In the decades since James Watson and Francis Crick determined its double helical structure, much has become known about DNA. But the tiny molecular machines known as ribosomes, which are responsible for translating the information of genes into proteins via a chemical intermediate known as messenger RNA, have presented a more significant challenge to scientists. Indeed, Watson once stated that the structure of ribosomes was so complex that it would be impossible ever to comprehend it. To attempt to do so would be tantamount to career suicide.
In his candid and carefully observed book Gene Machine: The Race to Decipher the Secrets of the Ribosome, Nobel Laureate Venki Ramakrishnan provides a lucid, charming and eminently understandable first-hand account of how he and an assorted collection of fearless scientific pioneers attempted to unravel the structural secrets of the ribosome. The book has all the excitement of a detective novel, successfully communicating the thrill of the chase while also stressing the importance of the MRC Laboratory of Molecular Biology in Cambridge, known as the LMB, in which much of the modern science of molecular biology was invented. The LMB achieved this, in part, by insisting that investigators work in small but carefully selected groups and focus on only the most important scientific problems. It also helped buffer the immense career risk that embarking on such projects entailed by not insisting that its scientists produced regular articles for publication. The eventual success of Ramakrishnan’s team represented a major milestone in scientific history.
In She Has Her Mother’s Laugh: The Powers, Perversions, and Potential of Heredity, Carl Zimmer examines the concept of heredity and delves into the history of genetics. He does so, in part, by exploring his own genome and Jewish ancestry and delivering a series of thoughtful, artfully interwoven historical anecdotes. He charts some early examples of mankind’s attempts to manipulate heredity through selective breeding. The 18th-century farmer Robert Bakewell, for example, once described as having ‘invented sheep’, scoured the country for the finest specimens of rams. He then crossbred them with a humdrum local breed called Old Leicester to produce the transformed New Leicester breed of super-sheep. The successes of this type of breeding project led to the convoluted logic of eugenics. One of the earliest eugenicists, Francis Galton, predicted that the ‘men and women of the present day are, to those we might hope to bring into existence, what the pariah dogs of the streets of an Eastern town are to our own highly-bred varieties’.
Zimmer demonstrates the fallacies behind the simplistic and poorly contrived ideas of eugenics, emphasising the influence of extensive interbreeding on human evolution and the role played by the environment and a host of other non-genetic factors in determining the way we are. It turns out that many human characteristics are not controlled by single genes or even by small groups of genes. They are instead ‘omnigenic’, being influenced by complex networks of genes that operate in concert. He argues that the concept of heredity must be adapted to accommodate this. His book is erudite, well researched and highly engaging.
In his entertaining The Book of Humans: The Story of How We Became Us, Adam Rutherford assails the notion of human exceptionalism while simultaneously detailing why it is that humans are, nevertheless, a highly distinctive species. Not unsurprisingly it is once again the extragenetic agencies of human culture and social organisation that differentiate us from all other species and establish us as the ‘paragon of animals’.
Although some of the characteristics once thought to be uniquely human are discernible in other organisms, our ability to make, in the words of Wilhelm von Humboldt, ‘infinite use of finite means’ through language, writing and combinatorial technologies such as printing and word processing enabled humankind to develop in an unprecedented manner. These abilities have their roots in the evolution of a brain capable of abstract thought.
Rudimentary examples of some of the capabilities previously thought to be uniquely human may be found in several species of animals. Tool use, for example, has been observed in creatures ranging from octopuses to monkeys. Elephants are known to break branches off trees and use them to swat flies. Chimps use sticks to extract honey from beehives and stones to crack open nuts, while New Caledonian crows use hooked tools to extract grubs. Black kites appear to have developed the ability to manipulate fire by picking up smouldering twigs and depositing them selectively so that they can perform a ‘turkey shoot’ on fleeing animals.
Perhaps the most important challenge to the doctrine of genetic essentialism – the reductionist notion that information in genes is the principal causal determinant of human structure and behaviour – has come from the emerging field of heritable epigenetics. In Lamarck’s Revenge: How Epigenetics is Revolutionizing Our Understanding of Evolution’s Past and Present, Peter Ward puts forward an original and compelling case for the role of epigenetic inheritance in life’s history. Although many aspects of Jean-Baptiste Lamarck’s theory, including his idea that evolution is driven by a force compelling species to a state of continued perfection, were manifestly wrong, emerging evidence suggests that, in certain species and specific situations, some life events may indeed impact genes, permanently altering the chemical marks attached to DNA through a chemical process known as methylation. Such ‘imprinted’ genes may in some instances be passed on to offspring.
Ward argues that at times of significant environmental stress, such as mass extinctions and ice ages, and also periods of social stress, such as famines, epigenetic modes of evolution become more prominent. Unfortunately, he fails to provide compelling evidence for the relevance of this type of epigenetic development to humans, reviewing the literature inadequately and not making a clear distinction between the evidence for epigenetic inheritance in species other than humans and in humans themselves.
In his entertaining and thought-provoking Primate Change: How the World We Made is Remaking Us, Vybarr Cregan-Reid explores how genes comprise just a portion of the overall story of heredity. He argues that DNA sequences are like the script of a Shakespeare play. The same script will be used in a production put on by the Royal Shakespeare Company and at an elementary school, but might generate quite different results.
Whereas genetic evolution operates over protracted timelines, cultural evolution is rapid and occasionally immediate. As a result, the physical and biochemical configuration of our bodies is out of step with the environment that we now inhabit. The sedentary lifestyle of current times is a case in point. Rather than sitting at desks in offices, our hunter-gather ancestors spent thirty to forty hours a week foraging for food. The cultural change that has fostered inactivity has been a potent contributor to many of the illnesses that afflict us, including diabetes and heart disease. It is compounded by the large quantities of processed foods we consume that are laced with sugar.
The artefacts that we have created reinforce our self-imposed maladaptive tendencies. Chairs, for example, were rare in the past – the 18th-century poet William Cowper extolled the exotic experience of reclining on a sofa in 1785 – but these items are now commonplace. There are today more than fifty billion sofas scattered across the planet.
As Carl Zimmer states in his book, if we wish to comprehensively capture the diverse factors that shape human nature, we will need to ‘loosen the boundaries of what we call heredity’. I suggest that the term ‘informiome’ be used to encompass both the genetic and the extragenetic information that together define human nature and contribute to human heredity. In the future, human genomes will be written and rewritten, reconfigured, repaired and redesigned with the same ease with which we edit text on computer screens. The ethical issues are unfathomable. Despite the obvious medical advantages, the potential for the coupling of eugenic principles with this unprecedented new power looms menacingly over humankind’s future.