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A provocative history probes the connections that are helping to unify scientific disciplines

Convergence: The Idea at the Heart of Science

Peter Watson
Simon and Schuster
573 pp.
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We often need different scientific fields to work together to make sense of the world. Take photosynthesis. Figuring out how plants convert light into energy requires quantum physics to understand how light excites electrons in chloroplasts, as well as cell biology and biochemistry to explain how plants harness those electrons to produce chemical energy.

For multidisciplinary approaches to work, a common ground first needs to exist between scientific fields. However, finding shared territory has not always been easy. In the late 19th century, for example, biologists were investigating whether a “vital force” was inherently necessary for life, and physicists were just about to discover the electron. At that time, it would have been an enormous leap to suggest that energy from electrons could be harvested by plants and that this energy was part of the mysterious force biologists were searching for.

Historian Peter Watson’s new book, Convergence, chronicles a series of major scientific milestones spanning the past two centuries, with the purpose of identifying when overlaps between different research fields began to occur.

One gets a sense that sciences meet almost serendipitously. In 1785, for example, James Hutton suggested that the heat of Earth was responsible for slowly turning mud and sand into sedimentary rocks, a theory that would become one of the fundamental principles of geology. A caveat of Hutton’s hypothesis was that Earth was millions, not thousands, of years old, as had previously been assumed.

This revision to Earth’s age was of use to Darwin, whose theory of evolution would have been difficult to reconcile with a shorter time frame. Indeed, it was later found that more biologically complex fossil specimens appear in younger rocks, a discovery that lent support to both Hutton and Darwin’s theories and gave way to the field of paleobiology.

When disparate sciences move closer together, the traditional borders that once kept them apart begin to weaken. This opens the door for imagining new questions that can only be addressed by drawing on the knowledge and techniques found in two converged fields.


Convergence in the fields of ethology and psychology led to the theory of attachment, argues Watson. The theory places the mother-infant bond in biological and evolutionary context.

Watson sheds light on what can be gained when different research areas achieve such convergence. One of the benefits that he identifies is the ability to break disciplines up into smaller pieces. For instance, our understanding of ecology is enriched by knowing the role that is played by genetics and is enhanced further still when we understand that genetics can be broken down into biochemistry and physics.

Reductionism is only one side of the coin. Just as much can be gained by investigating how systems-level sciences emerge out of more fundamental fields. It’s useful, for example, to describe a gene by the physical forces that hold it together, but it’s also worth asking what evolutionary pressures are responsible for causing that gene to exist in the first place.

Watson makes clear that convergence between different scientific branches is ongoing and that we are still struggling to understand how some phenomena fit together. We’re still unsure, for example, how consciousness can be produced from neuronal circuits or why subatomic particles are allowed to be in two places at once, whereas the macroscopic objects they make up are not.

Will we ever achieve complete convergence across every scientific field, thus producing a “master set of rules from which all truth would flow” (1)? Although we may not get that far, Watson is impressed by the progress made in the past 200 years and seems convinced that we are at least on the right path.
While Watson examines an impressive array of connections between disciplines, what’s missing is a rigorous evaluation of the strength of the associations being made. This is especially critical when exploring new frontiers of convergence, where the strong desire for a unified theory could encourage connections that are at best superficial. For instance, is the way that organisms code and express genes truly convergent with computer processing and information theory, or is this merely an analogy?

Although the links between fields may seem fragile in some places, Watson’s overall argument remains convincing. Whether you identify as a biologist, an astrophysicist, or a mathematician, one thing’s for certain: We’re all ultimately working with the same fabric.


  1. R. B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (Basic Books, 2006)

About the author

The reviewer is in the Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA.