Developmental systems theory
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Developmental systems theory (DST) is an overarching theoretical perspective on
biological development Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem c ...
,
heredity Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inform ...
, and
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
. It emphasizes the shared contributions of
genes In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
, environment, and
epigenetic In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are "o ...
factors on developmental processes. DST, unlike conventional scientific theories, is not directly used to help make predictions for testing experimental results; instead, it is seen as a collection of philosophical, psychological, and
scientific models Scientific modelling is a scientific activity, the aim of which is to make a particular part or feature of the world easier to understand, define, quantify, visualize, or simulate by referencing it to existing and usually commonly accepted ...
of
development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...
and
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
. As a whole, these models argue the inadequacy of the
modern evolutionary synthesis Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely: * Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and s ...
on the roles of genes and
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...
as the principal explanation of living structures. Developmental systems theory embraces a large range of positions that expand biological explanations of organismal development and hold modern evolutionary theory as a misconception of the nature of living processes.


Overview

All versions of developmental systems theory espouse the view that: * All
biological process Biological processes are those processes that are vital for an organism to live, and that shape its capacities for interacting with its environment. Biological processes are made of many chemical reactions or other events that are involved in the ...
es (including both evolution and development) operate by continually assembling new structures. * Each such
structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
transcends the structures from which it arose and has its own systematic characteristics, information, functions and laws. * Conversely, each such structure is ultimately
irreducible In philosophy, systems theory, science, and art, emergence occurs when an entity is observed to have properties its parts do not have on their own, properties or behaviors that emerge only when the parts interact in a wider whole. Emergence ...
to any lower (or higher) level of structure, and can be described and explained only on its own terms. * Furthermore, the major processes through which
life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...
as a whole operates, including
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
, heredity and the development of particular organisms, can only be accounted for by incorporating many more layers of structure and process than the conventional concepts of ‘
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
’ and ‘
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
’ normally allow for. In other words, although it does not claim that all structures are equal, development systems theory is fundamentally opposed to
reductionism Reductionism is any of several related philosophical ideas regarding the associations between phenomena which can be described in terms of other simpler or more fundamental phenomena. It is also described as an intellectual and philosophical pos ...
of all kinds. In short, developmental systems theory intends to formulate a perspective which does not presume the causal (or
ontological In metaphysics, ontology is the philosophical study of being, as well as related concepts such as existence, becoming, and reality. Ontology addresses questions like how entities are grouped into categories and which of these entities exis ...
) priority of any particular entity and thereby maintains an explanatory openness on all empirical fronts. For example, there is vigorous resistance to the widespread assumptions that one can legitimately speak of genes ‘for’ specific
phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
characters or that adaptation consists of evolution ‘shaping’ the more or less passive species, as opposed to adaptation consisting of organisms actively selecting, defining, shaping and often creating their niches.


Developmental systems theory: Topics


Six Themes of DST

#Joint Determination by Multiple Causes: Development is a product of multiple interacting sources. #Context Sensitivity and Contingency: Development depends on the current state of the organism. #Extended Inheritance: An organism inherits resources from the environment in addition to ''genes.'' #Development as a process of construction: The organism helps shape its own environment, such as the way a beaver builds a dam to raise the water level to build a lodge. #Distributed Control: Idea that no single source of influence has central control over an organism's development. #Evolution As Construction: The evolution of an entire developmental system, including whole ecosystems of which given organisms are parts, not just the changes of a particular being or population.


A computing metaphor

To adopt a computing metaphor, the reductionists (whom developmental systems theory opposes) assume that causal factors can be divided into ‘processes’ and ‘data’, as in the Harvard computer architecture. Data (inputs, resources, content, and so on) is required by all processes, and must often fall within certain limits if the process in question is to have its ‘normal’ outcome. However, the data alone is helpless to create this outcome, while the process may be ‘satisfied’ with a considerable range of alternative data. Developmental systems theory, by contrast, assumes that the process/data distinction is at best misleading and at worst completely false, and that while it may be helpful for very specific pragmatic or theoretical reasons to treat a structure now as a process and now as a datum, there is always a risk (to which reductionists routinely succumb) that this methodological convenience will be promoted into an ontological conclusion. In fact, for the proponents of DST, either all structures are both process and data, depending on context, or even more radically, no structure is either.


Fundamental asymmetry

For reductionists there is a fundamental asymmetry between different causal factors, whereas for DST such asymmetries can only be justified by specific purposes, and argue that many of the (generally unspoken) purposes to which such (generally exaggerated) asymmetries have been put are scientifically illegitimate. Thus, for developmental systems theory, many of the most widely applied, asymmetric and entirely legitimate distinctions biologists draw (between, say, genetic factors that create potential and environmental factors that select outcomes or genetic factors of determination and environmental factors of realisation) obtain their legitimacy from the conceptual clarity and specificity with which they are applied, not from their having tapped a profound and irreducible ontological truth about biological causation. One problem might be solved by reversing the direction of causation correctly identified in another. This parity of treatment is especially important when comparing the evolutionary and developmental explanations for one and the same character of an organism.


DST approach

One upshot of this approach is that developmental systems theory also argues that what is inherited from generation to generation is a good deal more than simply genes (or even the other items, such as the fertilised zygote, that are also sometimes conceded). As a result, much of the conceptual framework that justifies ‘ selfish gene’ models is regarded by developmental systems theory as not merely weak but actually false. Not only are major elements of the environment built and inherited as materially as any gene but active modifications to the environment by the organism (for example, a termite mound or a beaver’s dam) demonstrably become major environmental factors to which future adaptation is addressed. Thus, once termites have begun to build their monumental nests, it is the demands of living in those very nests to which future generations of termite must adapt. This inheritance may take many forms and operate on many scales, with a multiplicity of systems of inheritance complementing the genes. From position and maternal effects on gene expression to epigenetic inheritance to the active construction and intergenerational transmission of enduring niches, development systems theory argues that not only inheritance but evolution as a whole can be understood only by taking into account a far wider range of ‘reproducers’ or ‘inheritance systems’ – genetic, epigenetic, behavioural and symbolic – than
neo-Darwinism Neo-Darwinism is generally used to describe any integration of Charles Darwin's theory of evolution by natural selection with Gregor Mendel's theory of genetics. It mostly refers to evolutionary theory from either 1895 (for the combinations of Dar ...
’s ‘atomic’ genes and gene-like ‘replicators’. DST regards every level of biological structure as susceptible to influence from all the structures by which they are surrounded, be it from above, below, or any other direction – a proposition that throws into question some of (popular and professional) biology’s most central and celebrated claims, not least the ‘central dogma’ of Mendelian genetics, any direct determination of phenotype by genotype, and the very notion that any aspect of biological (or psychological, or any other higher form) activity or experience is capable of direct or exhaustive genetic or evolutionary ‘explanation’. Developmental systems theory is plainly radically incompatible with both neo-Darwinism and information processing theory. Whereas neo-Darwinism defines evolution in terms of changes in gene distribution, the possibility that an evolutionarily significant change may arise and be sustained without any directly corresponding change in gene frequencies is an elementary assumption of developmental systems theory, just as neo-Darwinism’s ‘explanation’ of phenomena in terms of reproductive fitness is regarded as fundamentally shallow. Even the widespread mechanistic equation of ‘gene’ with a specific DNA sequence has been thrown into question, as have the analogous interpretations of evolution and adaptation.Levins and Lewontin 1985. Likewise, the wholly generic, functional and anti-developmental models offered by information processing theory are comprehensively challenged by DST’s evidence that nothing is explained without an explicit structural and developmental analysis on the appropriate levels. As a result, what qualifies as ‘information’ depends wholly on the content and context out of which that information arises, within which it is translated and to which it is applied.


Criticism

Philosopher Neven Sesardić, while not dismissive of developmental systems theory, argues that its proponents forget that the role between levels of interaction is ultimately an empirical issue, which cannot be settled by ''a priori'' speculation; Sesardić observes that while the emergence of lung cancer is a highly complicated process involving the combined action of many factors and interactions, it is not unreasonable to believe that smoking has an effect on developing lung cancer. Therefore, though developmental processes are highly interactive, context dependent, and extremely complex, it is incorrect to conclude main effects of heredity and environment are unlikely to be found in the "messiness". Sesardić argues that the idea that changing the effect of one factor always depends on what is happening in other factors is an empirical claim, as well as a false one; for example, the bacterium Bacillus thuringiensis produces a protein that is toxic to caterpillars. Genes from this bacterium have been placed into plants vulnerable to caterpillars and the insects proceed to die when they eat part of the plant, as they consume the toxic protein. Thus, developmental approaches must be assessed on a case by case basis and in Sesardić's view, DST does not offer much if only posed in general terms.
Hereditarian Hereditarianism is the doctrine or school of thought that heredity plays a significant role in determining human nature and character traits, such as intelligence and personality. Hereditarians believe in the power of genetics to explain human c ...
Psychologist
Linda Gottfredson Linda Susanne Gottfredson (née Howarth; born 1947) is an American psychologist and writer. She is professor emeritus of educational psychology at the University of Delaware and co-director of the Delaware-Johns Hopkins Project for the Study of I ...
differentiates the "fallacy of so–called "interactionism"" from the technical use of ''gene-environment interaction'' to denote a non–additive environmental effect conditioned upon genotype. “Interactionism's” over–generalization cannot render attempts to identify genetic and environmental contributions meaningless. Where behavioural genetics attempts to determine portions of ''variation'' accounted for by genetics, environmental–developmentalistics like DST attempt to determine the ''typical'' course of human development and erroneously conclude the common theme is readily changed. Another Sesardić argument counters another DST claim of impossibility of determining contribution of trait influence (genetic vs. environment). It necessarily follows a trait cannot be causally attributed to environment as genes and environment are inseparable in DST. Yet DST, critical of genetic heritability, advocates developmentalist research of environmental effects, a logical inconsistency. Barnes et al., made similar criticisms observing that the innate human capacity for language (deeply genetic) does not determine the specific language spoken (a contextually environmental effect). It is then, in principle, possible to separate the effects of genes and environment. Similarly, Steven Pinker argues if genes and environment couldn't actually be separated then speakers have a deterministic genetic disposition to learn a specific native language upon exposure. Though seemingly consistent with the idea of gene–environment interaction, Pinker argues it is nonetheless an absurd position since empirical evidence shows ancestry has no effect on language acquisition — environmental effects are often separable from genetic ones.


Related theories

Developmental systems theory is not a narrowly defined collection of ideas, and the boundaries with neighbouring models are porous. Notable related ideas (with key texts) include: * The
Baldwin effect In evolutionary biology, the Baldwin effect, a phenotype-first theory of evolution, describes the effect of learned behaviour on evolution. James Mark Baldwin and others suggested during the eclipse of Darwinism in the late 19th century that an ...
*
Evolutionary developmental biology Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved. The field grew from 19th-century beginni ...
*
Neural Darwinism Neural Darwinism is a biological, and more specifically Darwinian and selectionist, approach to understanding global brain function, originally proposed by American biologist, researcher and Nobel-Prize recipient Gerald Maurice Edelman (July 1, ...
*
Probabilistic epigenesis Probabilistic epigenesis is a way of understanding human behavior based on the relationship between experience and biology. It is a variant form of epigenetics, proposed by American psychologist Gilbert Gottlieb in 1991. Gottlieb’s model is based ...
* Relational developmental systems


See also

*
Systems theory Systems theory is the interdisciplinary study of systems, i.e. cohesive groups of interrelated, interdependent components that can be natural or human-made. Every system has causal boundaries, is influenced by its context, defined by its structu ...
*
Complex adaptive system A complex adaptive system is a system that is ''complex'' in that it is a dynamic network of interactions, but the behavior of the ensemble may not be predictable according to the behavior of the components. It is ''adaptive'' in that the individ ...
*
Developmental psychobiology Developmental psychobiology is an interdisciplinary field, encompassing developmental psychology, biological psychology, neuroscience and many other areas of biology. The field covers all phases of ontogeny, with particular emphasis on prenatal, p ...
* '' The Dialectical Biologist'' - a 1985 book by
Richard Levins Richard "Dick" Levins (June 1, 1930 – January 19, 2016) was an ex-tropical farmer turned ecologist, a population geneticist, biomathematician, mathematical ecologist, and philosopher of science who researched diversity in human populations. Un ...
and
Richard Lewontin Richard Charles Lewontin (March 29, 1929 – July 4, 2021) was an American evolutionary biologist, mathematician, geneticist, and social commentator. A leader in developing the mathematical basis of population genetics and evolutionary theory, h ...
which describe a related approach. *
Living systems Living systems are open self-organizing life forms that interact with their environment. These systems are maintained by flows of information, energy and matter. In the last few decades, some scientists have proposed that a general living systems ...


References


Bibliography

* ::Reprinted as: : : : * Dawkins, R. (1976). ''The Selfish Gene''. New York: Oxford University Press. * Dawkins, R. (1982). ''The Extended Phenotype''. Oxford: Oxford University Press. * Oyama, S. (1985). The Ontogeny of Information: Developmental Systems and Evolution. Durham, N.C.: Duke University Press. * Edelman, G.M. (1987). ''Neural Darwinism: Theory of Neuronal Group Selection''. New York: Basic Books. * Edelman, G.M. and Tononi, G. (2001). ''Consciousness. How Mind Becomes Imagination''. London: Penguin. * Goodwin, B.C. (1995). ''How the Leopard Changed its Spots''. London: Orion. * Goodwin, B.C. and Saunders, P. (1992). ''Theoretical Biology. Epigenetic and Evolutionary Order from Complex Systems''. Baltimore: Johns Hopkins University Press. * Jablonka, E., and Lamb, M.J. (1995). ''Epigenetic Inheritance and Evolution. The Lamarckian Dimension''. London: Oxford University Press. * Kauffman, S.A. (1993). ''The Origins of Order: Self-Organization and Selection in Evolution''. Oxford: Oxford University Press. * Levins, R. and Lewontin, R. (1985). '' The Dialectical Biologist''. London: Harvard University Press. * * Neumann-Held, E.M. (1999). The gene is dead- long live the gene. Conceptualizing genes the constructionist way. In P. Koslowski (ed.). Sociobiology and Bioeconomics: The Theory of Evolution in Economic and Biological Thinking, pp. 105–137. Berlin: Springer. * * * Waddington, C.H. (1957). ''The Strategy of the Genes''. London: Allen and Unwin.


Further reading

* Depew, D.J. and Weber, B.H. (1995). ''Darwinism Evolving. System Dynamics and the Genealogy of Natural Selection''. Cambridge, Massachusetts: MIT Press. * Eigen, M. (1992). ''Steps Towards Life''. Oxford: Oxford University Press. * Gray, R.D. (2000). Selfish genes or developmental systems? In Singh, R.S., Krimbas, C.B., Paul, D.B., and Beatty, J. (2000). ''Thinking about Evolution: Historical, Philosophical, and Political Perspectives''. Cambridge University Press: Cambridge. (184-207). * Koestler, A., and Smythies, J.R. (1969). ''Beyond Reductionism''. London: Hutchinson. * Lehrman, D.S. (1953). A critique of Konrad Lorenz’s theory of instinctive behaviour. ''Quarterly Review of Biology'' 28: 337-363. * Thelen, E. and Smith, L.B. (1994). ''A Dynamic Systems Approach to the Development of Cognition and Action''. Cambridge, Massachusetts: MIT Press.


External links

* William Bechtel
Developmental Systems Theory and Beyond
presentation, winter 2006. {{DEFAULTSORT:Developmental Systems Theory Biological systems Systems theory Evolutionary biology