Charalambos Kyriacou on the spicy world of evolutionary genetics.
The origin of life is one of the most intriguing areas in biology. Assuming divine intervention was not involved, scientists from a number of disciplines have been making some significant headway into this problem over the past few decades. The suggestion that life may have emerged from the pre-biotic ingredients of the primeval soup some 3.5 billion years ago, was first made in the 1920s. In 1953, Stanley Miller passed an electric discharge through an atmosphere of methane, ammonia, water and hydrogen and found that a number of organic molecules had been created. These included precursors of ribose (the sugar constituent of RNA), nucleic acids (chemicals A, C, G and U, or T in RNA and DNA) and a number of amino acids (from which proteins are made).
Moving from these molecules to "life", in which replication becomes the most significant feature, requires some quantum leaps of the imagination. Nevertheless, a consensus view has emerged over the past 25 years that RNA was the first replicating molecule that gave way to the extant "DNA world".
This is not just fanciful thinking. In 1982, Thomas Cech was studying a short RNA molecule in an unfashionable single-celled ciliate, Tetrahymena, that seemed to have magic, catalytic properties reminiscent of modern enzymes. This RNA molecule folded into a complex shape that, with a little bit of energy, resulted in its cutting itself into smaller pieces then sticking together what was left. Not very exciting you might think, but the discovery of ribozymes (RNA molecules with catalytic activity), earned Cech the Nobel prize.
Later, in the 1990s, a cottage industry developed in which random pools of RNA molecules were selected for having catalytic properties, such as the ability to stick together two amino acids (the beginning of the polypeptide chain). To cut a long story short, if ribozymes are catalytic, it is not beyond the realms of possibility that they evolved the ability to replicate themselves and, after a few billion years of Darwinian evolution, Bob's-your-uncle, and here we are.
Adrian Woolfson's Life without Genes describes some of these developments and also attempts to convince us that replicating systems need not be based around RNA. His thesis is that even before RNA, there was, nonetheless, a form of life. He takes theoretical and experimental evidence from a variety of disciplines, particularly chemistry and mathematics, and juxtaposes them, showing how interlocked chemical reactions can autocatalyse themselves, in effect, replicating their constituent molecules. For example, a string of 36 amino acids can replicate itself without an RNA template, representing life without genes.
Using simple analogies, Woolfson skilfully guides us through some of the relevant experiments and computer models that demonstrate the auto-assembly of complex systems from simple precursors, order from chaos. He writes beautifully and at the same time, he entertains and informs. His final chapter takes us from his version of life's origins to modern organisms, including an all-too-brief look (do not believe the hype on the cover) at the dark possibilities of "improving" the competitive Darwinian efficiency of organisms (read "us") by incorporating synthetic materials.
My main criticism of this book is that the first 100 or so pages are somewhat contrived and seem to be a vehicle for repeating what the reader already knows. The fact that there are infinite possibilities for apples, animals, toys, genes or proteins or whatever, and that what has gone on before constrains the possibilities that follow, can be written in a paragraph.
The rest of the book is also rather wordy, in that the 350 pages of text could easily have been compressed into half the volume. Nevertheless, once I got into it, I thoroughly enjoyed it, so please persevere. Woolfson has managed successfully to negotiate the tightrope between a serious academic and a popular science book (and it has a gorgeous cover). Because I teach a final-year module on evolutionary genetics in which I discuss the origins of life, I will put my money where my word processor is and recommend that my students read from page 103 onwards.
A Monk and Two Peas by Robin Henig is a little more prosaic than the title suggests. It gives us some idea of the personality of Gregor Mendel, the somewhat mysterious Czech monk who was to become (after his lifetime) the founder of modern genetics. Not only does it describe Mendel as a quiet, lonely, gentle, extremely popular, yet mischievous soul, but also points out that he did have some idea about how important he was to become. He sent his reprints describing his classic pea-crossing experiments to Darwin, as well as other leading biologists of the period. How-ever, even if Darwin had bothered to read them (he clearly did not, as the page folds had not been cut), Henig doubts that Darwin was bright enough to understand the implications. Curiously, as Mendel knew about Darwin, but not vice versa, one wonders why the monk did not develop the theory of natural selection based on the hereditary principles that he himself had discovered. The answer to this is that once he was promoted to abbot, he spent more of his time running the monastery at Brno or following up his work with other plants. These would never give him the same crystal-clear results as his peas.
Mendel is not the only player in the saga, but he is definitely one of the good guys, as is Darwin. The bad guy is William Bateson, the garrulous Cambridge biologist who, in the early 1900s, over-aggressively championed Mendelism after its rediscovery in 1900 by Hugo de Vries, Karl Correns and Erich von Tschermack, 35 years after Mendel's original publications. These three do not come across as nice guys either. Correns, who named Mendel's laws, was grumpy at continually being scooped by the brilliant and nasty old misogynist de Vries (who was probably gay). Tschermack, an intellectual lightweight, would later figure as a prominent Nazi. This is all good, spicy, gossipy stuff that paints an interesting picture of a bygone scientific world that nevertheless has echoes in today's competitive academic environment. The narrative moves along nicely, is never dull and the book is definitely one to put on the general reading list for first-year biology undergraduates.
Charalambos P. Kyriacou is professor of behavioural genetics, University of Leicester.
Life Without Genes
Author - Adrian Woolfson
ISBN - 0 00 255618 9 and 654874 1
Publisher - HarperCollins
Price - £17.99 and £8.99
Pages - 409