In 2010 the journal Nature included a supplement devoted to recent insights on the concept of plasticity. This publication pointed out that uncovering the molecular and cellular mechanisms underlying this plasticity is a dynamic area of biology and biomedicine. Indeed, as the introduction stressed, the topic’s appeal is in part due to multiple studies over the past few decades that have shown that cells are considerably more plastic than had been thought. In other words, research has shown the capacity of cells or organisms to vary their properties or behavior when environmental conditions change. As the editors put it,

“Plasticity refers to the capacity of organisms or cells to alter their phenotype in response to changes in their environment. This property can be studied at the level of the genome (by analysing epigenetic modifications), the individual cell, and the organism (during development of the embryo or changes in behaviour in adults, for example). In contrast to previously held views, recent studies show that cells are remarkably plastic. Revealing the molecular and cellular mechanisms that underlie this plasticity is a dynamic area of biology and one that holds great promise for developing new therapies.” [1]

Plasticity in the Life Sciences by philosopher Antonine Nicoglou is another example of the expanded interest in this topic. She details the subject from early, historical embryological research and expands her analysis into what is called the extended synthesis today. The extended synthesis is a set of theoretical concepts said to be more comprehensive than what is seen as the earlier modern synthesis of evolutionary biology that took place between 1918 and 1942, the year that Evolution: The Modern Synthesis by Julian Huxley set out his vision of the modern synthesis of evolutionary biology of the mid-20th century [2].

Nicoglou’s quite comprehensive book is a complex inquiry that grew out of her 2013 PhD thesis. She offers a compendium of ideas that will appeal more to specialists than general readers of scientific literature. With this in mind, let me begin this review by admitting that I am in the latter category. While reading the book I found myself at times exhausted by the extensive detail within this quite technical commentary. In other words, I am not equipped to fully critique this treatise’s philosophical arguments and analysis to the degree a philosopher could. Indeed, the philosophical discussions left me with the impression that Nicoglou had left no stone unturned. Yet, it was also clear from the beginning that the biological literature she references stresses the epistemological rather than the medico-social dimension. She does not interweave plasticity with medical research, developing therapeutics, the importance of novel technologies in advancing the studies of organisms, and how social ideas (e.g., historical ideas about the soul) impact analyses and assumptions.

More specifically, in Nicoglou’s view, the constant presence of the concept of plasticity in the biological literature can be interpreted in two different ways:

“The first interpretation implies that there is a kind of resistance of plasticity in biology, as one would speak of the “resistance of the wind,” which is the means by which the wind manifests its own presence. In this interpretation the persistence of the concept of plasticity is a sign of the resistance of a theoretical approach that biologists have tried to maintain throughout the history of the discipline despite the constant changes that exist in the understanding of biological reality. The second interpretation that I propose is to see this constant presence as the recurrence of the same concept throughout history and in the different sciences of life: the concept of plasticity can then be seen as an index of an invariable and indispensable constant to account for the specificity of life, even if it remains difficult to define clearly.” (p. 232)

The book itself includes a quite tantalizing introduction followed by two substantive parts. The introduction offers a series of examples that suggested the book would examine modifications, mutations, and experimentation to a greater degree than it does. The fascinating examples she opens with included the reorganization of the internal structures of locomotion of a bipedal goal; the transformation of a male clown fish into a female clown fish; the different types of patterns that the map butterfly adopts depending on whether it develops in spring or in summer; the different shapes of the leaves of the water buttercup depending on their position above or below the surface of the water; and the stem cells that divide, multiply, and differentiate into muscle cells, “each time the biologist invokes the remarkable ‘plasticity of the living world’ ” (p. 3). She introduces these concepts to underscore that her intention is to move beyond the genetic determinism she sees as prevalent in the field and intertwined with older philosophical ideas.

In the first part, titled “Concepts of Plasticity in the History of the Life Sciences,” Nicoglou presents five chapters that delineate her arguments. These take plasticity from Aristotle to contemporary biology. Chapter One begins with “Theories of Plasticity in the Philosophy of Nature.” In this chapter the author identifies the origins of what she sees as the two major trends that show how the term plasticity is used, and she dates this coupled usage back to Aristotle. The first is usage in an active sense, “as the ability to generate form.” The second is based on its passive sense, “the ability to adopt a variety of possible forms” (p. 3). These two positionings are the foundation to the epistemological analysis of the concept she develops in Chapter Two.

Chapter 2, “The Plastic Embryo,” is used to develop an epistemological analysis of the concept of plasticity from the seventeenth century until the end of the twentieth century, with Chapter 3, “The Emergence of an Operational Concept of Plasticity in Genetics” adding genetics to the mix. According to Nicoglou, comparing the concept of plasticity in embryology and the concept of plasticity in genetics allows her to show that the epistemological concepts go back to Aristotle and seventeenth century theories of generation.

In Chapter 4, “Plasticity in Evolutionary Biology: A Boundary Concept,” she introduces her ideas on boundary, a topic that comes up repeatedly throughout the book. Nicoglou argues that genetics opened a new page, and it was one that came to be articulated within the theory of natural selection, especially once natural selection was extended into all areas of biology. She also notes that part of the value in including the boundary concept stems from how it makes it possible to mark certain limits rather than sealing off the links between different explanations. Boundaries offer a means for thinking of different biological signals as existing in a place where they can be distinctly different from one another.

By this point it was increasingly clear that the author thought that the idea of plasticity has always had an important role in the way we think about life processes and continues to play a role in contemporary biological accounts of the specific nature of living systems. Nonetheless, I found myself increasingly flummoxed by my inability to put a conceptual finger on precisely what she meant by plasticity. She clarifies this sense that there is a definitional problem in Chapter Four when she introduces Gavin Rylands de Beer’s (1899-1972) Embryology and Evolution, published in 1930. As she explains, his was the “first work to highlight the rampant polysemy of the term plasticity in biology and the theoretical difficulties that can arise from it” (p. 92). In other words, like consciousness, the word plasticity has many possible meanings, and this is one of the difficulties in writing abut it. As a reader trying to keep track of the theories and ideas that Nicoglou presented, the polysemy problem was equally in play in the author’s well-researched and highly nuanced discussion.

The second part of the book, “Biological Plasticity: Two Ways to Explain Variation,” proposes a way of distinguishing between different phenomena described by the term plasticity. The first approach concerns cases where the concept of plasticity is used by biologists to refer to phenomena that explain developmental or physiological variation (Chapter 6, “Biological Plasticity, an Explanans in Developmental Process”). The second concerns cases where the concept is used to account for phenomena that are specifically subject to natural selection and are therefore understood from an evolutionary perspective (Chapter 8 “Biological Plasticity, an Explanandum in Evolutionary Process”). It should be noted that an explanans is a collection of propositions that, taken together, explain another proposition (the explanandum). This approach underscored that the study has a philosophical foundation. Between the explanans and explanandum is Chapter 7, which frames a question biologists wrestle with, “Biological Plasticity, a Synonym for Biological Regulation?”

Chapter 9, “Plasticity in the Evolutionary Developmental Synthesis: Toward an Integration of Explanations?” is perhaps the strongest chapter in the book. Nicoglou attempts to offer a synthesis and therefore weighs how biologists have begun to qualify the importance of genetic information relative to other factors such as the environment and developmental factors. This evo-devo framework was effectively presented because the author expands beyond the theoretical qualification element and includes more experimental approaches.

By Chapter 10, “Plasticity in the Life Sciences: Resistance or Recurrence,” the discussion has confirmed that the plasticity debate is lively and ongoing. In this last chapter, Nicoglou concludes that a unified and coherent synthesis is possible even if the questions philosophers ask about plasticity are not resolved so much as they are reframed over the course of time. Admittedly, I don’t think I would state it that way. Although many of the theoretical ideas of concern in developmental biology, embryology, genetics, evolution and their synthesis are recurring, I nonetheless think that we currently know move about living systems than earlier epochs did, as is evident in research ranging from studies on congenital disorders to topics like neuroplasticity. I also think that technological innovations have given a multi-dimensional perspective to theoretical debates. So, there is indeed a continual reframing of the debates in the light of new knowledge that makes it challenging to maintain a coherent synthesis.

References

[1] Skipper, M., Weiss, U., & Gray, N. (2010). Plasticity. Nature, 465(7299), 703-703. https://doi.org/10.1038/465703a.

[2] Huxley, Julian. Evolution: The Modern Synthesis. G. Allen & Unwin Ltd, 1942.