Developmental systems theory

Developmental systems theory (DST) is an overarching theoretical perspective on biological development, heredity, and evolution. It emphasizes the shared contributions of genes, environment, and epigenetic 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 of development and evolution. As a whole, these models argue the inadequacy of the modern evolutionary synthesis on the roles of genes and natural selection as the principle 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 processes (including both evolution and development) operate by continually assembling new structures.
• Each such structure transcends the structures from which it arose and has its own systematic characteristics, information, functions and laws.
• Conversely, each such structure is ultimately irreducible 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 as a whole operates, including evolution, 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’ and ‘environment’ normally allow for.

In other words, although it does not claim that all structures are equal, development systems theory is fundamentally opposed to reductionism of all kinds. In short, developmental systems theory intends to formulate a perspective which does not presume the causal (or ontological) 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 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

1. Joint Determination by Multiple Causes

Development is a product of multiple interacting sources.

2. Context Sensitivity and Contingency

Development depends on the current state of the organism.

3. Extended Inheritance

An organism inherits resources from the environment in addition to genes.

4. 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.

5. Distributed Control

Idea that no single source of influence has central control over an organism's development.

6. 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’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.

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; Sesardic observes that while the emergence of lung cancer is a highly complicated process involving the combined action of many factors and interactions, this does not mean that is unreasonable to believe that smoking has an effect on developing lung cancer. Thus while even if at some level developmental processes are highly interactive, context dependent and extremely complex, it is incorrect to conclude that just because of this "messiness" that the main effects of heredity and environment are unlikely to be found. Sesardic 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 Sesardic's view, developmental systems theory does not offer much if only posed in general terms. Biologist Linda Gottfredson argues that while it is true interaction occurs, this does not mean that attempting to identify the genetic and environmental contributions is meaningless. Gottfredson argues that behavioural genetics attempts to determine how much of the variation between humans can be accounted for by genetics, whereas developmental systems theory is attempting to determine the typical course of human development. One can thus try to determine how much phenotype variation correlates to genetic variation, as opposed to environmental variation.

Sesardic also argued that if it is impossible to determine how much a trait is influenced by genetics and how much by environment, then this would mean that it cannot be meaningfully said that a trait was caused by environment (since genes and environment are, under developmental systems theory, inseparable), yet those advocating developmentalism do not have an issue with research into environmental effects, which Sesardic argues is inconsistent. Barnes et al made similar criticisms, observing that while language is an innate human capacity, the specific language a person speaks is determined by their environment, thus it is in principle possible to separate the effects of genes and environment. Steven Pinker argued that if genes and environment couldn't actually be separated, it would have to be argued, for example, that the English and Japanese speakers had a genetic predisposition to their native languages but required exposure to learn it all. Pinker argues that while this is consistent with the idea of the interaction of genes and environment, it is nonetheless an absurd position, since empirical evidence shows that ancestry has no effect on the language a person can acquire, showing that environmental effects can be separated 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
• Evolutionary developmental biology
• Neural Darwinism
• Probabilistic epigenesis
• Relational developmental systems

See also

• Systems theory
• Complex adaptive system
• Developmental psychobiology
• The Dialectical Biologist - a 1985 book by Richard Levins and Richard Lewontin which describe a related approach.
• Living systems

References

Bibliography

• Baldwin, J. Mark (23 August 1895). "Consciousness and Evolution". Science. 2 (34): 219–223. Bibcode:1895Sci.....2..219B. doi:10.1126/science.2.34.219. ISSN 0036-8075. PMID 17835006. {{cite journal}}: Invalid |ref=harv (help)

Reprinted as: Baldwin, J. Mark (1896). "Psychology". The American Naturalist. 30 (351): 249–255. doi:10.1086/276362. ISSN 0003-0147. JSTOR 2452622.

Baldwin, J. Mark (1896). "A New Factor in Evolution". The American Naturalist. 30 (354): 441–451. doi:10.1086/276408. ISSN 0003-0147. JSTOR 2453130. {{cite journal}}: Invalid |ref=harv (help)

Baldwin, J. Mark (1896). "A New Factor in Evolution (Continued)". The American Naturalist. 30 (355): 536–553. doi:10.1086/276428. ISSN 0003-0147. JSTOR 2453231.

Baldwin, J. Mark (1902). Development and Evolution. New York : Macmillan. Retrieved 1 January 2020. {{cite book}}: Invalid |ref=harv (help)

• Dawkins, R. (1976). The Selfish Gene. New York: Oxford University Press.
• Dawkins, R. (1982). The Extended Phenotype. Oxford: Oxford 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.
• Lewontin, Richard C. (2000). The Triple Helix: Gene, Organism, and Environment. Harvard University Press. ISBN 0-674-00159-1. {{cite book}}: Invalid |ref=harv (help)
• 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.
• Oyama, S. (2000). The Ontogeny of Information: Developmental Systems and Evolution, Second Edition. Durham, N.C.: Duke University Press.
• Oyama, Susan; Griffiths, Paul E.; Gray, Russell D., eds. (2001). Cycles of contingency : developmental systems and evolution. MIT Press. ISBN 9780262150538. {{cite book}}: Invalid |ref=harv (help); Unknown parameter |editorlink1= ignored (|editor-link1= suggested) (help); Unknown parameter |editorlink2= ignored (|editor-link2= suggested) (help); Unknown parameter |editorlink3= ignored (|editor-link3= suggested) (help)
• Gottfredson, Linda (2009). "Logical Fallacies Used to Dismiss the Evidence on Intelligence Testing". In Phelps, Richard P. (ed.). Correcting Fallacies About Educational and Psychological Testing (1st ed.). American Psychological Association. ISBN 978-1-4338-0392-5. {{cite book}}: Invalid |ref=harv (help)
• 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.