This review is part of a double bill. Cold Spring Harbor Laboratory Press recently published How Scientific Progress Occurs: Incrementalism and the Life Sciences. In it, Elof Axel Carlson explores the relevance to biology of the ideas Thomas S. Kuhn formulated in his book The Structure of Scientific Revolutions. Having read both books back-to-back, this review follows on the one of Kuhn’s book.

Carlson, a retired geneticist and historian of science, had the good fortune of meeting Kuhn around 1974. Not convinced that Kuhn’s model of scientific revolutions applied to the history of genetics, he asked Kuhn why the life sciences did not seem to show a history of paradigm shifts. Kuhn’s answer? The physical sciences depend more on theory than biology, and biology is largely descriptive. Beyond that, nothing more came of this exchange. Now, over four decades later, Carlson has set himself the task to revisit this topic and reflect more in-depth on how the life sciences have advanced and whether they obey Kuhn’s idea of paradigm shifts.

In eleven short chapters, Carlson gives canned histories of the rise of biological disciplines such as cell biology, genetics, microbiology, embryology, and evolution. Each chapter reaches deep back into history (regularly the 16th century, but Ancient Greece if necessary), highlighting the major players and key findings, adding colour and black-and-white illustrations, and ending each chapter with a helpful flowchart.

As you might have already guessed from the book’s subtitle, Carlson does not see paradigm shifts in any of these fields. Instead, he champions the idea of incrementalism: the life sciences advance in smaller and larger steps by constant experimentation, introduction of new technologies and tools, and emergence, fusion or splitting of fields of knowledge. Notably, Carlson says, new tools generate new theories rather than vice-versa. X-ray diffraction, for example, allowed the elucidation of the molecular structure of DNA, while the electron microscope increased our understanding of the internal structure of animal and plant cells.

“Carlson does not see paradigm shifts […] instead, he champions the idea of incrementalism: the life sciences advance in smaller and larger steps”

I admit that I started this book somewhat sceptical. Take for example the idea of spontaneous generation (see my review of Creatures Born of Mud and Slime: The Wonder and Complexity of Spontaneous Generation), this was a fully-fledged, well-reasoned idea that saw various explanations over time. It took several scholars (notably Louis Pasteur) experimentally showing that sterilisation prevents life from spontaneously emerging in, say, broth or a piece of meat for the majority of the scientific establishment to convert to the idea that life arises from pre-existing life. And, much like Kuhn says, Pasteur’s germ theory initially raised all sorts of new questions. It did not have all the answers, but it performed better as an explanation than spontaneous generation. To me, this seems like the archetypal example of a paradigm shift.

Carlson places this historical episode in a larger network of developments in our understanding of life cycles and does not think it a paradigm shift. Are we then to consider the various ideas of spontaneous generation as an example of what Kuhn calls the pre-paradigm period? A period in which everyone started from first principles and came up with completely different ideas to try and explain the observation of life arising, with germ theory being the first unifying paradigm to arise?

I admit that most of the historical episodes Carlson describes are best characterised as incrementalism rather than paradigm shifts (the history of evolutionary biology, the rise of genetics – these are examples where Carlson’s narrative leaves little doubt). And yet I cannot escape the nagging feeling that it almost depends on the resolution of your analysis, i.e. on what level you look at knowledge development. Zoom out far enough, and everything starts looking like a web of interconnected developments spawning new disciplines. But at a higher resolution, could some of these steps not be considered paradigm shifts for the research communities involved?

“Carlson thinks there are plenty of examples of revolutions in the life sciences, but […] not all revolutions are paradigm shifts.”

Carlson thinks not and seems to apply a strict definition of Kuhn’s paradigm shifts (i.e. asking: was there a preceding unifying theory? Was there a piling up of anomalies?). And yes, he thinks that there are plenty of examples of revolutions in the life sciences, but they are more often a consequence of new tools and procedures birthing new fields, without necessarily overthrowing old ones. Not all revolutions are paradigm shifts.

As you can see, I found How Scientific Progress Occurs an intellectually stimulating read, though it generated more questions that answers for me. Carlson concludes, reasonably, that other disciplines have a history of genuine paradigm shifts, and he, reasonably, does not seek to impose incrementalism on these disciplines either. Having explored Kuhn’s idea of paradigm shifts in my previous review of The Structure of Scientific Revolutions, I was very impressed with Kuhn’s book. Is biology special? Of course, as a biologist, I am predisposed to saying “yes!” – and Carlson’s well-written book provides much to sway me in that direction – but I cannot deny that I remain open to counterarguments.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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