Nature's Magic Algebra; or, How One Plus One Still Equaled One
Mark van der Giezen · BioScience · 2015
One who has never wondered about our origins has never truly lived. The origin of life is at the base of many religions, and the same topic has vexed scientists for centuries. It is also the basis of many heated debates regarding evolution. In One Plus One Equals One, John Archibald takes the reader along the scientific path of the origin and evolution of complex life. By taking a careful, stepwise scientific approach interspersed with anecdotes, Archibald shows that unweaving the rainbow does not make it less beautiful. We can still be in awe of the beauty of complex life despite knowing the molecular basis of many steps that led to its origin. The title of the book refers to one of the most sensational events in life: the transition from simple life (prokaryotes) to complex life (eukaryotes). This unique event in the history of life on our planet—in which one organism managed to establish itself (or was forced) inside another organism and then continued to live as a wholly new organism—dramatically changed the fate of our planet. Endosymbiosis has had long-reaching consequences for life on our planet, including our own lives. Archibald provides a journey through time, both on an evolutionary timescale and a more human one, describing key scientists’ insights that led to our current understanding of the eukaryotic cell. This provides a good introduction to modern cell biology, with a special emphasis on the two organelles of endosymbiotic origin, the mitochondrion and the chloroplast. Although perhaps ideally suited to biologists with an interest in (cellular) evolution, the book does contain good introductions to cell biology and molecular biology that will aid interested readers from diverse fields. John Archibald is a professor of biochemistry and molecular biology at Dalhousie University, in Canada, and is an internationally recognized expert on secondary endosymbiosis—in particular, nucleomorph evolution. In his book, he shares lively anecdotes of those who played key roles in this field, many of these from firsthand information. Throughout the book, Archibald leaves no doubt that plain curiosity and determination drove these scientists to their seminal discoveries. The description of Mike Gray getting giant sacks of wheat germ from a local mill to isolate enough starting material for his experiments or of Ford Doolittle dictating the 16S ribosomal RNA sequence from Escherichia coli over the phone to Carl Woese, who couldn't wait until the journal arrived at his own desk, are very entertaining. Such information enlivens the information that someone would get from merely reading the influential papers from Gray and Woese in Nucleic Acids Research and the Proceedings of the National Academy of Sciences, respectively. This is also one of the strengths of the book: It demonstrates that science is an endeavor like no other human enterprise, lived and conducted by real human beings of flesh and blood who have a lifelong passion for their field. That this passion sometimes turns into very heated debate is hardly surprising. Archibald describes the tensions that arise from new theories that challenge dogma—or established careers. What Archibald makes pretty clear, however, is that the advance of molecular biology turned a lot of speculative “chatter” into testable predictions and, boy, how unequivocal the outcomes of these experiments have been. Archibald describes the early struggles of visionaries such as Mereschkowsky over a century ago (whose observations and theories on the nature of chloroplasts were spot on), and he narrates the discovery of extranuclear DNA in this organelle in the 1960s and how it made for uncomfortable reading for those opposing an endosymbiotic origin of chloroplasts. Advances in molecular biology—from the struggles to demonstrate that DNA was the carrier of heritable information to the ability to read the molecular information of DNA—are described in vivid detail. Archibald's descriptions of the personal struggles of scientists in their dogged determination to succeed especially make this an entertaining read. The book starts with an accessible introduction to cell biology and molecular biology. This is crucial because later chapters are dependent on a sound understanding of these basic concepts. What follows are historical paths into our modern understanding of endosymbiosis. Schwendener's realization in the late nineteenth century that lichens are actually two organisms living together might be seen as the start of the path that ultimately led to the acceptance that mitochondria and chloroplasts were once free-living bacteria. Archibald paints a path of painful opposition by established scientists and subsequent years lacking progress. Ultimately, as a culmination of several unlikely converging events, Lynn Margulis's Origin of Eukaryotic Cells was published at the right time. Advances in molecular biology had led to the isolation of DNA in mitochondria and chloroplasts, and progress in protein and DNA sequencing enabled comparative analyses leading to the realization that molecular genealogies could be reconstructed. This ultimately resulted in the acceptance that mitochondria and chloroplasts were once—long ago—free-living bacteria. “Why would this be important?” asks Archibald. The greening of the continents and the rise of atmospheric oxygen are all due to the evolution of complex life. Although the title of the book is One Plus One Equals One, Archibald presents even more of nature's magic algebra: the mind-boggling cases of secondary endosymbiosis, in which yet more partners converge to produce very complex eukaryotes. Here, one eukaryotic cell engulfed a photosynthetic eukaryotic cell, and one way or another, this resulted in a truly complex eukaryotic organism with up to four genomes. This is Archibald's home turf, and this chapter is possibly the most exciting to read. Archibald stops short of discussing the nature of the host that took up the mitochondrion. Woese's discovery of the third domain of life, the Archaea, and the hydrogen hypothesis as was posited by Müller and Martin would have been a straightforward springboard into the recent discoveries regarding the nature of the host of the endosymbiosis. But then Jim Lake's chimeric nature of the eukaryotic nuclear genome was omitted from the text as well. Perhaps this could be material for a further chapter in a later edition. All of the chapters provide an entertaining but authoritative read. Archibald knows his material and is well versed to present this book. In particular, the last chapter on Paulinella and Rhopalodia provides food for thought. The discovery of apparently independent acquisitions of novel chloroplasts continues to demonstrate that nature is on a roll.