Monday, January 26, 2015

The Logic of Life, by François Jacob

The Logic of Life (La logique du vivant) opens with the following quote by the French philosopher and Enlightenment figure Denis Diderot:
"Do you see this egg? It's with it that we overturn all theological schools and all temples on Earth".
[All translations in this post are mine.]
The choice of a 18th century thinker for the epigraph prefigures a lot of this book, which was published by the late Nobel laureate François Jacob in 1970. The booksubtitled "a history of heredity"thus proves to be of great erudition and cites the original work of, among many names, Paré, Montaigne, Paracelse, Descartes, Galilée, Harvey, Réaumur, Buffon, Redi, Leibniz, D'Holbach, La Mettrie, Lamarck, Linné, Geoffroy Saint-Hilaire... and I haven't even mentioned the 20th century references yet! Excusez du peu!

This story of heredity truly is a huge endeavor, spanning about four centuries of philosophical and scientific attempts to understand what kind of stuff we're made of. Articulated in long chapters that correspond to conceptual milestones ("visible structure", "organization", "time", "gene", "molecule", and "integron"), the book follows the chronological development of our biological knowledge (which was part of "natural philosophy") with plenty of referenced sources and with a quality of writing that is hardly matched today.

This "history of heredity" reads also somewhat as a history of biology. Our understanding of living things ("le vivant"), interestingly, evolved through extreme stages, as Jacob explains throughout the book: from being of the same essence than the inert world (17th century and before), to being something different altogether, possessing a vital force (18th)—and back to being not fundamentally different from the rest of the physical world (19th century to this day).

One thing I particularly enjoy about the logic of life is how it shows us the genius of minds from the past, as they show extraordinary insights given the limits of their time. For instance (translations are mine):

Geoffroy Saint-Hilaire:
"Nature constantly uses the same materials and is ingenious only in varying its forms."
Cuvier, talking about an organism and how it interacts with its environment:
"Its sphere spreads beyond the limits of the living body itself."
"The animal machine is governed by three principal regulators: respiration, which consumes oxygen and carbon and produces calorific; transpiration, which increases or decreases depending on calorific needs; finally digestion, which gives back to blood what it loses by respiration and transpiration."
Jacob is undoubtedly one of these great minds (he helped create molecular biology!). Interestingly, Jacob shows us in his book how the development of biology is tightly intertwined with the development of the other sciences, notably physics and chemistry.  He insists, for instance, on the parallels between population biology (starting with Darwin) and statistical mechanics (with Gibbs and Boltzmann): both are laws that consider very large numbers (of organisms or atoms). He writes (p. 213): "The concepts of energy and equivalence thus come play one of the roles that biology in its youth had to give to vital force."
And this analysis, p. 266:
"To constitute itself as a science, biology had to distantiate itself radically from physics and chemistry. In the middle of the twentieth century, to continue the analysis of the structure of living beings and their functioning, it has to closely associate with them. From this union will come molecular biology."
This is a clever and important book, highly recommended!


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