Extended Evolutionary Synthesis
The Extended Evolutionary Synthesis (EES) is a contemporary research program in evolutionary biology that argues classical Modern Synthesis theory is incomplete and requires significant extension to accommodate phenomena that have become well-documented in the last fifty years.
The program does not reject the Modern Synthesis but proposes that its conceptual apparatus needs to be broadened to include developmental, epigenetic, ecological, and behavioral processes that the original synthesis treated as peripheral or did not address at all.
The term itself was introduced by Massimo Pigliucci and Gerd Müller in their 2010 edited volume Evolution: The Extended Synthesis. The program has been developed substantially by Kevin Laland, Tobias Uller, Marcus Feldman, Eva Jablonka, Marion Lamb, Sonia Sultan, Denis Walsh, John Odling-Smee, and others.
A key statement of the position is Laland and colleagues' 2015 paper "The extended evolutionary synthesis: its structure, assumptions and predictions" in Proceedings of the Royal Society B.
A substantial faction of evolutionary biologists, including prominent figures like Jerry Coyne and Douglas Futuyma, argue that the Modern Synthesis already accommodates most of what EES proposes, or that EES proponents overstate the novelty and importance of their claims. The debate continues, and the EES should be understood as a contested research program rather than as established theory.
What the EES extends
The Modern Synthesis, consolidated in the 1930s and 1940s through the work of R. A. Fisher, J. B. S. Haldane, Sewall Wright, Theodosius Dobzhansky, Ernst Mayr, and others, established evolutionary biology on a foundation of population genetics, Mendelian inheritance, and natural selection.
Its core claims were that evolution consists of changes in allele frequencies in populations, that variation arises through genetic mutation and recombination, that selection operates on phenotypes determined largely by genotypes, and that inheritance occurs through DNA transmission across generations.
The Modern Synthesis was a remarkable achievement and remains the backbone of evolutionary thinking. But its formulation left several features of biology underemphasized or unaddressed. The EES proposes that the following features should be brought into the center of evolutionary theory.
Developmental bias. The variation on which selection acts is not random with respect to phenotype. Developmental systems channel variation in particular directions, making some phenotypes more accessible than others. This means that the available variants are biased by the structure of developmental processes, not produced by uniform random sampling of phenotype space. Evolutionary outcomes are therefore shaped by what development makes possible, not only by what selection favors.
Inclusive inheritance. Information is transmitted across generations through multiple channels, not only through DNA. Epigenetic inheritance (DNA methylation patterns, histone modifications, small RNAs) can transmit acquired states across one to several generations. Parental effects transmit nutritional, hormonal, and behavioral information independent of genetic transmission. Cultural inheritance, particularly in humans, transmits learned information across generations on much faster timescales than genetic inheritance. Niche construction transmits modified environmental conditions to descendants through physical persistence.
Niche construction. Organisms actively modify their environments through metabolic activity, physical structures, and behavior. These modifications change the selection pressures that act on themselves and their descendants. The environment is therefore partly endogenous to evolutionary processes rather than an external selecting force. (See Niche construction for fuller treatment.)
Developmental plasticity. Organisms produce different phenotypes in response to different environmental conditions, using the same underlying genome. This plasticity is itself a product of evolution and can be the leading edge of evolutionary change, with genetic variation following behind to accommodate phenotypes that have proved successful through plastic response.
These four extensions form the core of the EES, though different proponents emphasize different elements. The program is therefore not a single unified theory but a research community with overlapping commitments.
What the EES claims and does not claim
To prevent misreadings, it is worth being explicit about what the EES actually proposes.
The EES does not claim that natural selection is wrong, that genes are unimportant, or that the Modern Synthesis should be abandoned. It claims that selection and genetic inheritance are real and important but not exhaustive, and that other processes operate alongside them in shaping evolutionary outcomes.
The EES does not revive Lamarckism in the strict sense. Lamarckian somatic-to-germline transfer of acquired characteristics is not what epigenetic inheritance, ecological inheritance, or cultural inheritance involves. The EES recovers some Lamarckian intuitions through non-Lamarckian mechanisms. (See Lamarckism and Covolution.)
The EES does claim that evolutionary processes involve more channels of variation, more channels of inheritance, and more directions of causation than the Modern Synthesis incorporated. It claims that organisms are active participants in evolution rather than passive subjects of selection. It claims that development, ecology, behavior, and culture are not peripheral to evolution but integral to it.
The EES does propose specific empirical predictions that differ from those of the classical synthesis. For example, EES proponents predict that organisms in stable environments will accumulate developmental robustness rather than continuing to vary genetically, that niche-constructing species will show coevolutionary patterns with their modified environments, and that plastic responses to novel conditions will precede genetic accommodation rather than being driven by it. These predictions are being tested in ongoing empirical research.
The current state of the debate
The EES is contested within evolutionary biology, and the contest is partly substantive and partly framing.
The substantive contest concerns whether the processes EES emphasizes really do produce evolutionary outcomes that classical theory cannot accommodate. Critics argue that classical population genetics is more flexible than EES proponents acknowledge and that most or all of the phenomena cited can be incorporated into existing models without fundamental revision. Defenders argue that the existing models have to be stretched substantially to accommodate the phenomena and that the resulting theory is meaningfully different from the original synthesis.
The framing contest concerns whether the EES is a genuine paradigm shift, a modest extension, or rhetorical packaging of established ideas. Proponents have sometimes spoken in revolutionary terms; critics have often responded that no revolution is occurring. The reality is probably between these positions: the EES does represent meaningful changes in how evolutionary biology is framed, but it does not constitute a Kuhnian paradigm shift in the strong sense.
The empirical work continues regardless of the framing debate. Researchers studying niche construction, developmental plasticity, epigenetic inheritance, and cultural evolution are producing real findings that any complete evolutionary theory must accommodate. Whether these findings require formal extension of the synthesis or can be absorbed into existing frameworks is partly a matter of theoretical taste and partly a substantive question that future work will continue to address.
How the EES relates to covolution
The covolution framework and the EES share substantial conceptual territory. Both treat organisms as active participants in evolution rather than passive subjects of selection. Both recognize multiple channels of inheritance beyond DNA. Both emphasize the importance of organism-environment co-construction. Both extend evolutionary thinking beyond the strict variation-and-selection model of the Modern Synthesis.
But the two frameworks are not identical, and the differences matter.
Scope. The EES is a research program within evolutionary biology, focused on extending biological theory to accommodate phenomena that classical evolution underemphasized. Covolution is a broader framework that extends across substrates — biological, cognitive, social, technological — and addresses phenomena beyond strict biological evolution. The EES is concerned with how lineages change across generations; covolution is concerned with how horons at any scale construct and refine their possibility-spaces. The EES is a subset of what covolution addresses; covolution is broader than the EES.
Vocabulary. The EES uses biological terminology — alleles, phenotypes, selection, inheritance, plasticity. Covolution uses framework-specific terminology — horons, switches, symvironments, parafates, paradetermination. The two vocabularies map onto each other in many cases (a biological horon is an organism; a biological symvironment is a niche; covolutionary activity in biology includes much of what EES calls niche construction and developmental plasticity), but they are not identical, and the covolution vocabulary is more abstract and substrate-independent.
Status. The EES is an active research program within evolutionary biology, with empirical investigators, theoretical models, and ongoing debates. Covolution is a theoretical framework developed primarily by Jong Bhak that is at an earlier stage of development. The EES has more institutional standing, more empirical grounding, and more contested debate within biology. Covolution has broader scope but less developed empirical infrastructure.
Compatibility. The frameworks are compatible. Covolution accepts EES findings about niche construction, developmental plasticity, inclusive inheritance, and developmental bias as describing real phenomena. The covolution framework treats these as biological cases of more general patterns that operate across substrates. A biologist working within the EES could adopt the covolution framework as a broader theoretical context without revising their empirical commitments. A covolution-aligned researcher could adopt EES findings as the most developed biological articulation of phenomena the covolution framework addresses more abstractly.
The right relationship is collaborative rather than competitive. The EES is the leading edge of biological work in the territory covolution addresses, and covolution is a broader theoretical framing in which EES findings find natural placement.
What covolution adds beyond the EES
The covolution framework offers several things that the EES does not develop, or develops only narrowly.
Substrate generality. The EES is a biological program. Covolution treats biological evolution as one case of a broader pattern that includes cognitive, social, and technological evolution. This generality lets covolution address phenomena like cultural evolution, institutional change, and technological development with the same theoretical apparatus rather than treating them as separate domains.
Foundational vocabulary. Covolution provides terms like horon, horogenesis, horotropy, symvironment, parafate, and paradetermination that do not have direct counterparts in the EES literature. These terms allow conceptual moves that the EES cannot easily make, particularly around the formal characterization of distinguishability and the recursive multi-scale structure of horonic organization.
Connection to deeper foundations. Covolution connects biological evolution to the Zeroth State Hypothesis and the cosmological emergence of state-spaces. This places biological evolution within a broader account of how distinguishability and informational structure arise in the universe. The EES has no comparable cosmological framing because it is focused specifically on biological lineages.
Treatment of cognition and technology. The EES has some treatment of cultural evolution (particularly through Laland's work on niche construction in humans), but it does not have a developed account of cognitive horons or technological horons. Covolution provides a framework for thinking about these as continuous with biological evolution rather than as separate domains, which becomes increasingly important as artificial intelligence, biotechnology, and cognitive enhancement reshape the evolutionary landscape.
What the EES has that covolution should learn from
Honesty requires acknowledging that the EES has things the covolution framework currently lacks.
Empirical grounding. EES proponents work with real biological data, experimental studies of plasticity, comparative analyses of niche construction, mathematical models of inclusive inheritance.
The covolution framework is currently more conceptual than empirical.
Becoming as empirically grounded as the EES would require substantial work translating the framework's commitments into specific testable claims.
Disciplinary integration. EES is embedded in evolutionary biology with its conferences, journals, peer review, and intellectual community.
The covolution framework is more isolated, primarily developed within Jong Bhak's work and the covolution.org wiki.
Refined arguments with critics. EES proponents have responded to critics for over a decade, sharpening their claims and qualifying their commitments in response to substantive objections. The covolution framework has not been subjected to comparable critical pressure, and some of its claims are probably less defensible than they currently appear because the strongest objections have not yet been articulated.
Specific predictions. The EES has produced specific empirical predictions that differ from classical theory.
The covolution framework has not yet produced comparable predictions at this level of specificity.
Doing so would require working out what covolution actually predicts in concrete biological, cognitive, social, or technological systems, a substantial theoretical project.
These are areas where the covolution framework can productively learn from the EES rather than positioning itself as alternative or superior.
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