ORIGINS OF LIFE An improbable journey Adrian Woolfson enjoys two studies on microbial life’s trek towards complexity. n 1676, the Dutch merchant and amateur rise to bacteria and archaea, which have no The Vital Question: Why is Life the Way it is? scientist Antoni van Leeuwenhoek sub- nucleus or other sub-cellular organelles. NICK LANE mitted an essay to the Royal Society of The evolutionary engine of life then seems Profile: 2015. ILondon detailing a singular discovery. This to have got stuck, idling along at the unicel- Life’s Engines: How Microbes Made Earth was the world of unicellular organisms, lular level for another 2 billion to 3 billion Habitable which he observed using a self-designed years. Falkowski explains how unicellu- PAUL G. FALKOWSKI microscope. Three hundred years later, lar organisms, although morphologically Princeton Univ. Press: 2015. Leeuwenhoek’s “animalcules” were shown challenged, managed to perfect the basic to hold the secret to the evolution of complex biochemical ‘engines’ that would power all ancestral archaean host engulfed a small life on Earth. forms of life on Earth. According to Lane, population of symbiotic bacteria, resulting In his imaginative and beautifully written the stagnation occurred because the molec- in the first eukaryotic cell, the forebear of The Vital Question, evolutionary biochem- ular motors that drive the biochemistry of complex life. ist Nick Lane defines a genealogy that links bacteria and archaea were unable to cross Lane recounts how over time, the engulfed the descendants of the Cambrian explosion the energetic threshold necessary for the bacteria jettisoned most of their genes that — the first appearance of morphologically evolution of complex form. This energetic were unrelated to energy production; these complex animals in the fossil record, were either lost permanently or relo- about 540 million years ago — to the cated to the cell nucleus. There they simple organisms that preceded them. continued to fulfil their original func- In so doing, he persuades us that com- THE EVOLUTIONARY ENGINE tions, or formed the raw material for prehending the structure, function, the evolution of new genes with unex- behaviour, genetics and evolution of GOT STUCK, pected roles, such as transcription fac- microorganisms is necessary for a tors — proteins that bind to DNA. This deep understanding of complex life, IDLING ALONG AT THE allowed embryonic stem cells to be and of the processes that undermine it, patterned in three-dimensional space. including diseases and ageing. This vis- UNICELLULAR LEVEL. What remained of the imbibed bacte- ceral insight into the largely uncharted ria, with their pared-down genomes expanses of microbial existence could and surrounding membranes, became also form the basis of a predictive science constraint on life is the central focus of The energy-generating mitochondria. The acqui- enabling us to speculate about the nature of Vital Question. sition of these organelles enabled eukaryotic potential life on other planets. It derives, Lane explains, from two princi- cells to expand their volume by up to 15,000 Biophysicist Paul Falkowski’s entertain- pal design features that all living things use times that of the average bacterium, and to ing, easy-to-read and historically rich Life’s to power themselves. The first is the use of support a genome around 5,000 times larger. Engines, meanwhile, uses the work of micro- high-energy molecules of ATP, the chemi- Lane’s important realization is that this also biologist Carl Woese to trace complex life cal currency of energy transfer. The second gifted eukaryotic cells with about 200,000 back to its three lines of descent: bacteria, is the idiosyncratic ‘chemiosmotic’ force, times more energy per gene than the aver- archaea and eukaryotes. By studying the which moves protons and facilitates the age prokaryotic cell. This over-cranking RNA sequences of ribosomes — the cellular continuous generation of ATP. Both Lane of the evolutionary engine allowed for the machines that make proteins — Woese was and Falkowski describe these molecular development of a baroque diversity in the able to show that Charles Darwin was cor- processes compellingly. Although adequate nature and extent of cellular gene and pro- rect in suggesting that all life arose from a to power single bacteria-sized cells, the tein expression. single, now-extinct, common ancestor. method constrains the allowable surface- Although readily accommodated by It remains unclear how and when life first to-volume ratio of a living cell. Lane argues, classic Darwinian evolutionary theory, the originated on Earth, but we know that the however, that around 1.5 billion years ago horizontal, sudden and co-operative nature first unicellular organism emerged between this energetic constraint was overcome by of Lane’s evolutionary narrative differs from 3.6 billion and 2.7 billion years ago, giving an improbable endosymbiosis event: an the incremental, vertical and competitive The Homing Instinct: Meaning and Mystery in The Accidental Species: Misunderstandings of Animal Migration Human Evolution Bernd Heinrich MARINER 2015 Henry Gee UNIV. CHICAGO UNIVERSITY PRESS 2015 Erudite naturalist Bernd Heinrich attributes the Nature’s palaeontology editor, Henry Gee, instinct for migration to an affinity for ‘home’, from condemns the idea that our species is the beavers’ skilful dam-building to the joyful dance of pinnacle of evolution, arguing that traits prized as Alaskan cranes returned to their nesting pond. (See uniquely human, such as creativity, are not. (See Joel Greenberg’s review: Nature 508, 317; 2014.) Tim Radford’s review: Nature 503, 34–35; 2013.) 30 APRIL 2015 | VOL 520 | NATURE | 617 © 2015 Macmillan Publishers Limited. All rights reserved COMMENT SPRING BOOKS features of the more canonical one. As elegant as the details underpinning the thesis seem, it is occasionally hard to distinguish between fact and specula- tion. Lane has, nevertheless, made a bold and commendable attempt to sketch out a highly challenging scientific issue for a general audience. In so doing, he has reaffirmed the importance of a largely overlooked area of basic research, and has generated testable hypotheses about the origins of complex life. Falkowski covers some of the same details of the evolution of microbes and their contribution to complexity, includ- ing the historical origins of the concept of endosymbiosis. However, his focus is primarily on how microorganisms have made Earth habitable, perhaps most notably with the development of oxygen-generating photosynthesis by cyanobacteria. This leads him to touch on humanity’s potential to undermine Earth’s systems. History has shown how modifications to microbial biochemistry affect global geophysical processes. For example, fol- lowing 200 million to 300 million years of VIROLOGY photosynthesis by ancient microorgan- isms, oxygen became a significant com- ponent of Earth’s atmosphere, increasing ozone levels, reducing the greenhouse Journal of the effects of gases such as methane and lead- ing to one of the most extensive glacia- tions in the planet’s history. Humanity’s interference with natural biological pro- plague years cesses risks damaging Earth in ways that cannot be predicted. What is clear is that a deep understand- Mark Dybul applauds the latest chapter in an account of ing of how complex life originated will a life at the leading edge of HIV research and policy. provide insights into human biology and the nature of disease processes. It may also enable the generation of forms irologist Peter Piot’s AIDS Between Programme on HIV/AIDS (UNAIDS). of life unconstrained by the contingent Science and Politics is a terrific follow- Three messages underpin the book’s nine processes that locked life into its current up to his highly acclaimed memoir chapters. One is that the HIV epidemic gen- trajectory. Life as we know it may eventu- VNo Time to Lose (W. W. Norton, 2012). It erated an unprecedented local and global ally be supplanted, perhaps one day even demonstrates the deep intellectual lessons of response, recast many develop­ment and being viewed as a primordial soup that a lifetime at the cutting edge of science and health paradigms, and ultimately triggered facilitated the emergence of silicon-based politics. Piot’s narrative ranges from his thrill- treatments that have saved millions of lives. existence. ■ ing, on-the-ground experiences in remote The second is that progress was made only regions of Africa as a young scientist and when various scientific disciplines, on- Adrian Woolfson is the author of Life member of the team that identified Ebola, the-ground implementation strategies and Without Genes. to the high-altitude reflections of his years as politics were aligned. And the third? That e-mail: [email protected] executive director of the Joint United Nations AIDS is not over. This Changes Everything: Capitalism vs the Climate The Boom: How Fracking Ignited the American Naomi Klein ALLEN LANE 2015 Energy Revolution and Changed the World Unafraid to name and shame fossil-fuel junkies Russell Gold SImON AND SCHuSTER 2015 hooked on a billion-dollar industry, Naomi Klein Journalist Russell Gold traces the rise of fracking, investigates capitalism and climate change. She sees a tale of innovation and investment — such as the global crisis as a potential spur to positive action, ex-oilman Aubrey McClendon’s 260,000 land as happened with the women’s rights movement. acquisitions in Texas’s Barnett Shale. (See Chris (See Nico Stehr’s review: Nature 513, 312; 2014.) Nelder’s review: Nature 508, 185; 2014.) 618 | NATURE | VOL 520 | 30 APRIL 2015 © 2015 Macmillan Publishers Limited. All rights reserved.