Book review of D'Arcy Thompson

D'Arcy Thompson:
ON GROWTH AND FORM (Cambridge University Press, 1917)

Home | The whole bibliography | My book on Consciousness

In this 1917 classic, D'Arcy Thompson provides a mathematical analysis of biological processes, especially growth and form. D'Arcy believes that natural selection has a limited function in evolution: it removes the "unfit", but it does not account for significant progress. D'Arcy believes that new structures arise because of mathematical and physical properties of living matter, just like the shape of nonliving matter. Form is a mathematical problem, and growth is a physical problem. The form of an object is the resultant of forces. By simply observing the object, we can deduce the forces that have acted or are acting on it. This is easily proved of a gas or a liquid, whose shape is due to the forces that "contain it", buit it is also true of solid objects like rocks and car bodies, whose shapes are due to forces that were applied to them. D'Arcy believes that living organisms also owe their form to a combination of internal forces of molecular cohesion, electrical or chemical interaction with adjacent matter, and global forces like gravity. The formative power of natural forces expresses itself in different ways depending on the "scale" of the organism. Mammals live in a world that is dominated by gravity. Bacteria live in a world where gravity is hardly visible but chemical and electrical properties are significant. D'Arcy investigates what physical forces would be responsible for the surface-tension that holds together and shapes the membrane of a cell, and then analogously for cell aggregates, i.e. tissues, and then skeletons. While his formulas have not stood up to experimental data, the underlying principle is still powerful: D'Arcy believes that genetic information alone does not fully specify form. Form is due to the action of the environment (natural forces) and to mathematical laws. D'Arcy was fascinated by the geometric shapes of shells and sponges and believed that their geometry could not be explained on the basis of genetics but would be explained in terms of mathematical relationships. D'Arcy discovered an interesting property of life. Many animal forms can be shown to be homologous on a warped Cartesian diagram: bend the space a bit and the shape of an animal becomes the shape of another animal.

Permission is granted to download/print out/redistribute this file provided it is unaltered, including credits.