The historical impact of What is Life? by Erwin "Has anybody seen my cat?" Schrodinger (1944) was massive- although it has never been satisfactorily explained.
In a nutshell, the book, and the men it brought into biology (mostly from physics) and the approach they took; transformed - or redefined - biology from the study of living things to the study of replicating things.
Schrodinger was one of the greats of quantum physics, towards the end of the era in which theoretical physics has been perhaps the greatest intellectual endeavour in the history of Man. He was awarded the Nobel prize in 1933. Then he turned his mind to consider biology - to consider Life.
Schrodinger's little 91 page book was written from lectures given to the 'general public' in Dubln, and substantially based on ideas from ex-physicist Max "phage" Delbruck, who became the father of molecular biology; and What is Life seems to have been decisive in bringing Francis Crick from Physics to biology (who took-over from Delbruck as the intellectual leader), and was instrumental in converting James Watson from old-style biology, attracting physicists such as Maurice Wilkins and Gunther Stent into the field, and others.
"Everybody" read it.
When a book of 'popular science' has this kind of impact, it is less a matter of what is in the book, and more a matter of what people got out of it.
In a straightforward way, what the physicists got from What is Life? was the intellectual approach: the way that Schrodinger talked about 'the gene' as a physical entity - its probable size, structure - of great stability and yet great variety, and of the notion of a genetic 'code'.
In a deeper way, I think, the book was important for what it did not say. In particular, it did not say anything to answer the question What is Life?
Schrodinger changed the subject in both senses of transforming the professional practice of biology (and the nature of its practitioners) and the less admirable sense of cutting-off the previous conversation and beginning another.
In this sense, the book was a classic 'bait and switch' - the reader expects to learn what life is, but by the end he has 'bought' a new vision of biology in which the question 'what is life?' has been discarded, and a novel focus on genes, information and replication has been substituted.
The reader is, or was, so entranced and excited by the possibilities of the new vision - possibilities which were which were more-than-amply fulfilled over the next three decades - that he probably fails to notice what has happened.
Schrodinger barely talks about the nature of life, and living things, except to dismiss as incoherent the idea that it has to do with 'metabolism'.
So another deep message of Schrodinger's book is to discard any remnants of 'vitalism' from biology - any notion of a subject unified by being specifically about 'living things' - the perspective from which the discovery of the structure of DNA could be seen as being the 'meaning' of life.
In a nutshell - Schrodinger killed 'vitalism' - the idea that there was 'something special' about living things, which set them apart from non-living things. This was one way of getting rid of a troublesome notion which seemed to be going nowhere, and was congenial to the atheist anti-religiousness of the new generation - Francis Crick said that this was a major motivation in moving from physics: to destroy the vestiges of religious thinking in biology and thereby in culture generally.
So Schrodinger treated biology as if its essence consisted wholly of problems in mathematics, physics, and chemistry. Later thinkers then (usually implicitly) redefined biology from the study of 'alive' things to the study of things-that-replicated by natural selection.
Natural selection (which had, in the period coming up to Schrodinger's book, been put onto a solidly genetic foundation with the Modern Synthesis) became the sole and sufficient cohering feature of the subject of biology - so that Dobzhansky could later accurately state that nothing in biology makes sense except in the light of evolution. And gene replication was at the centre of it all.
So the expert 'biologists', the high status biologists, became those who had the technical ability to study the gene.
From What is Life onwards, biology as a subject fell apart. High status 'biology', the kind that has the influence, gets the jobs, the major publications and (most importantly) the money - has not been biological in its orientation, but mathematics, physics, chemistry and, nowadays, medicine (the boast, promise or hope to alleviate human suffering).
Other parts of biology have linked up with other external forces - ecology with green politics, systematics with conservation politics, breeding with commercial interests and so on.
Biology qua biology has virtually disappeared - indeed it has come to seem meaningless; embarrassing even - naive, gauche, soft-headed and quasi religious.
Post-Schrodinger biology cannot say anything about what is life, cannot tell the difference between being alive and dead, is almost indifferent to question of the origins of life on earth; and indeed regards life as merely an elaborate and roundabout mechanism to ensure gene replication.
And, because of the anti-vitalism and anti-religiousness which was built-into this project from the start, the stunning successes of molecular biology and what came after have been taken as proof that life - for humans as well as every other animal and the plants - really-is nothing-but gene replication.