10 September 2018 (Crete, Greece) — In the winter of 1943, the physicist Erwin Schrödinger invited the Dublin public to hear him deliver a series of lectures he described as “difficult” and that “could not be termed popular”. Some 400 people were undeterred and were among the first to hear Schrödinger offer his views on how physics could shed light on the puzzling ability of living organisms to maintain molecular order and organization in the face of what seemed to be the randomizing forces of nature.
Seventy-five years on, some of his ideas remain difficult — controversial even. But they are popular, and are once again drawing people to the Irish capital. This past week Trinity College Dublin hosted “Schrödinger at 75 — The Future of Biology”, at which a stellar cast of speakers will consider the future of disciplines ranging from ageing and plant science to infectious disease and consciousness.
Note: Schrödinger gave those lectures in the depths of the Second World War. Exiled from Austria when it was annexed by Nazi Germany, Schrödinger had been invited to Ireland to help establish the Dublin Institute for Advanced Studies.
Schrödinger’s lectures were collected into what he called his “little book”, and published in 1944 under the title What is Life? It was reprinted in 2012 and you can get it on Amazon. Some consider it one of the most influential scientific books of the twentieth century. I think it is still good reading today for his look at in diverse interdisciplinary fields. He was indeed a man far ahead of his time.
And you need to see the historical perspective. The introduction to the recent reprint notes that since the 1930s, biology had been turning from a largely descriptive science into one concerned with mechanism. Thanks to studies such as those by geneticist Thomas Hunt Morgan on fruit flies, researchers were starting to understand heredity in terms of the transmission of genes, envisaged as large molecules arranged on chromosomes. Many expected genes to be proteins. However, even as Schrödinger was preparing his lectures, the microbiologist Oswald Avery was finding evidence that they were nucleic acids. Thus, What Is Life? dropped into a tumultuous time for science as well as for sociopolitics.
It is also important to note that Schrödinger steps into these cross-disciplinary waters cautiously. He declared himself a “naive physicist”, pondering how life sustains itself and transmits genetic mutations stably across generations. His work on quantum mechanics had earned him a Nobel prize in 1933, but that was hardly qualification for commenting on biology, in which Schrödinger had previously shown little interest beyond forays into the physiology of vision. Arguably … and this is me talking as an armchair physicist (my minor degree at university) … that naivety is the source of the book’s strengths as well as its weaknesses.
The book attracted scientists from other fields to the study of genetics and the molecular mechanisms of life, among them physicists Francis Crick, Maurice Wilkins and Seymour Benzer, chemist Gunther Stent and zoologist James Watson. But can the ideas in this slim volume really supply sufficient motivation for such a diverse programme?
Critics have rightly argued that the book was neither particularly original nor up to date. It limited itself mostly to a discussion of the molecular basis of inheritance through chromosomes. Here Schrödinger made the auspicious proposal that the genetic material is an “aperiodic crystal”: a structure with a specific but not periodic arrangement of atoms, encoding information that somehow guides the development of the organism. He said life is distinguished by a “code-script” that directs cellular organization and heredity, while apparently enabling organisms to suspend the second law of thermodynamics. As noted in their autobiographies, that vision resonated with Crick and Watson as they contemplated the structure of DNA in the following decade. But it wasn’t wholly original. As to how the genetic machinery works, Schrödinger could only point out that it seems to suspend the second law of thermodynamics, which states that total entropy must increase.
But there is one obvious concept missing from his analysis: information. The information theory of Claude Shannon and the cybernetics of Norbert Wiener in the 1940s and 1950s began to fill that lacuna, although only more recently have researchers begun to understand how information truly features in biology. As Schrödinger’s talk of negative entropy hinted, and what Crick and Watson would tell us, life is a pocket of out-of-equilibrium order in an open system, and the DNA code is just part of what sustains it.
The impact of What Is Life? lies more in its spirit than its substance. And as rhetorical theorist Leah Ceccarelli argued its success was really down to Schrödinger’s writing style: he managed to bridge physics and biology without privileging either. Schrödinger presented the problem of life as a puzzle posed to no single discipline. And his timing was perfect: biology was already changing from a largely descriptive, historical and organismal science to a mechanistic and microscopic one. This cross-disciplinary relevance applies equally to the topics addressed at the Dublin meeting. The physical-sciences content of artificial intelligence and complex systems is obvious, but understanding of (say) cognitive neuroscience, learning and memory and infectious disease can also benefit from wide-ranging expertise: for example, from the study of network topologies, the thermodynamics of information, and ergodicity (how widely a dynamic system explores its available states).
Happily, chemistry is welcomed to this table too. That subject, after all, is what biologists relied on mid-century to probe and better understand DNA, enzymes and cell signalling. The subsequent emergence of molecular biology, due in large part to some of those inspired by What Is Life?, means that whether Nobel prizes get assigned to ‘chemistry’ or ‘physiology or medicine’ is now as arbitrary as whether Nobels in nuclear science in the early twentieth century were awarded in chemistry or physics.
What Is Life? made the case that profound questions about the natural world aren’t owned by any academic discipline. Indeed, the Dublin meeting could have gone further by embracing Schrödinger’s epilogue on determinism and free will, which invoked philosopher Immanuel Kant and Hinduism (and spoilt the book’s chances of publication in devoutly Catholic Ireland). Some eyebrows were raised at this material, but Schrödinger’s friend Albert Einstein would have seen nothing amiss in it. Philosophers, ethicists, poets and theologians also have a stake in the future of life. Perhaps they will be invited to the centenary.