The Logic of Life – Francois Jacob

This is one of those pieces where they ask you to revisit books that were important to you – so, after quite a few more years,  I’m now looking back at me looking back – an awkward posture, I agree.

However, I still think Jacob’s book (happily still in print from Princeton) is recommendable, as are his others like The Possible and the Actual and his unusually graceful autobiography The Statue Within. If I was proposing books for biologists now I’d probably start with Lewis Thomas or, even better, Loren Eiseley. But Jacob also allowed me to say some things about the Human Genome Project which don’t sound too far off the mark in retrospect…  Systems biology, anyone?


Brilliantly successful science often loses its memory. It was like that in the heroic days of molecular biology in the 1960s. A band of revolutionaries were sweeping all before them. Past approaches and techniques were of little interest in laboratories where the molecular machines which read, write and edit the genetic code were being taken apart piece by piece. Real biology was about doing experiments, preferably on organisms which reproduced as fast as bacteria (around 20 minutes) or even bacterial viruses. Everything else was mere natural history.

It was not a time for contemplation. As Watson says to Crick in the BBC’s Life Story, “If the apple won’t fall, let’s go shake the tree”. And the Anglo-American pair’s success in teasing out the structure of DNA had a style about it that others were inspired to emulate. By the end of the ’60s, the accumulated successes were so startling that some, notably the American geneticist Gunther Stent, were claiming there would soon be nothing left to discover. Others, like the French Nobel laureate  Jacques Monod in Chance and Necessity, wanted to build a philosophy of life on the new picture of molecules in motion inside the cell. His existentialist tract, now almost forgotten, was a surprising popular success at the time.

For his colleague (and co-winner of that Nobel) Francois Jacob, things looked quite different. As brilliant as any in the laboratory, he saw their collective endeavour as simply one stage in the unfolding of ideas about living systems. And his history was not the Whiggish retrospect typical of elderly scientists, but the recovery of how worldviews are constructed in accord with the dominant ideas of the time. Nor was it a breathless popularisation of the kind so prevalent then and now. To encounter his cooly composed account of the development of our understanding of heredity as a biologically-ignorant undergraduate in the 1970s, who was nevertheless being trained in molecular genetics, was to experience for the first time a completely different way of writing about science.

Part of the experience was to see an idea I had been groping for, without realising it, put into words. “Science”, Jacob told me, “is enclosed in its own explanatory system, and cannot escape from it”. It was not a formulation which would have occurred to my lecturers. It didn’t mean that the scientific story they were telling was any less splendid. But it did mean that one could grasp, dimly, how there might be other ways of looking at organisms which were equally revealing.

Certainly, such shifts had happened in the past, through a combination of advances in technique defining new objects of investigation, and reorganising biological knowledge around the concepts which arose in studying those objects. In a series of beautifully written chapters (I see more clearly now how beautifully written they are) Jacob told the story of ideas about the begetting of like by like. Once, they simply concerned the surfaces and shapes of creatures, the visible structure. As successive layers of organisation were revealed, so the ideas changed, influenced by the new phenomena thus uncovered and the cultural preoccupations of the time. The ancient tangle of forms, signs, affinities and resemblances yielded to species, then to the characteristics making up individual members of a species, then to cells, genes within cells, and finally to molecules composing the genes. Each shift in focus meant a reinvention of key features of the biological world.

Later, I read Kuhn’s startling Structure of Scientific Revolutions, and other philosophy of science, became acquainted with other sciences, other episodes from their history. But The Logic of Life alone was a superb corrective to the main weakness of an undergraduate education in a single science: the failure to acknowledge that there are varied styles of thought, and a range of ways of approaching problems. In any particular science there may be no immediate need to know this. In life, it is as well to bear it in mind.

Twenty years on, the dizzy onward rush of the human genome project is reinforcing the idea that everything in biology can be explained by teasing out the DNA text in more and more detail. Jacob, who help make such a project possible, cautions us to be open to the possibility that taking one kind of analysis to its limit will open the way to a new transformation in understanding. Just as in the past, it may only be when we have finally catalogued and read every gene that it is clear what genes are really good for, and what they are not. They will always be a crucial part of the logic of life, but there may yet be other logics to explore at other levels of organisation. The continuing appeal of Jacob’s fine book is that it implies that the most recent conclusions need not be the end of the story. (1996)

Francois Jacob, The Logic of Living Systems, trans Betty E Spillman. Allen Lane, 1974. (Logic of Life in the USA)

Life Story, BTW, was a BBC drama about the DNA discovery, scripted by William Nicolson, with Tim Piggott-Smith excellent as Batman Francis Crick, Jeff Goldblum as a memorably intense Robin James Watson, and Juliet Stephenson brilliantly cast as Rosalind Franklin. Also worth looking out.


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