Basics in Human Evolution

 
 
Academic Press
  • 1. Auflage
  • |
  • erschienen am 24. Juli 2015
  • |
  • 584 Seiten
 
E-Book | ePUB mit Adobe DRM | Systemvoraussetzungen
E-Book | PDF mit Adobe DRM | Systemvoraussetzungen
978-0-12-802693-9 (ISBN)
 

Basics in Human Evolution offers a broad view of evolutionary biology and medicine. The book is written for a non-expert audience, providing accessible and convenient content that will appeal to numerous readers across the interdisciplinary field.

From evolutionary theory, to the cultural evolution, this book fills gaps in the readers' knowledge from various backgrounds and introduces readers to thought leaders in human evolution research.


  • Offers comprehensive coverage of the wide ranging field of human evolution
  • Written for a non-expert audience, providing accessible and convenient content that will appeal to numerous readers across the interdisciplinary field
  • Provides expertise from leading minds in the field
  • Allows the reader the ability to gain exposure to various topics in one publication
  • Englisch
  • San Diego
  • |
  • USA
Elsevier Science
  • 58,20 MB
978-0-12-802693-9 (9780128026939)
0128026936 (0128026936)
weitere Ausgaben werden ermittelt
  • Front Cover
  • Basics in Human Evolution
  • Copyright
  • Dedication
  • Contents
  • Contributors
  • Preface
  • Part I - Positioning Human Evolution
  • Chapter 1 - Basic Evolutionary Theory
  • SYNOPSIS
  • INTRODUCTION
  • THE ORIGIN OF GENETIC VARIATION
  • VARIATION WITHIN POPULATIONS
  • GENETIC DRIFT
  • NATURAL SELECTION
  • LEVELS OF SELECTION
  • SPECIATION
  • FROM MICROEVOLUTION TO MACROEVOLUTION
  • EVOLUTIONARY THEORY TODAY
  • REFERENCES
  • Chapter 2 - Evolution, Creationism, and Intelligent Design
  • SYNOPSIS
  • INTRODUCTION
  • A SCIENTIFIC CREATIONISM
  • INTELLIGENT DESIGN
  • CONCLUSIONS
  • REFERENCES
  • Part II - Primates
  • Chapter 3 - Primate Evolution
  • SYNOPSIS
  • INTRODUCTION
  • EXTANT GROUPS OF PRIMATES
  • HIGHER-LEVEL RELATIONSHIPS
  • PRIMATES ON AN ASCENDING SCALE?
  • DEFINING FEATURES OF PRIMATES
  • FOSSIL PRIMATES
  • OVERALL EVOLUTIONARY RELATIONSHIPS
  • REFERENCES
  • Chapter 4 - Comparative Anatomy of Primates
  • SYNOPSIS
  • OSTEOLOGY
  • MYOLOGY
  • EXTERNAL FEATURES AND INTERNAL ORGANS
  • REFERENCES
  • Chapter 5 - Primate Behavior
  • SYNOPSIS
  • SOCIAL ORGANIZATION, PREDATION, AND GROUP LIVING
  • SOCIAL ORGANIZATION AND SOCIAL RELATIONSHIPS
  • DOMINANCE, LEVERAGE, AND POWER
  • THE "SOCIOECOLOGICAL MODEL"
  • SEXUAL CONFLICT AND "INTERSEXUAL MUTUALISM"
  • COOPERATION
  • SOCIALITY AND FITNESS
  • REFERENCES
  • Chapter 6 - Primate Models for Human Evolution
  • SYNOPSIS
  • MODELS OF HUMAN EVOLUTION
  • DENTITION AND DIET
  • LOCOMOTION
  • HABITAT OF OUR EARLIEST ANCESTORS
  • THE MACAQUE MODEL
  • FOSSILS AND LIVING PRIMATES
  • MAN THE HUNTED
  • REFERENCES
  • Part III - Hominins
  • Chapter 7 - Early Hominin Ecology
  • SYNOPSIS
  • THE EARLY HOMININ RECORD
  • MACRO PALEOENVIRONMENTAL CONTEXT
  • RECONSTRUCTING TERRESTRIAL HABITATS
  • GEOLOGICAL EVIDENCE
  • INFERRING HOMININ HABITATS AND ADAPTATIONS
  • LATE PLIOCENE ADAPTIVE RADIATIONS
  • SUMMARY: THE LIMITS AND POTENTIAL OF OUR PALEOECOLOGICAL KNOWLEDGE
  • REFERENCES
  • Chapter 8 - Bipedalism
  • SYNOPSIS
  • HOW DO HUMANS WALK?
  • ANATOMICAL FEATURES ASSOCIATED WITH BIPEDALISM
  • WHEN DID BIPEDALISM EVOLVE, AND WHAT EVOLUTIONARY STAGES OF BIPEDALISM DID WE PASS THROUGH?
  • WHY DID BIPEDALISM EVOLVE?
  • REFERENCES
  • Chapter 9 - Early Hominins
  • SYNOPSIS
  • TAXONOMY
  • PURPORTED EARLY HOMININ SPECIES
  • CONTEXT: CHIMPANZEE MORPHOLOGY
  • CONTEXT: MIDDLE MIOCENE APES
  • CONTEXT: LATE MIOCENE APES
  • THE MORPHOLOGY OF PURPORTED EARLY HOMININS
  • EARLY POSSIBLE HOMININS' ADAPTATIONS
  • EARLY POSSIBLE HOMININS' PLACE IN NATURE
  • REFERENCES
  • Chapter 10 - Australopithecines
  • SYNOPSIS
  • AUSTRALOPITHECUS
  • AUSTRALOPITHECUS AFARENSIS
  • AUSTRALOPITHECUS BAHRELGHAZALI
  • AUSTRALOPITHECUS ANAMENSIS
  • AUSTRALOPITHECUS GARHI
  • KENYANTHROPUS (AUSTRALOPITHECUS) PLATYOPS
  • AUSTRALOPITHECUS SEDIBA
  • AUSTRALOPITHECINE ADAPTATIONS
  • REFERENCES
  • Chapter 11 - Early Pleistocene Homo
  • SYNOPSIS
  • DEFINING THE GENUS HOMO
  • HISTORY OF DISCOVERY OF EARLY HOMO FOSSILS
  • TAXONOMIC DIVERSITY IN THE GENUS HOMO
  • TAXONOMIC AND PHYLOGENETIC ISSUES: HOMO HABILIS AND HOMO RUDOLFENSIS
  • PHYLETIC ORIGINS AND THE DATING OF EARLY HOMO
  • CONTEXT OF ORIGINS AND EXISTENCE
  • MUSCULOSKELETAL ADAPTATIONS IN EARLY HOMO
  • ASSOCIATION WITH STONE TOOLS
  • FUTURE DIRECTIONS
  • REFERENCES
  • Chapter 12 - Archaic Homo
  • SYNOPSIS
  • GEOGRAPHICAL DISTRIBUTION
  • CHRONOLOGICAL VARIATION
  • REGIONAL VARIATION
  • GROWTH, DEVELOPMENT, AND ENERGETICS
  • LANGUAGE, BEHAVIOR, AND CULTURE
  • EVOLUTIONARY RELATIONSHIPS AND TAXONOMY
  • SUMMARY
  • REFERENCES
  • Chapter 13 - Anatomically Modern Homo sapiens
  • SYNOPSIS
  • HISTORY OF DISCOVERY
  • EARLIEST FOSSIL EVIDENCE OF MODERN HUMANS
  • CLIMATIC CONDITIONS FOR THE SPREAD OF MODERN HUMANS
  • ORIGINS OF MODERN HUMANS
  • RELATIONSHIPS WITH ARCHAIC HOMO
  • PALEOBIOLOGY OF ANATOMICALLY MODERN HOMO SAPIENS
  • REFERENCES
  • Chapter 14 - Evolution of Tool Use
  • SYNOPSIS
  • EVOLVING HOMININ FORMS AND TECHNOLOGIES: A REVIEW
  • TOOLS IN THE ANIMAL WORLD
  • CHIMPANZEE TOOL USE AS A MODEL FOR EARLY HOMININS
  • THE EARLIEST KNOWN STONE TOOLS
  • THE OLDOWAN (EARLIER LOWER PALAEOLITHIC/EARLY STONE AGE)
  • THE ACHEULEAN AND CONTEMPORANEOUS INDUSTRIES (LATER LOWER PALAEOLITHIC)
  • THE MIDDLE PALAEOLITHIC/MIDDLE STONE AGE
  • THE UPPER PALAEOLITHIC/LATE STONE AGE
  • LATER DEVELOPMENTS
  • REFERENCES
  • Part IV - Genetics and Biology
  • Chapter 15 - Contemporary Human Genetic Variation
  • SYNOPSIS
  • INTRODUCTION
  • A BRIEF HISTORY OF HUMAN EVOLUTION
  • OUR SPECIES HAS A RELATIVELY LOW LEVEL OF GENETIC VARIATION
  • THERE IS HIGHER GENETIC VARIATION IN SUB-SAHARAN AFRICAN POPULATIONS THAN IN OTHER GEOGRAPHIC REGIONS
  • GENETIC DIVERSITY DECLINES WITH DISTANCE OUT OF AFRICA
  • THERE ARE LOW LEVELS OF GENETIC DIFFERENTIATION BETWEEN GEOGRAPHIC REGIONS
  • GENETIC DISTANCE IS CORRELATED WITH GEOGRAPHY
  • THE HUMAN GENOME SHOWS EVIDENCE OF ADMIXTURE FROM NEANDERTALS . AND OTHERS
  • NATURAL SELECTION HAS FURTHER AFFECTED THE PATTERN OF CONTEMPORARY GENETIC VARIATION
  • SUMMARY
  • REFERENCES
  • Chapter 16 - Human Population Movements: A Genetic Perspective
  • SYNOPSIS
  • INTRODUCTION
  • OUT OF AFRICA MIGRATION OF ARCHAIC HUMANS
  • OUT OF AFRICA MIGRATION OF ANATOMICALLY MODERN HUMANS
  • GENETIC ADMIXTURE BETWEEN ARCHAIC AND MODERN HUMANS
  • TECHNOLOGICAL ADVANCES AND MIGRATION: THE CASE OF THE EUROPEAN FARMERS
  • HISTORIC MIGRATIONS INTO A PREVIOUSLY OCCUPIED TERRITORY: THE CASE OF THE ROMANI
  • MOST RECENT MIGRATIONS INTO A NEWFOUND LAND: THE CASE OF THE POLYNESIANS
  • CONCLUSIONS AND FUTURE PROSPECTS
  • REFERENCES
  • Chapter 17 - Brain Evolution
  • SYNOPSIS
  • INTRODUCTION
  • LINES OF EVIDENCE
  • CHARACTERISTICS OF THE HUMAN BRAIN
  • SYNTHESIS: PUTTING TOGETHER SIZE, ORGANIZATION, AND ASYMMETRY DURING HUMAN EVOLUTION
  • AND TO THE FUTURE?
  • REFERENCES
  • Chapter 18 - Physiological Adaptations to Environmental Stressors
  • SYNOPSIS
  • INTRODUCTION
  • PRINCIPLES OF THERMOREGULATION
  • CLIMATE AND BODY MORPHOLOGY
  • PHYSIOLOGICAL ADAPTATIONS TO COLD STRESS
  • PHYSIOLOGICAL ADAPTATIONS TO HEAT STRESS
  • PHYSIOLOGICAL ADAPTATIONS TO HIGH ALTITUDE HYPOXIA
  • SUMMARY
  • REFERENCES
  • Chapter 19 - Evolution of Skin Color
  • SYNOPSIS
  • WHEN AND WHY EPIDERMAL PIGMENTATION EVOLVED
  • BASIS FOR PIGMENT DILUTION IN MODERN HUMANS
  • CONSERVATION OF METABOLIC ENERGY
  • SUMMARY
  • REFERENCES
  • Chapter 20 - Human Growth and Development
  • SYNOPSIS
  • GROWTH AND EVOLUTION
  • HUMAN VERSUS CHIMPANZEE GROWTH
  • ADOLESCENCE
  • EVOLUTION OF HUMAN ADOLESCENCE
  • GIRLS AND BOYS: SEPARATE PATHS THROUGH ADOLESCENCE
  • ADOLESCENT CONTRIBUTIONS TO THE REPRODUCTIVE SUCCESS OF ADULTS
  • RISKS OF CHILDHOOD AND ADOLESCENCE
  • CONCLUSIONS
  • REFERENCES
  • Chapter 21 - Human Reproductive Ecology
  • SYNOPSIS
  • INTRODUCTION
  • HUMAN LIFE HISTORY
  • HUMAN REPRODUCTIVE PHYSIOLOGY: THE BASICS
  • FEMALE REPRODUCTIVE ECOLOGY
  • TESTICULAR FUNCTION DURING EARLY DEVELOPMENT
  • CHALLENGES AND FUTURE DIRECTIONS OF THE FIELD OF HUMAN REPRODUCTIVE ECOLOGY
  • REFERENCES
  • Chapter 22 - Human Senescence
  • SYNOPSIS
  • INTRODUCTION
  • THE EVOLUTION OF SENESCENCE
  • REPRODUCTIVE SENESCENCE
  • FUTURE DIRECTIONS
  • REFERENCES
  • Part V - Lifeways
  • Chapter 23 - Hunter-Gatherers
  • SYNOPSIS
  • EARLY HUNTING AND GATHERING SUBSISTENCE
  • HUNTER-GATHERERS DURING THE HISTORICAL ERA
  • MIGRATION, BIOGEOGRAPHY, AND CONTEMPORARY POPULATIONS
  • HUNTER-GATHERERS AND EVOLUTION
  • HUNTER-GATHERERS IN EVOLUTIONARY PERSPECTIVE: SUMMARY
  • REFERENCES
  • Chapter 24 - Pastoralism
  • SYNOPSIS
  • PASTORALISM AS SUBSISTENCE
  • PREHISTORY OF PASTORALISM
  • BIOGEOGRAPHY OF PASTORALISM
  • FOOD, DIET, AND CUISINE
  • MILK AND THE EVOLUTIONARY BASIS FOR LACTOSE TOLERANCE
  • HEALTH, DISEASE, AND PASTORALISM
  • COEVOLUTION OF LIVESTOCK AND THEIR HUMAN HOSTS
  • REFERENCES
  • Chapter 25 - Agriculturalism
  • SYNOPSIS
  • INTRODUCTION
  • AGRICULTURAL ORIGINS
  • COMPETING HYPOTHESES
  • THE SPREAD OF AGRICULTURE
  • THE COLUMBIAN EXCHANGE
  • "SCIENTIFIC BREEDING," AND THE INDUSTRIAL REVOLUTION
  • CROP EVOLUTION
  • EVALUATING THE PALEO DIET HYPOTHESIS
  • CONCLUSIONS
  • REFERENCES
  • Part VI - Health
  • Chapter 26 - Evolutionary and Developmental Origins of Chronic Disease
  • SYNOPSIS
  • EVOLUTIONARY PERSPECTIVE ON HUMAN DISEASE
  • DEVELOPMENTAL ORIGINS OF HEALTH AND DISEASE
  • DEVELOPMENTAL PLASTICITY AND PREDICTIVE ADAPTIVE RESPONSES
  • EPIGENETICS AS AN UNDERPINNING MECHANISM
  • EVOLUTIONARY AND DEVELOPMENTAL MISMATCH: THE CASE OF OBESITY AND RELATED CHRONIC DISEASES
  • TRANSGENERATIONAL INHERITANCE
  • CONCLUDING REMARKS
  • REFERENCES
  • Chapter 27 - Modernization and Disease
  • SYNOPSIS
  • INTRODUCTION
  • MODERNIZATION AND DISEASE: BASIC FINDINGS
  • CRITIQUES OF STUDIES OF MODERNIZATION
  • NEW APPROACHES TO THE STUDY OF MODERNIZATION AND DISEASE
  • DISCUSSION
  • REFERENCES
  • Chapter 28 - Modern Human Diet
  • SYNOPSIS
  • INTRODUCTION
  • THE ROLE OF DIET IN HOMININ EVOLUTION
  • AGRICULTURAL TRANSITION: DIETARY AND EVOLUTIONARY CONSEQUENCES
  • INDUSTRIALIZATION OF THE DIET AND CONSEQUENCES FOR HUMAN BIOLOGY
  • PALEOLITHIC PRESCRIPTIONS
  • CONCLUSION
  • REFERENCES
  • Chapter 29 - Diversity and Origins of Human Infectious Diseases
  • SYNOPSIS
  • THE DIVERSITY OF INFECTIOUS DISEASES IN SPACE
  • ORIGINS OF INFECTIOUS DISEASES IN NONHUMAN PRIMATES
  • THE FIRST EPIDEMIOLOGICAL TRANSITION: OUT OF AFRICA
  • THE SECOND EPIDEMIOLOGICAL TRANSITION: ANIMAL DOMESTICATION
  • THE THIRD EPIDEMIOLOGICAL TRANSITION: FIRST GLOBALIZATIONS
  • THE FOURTH EPIDEMIOLOGICAL TRANSITION: RECENT EMERGENCES AND THE HOMOGENIZATION OF INFECTIOUS DISEASES
  • CONCLUDING REMARKS
  • REFERENCES
  • Chapter 30 - Coevolution of Humans and Pathogens
  • SYNOPSIS
  • THE IMPORTANCE OF COEVOLUTION BETWEEN HOSTS AND PATHOGENS
  • ENSURING PATHOGEN PERSISTENCE OVER TIME: MODES OF TRANSMISSION
  • MECHANISMS OF HOST-PATHOGEN COEVOLUTION
  • EXAMPLES OF PATHOGENS THAT HAVE COEVOLVED WITH HUMANS
  • CONCLUSIONS
  • REFERENCES
  • Chapter 31 - Paleopathology
  • SYNOPSIS
  • FOSSIL HUMANS AND DISEASE
  • DISEASES IN THE PAST
  • BIOARCHAEOLOGY
  • OSTEOBIOGRAPHY
  • INTERDISCIPLINARITY AND DIFFICULTIES IN COMMUNICATION
  • QUESTIONS FOR THE FUTURE
  • REFERENCES
  • Part VII - Behavior and Culture
  • Chapter 32 - Evolutionary Biology of Human Stress
  • SYNOPSIS
  • EVOLVING CONCEPTS OF STRESS AND ADAPTATION
  • HOW STRESS WORKS
  • STRESS MODERATORS AND BUFFERS
  • DEVELOPMENTAL AND INTERGENERATIONAL PROCESSES
  • STRESS AND HEALTH
  • STRESS AND LIFE HISTORY
  • REFERENCES
  • Chapter 33 - Aggression, Affiliation, and Parenting
  • SYNOPSIS
  • BRAIN, CHILDHOOD, AND PARENTING
  • THE HUMAN FAMILY
  • NEUROLOGICAL AND PHYSIOLOGICAL MECHANISMS
  • CONCLUSIONS
  • REFERENCES
  • Chapter 34 - Human Mating Systems
  • SYNOPSIS
  • MATING SYSTEMS: BASIC CONCEPTS AND UNDERSTANDINGS
  • A BASIC CLASSIFICATION OF MATING SYSTEMS
  • WHAT SELECTION PRESSURES GIVE RISE TO MATING SYSTEMS?
  • THE POLYANDRY "REVOLUTION" WITHIN BEHAVIORAL BIOLOGY
  • NEW MODELS OF SEXUAL SELECTION
  • HUMAN MATING SYSTEMS
  • THE HUMAN CASE: DO MALES POSSESS ADAPTATIONS FOR CARE?
  • EXTRA-PAIR PATERNITY: SEXUAL OR SOCIAL MONOGAMY?
  • ADAPTATIONS FOR MATING
  • CONCLUSIONS
  • REFERENCES
  • Chapter 35 - Evolution of Cognition
  • SYNOPSIS
  • EVOLUTION OF COGNITION
  • CONSCIOUSNESS
  • LANGUAGE
  • ABSTRACTION
  • THEORY OF MIND
  • CAUSAL REASONING
  • AN ECONOMIC MIND
  • COOPERATION
  • CONCLUSIONS
  • REFERENCES
  • Chapter 36 - Evolution of Language
  • SYNOPSIS
  • EVIDENCE FROM COMPARATIVE STUDIES
  • NEURAL CIRCUITS AND THE EVOLUTION OF HUMAN LANGUAGE
  • THE IMPLAUSIBILITY OF UNIVERSAL GRAMMAR
  • FULLY HUMAN LINGUISTIC AND COGNITIVE CAPABILITY
  • REFERENCES
  • Chapter 37 - Evolution of Moral Systems
  • SYNOPSIS
  • INTRODUCTION
  • MORAL BEHAVIOR
  • MORAL SYSTEMS
  • MORAL SENTIMENTS
  • MORALITY AND LEVELS OF SELECTION
  • REFERENCES
  • Chapter 38 - Race and Ethnicity
  • SYNOPSIS
  • INTRODUCTION
  • A HISTORY OF RACIAL SCIENCE
  • POSTWAR DEBATES
  • THE SOCIAL CONSTRUCTION OF RACE
  • RACE AND HEALTH
  • NEW GENETIC SCIENCES
  • POSTGENOMIC DEVELOPMENTS
  • COMMERCIAL ANCESTRY ESTIMATION
  • REFERENCES
  • Chapter 39 - Evolution of Culture
  • SYNOPSIS
  • HUMAN EXPANSIONS
  • COMPARATIVE CULTURAL DATA
  • PHYLOGENETIC COMPARATIVE METHODS
  • CULTURAL TRANSITION RATES
  • FUTURE WORK
  • REFERENCES
  • Glossary
  • Index
  • Color Plates
Chapter 1

Basic Evolutionary Theory


Douglas J. Futuyma     Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, USA

Abstract


This chapter provides a cursory view of the basic principles of modern evolutionary theory. The major topics treated include the origin and nature of genetic variation, effects of genetic drift and various forms of natural selection on phenotypic traits and the genetic constitution of populations, fitness and its components, models of adaptation, levels of selection, the origin of species by speciation, and some aspects of macroevolution, chiefly phylogenies, evolutionary trends and diversification, gradualism, and the role of development in phenotypic evolution.

Keywords


Adaptation; Adaptive radiation; Divergence; Diversity; Evolution; Evolutionary trend; Fitness; Genetic drift; Genetic variation; Kin selection; Macroevolution; Mutation; Natural selection; Phylogeny; Sexual selection; Speciation

Synopsis


This chapter provides a cursory view of the basic principles of modern evolutionary theory. The major topics treated include the origin and nature of genetic variation, effects of genetic drift and various forms of natural selection on phenotypic traits and the genetic constitution of populations, fitness and its components, models of adaptation, levels of selection, the origin of species by speciation, and some aspects of macroevolution, chiefly phylogenies, evolutionary trends and diversification, gradualism, and the role of development in phenotypic evolution.

Introduction


The modern theory of evolutionary change has grown out of the "Evolutionary Synthesis," from 1930 to 1950, in which researchers in genetics, zoology, botany, and paleontology united Darwin's theory of evolution by natural selection with Mendelian genetics. They showed that this formulation accurately described the variation and diversity of animals and plants, both living and extinct, and explained why competing theories, such as neo-Lamarckism and simple mutationism, were inadequate or simply false. Reduced to its simplest elements, the modern theory may be summarized as follows. Elementary evolutionary change consists of changes in the genetic constitution of a population of organisms, or in a group of populations of a species. These genetic changes may be reflected as changes in one or more phenotypic characteristics. Genetic change is based on variation that has originated by mutation and/or recombination of DNA sequences. The most elementary evolutionary process is an increase in the frequency of a mutation, or a set of mutations, within a population, and the corresponding decrease in the frequency of previously common alleles. The major causes of such frequency changes are random genetic drift and diverse forms of natural selection. Successive such changes in one or more characteristics cumulate over time, so that potentially indefinite divergence of a lineage from the ancestral state may result. Different populations of a species may remain similar due to gene flow and perhaps uniform selection, but they can diverge (become different from one another) due to differences in mutation, drift, and/or selection. Some of the genetic differences between them can generate biological barriers to gene exchange, resulting in speciation: the formation of different biological species from their common ancestor. The particulars of these processes in any specific population depend on many aspects of the physical and biological environment, and on the existing features of the population, resulting from its previous evolutionary history (see Futuyma, 2013, for elaboration).

The Origin of Genetic Variation


Mutational changes in DNA sequences range from single base-pair alterations to insertions, deletions, and rearrangements of genetic material, and even changes in ploidy (the number of sets of chromosomes). Mutations that have no effect on "fitness" (i.e., survival and/or reproduction) are said to be "selectively neutral." These may include synonymous mutations in protein-coding regions (those that do not alter amino acid sequence), and mutations in pseudogenes and other apparently nonfunctional regions. Nonsynonymous mutations in coding regions and mutations in regulatory sequences are more likely to affect fitness. The rate of mutation (usually on the order of 10-9 per base pair per gamete) is usually too low to appreciably drive allele frequency change within a population, but it can determine the rate of DNA sequence change in the long term, and can influence the level of genetic variation within a population. Whether or not the supply of suitable mutations often constrains rates and directions of phenotypic evolution is uncertain (Blows and Hoffmann, 2005; Futuyma, 2010). There is no known mechanism by which the environment can direct the mutational process in advantageous directions; in that sense, mutation is random with respect to utility.

Variation within Populations


Populations of most species carry substantial sequence variation in many gene loci, and most quantitative traits exhibit some heritable variation. The presence of two or more fairly common alleles or genotypes within a population is referred to as "polymorphism." Such variation has arisen by mutation. Variation is enhanced by mutation, recombination (often), gene flow from other populations, and some forms of natural selection (see below). Variation is eroded by genetic drift and by most forms of natural selection. Analysis of genetic variation is based on the frequencies (proportions, in a population) of the alleles and genotypes at individual genetic loci (see Hartl and Clark, 2007). For sexually reproducing populations, the Hardy-Weinberg (H-W) theorem states that the frequency of each allele (pi for allele i) will remain constant from generation to generation unless perturbed by mutation, gene flow, sampling error (genetic drift), or natural selection, and that the frequencies of the several genotypes will likewise remain constant, at values given by the binomial theorem (pi2 for homozygote AiAi, and 2pipj for heterozygote AiAj) if mating occurs at random. Alleles at two or more polymorphic loci are eventually randomized with respect to each other by the process of recombination (a state of linkage equilibrium) so that different alleles at one locus are not associated with those at the other locus. (If they are associated to any degree, the loci are in linkage disequilibrium.) These principles have important consequences; for example, at H-W equilibrium, a rare allele exists mostly in a heterozygous state, and so is concealed if it is recessive. Closely linked mutations can remain in linkage disequilibrium for many generations, enabling geneticists to use detectable mutations as genetic markers for nearby mutations of interest, such as those that cause inherited disease. Phenotypic variation in most quantitative traits is polygenic, based on segregating alleles at several or many loci, and also includes environmental (e.g., dietary) effects on the development or expression of a character (Falconer and Mackay, 1996). Thus, the variance in phenotype (VP) includes a genetic component (genetic variance, VG) and an environmental component (VE), and often an interaction effect (VG.E) as well. Although the individual phenotypic effects of alleles at various segregating loci are difficult to measure, most of the many loci appear to have small effects, and a few have fairly large effects, relative to the range of variation. One component of VG, the additive genetic variance (VA), is important for evolution by natural selection because it expresses the correlation between the phenotype of parents and their offspring. This component is attributable to the "additive" effects of alleles, that is, the phenotypic effect of each allelic substitution, averaged over all the genetic backgrounds in which it occurs. VA depends on the number of loci contributing to the character, on the evenness of allele frequencies at each locus, and on the average magnitude of the phenotypic effect of different alleles. The ratio VA/VP is termed the "heritability" of a trait (in the narrow sense); it is valid only for the particular population and the particular environment in which it was estimated, since other populations might differ in allele frequencies or in environment (which affects VE). All else being equal, the higher the VA (or VA/VP), the greater the potential rate of evolution of a character, in response to natural selection. A gene commonly affects two or more characters (pleiotropy), and so can contribute to a genetic correlation (rG) between them. Another possible cause of genetic correlation is linkage disequilibrium, nonrandom association of certain alleles at two or more loci within a population (e.g., an excess of AB and ab combinations and a deficiency of Ab and aB). Genetic correlations are important because if the population mean of one character is altered, perhaps by...

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