritanceGenetic inheritance is the bedrock of classical evolutionary theory. It involves the transmission of genes – specific sequences of DNA – from one generatio...

The Modern Synthesis, a fusion of Darwinian natural selection and Mendelian genetics, has been the main emphasis in evolutionary biology for nearly a century. It trys to explains the gradual adaptation of populations through the inheritance of gene variations acted upon by environmental pressures. However, the past few decades have witnessed a surge of discoveries that challenge the completeness of this framework, leading to a vibrant debate about the need for an "Extended Evolutionary Synthesis" (EES). At the heart of this discussion lies the burgeoning field of epigenetics and its profound implications for our understanding of heredity and evolutionary change, directly confronting some of the core tenets of neo-Darwinism. Neo-Darwinism, the prevailing interpretation of the Modern Synthesis, emphasizes the gene as the primary unit of inheritance and the sole source of heritable variation. Evolution, in this view, is driven by random genetic mutations ...

The paper "Unmodern Synthesis: Developmental Hierarchies and the Origin of Phenotypes" by Richard Gawne, Kenneth Z. McKenna, and H. Frederik Nijhout, published in BioEssays in 2018, presents a critical perspective on the Modern Evolutionary Synthesis (MES) and argues for a more integrated understanding of how phenotypes originate. The authors contend that while the MES has been successful in explaining the mechanisms of evolutionary change at the population genetic level, it falls short in providing a comprehensive account of the developmental processes that generate phenotypic variation, the raw material upon which natural selection acts. Gawne, McKenna, and Nijhout propose a hypothetical "Unmodern Synthesis" (UMS) as a contrasting framework. This UMS emphasizes the hierarchical nature of biological organization and the active role of developmental processes at all levels in shaping phenotypes. Unlike the gene-centric view often associated with the MES,...