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In biology the developmental systems theory (DST) is a collection of models of biological development and evolution that argue that the emphasis neo-Darwinism places on genes and natural selection as explanation of living structures and processes is inadequate. Foundations of modern biology There are five unifying principles The Movement for Democracy in Liberia (MODEL was a rebel group in Liberia that became active in March 2003, launching attacks from Côte d'Ivoire. eVolution is the third Album by eLDee, it was due to be released in 2008 Neo-Darwinism is a term used to describe certain ideas about the mechanisms of Evolution that were developed from Charles Darwin 's original Theory of History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Structure is a fundamental and sometimes Intangible notion covering the Recognition, Observation, nature, and Stability of Developmental systems theory embraces a range of positions, from the view that biological explanations need to include more elements than the genes and selection processes that neo-Darwinism emphasises to the view that neo-Darwinism profoundly misconceives the nature of living processes and should be rejected completely.

Contents

Overview

All versions of developmental systems theory espouse the view that:

In other words, although it does not claim that all structures are equal, development systems theory is fundamentally opposed to reductionism of all kinds. Reductionism can either mean (a an approach to understanding the nature of complex things by reducing them to the interactions of their parts or to simpler or more fundamental things 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. In Philosophy, ontology (from the Greek, genitive: of being (part [1] 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. [2].

Developmental systems theory: Topics

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’. 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. [3] 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. [4] 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. This, once termites have begun to built 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 [5] to the active construction and intergenerational transmission of enduring niches [6], 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 [7] – than neo-Darwinism’s ‘atomic’ genes and gene-like ‘replicators’ [8] 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’. [9]

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 [10], as have the analogous interpretations of evolution and adaptation. [11]

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. [12]

Related theories

Developmental systems theory is by no means a narrowly defined collection of ideas, and the boundaries with neighbouring models are very porous. Notable related ideas (with key texts) include:

See also

References

  1. ^ Moss in Oyama et al. The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is an early evolutionary Theory put forward in 1896 in a paper "A New Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Systems theory is an Interdisciplinary field of Science and the study of the nature of Complex systems in Nature, Society, and Living systems theory is a General theory about the existence of all living Systems their Structure, Interaction, Behavior and Developmental psychobiology is an interdisciplinary field encompassing Developmental psychology, Biological psychology, Neuroscience and many other areas 2001: 90.
  2. ^ Lewontin 2000
  3. ^ See, for example, Oyama’s discussion of the use and misuse of norms of reaction in Oyama et al. 2001: 179-184.
  4. ^ Oyama in Oyama et al. 2001: 177-184.
  5. ^ Jablonka and Lamb 1995.
  6. ^ Lewontin 2000
  7. ^ Jablonka in Oyama et al. 2001
  8. ^ Dawkins 1976, 1982.
  9. ^ Oyama 1985; Oyama et al. 2001; Lewontin 2000.
  10. ^ Neumann-Held 1999; Moss in Oyama et al. 2001: 90-91
  11. ^ Levins and Lewontin 1985.
  12. ^ See Oyama 2000 for a detailed critique of information processing theory from a developmental systems perspective)
  13. ^ Baldwin 1895, 1896a, 1896b.
  14. ^ Levins and Lewontin 1985.
  15. ^ Ludwig von Bertalanffy 1950, 1971.
  16. ^ Edelman 1987; Edelman and Tononi 2001

Further reading

External links

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