30-SECOND EVOLUTION The 50 most significant ideas and events, each explained in half a minute Editors Mark Fellowes Nicholas Battey Contributors Nicholas Battey Brian Clegg Isabelle De Groote Mark Fellowes Julie Hawkins Louise Johnson Ben Neuman Chris Venditti Adapt or die: it’s nature’s most famous imperative. But how does evolution actually happen? It’s too slow to see, but it’s going on all around you, all the time. Even if you’re on top of the key terms – variation? Natural selection? Parent-offspring conflict? – you still need some context to put them in. From populations to speciation and polymorphism to evolutionary psychology, here’s the onestop source for all you need to know. 30 Second Evolution unlocks the laboratory of life, dissecting it into the 50 most significant topics that provide the missing links to understand the natural world’s four-billion-year ancestry and the process of natural selection in which species either adapt in myriad ways – mutation, ingenuity, and intelligence – to meet the challenges of a changing environment, or die. Unravel the development of living organisms, at micro and macro level – from genes to geniuses. CONTENTS Introduction The History of Evolution GLOSSARY Before Evolution Transmutation & Archetypes Variation & Selection Profile: Charles Darwin The Rediscovery of Mendel Understanding Genes in Populations The Modern Synthesis Controversies The Origin of Species GLOSSARY Species & Taxonomy Building Phylogenies Making Species: Isolation Profile: Alfred Russel Wallace Mechanisms of Isolation Mutation & Speciation From Adaptation to Speciation Species Diversity Natural Selection GLOSSARY Populations The Need for Adaptation Genes Profile: J.B.S. Halbane Genetic Variation Polymorphism & Genetic Drift Types of Selection Units of Selection Evolutionary History & Extinction GLOSSARY How Life Began The Geological Record Geological Change & Mammalian Evolution Profile: Lynn Margulis Emergence of Major Plant and Animal Groups Evolutionary Rates & Extinctions The Mystery of the Cambrian Explosion Great Extinctions Causes of Extinction Evolution in Progress GLOSSARY Evolutionary Constraints Coevolution Convergent Evolution Industrial Melanism New Species Profile: Peter & Rosemary Grant Evolution of Animal Behaviour Altruism & Selfishness Sex & Death GLOSSARY The Paradox of Sex Sex Ratios Sexual Selection Sperm Competition Parent-Offspring Conflict Profile: Bill Hamilton Sex & Evolutionary Arms Races Inbreeding Avoidance Humans & Evolution GLOSSARY Ancestors & Timescale Tool Use by Humans & Other Apes Evolution of the Brain Evolution of Human Language Evolutionary Psychology Profile: The Leakey Family Humans Causing Evolution Human Evolution: The Future APPENDICES Resources Notes on Contributors Index Acknowledgements INTRODUCTION Nicholas Battey & Mark Fellowes Evolution, caused by the linked processes of natural and sexual selection, accounts for the diversity and interrelationships of all life forms on planet Earth. Although evolution is a theory in the sense that our understanding of it will be modified and developed as scientific understanding grows, it is also much more than that: it is a way of thinking that is fundamental to modern biology and natural history. From the development of language to practical species conservation, evolution is the core concept. Evolution also accounts for human origins and so conflicts with some religious explanations. It therefore has a colourful history. Charles Darwin’s On the Origin of Species sparked heated debate and in 1860 Bishop Samuel Wilberforce (‘Soapy Sam’ for his unguence) asked his debating opponent Thomas Huxley (‘Darwin’s bulldog’) ‘Is it on your grandmother’s or your grandfather’s side that you are descended from an ape?’ To which Huxley replied: ‘I would rather be descended from an ape than a man who uses his great faculties and influence for the purpose of ridicule.’ More recently the claims of sociobiology – to provide explanations for many aspects of human behaviour based on evolutionary adaptation – have been greeted with fierce opposition from some quarters, while the use of the word ‘selfish’ by Richard Dawkins in his popularization of evolutionary explanations for altruism added more fuel to the fires of controversy. And eugenics, the idea that human stock can be improved by selective breeding, is an offshoot of evolutionism which has dark associations with the racist programmes of Nazi Germany. Yet these controversies break out almost exclusively where evolutionary thinking is applied to humans and create a distorted picture of its significance. Evolution addresses the diversity of all life forms – plant, animal, fungal, bacterial and protist. It offers a coherent basis for understanding how the 8.7 million (or perhaps many, many more) species now present on the planet have come into being; through knowledge of population genetics, speciation processes and extinctions it provides not just an explanation of past events but predictions of future chapters in the story of life. These help us understand that every species is a chance event, a combination to be cherished as a never to be repeated expression of the incredible power of evolution. It is evolution acting through natural and sexual selection that has moulded life into the exuberant diversity of form and function that we see around us today. The evolution of life has depended on one ingredient more than any other: time. The scale of evolutionary time is hard for us to grasp because we naturally think in terms of our own lifespan, the rise and fall of nations and empires – or at most the millennia separating us from the ancient civilizations. Yet evolutionary processes typically occur over millions of years (about 7 million years in the case of the human species) or hundreds of millions of years (dinosaurs of one sort or another were around for 200 million years). The diagram on the following page summarizes the geological eras, periods and epochs referred to extensively in the chapters of this book. The more complex life forms evolved after the Cambrian explosion of life (about 550 million years ago), but about 4,000 million years separate the formation of our planet from the Cambrian epoch, time that was vital to the evolution of the basic elements of life (RNA, DNA, proteins, cells). The diagram also shows the ages of dominance of animal groups, but don’t forget that plants were also evolving: during the Carboniferous, vast forests of enormous lycopods, ferns and horsetails flourished; during the Cretaceous, angiosperms (flowering plants) became prominent – as well as the placental mammals. But this is not to say that evolution acts at this pace, more that this is the scale on which we can see the grand spectacle of evolution unfold. Just as mountains are constantly formed by great tectonic movements and constantly eroded by the elements, evolution and extinction are always at work; we only see the results given the perspective of time. We can, in fact, witness natural selection at work all around us. The evolution of resistance to antibiotics, or of insects to insecticides, is well known. There are many other examples, from the Galápagos finches to the apple maggot fly that show that natural selection is a part of life, and, with time, may give rise to new species. But hand in hand with evolution goes extinction, and given our own species’ malign influence there is no doubt that the creativity of natural selection is now unable to keep pace with our erosion of the Earth’s diversity of life. Our strategy here has been to view evolution from seven different perspectives. In the History of Evolution we explore how the modern theory came about, beginning with Darwin’s explanation of species origins through natural selection, and incorporating the growing understanding of genes as both agents of stable inheritance and individual variability. In Origin of Species modern views of speciation and its genetic underpinnings are described, while Natural Selection considers the way genes behave in populations, and populations adapt in response to selection pressure. Evolutionary History & Extinction focuses on the geological record and what it tells of life’s history; Evolution in Progress describes how evolution works, including contemporary examples such as industrial melanism in moths and explanations for apparently non-Darwinian altruism. Sex allows alleles to be exchanged, death is the means of winnowing genotypes; Sex & Death looks at how these key events work within an evolutionary framework. The final chapter, Humans & Evolution, describes how humans evolved and speculates on our evolutionary future, which paradoxically may involve an escape from natural selection. Evolutionary thinking has itself evolved – to such an extent that it finds its way into almost all aspects of life. To help capture this diversity each entry in this book is accompanied by a pithy encapsulation (the 3-Second Thrash) and something a bit more speculative – the 3-Minute Thought. This might be a slight mutation of normal thinking, a meme thrown into the mix of ideas that transmit from mind to mind but are rarely, if ever, reproduced as faithfully as genes. Finally, a thought on how to use this book: dip in, enjoy and be moved to explore further. Life awaits. THE HISTORY OF EVOLUTION THE HISTORY OF EVOLUTION GLOSSARY Biodiversity The range of animal and plant life within an environment, most commonly based on the number of distinct species. Divine Creation/Creationism theory The belief that the Earth and the rest of the Universe, together with all living things in their current forms, are the product of direct supernatural acts of creation by a god or gods, rather than of having evolved through a natural process. Eugenics Active promotion of the fittest offspring in humans. The English anthropologist and polymath Francis Galton (1822–1911) originally defined it as ‘The investigation of… the conditions under which men of a high type are produced.’ Fit/Fittest/Fitness Being well adapted or suited to conditions. In the evolutionary sense ‘survival of the fittest’ refers to those best suited to survive and pass on genetic material. Gametes The two kinds of reproductive cell that fuse during fertilization in sexual reproduction: egg cells and sperm cells. Genetic drift A change in the frequency of a particular variant of a gene that is due not to a selective process but to random fluctuations. Genotype The genetic instructions that specify what makes an individual organism or cell unique, including variants in parallel sets of chromosomes. Sometimes used to contrast with the phenotype. Geological epochs/periods/eras Geologists use units like these to divide up the geological timescale. There are fourteen eras, typically of hundreds of millions of years, divided into periods, which are subdivided into epochs. Periods are probably the most familiar, with names like Cretaceous, Jurassic, Silurian and Cambrian. Heredity The genetic process by which living organisms pass on characteristics to their offspring (and to the descendants of their offspring). The offspring are said to ‘inherit’ these characteristics. Genetics is the study of heredity. Homology A correspondence of an organ or part in its structure or function, whether between the sides of the body or between sexes or species. Reflects a shared genetic ancestry; homology is also used in relation to genes, as well as organs. Kingdom Originally the highest classification of natural objects (animal, vegetable and mineral kingdoms), but has come to be a taxonomic rank (classification of organisms) that comes above phylum and below domain. The kingdoms are animals, plants, fungi, protists or protoctists and prokaryotes (sometimes divided