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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This book combines recent information and discoveries in the field of human molecular biology and human molecular evolution. It provides an interdisciplinary approach drawing together data from various diverse disciplines to address both the more classical anthropological content and the current more contemporary molecular focus of courses. Chapters include a history of human evolutionary genetics; the human genome structure and function; population structure and variability; gene and genomic dynamics; culture; health and disease; bioethics; future.
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Veröffentlichungsjahr: 2016
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CONTENTS
Cover
Title Page
Copyright
Dedication
Preface
Chapter 1: The history of human evolutionary genetics
World Views
Science and Philosophy
The Biology of Mankind: Anatomy and Physiology in a Historical Context (up to the 16th Century)
Beginnings of the Present Scientific Model
Biological Evolution and Genetic Foundations: The Brilliant Quartet
Nineteenth Century: Cytology, Embryology, and Reproduction
Twentieth Century, the Century of Genetics
The Synthetic Theory of Evolution
Bacterial and Molecular Genetics
Parallel Developments: Paleoanthropology
Technical and Methodological Developments
Conclusions
Review Questions and Exercises
References
Chapter 2: The Human Genome: Structure, Function, and Variation
Science, Politics, and Ethics
Structural Aspects
Normal and Abnormal Phenotype Distribution
Function
Sex Chromosomes
Paleogenomics
Variability: mtDNA
Nuclear Variability
Exomes and Proteomes
Selection or Drift? History
Selection or Drift? Methods
Selection or Drift? Analyses
Nervous System and Culture
Conclusions
Review Questions and Exercises
References
Chapter 3: Population Structure
DNA-Based Marker Systems
SNPs, STRs, and Indels as DNA Markers
Population Genetic Tools for Analyzing Population Structure
Forces Affecting Population Dynamics, Structure, and Evolution
Applications of Population Genetics
From Populations to Races and Species
Review Questions and Exercises
References
Chapter 4: Genetic Variability
On the Nature of Variability
Mechanisms Responsible for Generating Genetic Variability
Randomness of Mutations
Inheritance and Environment
Selection Works on the Phenotype
The Impact of Selection
Cultural Expressions as Markers of Ancestry
Congruency Among Marker Systems
Does Junk DNA Exist?
How Genetic Diversity is Studied?
Epigenetic Diversity
Review Questions and Exercises
References
Chapter 5: Gene and Genomic Dynamics
Molecular Evidence for Punctuated Equilibrium and Gradualism
Next-Generation Sequencing
Genetic Variation
Variation, Population Structure, and Effective Population Size
Recombination and its Effect on Variation
Linkage Equilibrium and Disequilibrium
Forces Leading to Linkage Disequilibrium
Linkage Disequilibrium and SNP Haplotypes
Linkage Disequilibrium in Humans
Genome Structural Variations
CNV Classifications and Formation Mechanisms
Methods Used to Detect CNVs
CNVs Associated with Human Phenotypes
CNVs and Evolution
CNV in Primates
Chromosome Rearrangements and Selfish Genetic Elements
Transposable Elements
Population Dynamics of Transposable Elements
Transposons in Human Evolution
Selfish Genetic Elements in Evolution
Genome-Wide Association Studies
Concerns Over the Effective Use of GWAS
Conclusions
Review Questions and Exercises
References
Chapter 6: Human Origins and Early Diasporas
The on Switch to Humanity
Early Hominins
Emerging Themes and Variations in Hominin Evolution
The First Hominin Migrants
The Emergence of Modern Humans
The Saharan Pump
Early Migrations
Neanderthals Prevailed
Review Questions and Exercises
References
Chapter 7: Culture
Concept
Origin and Development
Factors that Could Condition Cultural Evolution
Biology–Culture Interaction
Language
Domestication
Art
Free will, Morality, and Religion
Conclusions
Review Questions and Exercises
References
Chapter 8: Health and Disease
Hopes and Reality
Concept of Health and Methods of Study
Darwinian Medicine
Parent–Offspring Conflict
Pathogen History
Evolution of Infectious Diseases
DNA Damage, Mutagenesis, and Teratogenesis
What is Better, More or Less Gene Product?
Genetic Manipulation of Animals to Study Health and Disease
Reproductive Fitness and Health
Consanguinity
Violence
Cancer
Degenerative Diseases
Ecogenetics, Pharmacogenetics, and Pharmacogenomics
Detection of Genetic Diseases
Genetic Counseling
Treatment
Conclusions
Review Questions and Exercises
References
Chapter 9: Recent Human Evolution: An Integrative Approach
Recent Human Evolution
Out of Africa
Back to Africa
Beyond Arabia
The Asian Agricultural Revolution and the Austronesian Expansion
Evidence from Plants and Animals
Contacts between South America and Polynesia
Review Questions and Exercises
References
Chapter 10: Bioethics: Consequences and Implications of Genetic Technology on Human Evolution
Social and Biological Evolution
Overview of Ethics and Philosophical Influences on Western Ethics
Evolution of Ethics and Morality
The History and Beginning of Modern-Day Bioethics
Reproductive Technologies and the New Eugenics: Unnatural Selection?
Enhancement through IVF, PGD, and CRISPR
Ethical Issues Associated with Medical Technology
Gene Therapy
Stem Cell Therapy
Biosimilars
Genetic Privacy
Genetic Testing
DNA Profiling
Conclusions
Review Questions and Exercises
References
Chapter 11: Future of Human Evolution
Gene and Culture Coevolution
Life Expectancy and Population Growth: Past, Present, and Future
Mutation Rates and Future Evolution
The Evolution of New Genes
Climate Change
Diet
Sex Selection
Artificial Selection
Transhumanism and Artificial Intelligence
Conclusions
Review questions and exercises
References
Appendix
General Information and Bibliography
Computer Instructions
Creating a Phylogenetic Tree
Exercise 4. Aligning Multiple Sequences and Creating Phylogenetic Tree (Continued).
Using Protein Structure Repository
Exercise 5. Working with Protein 3D Structures.
Visualizing Protein Structure
Exercise 5. Working with Protein 3D Structures (Continued).
Exercise 6. BLAST Search.
Exercise 7. RNA BLAST Search.
Using RNA Secondary Structures
Exercise 8. Predicting RNA Secondary Structure.
Exercise 9. Creating a Contig and Finding the Sequence Identity
List of Bioinformatics Databases
Questions
Reference
Index
End User License Agreement
List of Tables
Table 2.1
Table 2.2
Table 2.3
Table 7.1
Table 7.2
Table 8.1
Table 8.2
Table 8.3
Table 8.4
Table 9.1
Table 10.1
List of Illustrations
Figure 1.1
Figure 1.2
Figure 2.1
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
Figure 3.5
Figure 3.6
Figure 3.7
Figure 3.8
Figure 3.9
Figure 3.10
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Figure 4.7
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
Figure 5.1
Figure 5.2
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4
Figure 6.5
Figure 7.1
Figure 7.2
Figure 8.1
Figure 8.2
Figure 9.1
Figure 9.2
Figure 9.3
Figure 9.4
Figure 9.5
Figure 10.1
Figure 10.2
Guide
Cover
Table of Contents
Begin Reading
Chapter 1
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Genomes, Evolution, and Culture
Past, Present, and Future of Humankind
Rene J. Herrera
Department of Molecular Biology, Colorado College, USA
Ralph Garcia-Bertrand
Department of Molecular Biology, Colorado College, USA
Francisco M. Salzano
Emeritus, Department of Genetics, Universidade Federal do Rio Grande do Sul, Brazil
This edition first published 2016 © 2016 by John Wiley & Sons Ltd
Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
Editorial offices: 9600 Garsington Road, Oxford, OX4 2DQ, UKThe Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK111 River Street, Hoboken, NJ 07030-5774, USA
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All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.
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Library of Congress Cataloging-in-Publication Data
Names: Herrera, Rene J., author. | Garcia-Bertrand, Ralph, author. | Salzano, Francisco M., author.
Title: Genomes, evolution, and culture : past, present, and future of humankind / Rene J. Herrera, Ralph Garcia-Bertrand, Francisco M. Salzano.
Description: Chichester, West Sussex ; Hoboken, NJ : John Wiley & Sons, Inc., 2016. | Includes bibliographical references and index.
Identifiers: LCCN 2015048491 (print) | LCCN 2015049134 (ebook) | ISBN 9781118876404 (cloth) | ISBN 9781118876381 (pdf) | ISBN 9781118876398 (epub)
Subjects: | MESH: Genome, Human | Biological Evolution | Culture
Classification: LCC QH447 (print) | LCC QH447 (ebook) | NLM QU 460 | DDC 611/.0181663–dc 3
LC record available at http://lccn.loc.gov/2015048491
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Dedication
We dedicate this book to our families
(RJH)
Esther Martinez (Tata)
Diane
Giselle and Daniel
(RG-B)
Lydia Evans (Mom)
Dianne
Jacob, Zachary, and Daniel
(FMS)
Thereza
Felipe, Renato
Grandchildren and great-grandchild
As well as
To all those who contributed to construct humankind history, either as researchers or through the generous donation of time and biological material for this enterprise. With gratitude to the American Museum of Natural History, New York City, for the awe and inspiration provided over the years.
Preface
At the end of 2012, one of us (RJH), concerned about the lack of a book on human evolution that would include not only genetics and evolution, but also other areas of knowledge that could influence this process (cultural anthropology, linguistics, demography, and other disciplines of the so-called humanities), decided to write a piece of work that would contemplate all of these aspects. Contacts with RG-B and FMS resulted in the prompt acceptance of a specific collaboration.
We then prepared a specific proposal that was, after proper consideration, accepted by Wiley-Blackwell in December of the following year (2013). In the ensuing two and a half years, we worked in close contact by e-mail, on the manuscript, followed by a face-to-face meeting in Porto Alegre, Brazil, in March 2015. The result is now presented for the appreciation of the readers.
The book comprises 11 chapters, distributed as follows: Chapter 1: history; Chapter 2: basic structural aspects; Chapters 3–5: population structure, variability, and its dynamics; Chapter 6: early migrations; Chapter 7: culture; Chapter 8: health and disease; Chapter 9: recent human evolution; Chapter 10: bioethical aspects; and Chapter 11: the future. There was a determined attempt to provide a holistic approach to the subject. The readers will decide whether we have succeeded or not. It was a pleasure to write this book, and we hope that its contents will reflect this state of spirit.
It is a pleasure to acknowledge the help we had, in the preparation of some chapters, from Drs. Jason Somarelli (Duke University, Durham, NC), Robert Lowery (Indian River State College, Fort Pierce, FL), and Marion Hourdequin (Colorado College, Colorado Springs, CO). RG-B is grateful for the monetary support from Colorado College to travel to Brazil, and the support of his colleagues in the Molecular Biology Department at Colorado College. FMS is grateful to the inspiring environment of the Genetics Department, Biosciences Institute, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil, and especially to Dr. Maria Cátira Bortolini, a long-time colleague in the studies of human molecular evolution. Our research was financed by Colorado College, Colorado Springs, CO, a Howard Hughes Medical Institute Undergraduate Biological Sciences Program, a grant from the Freeman Foundation, in the United States, and by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), as well as Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS) in Brazil.
Miami, FL
Rene J. Herrera
Colorado Springs, CO
Ralph Garcia-Bertrand
Porto Alegre, Brazil
Francisco M. Salzano
Chapter 1The history of human evolutionary genetics
The conflation and confusion of functions, of aims and criteria, is the normal, original condition of mankind.
—Ernest Gellner [1]
Summary
We start by reviewing humanity's world views, and the relationship between science and philosophy. Afterward, a selected overview of what happened in the biological sciences during the 16th to the 20th century is presented, with special emphasis, in the 20th century, on the synthetic theory of evolution, as well as on bacterial and molecular genetics, emphasizing technical and methodological developments. Molecular evolution is opening now new horizons for the understanding of human history, and details of our present knowledge will be given in the following chapters.
World Views
We are a naturally curious species. Since we crossed the pre-human threshold, therefore, we developed theories about ourselves and the world in general. These theories can be classified into three world views as follows: (a) magical; (b) metaphysical; and (c) scientific.
The magical world view was established at the beginning of our history, from a prelogical mentality that would not distinguish between wishes and the external world. There was a belief that through prayer or the influence of supernatural gods one could influence the course of events, such as the occurrence of rain or success in hunting or gathering. Cause and effect could not be clearly distinguished, and daily life was characterized by inexplicable events, which could only be understood by creating a mythology as general as the natural world itself. Fire, whose manipulation can be regarded as one of our first technological applications, was identified as a divine entity. There was no need for a coherent relationship between facts on the basis of previous knowledge. The observations were influenced by beliefs.
Around the 7th century before Christ (BC), there was a substantial change in the history of humanity, with attempts to explain the world by a set of rational premises and not by revealed or empirical evidence. This separation of the knowledge of the individual and of the surrounding environment characterized the metaphysical view of the world.
The scientific view, on the other hand, is based on the application of the scientific method, which is defined by the basic tenet of the cause–effect relationship. From the perspective of the scientific world view, the detailed analysis of part of reality can lead to an explanation as how one event results from the other. This perspective is basically materialistic, with no need for supernatural explanations.
Science and Philosophy
So far, so good, but how do we separate science from philosophy? Mayr [2] defined science as “a body of facts (knowledge) and the concepts that permit explaining these facts.” Philosophy, on the other hand, is translated literally from Greek as “the love of wisdom,” and a dictionary definition describes it as “the general science of beings, principles, and causes.”
Mayr [2,3] was skeptical about the importance of philosophy for science, and in his 1982 book he expressed doubts whether philosophy would have made any contribution to science after 1800. In particular, he indicated three philosophical concepts that would not be applicable to biology. (a) Essentialism (typology): the world would consist of a limited number of sharply delimited and unchanging essences. This concept is unable to explain the vast organic variation present in our planet. (b) Determinism: everything would be rigidly conditioned by the structures of things. This view ignores stochastic and random processes that can lead to unpredictable evolutionary events. (c) Reductionism: the explanation of a system could be made if the system had been reduced to its smallest components. The concept of emergence is strictly related to reductionism and is characterized by three properties: (a) a genuine novelty is produced; (b) the characteristics of this novelty are qualitatively unlike anything that existed before; and (c) this novelty was unpredictable. Despite dissenting views of several scholars, it is now clear that evolutionary emergence occurs and that it is an empirical phenomenon without any metaphysical foundation.
The relationship between science and philosophy, however, should be explored, since both try to explain life and the universe, and this was aptly done by Bitsakis [4]. His main propositions are summarized in Box 1.1. To completely understand them, it is necessary to recall that epistemology deals with methods and grounds of knowledge, considering their limits and validity; therefore, it investigates the formation, status, classification, and development of the sciences, internal and external factors influencing it, and so on. On the other hand, ontology is the branch of knowledge that investigates the nature, essential properties, and relations of being. Propositions have to be tested through our senses and scientific instruments; they are derivative phenomena reflecting objective entities and processes. The real world can only be assessed through successive approximations to this reality.
Box 1.1 Basis for a Realistic and Evolutionary Epistemology.
1.
There is an objective world accessible through the senses and scientific instruments.
2.
Sense data are derivative phenomena that reflect objective entities and processes.
3.
Natural laws are not conventions. They are the transcription, in human language and mathematical formulas, of objective relations, processes, and entities. They are
a posteriori
propositions.
4.
Scientific propositions are subject to empirical testing.
5.
Observational and experimental data are decisive for scientific research. Many times, from observational data we arrive at a scientific hypothesis, and the knowledge of the essential structures and mechanisms may remove the elements of uncertainty present due to this empiricist view.
6.
Empiricism is a simplistic epistemology. Science does not recognize the dichotomy between phenomenon and essence, and a phenomenon both manifests and conceals deep structures and relations.
7.
Simplistic, statistical empiricism leads to agnosticism. Theories are tested intersubjectively, since an objective criterion is not possible, and scientific laws are relative, and can be changed as knowledge progresses.
8.
Scientific truth is not absolute, but we can successively reach objective truths.
9.
The question of the truth or falsity of a proposition cannot be exhaustively answered by the criteria of empiricism. In the same way, philosophical propositions are not formulated independently of a number of ideological, social, and political factors. However, they can be tested using scientific data.
10.
Sciences emerge and develop as theoretical appropriations of the laws of the objective world. Formalist epistemologies have stressed the importance of the laws of the objective world, but they also have stressed the importance of either internal or external factors, being unable to understand their dialectic unity. Scientific revolutions do not mean formal negation of the older proposition, but a dialectic transcending of alternative visions of reality.
11.
Science includes, but at the same time produces, ideology.
12.
Dogmatic metaphysics is historically obsolete. This, however, does not mean that philosophy as a whole is also dead. There is no science without ontological and epistemological presuppositions.
13.
Science is structured with concepts, while philosophy deals with object categories. However, there is need for a mediation between the two.
14.
Philosophy does not produce specific knowledge, but produces knowledge at the ontological and epistemological levels.
15.
Epistemology has its own object and methods, and their relationship with scientific knowledge should be explored.
Source
: Reference 4.
The content of Box 1.1 can be summarized by the following six main points: (a) there exists an objective world that can be investigated through the senses and scientific instruments; (b) scientific propositions can be empirically tested; (c) in epistemological terms, a distinction should be made between the phenomena seen and their essence; (d) scientific truth is not absolute, but we can successively reach objective truths; (e) dialectics is important; scientific revolutions do not mean formal negation of the older proposition, but a dialectic transcending of alternative views of reality; and (f) neither science, nor philosophy is free of ideological influences.
The Biology of Mankind: Anatomy and Physiology in a Historical Context (up to the 16th Century)
How did the knowledge of the anatomy and physiology of mankind evolve with time? Box 1.2 lists 20 key persons who contributed in a significant way to this knowledge. It is broken down into five chronological periods that are further classified on the basis of geography.
Box 1.2 Selected List of Main Contributors to the Anatomical and Physiological Knowledge of Mankind, 500 BC to the 16th Century.
Historical/geographical periods and names
Time
Contributions
Ancient Greece
Alcmaeon of Croton
ca. 500 BC
Anatomy, brain, mouth, and ear dissections.
Empedocles
504–433 BC
Humoral theory of disease.
Hippocrates
460–375 BC
Considered the Father of Medicine. Treatment of individuals rather than diseases.
Aristotle
384–322 BC
Comparative anatomy and physiology.
Alexandria School
Herophilus
325 BC
Anatomy of the nervous system, study of pulse and lung rhythms.
Erasistratus
ca. 280 BC
Anatomy, physiology of arteries and veins.
Rome
Aulus Cornelius
1st century AD
Author of the most famous Latin compilation of medical works.
Dioscorides
54–68 AD
Identification and description of about 600 plants with medicinal value.
Galen
131–200 AD
On Anatomical Preparations
, the standard medical text for about 1400 years.
Middle Ages
Rhazes
852–925 AD
He is credited with 237 medical books, including
Continens Liber
, widely used.
Avicenna
980–1037 AD
His book
The Canon of Medicine
was used for five centuries in European universities.
Averroes (Ibn Rushd)
1126–1198
Physician, condemned by the church due to his materialistic and pantheist opinions.
Theodoric of Lucca
1205–1298
Wound treatment.
Renaissance
Guy de Chauliac
1300–1370
Surgery of cancerous tissues and ulcers. Traction as a treatment for fractures.
Leonardo da Vinci
1452–1519
Detailed anatomical studies and artistic reproduction of the human body.
Michelangelo Buonarroti
1475–1564
Detailed anatomical studies and artistic reproduction of the human body.
Andreas Vesalius
1514–1564
The Father of Modern Anatomy.
Ambroise Paré
1517–1590
Ligature of blood vessels to stop bleeding, introduction of artificial limbs.
Gabriele Falloppio
1523–1562
Observationes Anatomicae
, detailed description of the female reproductive organs.
William Harvey
1578–1627
de Motu Cordis
, the first book to clearly explain blood circulation. Description of the developmental stages of human embryos.
Sources
: References 5 and 6.
From the perspective of the occidental tradition, the intellectual history of humankind started around 600 BC in Greece. The four paradigmatic persons listed as living in ancient Greece were important not only for their contribution to anatomy and physiology in general, but also in relation specifically to applications for medical practice. Alcmaeon described the human optic nerves, established the distinction between arterial and venous blood, identified the trachea, and assigned the brain as the center of reasoning in humans. Empedocles is best known by his humoral theory of disease. In this theory, the four elements fire, water, earth, and air were associated with four body humors, blood, black bile, phlegm, and yellow bile. Empedocles proposed that good health would result if there were a balance among these humors, and different types of personality and health problems would occur if an imbalance existed. Although the theory was wrong, its emphasis on internal factors in the causation of diseases was laudable. He was also concerned with other biological questions, such as the origin of living beings. Hippocrates is considered the Father of Medicine, and he especially stressed the need to consider the individual patient rather than the disease, an underlying principle of the modern goal of individualized medicine. Finally, Aristotle had an important contribution to modern thinking by his empirical application to the problems considered, leading to what is today known as the scientific method. He applied this method to develop a formal classification of animals, separating, for instance, vertebrates from invertebrates.
After the conquest of Greece by Macedonia, the world cultural–scientific center was transferred first to Alexandria and then to Rome. The Alexandrian, Herophilus, has been reported as having dissected not less than 600 human bodies. He located the brain as the center of the nervous system and the seat of intelligence, and his studies of pulse and lung rhythms were important for the discovery of blood circulation. Erasistratus closely examined the passage of the blood through the veins and into the arteries and was also responsible for a series of studies related to the digestive system.
With the passage of the center of power to Rome, the emphasis of the studies turned to practical applications. Aulus Cornelius, Dioscorides, and Galen, however, should be remembered, especially Galen, whose book On Anatomical Preparations was used as a medical text for not less than 1400 years, probably being the longest textbook in print in history.
The Middle Ages can be characterized as a period of extreme religiosity, with an unfavorable climate for science and open inquiry. During this time, however, four persons who contributed significantly to our understanding of anatomy and medicine are listed in Box 1.2. Two of them (Rhazes and Avicenna) lived mostly in Persia, practicing medicine and contributing to the medical literature, while Averroes and Theodoric of Lucca lived, respectively, in Spain and Italy. Averroes, also a physician, developed materialistic visions of the world, and due to them was banished by the church, although a few years before his death the banishment was terminated. Theodoric of Lucca devised many procedures that were important in surgery.
Human history is characterized by several cycles of authoritarianism that, however, do not last forever. It seems that human nature considers freedom as an essential characteristic for an appropriate living. The Middle Age ecclesiastic repression, therefore, could not last forever, and it gave space to a splendid development of art, literature, and science, the Renaissance. Seven paradigmatic figures are listed in Box 1.2, and Leonardo da Vinci and Michelangelo Buonarroti are well-known personalities who do not need comments. Guy de Chauliac, Ambroise Paré, Gabriele Falloppio, and especially Andreas Vesalius excelled in different aspects of anatomy and surgery, while William Harvey, of course, was the first scholar to have a clear and accurate picture of blood circulation.
Beginnings of the Present Scientific Model
Selected key persons responsible for the development of biology in the 17th and 18th centuries are presented in Box 1.3. Three of them (Malpighi, van Leeuwenhoek, and Hooke) were mainly microscopists, responsible for the improvement and use of this very important research tool in that period. Hooke was the first to describe and name a cell, while Malpighi gave a detailed description of the capillaries and van Leeuwenhoek of the human sperm. Regnier de Graaf, on the other hand, furnished a description of the ovulation process, indicating the role of follicles in the ovary.
Box 1.3 Key Persons Responsible for the Development of Biology in the 17th and 18th Centuries.
Names
Time
Contributions
Marcello Malpighi
1628–1694
One of the first to use the microscope, he made a complete description of the capillaries.
Antonie van Leeuwenhoek
1632–1723
Extensive and detailed microscopic observations, including of human sperm.
Robert Hooke
1635–1703
Responsible for the improvement of microscopy, and was the first to use the word cell.
Regnier de Graaf
1641–1673
Description of the ovulation process, indicating the follicle's role in the ovary.
Pierre L.M. de Maupertuis
1698–1759
Investigations about inheritance, negation of creationism.
Georges-Louis Leclerc, Comte de Buffon
1707–1788
Contributed to the discussion about evolutionism and is considered the Father of Biogeography.
Thomas R. Malthus
1766–1834
His book
An Essay on the Principle of Population
greatly influenced the thinking of both Alfred R. Wallace and Charles Darwin.
Georges L. Cuvier
1769–1832
He made important contributions to comparative anatomy and paleontology.
Etienne Geoffroy
1772–1844
Favorable to evolution.
Saint-Hilaire
Morphologist, contributed in an important way to the homology principle.
Sources
: References 3, 5, and 6.
The five other selected persons were mainly concerned with genetics and evolution. Maupertuis investigated the area of biological inheritance, and clearly opposed creationism, Buffon, Cuvier, and Saint-Hilaire were concerned with different aspects of organismal variability and its distribution, while Malthus, with his demographic studies, decisively influenced Alfred R. Wallace and Charles Darwin in their thinking about the evolutionary process, as detailed in the next section.
Biological Evolution and Genetic Foundations: The Brilliant Quartet
The history in the fields of evolution of genetics is dominated in the 19th century by four paradigmatic persons, listed in the order of their births: Jean-Baptiste Lamarck, Charles Darwin, Gregor Mendel, and Alfred R. Wallace. Information about the life histories of each of these influential scientists is given in Boxes 1.4–1.7.
Mayr [3] considers Lamarck one of the most difficult persons to evaluate in the history of science due to the failure of his critics of separating his ideas on evolutionary changes per se and Lamarck's attempts to explain the physiological and genetic mechanisms responsible for them. Two common errors are that he postulated a direct induction of new characters by the environment, and attributed a nonmechanistic explanation to volition. Neither Lamarck's strongest critics (Darwin was one of them, classifying his main work as “trash”) nor his most extreme followers (like the French, who delayed the generalized acceptance of Darwinism in their country for at least 75 years) were strictly correct.
Box 1.4 presents some of the main events of Lamarck's life. In marked contrast with Darwin, he never escaped poverty. He was unhappy in his four marriages and died blind, without due recognition for his merits. However, despite these adversities, he was able to contribute in a significant way to the science of his time.
Box 1.4 Selected Aspects of the Life of Jean-Baptiste Pierre Antoine De Monet, Chevalier de Lamarck.
Year
Event
1744
Birth at Picardy, north of France, the youngest in a sibship of 11.
1760
His father dies, leaving the family in poverty.
1761–1763
Enrollment in the French army, fighting in the Seven Years' War. Wounded, returns to Paris for treatment, but never totally recovers from a lymphatic tissue lesion.
1764–1787
Lives in Paris from a small pension and works part-time in a bank. In his free time starts to work in botany. Makes acquaintance with Antoine-Laurent de Jussieu and writes a book in four volumes about the French vegetation (1778). Becomes the tutor of Comte de Buffon's son. Travels to several European countries.
1786
Buffon indicates him as assistant in the Department of Botany, Paris Natural Museum.
1793
Becomes Professor of Invertebrate Zoology in the above-mentioned museum, turning his interest to extinct and extant mollusks.
1800
Presents his theory of evolution for the first time in his
Discours d'ouverture
to students.
1802
Proposes the term
biology
for the study of living organisms. It was also him who for the first time used the term
species
in its modern meaning.
1809
Publishes his most important book,
Philosophie Zoologique
, with a detailed description of his theory.
1815–1822
Publishes
Histoire Naturelle des Animaux sans Vertèbres
, in seven volumes.
1822–1829
In the last years of his life becomes blind and, although he had been married four times, he is only assisted by his two sisters. He died in 1829, poor and without due recognition for his merits.
Sources
: References 3 and 5–7.
Lamarck proposed that evolutionary change took place via two factors. The first would be an intrinsic property of the living being, which would make possible the acquisition of always higher perfection and complexity. The second would be the ability of the living being to react to special environmental conditions. The second proposal involved the principle of use and disuse; the continuous utilization of an organ would lead to its development, and the lack of use to its deterioration. These changes would then be transmitted to their descendants (inheritance of acquired characteristics).
Developments in the 20th century clearly indicated that this type of inheritance does not exist (although recent developments in epigenetics suggest a parental or an environmental influence, in some cases). Yet, despite the fact that Lamarck seemingly missed the mark with his theory, why is he still considered important for the history of science? First, because he was the first consistent evolutionist, discarding the hypothesis of a static world for that of a dynamic, ever-changing world. In addition, his emphasis on the importance of behavior, environment, and adaptation should be stressed. Other positive factors of his theory were the following: (a) his acceptance of only mechanistic factors for the phenomena considered; (b) his emphasis on the Earth's old age and in the gradual nature of evolution; and (c) his courage to include the human species in the evolutionary chain. He also contributed in a significant way to the knowledge of the French flora and the classification of invertebrates.
There is quite possibly no other scientist whose life and work has been as intricately examined and interpreted as that of Charles Darwin. This is due to not only the impact caused by his theory (it is said that the world would never be the same after the publication, in 1859, of The Origin of Species), but also the fact that he was an obsessive and incredibly methodical writer. His diaries informed everything that would happen to him, in both personal and professional terms, and his correspondence with people all over the world amounts to about 14 thousand letters.
Some of the main events related to Darwin's life are listed in Box 1.5. He had 73 years of life intensively dedicated to his family (he had not less than 10 children) and to science. Rich, he never needed an employment for his living. In the 6 years of his voyage around the world, he obtained a massive knowledge about the planet's geology, flora, and fauna. His dedication to science should also be stressed, in spite of the health problems that he had during a significant period of his life.
Box 1.5 Selected Aspects of the Life of Charles Robert Darwin.
Year
Event
1807
Birth at Shrewsbury, west of England.
1825–1831
Studies in Edinburgh (medicine, up to 1827) and Cambridge (theology).
1831–1836
Voyage around the world in the ship Beagle.
1836
Return to London and marriage with his cousin Emma Wedgwood, with whom he had 10 children. Only seven, however, survived to adulthood.
1839
Publication of the book
Journal of Researches into the Natural History and Geology of Countries Visited by H.M.S. Beagle
. Admitted to the Royal Society.
1842–1844
Change of residence, from London to Down, First sketch of the theory of natural selection.
1858
Receives a letter from Alfred R. Wallace in which he presents the independent elaboration of the theory of natural selection. Joint communication of the two to the Linnean Society on July 1. Voyage to the Wight Island and beginning of the elaboration of the book that would be his masterpiece.
1859
Publication, at the age of 50 years, of his masterpiece,
The Origin of Species
. The first edition, of 1500 copies, was all sold in 1 day. Five other editions, published between 1860 and 1887, have been produced under his supervision.
1868
Publication of
The Variation of Animals and Plants Under Domestication
, in which he presents his theory of pangenesis, completely wrong.
1871
Publication of
The Descent of Man
, in which he applies the concepts of natural selection and sexual selection to the evolution of the human species.
1872
Publication of
The Expression of the Emotions in Man and Animals
, in which he considers different aspects of the human and animal behavior.
1882
Dies and, in spite of the resistance of the church and of conservative persons, is buried in the Westminster Abbey, together with other distinguished members of the kingdom.
Sources
: References 8–11.
The theory of natural selection developed by Darwin had a long gestation. The first sketch was made between 1842 and 1844, but the book presenting it was published in 1859 only under the pressure that Alfred R. Wallace had independently arrived at the same idea.
One of the weaknesses of Darwin's theory, which he himself recognized, was the ignorance at the time of the laws that determined the biological inheritance in living organisms. Yet, the fundamentals of these laws would be clearly delineated in 1866, 7 years after the publication of The Origin of Species, by Gregor Mendel. Interestingly, Gregor Mendel had sent a copy of his remarkable article to Darwin, who either never read it or was unaware of its importance in framing Darwin's own hypotheses.
Box 1.6 gives some selected aspects of Gregor Mendel's life. There are doubts as to whether he adopted the ecclesiastic career due to vocation or was pressed by poverty or health problems. In any case, throughout his life, Mendel demonstrated his remarkable proficiency to his chosen career, leading to his election as Abbey and the concomitant task of administering the Saint Thomas Monastery for 16 years, until his death. Throughout his life, however, he always showed a keen interest for science, performing experiments at the monastery's garden. His seminal work in peas, which established the basis for all genetic research, was published, as indicated above, in 1866, but it was largely ignored by the scientific world.
Box 1.6 Selected Aspects of the Life of Gregor Mendel.
Year
Event
1822
Birth in Heinzendorf, Austrian–Hungarian Empire, now Hyňcice, Czech Republic.
1839
His father has an accident in active service that unables him to work, leaving the family in financial difficulties.
1840
Finishes his basic studies and enters the Philosophical Institute at Olomouc University, to become a priest.
1843
Starts his apprenticeship at the Saint Thomas Monastery in Brünn (now Brno).
1844–1847
Theological and agricultural studies in Brno's Episcopal Seminar and Philosophical Institute, respectively. Ordainment.
1849
Adjunct Instructor at Znaim.
1851–1853
Studies at the University of Vienna.
1854
Substitute Teacher at Brno's Royal School.
1857
Beginning of the research on peas and beans.
1861
Associates with Brno's Society of Naturalists.
1862
Touristic trip to Paris and London.
1864
Finishes the research with peas.
1865
Presentation of his seminal work
Versuche über Pflanzen-Hybriden
in Brno's Society of Naturalists. This work established the basis for all genetics.
1866
Publication of the work in
Verhandlungen des naturforschenden Vereines in Brünn
(Vol. 4, pp. 3–47).
1868
Elected Abbey.
1870
Publication of the work on
Hieracium
.
1874
Questions the government about the taxes that the Monastery should pay.
1876
Becomes the Vice Director of Moravia's Loan Bank.
1881
Director of the same bank. First symptoms of Bright's disease.
1884
Dies due to uremia caused by the indicated disease.
Source
: Reference 12.
Why was Mendel's work ignored? Perhaps the scientific world at the time was not yet prepared to understand its real importance. Only after a series of discoveries and analyses that were performed in the following three decades would it become possible to relate his laws with concrete cytological and reproductive events. However, there is no doubt, also, that the fact that he lived far from the more important centers of biological research, and that he was not affiliated with any scientific institution may have also contributed to his lack of recognition.
The fourth paradigmatic person deserving special mention in the 19th century is Alfred R. Wallace. Selected information about him is given in Box 1.7. Similar to Darwin, he never had a position with a scientific institution; however, contrary to Darwin, Wallace was not as wealthy. Wallace made his living and paid the expenses of his travels by selling specimens, giving lectures, and writing books and popular articles. Unlike Darwin, who developed his theory about natural selection over many years of observation, Wallace arrived at the conclusion about the evolutionary importance of natural selection in a single flash of insight. This happened when he was confined to bed due to an attack of yellow fever, under Malthus' influence (cf. Box 1.3). By the evening of that day, he had prepared a rough outline of the idea, and sent a letter to Darwin 2 days later.
Box 1.7 Selected Aspects of the Life of Alfred Russel Wallace.
Year
Event
1823
Birth in Llanbadoc, Monmouthshire, Wales.
1837
Apprenticeship in surveying, in partnership with his brother, William.
1844
Takes a job as School Master in Leicester.
1848
Together with Henry Walter Bates (1825–1892) he sailed from England to South America in a collecting trip. The following year a younger brother, Herbert, joined them, but he died 1 year later with yellow fever.
1852
Return to England, but his ship burned in the way and he lost most of the specimens and notes he had collected.
1854–1862
Expedition to the Malay Archipelago. Noting differences between the eastern and western regions, he devised a line between Borneo and Celebes, and between Bali and Lombok, now known as Wallace's Line.
1866
Marriage with Annie Mitten and definitive settlement in London.
1870
Publication of
Contributions to the Theory of Natural Selection
.
1876
Publication of
Geographical Distribution of Animals
, a landmark in biogeography, in which he divides the world into six regions, recognized up to the present.
1903
Publication of
Man's Place in the Universe
. In this and the 1870 book, he sets human evolution apart from natural selection and biology, developing a mystical approach.
1905
Publication of an autobiography,
My Life
.
1913
Dies in London.
Sources
: References 5 and 6.
In addition to Wallace's contributions to evolutionary principles, Wallace was also well recognized as a leader in the field of biogeography, and some of the regions he identified as important in animal distribution are still recognized today.
Nineteenth Century: Cytology, Embryology, and Reproduction
Twenty-four of the persons who, besides Lamarck, Darwin, Mendel, and Wallace, contributed in a significant way for the development of cytology, embryology, reproduction, and related subjects in the 19th century, are listed in Box 1.8. Their contributions could be classified, somewhat artificially, as follows: (a) biochemistry: Nägeli, Miescher, and Altman; (b) cytology: Schleiden, Schwann, Virchow, Balbiani, Flemming, Strasburger, van Beneden, Wilson, and Boverí; (c) embryology/reproduction: Purkinje, von Baer, Kölliker, Hertwig, Roux, and Driesch; (d) inheritance: Galton and Weismann; and (e) evolution: Spencer, Huxley, Haeckel, and de Vries.
Box 1.8 Key Persons Responsible for the Development of Biology in the 19th Century.
Names
Time
Contributions
J.E. Purkinje
1787–1869
Discovery of the germinal vesicle in bird's eggs (1825). Introduction of the term protoplasm (1839).
Karl E. van Baer
1792–1876
First accurate description of the human egg (1827). His 1828 book
Entwicklungsgeschichte der Thiere
was the standard embryology text for many years.
Matthias J. Schleiden
1804–1881
Together with T. Schwann was responsible for the cellular theory, according to which all living organisms are composed of cells (1838–1839).
Theodor Schwann
1810–1882
Co-responsible, with M.J. Schleiden, for the cellular theory.
Albrecht Kölliker
1817–1905
Applied the cellular theory to embryology and histology. In 1841 demonstrated that spermatozoids were sexual cells originated in the testicles.
Carl von Nägeli
1817–1891
Developed a series of chemical tests in plants, but did not understand Mendel's work and in 1884 presented a completely wrong theory about biological inheritance.
Herbert Spencer
1820–1903
Philosopher, he created the “survival of the fittest” expression, and extended it to the social sciences.
Rudolf Virchow
1821–1902
Extended the cellular theory to pathology (1858). Three years before established the principle that new cells could only appear from preexisting ones.
Francis Galton
1822–1911
One of the founders of biometry and of the statistical study of variation. Application of the twin method for the investigation of human behavior (1875).
E.G. Balbiani
1825–1899
Described mitosis in one protozoan in 1861, and in 1881 the giant polytenic chromosomes of
Chironomus
.
T.H. Huxley
1825–1895
Important studies in comparative anatomy. In 1868 concluded that
Archaeopteryx
should be an intermediate between reptiles and birds. Had an important role in the defense of Darwinism.
Ernst Haeckel
1834–1919
In his 1866 book
Generelle Morphologie der Organismen
developed the concept that ontogeny recapitulates phylogeny. While not correct, this principle generated a series of important studies in comparative embryology. In the same book, he created the term
ecology
.
August Weismann
1834–1914
Important theoretician, he emphasized in 1883 the distinction between somatic and germ cells. In 1885, he postulated the continuity of the germplasm and, in 1887, the need for a periodic reduction of the chromosome number in sexual organisms.
Walther Flemming
1843–1915
Studied mitosis in detail, creating terms used up to the present (
chromatin
,
prophase
,
metaphase
,
anaphase
,
telophase
). In 1882 described amphibian's lampbrush chromosomes.
Friedrich Miescher
1844–1895
In 1871 described a technique for the isolation of nuclei and one substance that he called nuclein, from which Richard Altman extracted ribonucleic acid, the genetic material.
Eduard Strasburger
1844–1912
Analyzed in detail cell division in plants, and in 1879 demonstrated that a nucleus could only be formed by another nucleus.
Edouard van Beneden
1845–1910
Described, in
Ascaris
, in 1883, chromosome reduction in meiosis and its reestablishment after fertilization.
Hugo de Vries
1848–1935
Extensive crossings in plants, rediscovery of Mendel's work. According to him, mutations would be the main factor in evolution.
Oscar Hertwig
1849–1922
Described the fertilization process in sea urchin in 1875. His book
Cell and Tissues
, published in 1893, was very well received at the time.
Wilhelm Roux
1850–1924
Pioneer in the area of experimental embryology, suggested in 1883 that the units of inheritance would be carried in the chromosomes.
Richard Altman
1852–1901
Isolation of the nucleic acid in 1889. Description of the mitochondria in 1890.
Edmund R. Wilson
1856–1939
Studies in cytology and embryology. His book
The Cell in Development and Inheritance
, published in 1896, was a landmark for the investigation in these areas.
Theodor Boverí
1862–1915
Described the mechanism of the formation of the mitotic spindle in 1888. At the beginning of the 20th century, together with W.S. Sutton, postulated that the chromosomes would be the carriers of the units of inheritance.
Hans Driesch
1867–1941
Studies in experimental embryology. Publication of
Analytische Theorie der organischen Entwicklung
, where he generalized his studies.
Sources
: References 3, 5, 6, 13, and 14.
Mayr [3] identified the period from 1830 to 1860 as one of the most exciting in the history of biology, in large measure due to these researchers and the above-mentioned evolutionists. He considered that much of this burst of knowledge was due to the increasing professionalization of science, the improvement of the microscope, and the rapid development of chemistry. However, even with these cultural and technological developments, the genius of some of the indicated persons, no doubt, was also of decisive importance.
Twentieth Century, the Century of Genetics
Due to the enormous impact that genetics had, not only in the scientific world, but also in the everyday life of common people, the 20th century can be deservedly considered the century of genetics. Carlson [14] divided the history of genetics in the 20th century in a more or less symmetrical way in two periods: (a) the period of classical genetics (1900–1953) and (b) the period of molecular genetics (1953–1999).
The century starts with the rediscovery of Mendel's law by a trinity of important individuals, the Dutch Hugo de Vries (1848–1935), the German Carl Correns (1864–1933), and the Austrian Erich von Tschermak (1871–1962). Of the three, the scientifically most important was undoubtedly Hugo de Vries. de Vries maintained that he had found Mendel's ratios before reading Mendel's paper (probably about 1896), but in his March 14, 1900 article in the German journal Berichte der Deutschen Botanischen Gesellschaft, in which he reports 3:1 ratios in 19 plant genera, he did acknowledge Mendel's prior contributions to this idea. Carl Correns submitted a paper on April 24, 1900, to the same journal that published de Vries' findings, clearly acknowledging Mendel's work in its title. His experiments were performed in peas and maize. Finally, Tschermak, 1 month and 9 days later (June 2, 1900) submitted also to the Berichte a paper describing his results in peas, also confirming Mendel's ratios.
The acceptance of Mendelism, however, was not without controversy, and intense debates raged between the so-called Mendelians, who were represented by William Bateson (1861–1926), and the biometrists, such as Karl Pearson (1857–1936) and Walter F.R. Weldon (1860–1906). Interestingly, the data that definitely established the Mendelian bases of heredity came from the other side of the ocean, largely deriving from the “fly room” of Columbia University in New York. Sturtevant [13] affirmed that with T.H. Morgan's et al. classical book in 1915, and C.B. Bridges' article of 1916, an important period in the history of genetics was closed. No more doubts existed about the chromosomal theory of inheritance, opening the room for a successful fusion between genetics and evolution, which is detailed in the next section.
The Synthetic Theory of Evolution
The fusion between Darwinism and Mendelism occurred in two very fertile decades of the 20th century, between 1930 and 1950, through the synthetic theory of evolution. Box 1.9 lists the 11 key books that furnished the fundamentals of the theory. Fisher, Wright, and Haldane elaborated the mathematical statistics bases, and Dobzhansky's (Figure 1.1) book is considered by many to be the main work that provided the fusion between these bases and the empirical studies. Dobzhansky apparently used Darwin's book as a model (as suggested by the title of his book), but in contrast to Darwin, who needed 17 years between the formulation of his theory and the publication of the book to document that theory, Dobzhansky wrote his classic in just 4 months! The extension of the theory to zoology and systematics was done by Ford, Mayr, and Rensch; to paleontology by Simpson; to cytogenetics by White; and to botany by Stebbins. Naming of the theory as synthetic was done by Huxley, who included embryology in its framework and developed general principles.
Box 1.9 The 11 Key Books that Furnished the Fundamentals of the Synthetic Theory of Evolution.
Names
Time
Title of the book
Year
Ronald Fisher
1890–1962
The Genetical Theory of Natural Selection
1930
Sewall Wright
1889–1988
Evolution in Mendelian Populations
1931
Edmund E. Ford
1901–1988
Mendelism and Evolution
1931
John B.S. Haldane
1892–1964
The Causes of Evolution
1932
Theodosius Dobzhansky
1900–1975
Genetics and the Origin of Species
1937
Julian S. Huxley
1887–1975
Evolution: The Modern Synthesis
1942
Ernst Mayr
1904–2005
Systematics and the Origin of Species
1942
George G. Simpson
1902–1984
Tempo and Mode in Evolution
1944
Michael J.D. White
1910–1983
Animal Cytology and Evolution
1945
Bernhard Rensch
1900–1990
Neuere Probleme der Abstammungslehre
1947
G. Ledyard Stebbins
1906–2000
Variation and Evolution in Plants
1950
Sources
: References 3, 15, and 16.
Figure 1.1 Theodosius Dobzhansky doing field work with Brazilian and Chilean colleagues in 1956. From left to right: Antonio R. Cordeiro, Francisco M. Salzano (both Brazilians), Danko Brncic (Chilean), and Luiz Glock (Brazilian). (Source: F.M. Salzano, personal collection.)
Bacterial and Molecular Genetics
In the middle of the century, another parallel revolution would occur in another area. Attention was turned to bacteriology, and as a result, a series of brilliant experiments established the importance of bacteria and bacteriophages for genetic analyses. Results of Oswald T. Avery (1877–1955), Colin M. MacLeod (1909–1972), and Maclyn McCarty (1911–2005) in 1944, and of Alfred D. Hershey (1908–1997) in 1952 made it clear that deoxyribonucleic acid (DNA) was the genetic material underlying these principles.
The molecular genetics era started in 1953 with the elegant DNA model devised by James D. Watson (born in 1928) and Francis H.C. Crick (1916–2004), to which Rosalind E. Franklin (1921–1958) and Maurice H.F. Wilkins (1916–2004) significantly contributed. The structure had been discovered, but it was necessary to know how it functioned, and it was Crick again who conceived the need for an intermediate in the road from DNA to protein, messenger ribonucleic acid (mRNA), and with three other colleagues [among them the also famous Sydney Brenner (born in 1927)] identified the nature of the genetic code.
Parallel Developments: Paleoanthropology
The field of paleoanthropology could only develop after it was realized that the biblical version of the creation narrative should not be interpreted at its face value, and that our species had an extreme antiquity. In the 19th century, for instance, the noted anatomist Georges Cuvier (see Box 1.3) asserted, wrongly, of course, that there were no human fossils.
This view started to change only in the late 1850s, when British geologists became convinced that the stone tools found in association with human remains indicated that our species had an antiquity that could be assigned to late geological periods.
The history of paleoanthropology can be conveniently traced to 1856, with the discovery of unique human remains in the Feldhofer Grotte located in the Neander Valley (Tal, in German). Hermann Schaaffhausen (1816–1893), an anatomist, introduced the “Neandertaler” to science, raising a controversy that remains to this day, whether what has been called Homo neanderthalensis is or is not an archaic hominin that is truly unique as compared to our own species.
Another landmark in the history of human origins was the book by Charles Darwin The Descent of Man, published in 1871. His views were essentially correct, as evaluated presently. He postulated that the human species originated in Africa and suggested an adaptive scenario that included a change from the trees to the open plains, where bipedalism was adopted as a means of locomotion. This adaptation onto land freed the humans hands for tool making, which subsequently stimulated the development of intelligence [17].
The next chapter in the development of our understanding of human origins can be dated to 1894, with the description by Eugène Dubois (1858–1940) of fossils that he named as Pithecanthropus, now classified as Homo erectus. His examination of the skullcap and a femur from these remains led him to postulate that Pithecanthropus was relatively small brained, but was capable of walking bipedally, placing him in a position that was intermediary between humans and apes.
While these discoveries and advances were critical, the main events of the 20th century began in 1924, when a cranium of what was previously thought to be a baboon fossil was discovered 10km southwest of Taung in South Africa. Raymond A. Dart (1893–1988), an anatomist at the University of Witwatersrand in Johannesburg, verified that the cranium had an unprecedented blend of pongid and hominid traits. Convinced of the evolutionary significance of the material, he assigned the Taung specimen to a new genus and species, Australopithecus africanus. Robert Broom (1866–1951), a medical doctor and paleontologist, agreed with Dart's evaluation and became an energetic advocate of the new entity. He also found an entirely different, robust form of australopithecine, which he named Paranthropus robustus.
The discoveries of paradigmatic fossil remains continued through the examination of material recovered from 1959 to 1963, which were described by Louis S.B. Leakey, Phillip V. Tobias (Figure 1.2), and John R. Napier in 1964 as a new species, Homo habilis. Evidence on the teeth, cranial bones, endocranial casts, and hand and foot bones indicated its distinction from everything previously known, justifying the new taxonomic unit.
Figure 1.2 Phillip V. Tobias, a key figure in paleoanthropology and a dedicated fighter for civil rights in South Africa. (Reproduced with kind permission of Jeffrey McKee.)
All the interpretation of the above-mentioned findings was subjected to intense controversy, and Tobias [18] compared the 20-year delay in the acceptance of Homo habilis to the 35-year delay of acceptance of Australopithecus africanus and proposed that both were premature discoveries in the sense that they could not be connected in simple logical steps to canonical or generally accepted knowledge. He suggested that the delay in the acceptance of these two entities could only be understood as a sustained resistance to a change in preexisting concepts.
More recent developments led to a flurry of new taxonomic entities, but Cela-Conde and Ayala [19] and Wood [20] maintained the existence of only five pre-sapiens hominins: (a) the Miocene forms (exemplified in Ardipithecus ramidus, proposed in 1995); (b) archaic (examples: Australopithecus afarensis and Australopithecus africanus); (c) archaic megadontic (Paranthropus robustus); (d) transitional (Homo habilis); and (e) pre-modern Homo (Homo erectus).
Technical and Methodological Developments
Which factors lead to scientific development? This question has been frequently asked by historians of science, and the answers can be broadly classified into internal and external factors. Among the latter, we could mention (a) favorable political and socioeconomic conditions and (b) technological progress. Yet, the presence of paradigmatic persons in a certain place and at a given time is also undoubtedly important in relation to a large number of advances. Kuhn [21] differentiated what was classified as “normal” contributions to scientific revolutions, discoveries that opened entirely new horizons in a given subject, and for these events to happen three things are important: personal competence, inspiration, and the development of new analytical tools.
Population variability has been scientifically studied since the 18th century, with various methods and techniques that have steadily improved over time, especially from the 20th century onward. Box 1.10 lists the main laboratory and analytical tools that have been used both currently and in the recent past.
Box 1.10 Main Laboratory and Analytic Methods for the Study of Population Variability.
1. Laboratory
1.1. Morphological
1.1.1. Qualitative visual inspection
1.1.2. Quantitative manual devices
1.1.3. Computerized morphometry
1.2. Immunological
1.2.1. Blood groups
1.2.2. Histocompatibility leukocyte antigens (HLA)
1.3. Cellular
1.3.1. Cell culture
1.4. Biochemical
1.4.1. Chromatography
1.4.2. Electrophoresis
1.5. Molecular
1.5.1. Restriction endonucleases
1.5.2. Cloning
1.5.3. Sequencing
1.5.4. Polymerase chain reaction (PCR)
2. Analysis
2.1. Calculating machines
2.2. Bioinformatics
2.2.1. Data banks
2.2.2. Electronic programs
2.2.3. Research networks
