30-Second Evolution E-Book

Mark Fellowes

• Herausgeber: Icon Books
• Kategorie: Wissenschaft und neue Technologien
• Serie: 30-Second
• Sprache: Englisch
• Veröffentlichungsjahr: 2015

Seitenzahl: 154

Beschreibung

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 one-stop source for all you need to know. 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.

Leseprobe

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 into archaea and bacteria).

Linnaean classification The taxonomy (classification) of organisms devised by Carl Linnaeus. The modern version of taxonomy has been developed considerably since Linnaeus and now uses kingdoms, classes, orders, families, genera and species.

Phenotype The visible characteristics of a specific organism, sometimes used to contrast with the ‘genotype’ which is the total set of genetic instructions – the combination of all the genes in a cell or organism.

Punctuated equilibrium An evolutionary theory championed by American biologist Stephen Jay Gould in which species exist for long periods of time with very little evolutionary change, punctuated by relatively rapid events where a species splits into two individual species. The most common alternative, phyletic gradualism, assumes that gradual change eventually results in variants becoming distinct species.

Saltation The idea that a large-scale mutation could produce a new species immediately (the word means a jump or bound). Sometimes confused with punctuated equilibrium, in which species are produced relatively quickly, but still over thousands or tens of thousands of years.

Species A unit of biological classification that is the lowest of the original taxonomic ranks, traditionally defined as a group of organisms capable of interbreeding, although this is not always the case in modern usage. In the traditional two-part name such as Homo sapiens, the second word is the species. Animals also may have subspecies, while other kingdoms may have several further sub-divisions.

Stasis Generally meaning inactivity or stagnation, in the punctuated equilibrium theory stasis refers to periods of time with low levels of evolutionary change.

Taxonomy The classification of a set of entities – in biology, of organisms – according to a structured set of principles.

BEFORE EVOLUTION

the 30-second evolution

For John Ray, the ‘father of natural history’, the world was divinely ordered. Every living thing was designed according to God’s plan, from the woodpecker, with its ‘short but very strong legs’, ‘convenient for the climbing of trees’; to leaves that ‘concoct and prepare the sap for the nourishment of the fruit, and the whole plant’. In revealing this plan humans would come closer to their maker and to a fuller appreciation of His rationality. There were those who fully supported this approach, including Linnaeus, who founded the modern system of taxonomy in which an organism is classified into species, genus, order, class and kingdom. There were also dissenters, such as Buffon, who believed the Earth to be much older than the 6,000 years derived from the account of creation in the biblical book of Genesis. Buffon’s idea was that the planets had originated from the Sun and gradually cooled. He put the Earth’s age at around 70,000 years, allowing him room to speculate that species had a natural origin. But Buffon was an exception. Even at the beginning of the 19th century, the natural world was generally believed to be populated by creatures fixed at the beginning of time by a divine hand.

3-SECOND THRASH

Everyday experience suggests that species are fixed; according to the Bible they were made by God.

3-MINUTE THOUGHT

Perhaps it’s not so silly that people thought species were fixed: after all, in the natural world it isn’t obvious that they change; and they are often well designed, both functionally and behaviourally. It took ages for people to work out that the obvious – the Sun goes round the Earth – was wrong. In the same way, the idea that species evolve was counterintuitive and so met with fierce resistance. Science has a habit of subverting common sense.

RELATED TOPICS

CONTROVERSIES

SPECIES & TAXONOMY

3-SECOND BIOGRAPHIES

JOHN RAY

1627–1705

English naturalist and early taxonomist

CAROLUS (CARL) LINNAEUS

1707–78

Swedish founder of modern taxonomy

GEORGES-LOUIS LECLERC, COMTE DE BUFFON

1707–88

French naturalist and author of the multi-volume Histoire Naturelle

30-SECOND TEXT

Nick Battey

Most people looked at the Universe and saw the elegantly designed handiwork of a divine creator.

TRANSMUTATION & ARCHETYPES

the 30-second evolution

During the first half of the 19th century a variety of ideas was circulating about the nature and origin of species. In France, leading naturalists were at odds: Lamarck spoke of organisms transmutating – or evolving – into other organisms, while palaeontologist Georges Cuvier denied such changes could occur. In Germany, poet Goethe had a more idealistic vision, of a bauplan (blueprint), which underpinned organism development and change. In Britain, Richard Owen in 1848 translated these disparate influences into the concept of the ‘archetype’ – specifically, the vertebrate archetype. This generalized the vertebrate skeleton into a blueprint used by God to fashion (in succession) the vertebrate species of the world, with humans the latest and closest to perfection. Although the archetype retained a role for a divine Creator, it also allowed for species change, as variations on a theme. In a sense, therefore, it anticipated Darwin’s evolutionary theory, published ten years later. But its links to philosophical idealism meant that the archetype had little influence on other scientists. T.H. Huxley, Owen’s arch-rival (later Darwin’s staunchest supporter), said that it was ‘fundamentally opposed to the spirit of modern science’. Yet it set the scene for Darwin to transform ideal archetypes into real ancestors.

3-SECOND THRASH

Before Darwin there was the archetype; after Darwin there were ancestors.

3-MINUTE THOUGHT

Mammals as diverse as a bat, a mole and a dolphin have very similar bones making up wing, paw and pectoral fin. This homology was contrasted by Richard Owen with organs that are analogous in terms of function but anatomically different (for example,

the wings of bats and birds). This distinction is a lasting legacy from Owen even though his treasured archetype was swept away with the tide of evolutionism.

RELATED TOPICS

EMERGENCE OF MAJOR ANIMAL & PLANT GROUPS

NEW SPECIES

3-SECOND BIOGRAPHIES

JOHANN WOLFGANG VON GOETHE

1749–1832

German poet who explored the metamorphosis of plants

BARON GEORGES CUVIER

1769–1832

French naturalist at the Musée d’Histoire Naturelle in Paris

RICHARD OWEN

1804–92

British anatomist, founder of the Natural History Museum in London

30-SECOND TEXT

Nick Battey

Richard Owen, developer of the theory of the archetype.

VARIATION & SELECTION

the 30-second evolution

Charles Darwin began his On theOrigin of Species with a discussion of variation in domestic plants and animals. He had taken up pigeon fancying and had been ‘permitted to join two of the London Pigeon Clubs’; in the process he discovered that ‘the diversity of breeds is something astonishing’. From the English carrier to the short-faced tumbler; the barb, the pouter, the turbit, the Jacobin, the trumpeter and laugher: all these pigeon breeds differed in truly remarkable ways. Yet, Darwin argued, they were all derived from a single wild species, the rock pigeon (Columba livia). How had this happened? During the process of domestication humans had picked out particular individuals: ‘The key is man’s power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to make for himself useful breeds.’ By analogy, in the wild individuals of a species vary, but here nature is the selector instead of a human. Competition for resources means that the best-adapted individuals flourish – in other words, they are selected. In this way new species are created in response to changing environments and circumstances. Natural selection was Darwin’s crucial idea, his decisive insight into the mechanism behind evolution.

3-SECOND THRASH

At the heart of Darwin’s theory of evolution is the idea that variation can be enhanced by selection.

3-MINUTE THOUGHT