December 25, 2014

Does the Concept of "Paradigm Shift" Need a Rethink?

A faux relationship between the paradigm shift and the theoretical resynthesis. Although in terms of advancing theory, perhaps they indeed do arise from a common ancestor.

As someone who is interested in both evolutionary and "meta-" theory I read a recent comment paper in Nature [1] called "Does Evolutionary Theory Need a Rethink?" with great interest. In fact, I discussed this paper a bit in a Synthetic Daisies post from last month. There are some interesting issues here regarding the role of "extended evolutionary synthesis" ideas in making evolutionary inferences and predictions. However, the real issue here is whether theory best proceeds through soft "paradigm shifts" (in this case, extending the framework) or through "resynthesis" (in this case, relentless synthesis). As an emerging approach to evolutionary theory, the extended evolutionary synthesis includes ideas not typically embraced by the modern evolutionary synthesis [2, 3]. These might include developmental plasticity, evolvabilityepigenetic phenomena, genetic assimilation, and cultural evolution. The primary argument is not just that evolution involves more than just changes in allele frequencies over time, but that such mechanisms should take a more central role in the process of evolutionary change [4].

The landscape of how evolutionary theory might be rethought. WHITE: Darwin's core contributions, LIGHT GRAY: modern evolutionary synthesis, DARK GRAY: extended evolutionary synthesis. Notice that this diagram implicitly favors the addition of rather than a shift towards new topical areas (e.g. resynthesis over paradigm shift). COURTESY: Figure 1.1 in [2].

But why do we need to rethink theories anyway? The classic observation of theoretical change comes from Thomas Kuhn [5], who advocated the dual concepts of "theoretical paradigms" and "paradigm shifts". In the evolution of a given scientific field, many new findings and concepts are introduced over time. Yet there is also an so-called essential tension between traditional and upstart concepts. Only very occasionally, a set of findings or concepts takes root that sweeps away the prevailing worldview. Paradigm shifts are thus low-frequency events that are nonetheless transformative in the way people think about a given scientific field. As events in intellectual history, paradigm shifts can often be a neccessary progression in the history of a scientific field. This is due to both the integrative nature of theory itself and conceptual inertia from the scientific establishment.

Although less appreciated by Kuhn, the integrative nature of theory thus serves to act as a form of conceptual inertia. In terms of theoretical evolution, incremental changes are hard to come by as singular findings and propositions do not often stand on their own. To really understand what is going on, the incremental progress of empirical science must coalesce into an intellectually coherent framework. According to paradigm shifters, prevailing theoretical models tend to be established through what is often called "saltationist" or non-gradualist change. Yet I would argue that whether such advances occur through paradigm shift or through resynthesis requires an underlying set of favorable conditions in the existing literature.

Yet perhaps the predominance of paradigm shifts throughout the history of science is largely based on assumption. Earlier, I mentioned a tension between "soft paradigm shifts" and "resynthesis". It may seem that paradigm shifts are neccessary in order to enable the novel insights in understanding. However, suppose that instead of acting as a neccessity for theoretical change, the paradigm shift served as a bias for those who would build theory itself. This might explain why all too often there is an expectation that new ideas either paradigm shift a field or languish insignificantly.

As an alternative to the paradigm shift, theoretical resynthesis allows for additional information to be incorporated into an existing theoretical framework. While more conservative, it may be no less transformative. In Darwin's original formulation of evolution by natural selection, the concept of heredity was without a formal mechanism [6]. The modern evolutionary synthesis was formulated in part to reconcile the ideas of evolution by natural selection and heredity by independent assortment. While a paradigm shift might give us a sorely needed new perspective, it can also live up to the idiom of throwing out the baby with the bathwater. It is worth noting that while it may be possible to achieve an extended evolutionary synthesis through theoretical resynthesis, the tone of contemporary arguments for an extended synthesis (e.g. the Altenberg 16) tend to be biased towards a soft paradigm shift.

An example of a directed conceptual network, in this case featuring the intellectual evolution (1940s-present) of cybernetics and systems science. As we can see, there are several distinct intellectual traditions that cross-fertilize the field to various degrees and at various points in time. COURTESY: Castellani, Wikimedia Commons.

To answer the question of whether or not evolutionary theory needs a rethink, a literature mining exercise might be helpful [7]. This type of approach would allow us to characterize to what extent extended synthesis concepts are being considered alongside modern evolutionary synthesis concepts and vice versa in the same context. This can be characterized using a conceptual network of empirical studies. In our conceptual network topology, the overall connectivity of (e.g. linkages between) various concepts would represent their relative conceptual integration in empirical studies and literature reviews, which in turn provides a basis for theoretical advances. Think of such pre-existing linkages as the histroical contingencies of theoretical change. This is not typically considered in the paradigm shift model, but has consequences for resynthesis and paradigm shifts alike.

To illustrate how this approach might be useful, I will give two examples from the contemporary biological literature. For example, how often does a published paper consider population genetics alongside evo-devo? Alternatively, how often does cultural evolution get characterized as part of an integrated evolutionary process? In the case of the former, relatively few studies seem to sufficiently bridge population genetics and evo-devo [8]. In the case of the latter, there are only but a few established approach for using the mathematics of population genetics to characterize both genetical and cultural evolution in the same framework [9].

In terms of a network topology, each of these examples would represent sparsely connected and a bit more densely connected concepts, respectively. This also illustrates the difference between the need for a paradigm shift and room for accomodation via resynthesis. On the other hand, perhaps the state of the literature serves to predict which outcome is more or less likely. Even in cases like the cultural evolution example, examples of resynthesis might not be representative of the dominant approach.

[1] Laland, K., Uller, T., Feldman, M., Sterelny, K., Muller, G.B., Moczek, A., Jablonka, E., Odling-Smee, J., Wray, G.A., Hoekstra, H.E., Futuyma, D.J., Lenski, R.E., Mackay, T.F.C., Schluter, D., and Strassmann, J.E.   Does evolutionary theory need a rethink? Nature, October 8 (2014).

[2] Pigliucci, M. and Muller, G.B.   Evolution: the extended synthesis. MIT Press, Cambridge, MA (2010).

[3] Muller, G.B.   Evo-devo: extending the evolutionary synthesis. Nature Reviews Genetics, 8(12), 943-949 (2007).

[4] Lamb, M.J. and Jablonka, E.   Evolution in Four Dimensions. MIT Press, Cambridge, MA (2006).

[5] Kuhn, T.S.   The Structure of Scientific Revolutions. University of Chicago Press, Chicago (1962).

[6] For more, please see: Charlesworth, B. and Charlesworth, D.   Darwin and Genetics. Genetics, 183(3), 757-766 (2009) AND West-Eberhard, M.J.   Toward a modern revival of Darwin's theory of evolutionary novelty. Philosophy of Science, 75(5), 899–908 (2008).

[7] I am merely offering the suggestion for a full-scale analysis rather than providing one.

[8] Based on a cursory survey of PubMed entries for the terms "evo-devo" + "population genetics" (21 results). Also:

a) Two reviews that provide a verbal analysis of evo-devo's theoretical underpinnings (circa early 2000's) can be found here: Arthur, W.   The emerging conceptual framework of evolutionary developmental biology. Nature, 415, 757-764 (2002) AND Gilbert, S.F.   The morphogenesis of evolutionary developmental biology. The International Journal of Developmental Biology, 47, 467-477 (2003).

b) There is also a burgeoning but small field called "micro evo-devo". For more, see: Nunes, M.D.S., Arif, S., Schlotterer, C., and McGregor, A.P.   A Perspective on Micro-Evo-Devo: Progress and Potential. Genetics, 195, 625-634 (2013).

[9] The approaches established by Boyd and Richerson (Culture and the Evolutionary Process) and Cavalli-Sforza and Feldman (Cultural Transmission and Evolution: a quantitative approach) are illustrative of such resyntheses. However, other models of culture are less integrative, and one might argue that these examples are not the most complete or parsimonious way to integrate of biology and culture.

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