What Makes Us Humans PDF Free Download
1 / 32
/32
100%
HUMAN EVOLUTION, BIOLOGICAL AND CULTURAL DOMAINS
WHAT MAKES US HUMANS
No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or
by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no
expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No
liability is assumed for incidental or consequential damages in connection with or arising out of information
contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in
rendering legal, medical or any other professional services.
Copyright © 2020 by Nova Science Publishers, Inc.
All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted
in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying,
recording or otherwise without the written permission of the Publisher.
We have partnered with Copyright Clearance Center to make it easy for you to obtain permissions to
reuse content from this publication. Simply navigate to this publication’s page on Nova’s website and
locate the “Get Permission” button below the title description. This button is linked directly to the title’s
permission page on copyright.com. Alternatively, you can visit copyright.com and search by title, ISBN,
or ISSN.
For further questions about using the service on copyright.com, please contact:
Copyright Clearance Center
Phone: +1-(978) 750-8400 Fax: +1-(978) 750-4470 E-mail: info@copyright.com.
NOTICE TO THE READER
The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or
implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is
assumed for incidental or consequential damages in connection with or arising out of information
contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary
damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts
of this book based on government reports are so indicated and copyright is claimed for those parts to the
extent applicable to compilations of such works.
Independent verification should be sought for any data, advice or recommendations contained in this
book. In addition, no responsibility is assumed by the Publisher for any injury and/or damage to persons
or property arising from any methods, products, instructions, ideas or otherwise contained in this
publication.
This publication is designed to provide accurate and authoritative information with regard to the subject
matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in
rendering legal or any other professional services. If legal or any other expert assistance is required, the
services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS
JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A
COMMITTEE OF PUBLISHERS.
Additional color graphics may be available in the e-book version of this book.
Library of Congress Cataloging-in-Publication Data
ISBN: HERRN
Library of Congress Control Number:2019955888
Published by Nova Science Publishers, Inc. † New York
CONTENTS
Introduction Human Nature: A Hot Spot for Storytelling,
Fake News, and Speculation xiii
Biology Is Not Enough xiii
This Book Is Definitely Based on a
Scientific Approach xiv
The Subject Is Ideologically and Politically Loaded xv
Hunting Propaganda and Fake News xvi
Unintentional, Although (Even More?) Harmful
Fake News in Speculative Science xvii
Anti-Fake News Toolkit: Back to the Original
Writing, Back to the Data xvii
Avoiding Confusion between Morals, Ethics,
Politics, and Knowledge xviii
Cultural Bias xx
A Book Accessible to Everybody xx
Chapter 1 Origins of Mankind: Human Lineages
and Archaic Adaptive Introgression 1
Introduction 1
A Major Factor of Uncertainty and Controversy:
The Problem of Taxonomy and Species Definition 3
When Did We Become “Real Men”? 16
When Did Homo Sapiens Appear? 18
Contents
vi
How Many Hominini/Homo Species
Have There Been? 22
Neanderthal, Cousin or Brother? 27
A Hint of Science Fiction:
Adaptive Archaic Introgression 34
The Out-of-Africa Controversy 37
Conclusion: Beautiful Pieces of Knowledge,
but Still Many Questions and Controversies 41
Chapter 2 Human Diversity:
Taxonomical and Medical Implications 43
1-Let Us Travel throughout General Human
Genetic Diversity 43
A General Population Genetics Framework Is
Indispensable for Applied Research 43
Is Overall Genetic Variation Greater within Major
Continental Groups than between Them?
Yes and No 44
Is Human Genetic Variation Clinal or Tree-Like? 45
Human Populations Remain Highly Stratified 48
Everybody Is Mixed Race:
Admixture Is a Ubiquitous Phenomenon 50
If We Are All Mixed Race, Do Human Populations
Tend Toward Homogenization? 51
Ancestry Informative Markers (AIM) vs.
Self-Reported Ancestry (SRA) 52
The Contribution of Ancient DNA:
Adaptive Archaic Introgression (AAI) 53
Ancient Myths And Enigma Revisited: The Origin
of Basques, Jews And Indo-Europeans 56
What Is the Origin of Human Genetic Variability? 61
The High Relevance of Rare and Low-Frequency
Variants 62
The Impact of Structural Variation 64
Contents
vii
The Considerable Role Played by Genetic
Regulation and Epigenetics 64
Geographical Distribution of Phenotypic Variation 67
Is Humankind Still Evolving? An Iconoclastic View 71
2- Human Geographical Populations and Disease: 80
What Does Genetics Tell Us? 80
Different Approaches to Exploring the Genetic
Basis of Disease:
Candidate Genes, GWAS, WGS, CD/CV, RV 81
What Are the Most Relevant Units of Analysis
for the Study of Disease? 81
Mendelian Diseases 82
Complex Diseases 84
Transmissible Diseases: A Two- to Three-Actor
Coevolution Phenomenon 86
Conclusion on Human Genetic Variability
and Differential Adaptation to Diseases 92
Chapter 3 Darwinian Medicine: Reinventing the Wheel? 93
“Nothing in Medicine Makes Sense Except in
the Light of Evolution” 93
A Revolutionary Panacea? 93
“Don’t Count Your Chickens before They Hatch” 94
Are Medical Doctors Ignorant of Evolution,
or Evolutionists Ignorant of What Doctors
Know about Evolution? 95
What Is a Disease? Two Illustrative Cases
in the Field of Psychiatry 97
Is Disease Obligatorily a Curse? 100
Are We All Really African Hunter–Gatherers?
No! Ample Evidence for Recent Evolution 101
Genetic Burden and Its Benefits:
The Cruel Trade-Off of Balanced Selection 104
Contents
viii
Transmissible Diseases and Coevolution: A Major
Field for Interaction between Evolutionists and
Medical Doctors (Some People Can Be Both) 106
Recent, Fashionable Hypotheses: The Hygiene Hypothesis,
Niche Construction Theory,
the Baldwin Effect, the Thrifty Gene
Hypothesis, the Smoke Detector Principle 109
The Paleolithic Lifestyle and Diet: Anything Truly
New or Only Semantic Innovation? 113
Darwinian Medicine: An Opportunity to Revisit
Disease Classifications? 113
An Evolutionary View of Cancer, Chronic
Diseases, and Aging 114
Ethno-Medicine: Geographic Genetic Phenotypic
Differences and Their Evolutionary Origin
Matter for Personalized Medicine 115
The Weight of History in Personalized Medicine:
Colonial Expansion and the Slave Trade 118
Comparisons with Animals:
Homologies and Apomorphies 118
The Weight of Phylogenetic Constraints:
Evolution Cannot Do Anything 119
Conclusion 120
Chapter 4 Brain Genes, Cognition, Psychiatry, and Genetics 121
A Central Debate: Monism vs. Dualism.
Are Mind/Soul and Brain Tantamount
to Each Other? 121
What Are the Differences Between Human and Ape
Brains? And What Are the Differences Between
Humans and Animals in General?
The Origins of Our Cognitive System 123
Brain Genes and Culture 125
What Is Happiness? A Quantum Story of the Brain 129
Empathy vs. Altruism: Nice vs. Truly Useful 131
Contents
ix
Are Female and Male, Homosexual and
Heterosexual, and Transgender
Brains and Minds Different? 133
Geographical Variation of Cognitive Features 136
(Undeserved) Glory and (Undeserved) Decadence
of Psychoanalysis 139
Mind Doctors Have a Tough Job to Get Done 143
The Future of Cognition Studies 146
Chapter 5 Scientific and Ethical Views on Discriminative
Thoughts: Science and Politics 149
The Never-Ending Debate about Nature and Nurture 149
Eugenics 159
Racism 164
Sexism 173
Innate Political Orientation 175
Conclusion 175
Chapter 6 Science and Religion: Is the Dialogue Possible? 177
Religious Authorities: From Conflict to Harmony 177
World Religions and Creation Myths 178
Greek Authors 180
Christian Authors 182
Modern Times 183
Darwin’s Revolution 185
Evolution and the Bible 188
The Problem of Evil 191
Evolution in Dialogue 194
The New Atheists 195
Evolution and Religious Beliefs 198
Chapter 7 Non-Scientific Accounts:
Creationism and Intelligent Design 201
The Book of Genesis 201
Evolution and the Bible 201
Dayton, Arkansas, Louisiana, Dover 204
Contents
x
The Design Argument 207
William Paley 209
The Bridgewater Treatises 212
Intelligent Design 213
Evolution Is “Only” a Theory 215
The Two-Explanations Fallacy 218
The Octopus and the Squid 219
Improbabilities 222
In Praise of Imperfection 227
Conclusion Sorting Out Well-Supported from (I) Still
Speculative and (II) Misleading,
Erroneous Knowledge 233
Our Book Should Satisfy Many Concerns
of Our Time 233
The Groundswell of Fake News through Social
Networks (But Not Only) 234
Science Should Be an Oasis in the Arid Desert
of Fake News 234
The Temptations of Scientific Imperialism
and Extrapolation 235
The Recurrent Temptation of Giving a Specific
Place to Humans 236
The Urgent Need to Sanctuarize Mutually
Science on the One Hand and Ethics
and Politics on the Other Hand 237
Again, Sorting Out the Strongly Supported,
The Tentative, The Doubtful, and the
Certainly Wrong 237
Glossary 241
References 249
Contents
xi
About the Authors 285
Index 287
Related Nova Publications 291
INTRODUCTION:
HUMAN NATURE: A HOT SPOT
FOR STORYTELLING, FAKE NEWS,
AND SPECULATION
What makes us specifically human? Put another way: What are the
characteristics that all humans share and are not found in other living
creatures? This crucial question has been addressed in numerous books. The
present book does not claim to exhaust the subject. It seeks to convey only
the personal views of two biologists who have very different backgrounds.
It deals with selected key topics that are assumed to distinctly enlighten the
question.
The book has been designed taking into account several fundamental
considerations.
BIOLOGY IS NOT ENOUGH
Biology has made huge progress in the past 20 years, for example,
through the massive development of DNA sequencing technology and the
analysis of megadata by supercomputers. Owing to these advances, a
Michel Tibayrenc and Francisco J. Ayala
xiv
biological and reductionist approach is quite informative for enlightening
human nature. However, biology is definitely not enough. “Umbrella
hypotheses,” intended to summarize the whole of human nature through a
single or a few concepts, although fascinating, are bound to be misleading
or at least incomplete. We call “scientific imperialism” the temptation of
many specialists to exaggerate the power of their discipline and its relevance
for many fields. Many biologists think that their discipline is able to explain
the whole of human nature.
A holistic approach will prevail here. A tight connection will be
established between biology, medicine, and human sciences: anthropology,
ethnology, history, psychology, and psychoanalysis. The dialogue between
specialists from drastically different disciplines is always difficult; however,
it is crucial.
THIS BOOK IS DEFINITELY BASED ON
A SCIENTIFIC APPROACH
We have chosen to debunk two fields that have recently flourished in
the United States and other countries, namely, creationism and intelligent
design, precisely with the goal of illustrating what a nonscientific approach
is. Science is taken here in a broad sense. As stated above, human sciences
are definitely included. The criteria for defining what a scientific approach
is are a never-ending debate. A simple criterion will be retained here: a
process of objective knowledge based on rational reasoning and reliable
data, in the present state of the art of the discipline concerned, under the
constant scrutiny and criticism of specialists in the field, with results
published in high-quality specialized media. More than in any other field of
knowledge, when human nature is concerned, it is crucial to consistently sort
out the robust, the probable, the speculative, the unknown, and the definitely
wrong. Some reliable tips may be used in this sorting process. In science,
there is no “truth,” there are only provisional models and hypotheses. The
Popperian criterion of falsifiability (Popper, 1934), although still quite
Introduction
xv
relevant, will not be considered here as mandatory. Particularly where
biomedical science and medicine are concerned, hypotheses are often
formulated through an inductive process of accumulating premises and
presumptions that are considered to be strong enough; the Popperian
criterion is too demanding. An inductive approach could be considered
wanting in a philosophical account; however, it is operational. With
medicine and biomedical research, and because decision-making is crucial,
one cannot afford to limit oneself to a strict Popperian process. Hypotheses
relying on an inductive process will often be used here.
THE SUBJECT IS IDEOLOGICALLY
AND POLITICALLY LOADED
Exploring human nature is a burning topic. It is definitely not
comparable to considering the biology and behavior of newts or carabid
beetles. The challenge is to remain neutral and objective when one is both
actor and spectator. Where politics is concerned, it is not astonishing that
our vision of human nature, since it has a considerable impact on societal
problems, remains the main line of cleavage between the right and the left,
the liberals and the conservatives, much more so than economics. This is
illustrated by the never-ending and even violent confrontations on nature and
nurture, intelligence heritability, innate differences among geographical
populations/races and so on. Indeed, the matter is a minefield of propaganda,
fake news, alternative truths, half-truths, half-empty and half-full glasses,
and even sheer lies (although often pious). A scientific vision of the subject,
therefore, requires clearing up the issues, even when the points made are
well intentioned and are made in the name of ethics and morals. The only
criterion should be scientific reliability and objectivity.
Michel Tibayrenc and Francisco J. Ayala
xvi
HUNTING PROPAGANDA AND FAKE NEWS
Since the topic is ideologically and politically loaded, the temptation is
great for ideologists to bombard the public with biased information. Social
networks (Facebook, etc.) are a major source for circulating unverified,
unreliable information and they provide a free and unlimited drug for the
pullulating followers of the conspiracy theory. The mainstream media grow
engaged by this phenomenon and establish specialized websites intended to
detect unreliable information. The current president of France, Emmanuel
Macron, is even proposing to design a new law to condemn the promoters
of fake news. The academic world has stressed the necessity to better
analyze the fake news phenomenon in order to counter it more efficiently
(Lazer et al., 2018). However, the definition of fake news given by these
authors is far from convincing. Every means of information outside
mainstream media is suspected of issuing fake news, while the mainstream
media such as the Washington Post and the Wall Street Journal would be a
priori reliable and could be in charge of hunting down fake news. Lazer et
al., (2018) ask: How can we create a news ecosystem and culture that values
and promotes truth? They simply forget to define what “truth” is. They seem
to (pretend to?) forget that, beyond rough facts (the gross national product
of a given country, for example), that are quite verifiable, the word of
information is an immense gray zone where facts are a matter of
interpretation: Vérité en deçà des Pyrénées, erreur au delà (truths on this
side of the Pyrenees are falsehoods on the other) (Michel de Montaigne).
This gray zone is manna for fake-news makers, who take the opportunity of
the gray zone’s ambiguities to bombard us with sophisms and made-up half-
truths. It is therefore crucial and very difficult to define what fake news is,
even more so since a great deal of fake news (whose obvious goal is to
mislead the reader) are admirably camouflaged. Sheer lies are rather easy to
refute. Clever sophisms are not. Moreover, it would be too naïve to believe
that mainstream media and even the scientific literature are ideally neutral
and innocent of any wrong information. Wouldn’t the specialized anti-fake
news websites be an attempt from the mainstream media to retain exclusivity
on fake news?
Introduction
xvii
UNINTENTIONAL, ALTHOUGH (EVEN MORE?) HARMFUL
FAKE NEWS IN SPECULATIVE SCIENCE
An efficient remedy against the loss of science credibility is a
rehabilitation of modest, careful science, close to crude observations and to
a simple description of the world. The lay public does not differentiate
between hard facts that are effectively supported and extremely speculative
science (“this is all science”). Today, speculative science is full of
unintentional fake news and is quite often refuted by rough facts. For
example, it has been long considered even in school textbooks that the
number of genes in humans was more than several hundred thousand,
without the slightest evidence for it. The progress of genomics has shown
that this number is much lower, around 20,000. This kind of gratuitous
statement, typical unintentional fake news, is extremely harmful for the
credibility of science and is abundantly exploited by its opponents.
Nowadays, science faces fierce opponents: creationists, supporters of non-
technological societies ("zero growth "). These opponents exploit the
weakness of science, chiefly speculative and sensationalistic science.
Scientists would regain substantial credibility by favoring cautious scientific
approaches and moderate writing. This is especially advisable to specialists
of human paleontology (Chapter 1).
ANTI-FAKE NEWS TOOLKIT: BACK TO THE ORIGINAL
WRITING, BACK TO THE DATA
Be it on social networks or in mainstream media or even in the scientific
literature, propagandists always use the same tricks: (1) avoiding truly citing
the original sources and preferably using second- or third-hand citations. For
example, it is widely believed that Trofim Lysenko was an obscurantist,
having paralyzed Soviet science for many years. This is most probably true.
Now, who has read Lysenko in the original Russian text? Very few people,
certainly. (2) Using “strawman strategies” by attacking a given theory, not
Michel Tibayrenc and Francisco J. Ayala
xviii
for what it actually is, but for erroneous, deformed statements of the theory.
An efficient cure against (2) is to widely use original sources and plain
citations. Words fly, writings remain, fortunately for science.
Another apt strategy, before a tough debate, is to go back to the data (see
Chapter 5: “The mismeasure of Boas and Gould?”).
Lastly, a useful trick to see whether a statement is either reliable or
untruthful is to consider the background of its author. If the author has
absolutely no interest or expected bias for supporting the statement, this
makes it more credible.
AVOIDING CONFUSION BETWEEN MORALS, ETHICS,
POLITICS, AND KNOWLEDGE
This is crucial for clearing up the issues mentioned above. Throughout
human history, there has been a distressing confusion between socially
acceptable knowledge and objective knowledge. Langaney (1999) has
unveiled some famous cases. The theory of heliocentrism (Nicolaus
Copernicus), strongly repressed by the Catholic Church, is a paradigmatic
example. Georges-Louis Leclerc de Buffon was forced to present his
iconoclastic theory of a long geological time (although his estimation was
quite modest: 75,000 years) in a very tentative way, in order to avoid
persecution. He was nevertheless exiled to Burgundy for having proposed it.
Closer to us, one can cite the theory of evolution: Lamarck, who formulated
an early proposal of it, was fiercely criticized by Cuvier (who nevertheless
was a great scientist), the defender of “catastrophism” and of the Biblical
universal flood. Cuvier was influential enough to ruin Lamarck’s reputation.
Darwin was also severely criticized by religious authorities. Sigmund
Freud’s hypothesis of infant sexuality was a scandal within the medical
profession; in return, the father of psychoanalysis was publicly criticized for
it. The hypothesis of the high antiquity of man (Boucher de Perthes) was
challenged by French (but not English) scientists, obviously because this
hypothesis clashed with a literal reading of the Bible. In the former Soviet
Introduction
xix
Union, Mendelian geneticists were persecuted because genetics was
considered a “bourgeois” science, contrary to Marxist dogma.
These examples illustrate the remarkable fact that many, if not most,
innovative theories were perceived as scandalous (according to the morals
of the time) when they were first advanced. It would be extremely naïve to
think that at present we have gotten rid of the problem of blurring the lines
between desirable, socially and morally acceptable ideas on one hand, and
objective facts on the other hand. Every period of history had its strong
conformisms and taboos, ours as much as others, even possibly more.
However, emotion, ethics, morals, politics, and propaganda, even when
well-intentioned, should not interfere with the scientific process. They
should come only downstream, to contribute to the adequate social and
political use of knowledge. Their role is definitely not to say what should be
the right (i.e., morally desirable) knowledge, but rather, what do we do with
valid knowledge. In his famous 1927 book La trahison des clercs (The
Treason of the Intellectuals), the French philosopher Julien Benda lashed
out at those intellectuals who had the pretension of defending the values of
truth and objectivity, while actually succumbing to the conformism and
passions of their time. Benda’s thesis seems a bit Manichaean, sorting out
between “true” intellectuals, the obedient servants of truth, and those who
are blinded by their prejudices and passions. Most intellectuals are probably
halfway between these two extremes. However, Benda’s book hit a nerve,
triggering an uproar among French intellectuals. Nowadays, Benda’s ideas
are more topical than ever.
While there is a tendency to reject theories because they are morally
shocking, the opposite is to support hypotheses, not on scientific or medical
grounds, but rather, for moral/ethical reasons. For example, the WHO has
recently decided to erase transsexualism from the list of mental disorders
(AFP, 2018), not because of new psychiatric or neurological discoveries, but
overtly to combat the social discrimination transsexual persons undergo.
While morally commendable, this approach definitely is not scientific and
distressingly confuses science and morals/ethics (Tibayrenc, 2016c, 2019).
Michel Tibayrenc and Francisco J. Ayala
xx
CULTURAL BIAS
Everyone is biased by his or her personal history, background, and
cultural upbringing, including of course the authors of this book.
The concept of totally objective, disembodied science is naïve, although
defended by eminent scientists, such as the Nobel Laureate André Lwoff
(1981). The Soviets were criminal when persecuting Mendelian geneticists.
However, their vision that all science is culturally biased was not erroneous.
For example, physical anthropology before World War II had a tendency to
be quite racist in Western countries. The superiority of White people over
other peoples was not questioned, which was a reflection of the common
thinking of the time. It was only when the racist crimes of Nazi Germany
were known that science reversed its view. The authors of this book have
cultural biases like everyone else. We have tried our best to clear our minds
of such prejudices, which is the basis for objective and reliable knowledge.
Moreover, we have tried to avoid the “scientific imperialism” of biologists
by taking into consideration the considerable contributions of social sciences
to the theme of this book. Specialists of social sciences will forgive any
possible naiveties concerning their fields: aux innocents les mains pleines
(beginners’ luck).
A BOOK ACCESSIBLE TO EVERYBODY
Finally, we have tried our best to make the scientific data collected for
the book definitively up to date, which makes it a relevant tool for
specialists, scientists, professors, and students. However, (1) we have not
limited the references to very recent ones, in order to avoid “scientific
amnesia,” that is: the attitudes of many scientists of our time who consider
that any science older than 5 years is obsolete (a possible trick for them to
artificially increase the novelty of their own research). Past science is a
poorly known gold mine of knowledge. Several key ancient publications and
books are listed in the references, so that the reader can go back to the source.
Introduction
xxi
(2) We have not limited our source of information to the specialized
scientific literature. When it appeared as informative and reliable, we also
collected information from general public media and nonofficial social
media.
Lastly, our goal has been to make the book as accessible as possible to
the general public. Specialized jargon has been avoided as much as possible.
Toward reaching this goal, a glossary of specialized terms has been added.
Note
Words marked with * in all chapters are explained in the glossary of
specialized terms.
Chapter 1
ORIGINS OF MANKIND: HUMAN LINEAGES
AND ARCHAIC ADAPTIVE INTROGRESSION*
“Le berceau de l’humanité est un berceau à roulettes.” (the cradle of
mankind is a cradle on wheels), Father Henri Breuil
“La nature se rit de nos classifications.” (Nature laughs at our
classifications), French Société Polytechnique, 1827
INTRODUCTION
Rather than giving an exhaustive and encyclopedic report of the present
state of the art, this chapter instead aims to call the reader’s attention to the
questions that today remain the most controversial of the topic. As far as our
prehistoric origin is concerned, the warning presented in the introduction of
this book on sorting out the robust and the speculative is sorely needed. The
robust is not that robust, the speculative is profuse. Each discovery of a new
paleo-human or a new set of tools upsets our theories. This is all the more
true since specialists of the discipline, possibly more than other scientists,
have a strong penchant for sensationalism and notoriety and have built a kind
of star system, with a fierce race to publication and description of new
Michel Tibayrenc and Francisco J. Ayala
2
species (Braga et al., 2016). Another sample of this star system is the hasty
announcement by the Natural History Museum in London
(http://www.nhm.ac.uk/about-us/news/2018/january/documentary-to-
reveal-surprising-face-of-cheddar-man.html) of the facial reconstitution of
the “Cheddar Man”. Particular samples of this sensationalism could be cases
suspected of “paleontological chauvinism” (Akhilesh et al., 2018; Martinón-
Torres, 2018) (see the Out of Africa [OOA] controversy).
Strong uncertainties about our origins have been humoristically
underlined by the above-cited charge by Father Henri Breuil, a well-known
French specialist on paleolithic paintings. Another obstacle to reliable and
objective knowledge is a kind of unexpected political correctness that
threatens thought in science in general, in paleoanthropology and prehistory
in particular (Hublin 2011). It leads some specialists to reject a priori the
idea that Neanderthals were “primitive,” that sapiens were more
sophisticated, and that Homo erectus was incapable of innovation. That
Neanderthal was more primitive than H. sapiens might be right or wrong,
but this should be ascertained by objective data, not decided by ethical and
moral prejudices (see the book’s introduction and Chapters 2, 4–6).
A strict biblical reading of our origin states that we were created by God
a few thousand years ago, and we are the last and most perfect achievement
of His Creation. At the beginning of the seventeenth century, James Ussher,
the archbishop of Armagh in Ireland, gave a very precise date for the creation
of the world: 4004 years B.C. (Cavalli-Sforza & Cavalli-Sforza, 1997). The
common belief has long been that the human species was only a few
thousand years old. It is fair to acknowledge that Catholic theologians have
since long ago abandoned a strict reading of the Bible. Today, they do not
consider the sacred book as a historical narrative, but rather as a symbolic
oeuvre of initiation. Catholic theology today integrates the theory of
evolution. However, sects such as Jehovah’s Witnesses and many Protestant
churches still adhere to the classic Biblical vision. The hard fight led by
Protestant churches in the United States to support the teaching of
creationism in American public schools (Le Bars, 2017) is a clear
manifestation of this belief (see Chapter 7). Needless to say, the concepts
Origins of Mankind
3
inferred by biology, especially paleoanthropology and evolution, clash
dramatically with this strict Biblical vision.
Biology considers that evolution started fortuitously (Cela-Conde &
Ayala, 2016a) and has no goal (Picq, 2005). These assertions, albeit made
quite plausible by evolutionary science, cannot be “proved.” However, both
the wealth of human fossils and abundant data from population genetics*
and phylogenetics* support robust and congruent evidence of a high
antiquity of man (Boucher de Perthes, 1847) and of our close evolutionary
relationships to apes: chimpanzees, bonobos, gorillas, orangutans, and
gibbons.
A MAJOR FACTOR OF UNCERTAINTY
AND CONTROVERSY: THE PROBLEM OF TAXONOMY
AND SPECIES DEFINITION
The Species Concept: A Headache
A central question about our origins and about the entire theme of this
book is: What is a human? And what is not a human? It could appear
surprising to the eyes of nonspecialists, but the very concept of species is
hotly debated among specialists. It therefore follows that defining the
species Homo sapiens is controversial, especially where ancient populations
are considered.
Relevant
Unit of Analysis
Defining the relevant units of analysis (Tibayrenc & Ayala, 2017)
should be a prerequisite to any scientific approach, in biology and elsewhere.
Such relevant units of analysis may not necessarily have strict limits.
However, they should be rigorously defined from a conceptual point of
view: The definition of a relevant unit of analysis is based on a working
Michel Tibayrenc and Francisco J. Ayala
4
hypothesis, making it possible to clearly state what this unit is and what it is
not, and most of all, what its predictable properties are. Many entities in the
living world and elsewhere have no discrete boundaries. This is the case for
pathogenic microorganism species, especially where bacteria are concerned.
For example, the bacterial species Escherichia coli does not have strict
borders, since most bacterial species are capable of some genetic exchange
with other species. However, E. coli is a clearly defined evolutionary entity
(Tibayrenc & Ayala, 2012).
What
Should One Do When Facing a Continuum?
Sometimes, one has to select slice out within a continuum. In this case,
it might be necessary to establish arbitrary limits, if they are useful for the
study or the discipline considered. For example, to separate blue from green
in the color spectrum, which is a perfect continuum, it may be convenient to
settle on a given wavelength limit.
Adjusting
the Relevant Units of Analysis According to the Goal
of the Study
Depending on the goal of the operator, the number of units of analysis
may vary within the same physical reality. When colors are considered,
artists are not satisfied with only the main colors of the spectrum, and define
many additional categories to handle the entities relevant to their art:
ultramarine blue, carmine, indigo, veronese green, etc. This frequently
occurs in science as well. For the same material reality, relevant units of
analysis may and should change according to the goal of the study
(Tibayrenc, 2016a). When analyzing human genetic diversity, the unit of
analysis might be either major geographical groupings (Africa, Europe,
Asia) or lesser entities (e.g., the population of the Fulani vs. neighboring
populations in West Africa where human genetic susceptibility to malaria is
Origins of Mankind
5
considered) or even populations of neighboring villages when analyzing the
fine genetic stratification of human populations.
Managing the Uncertainty of Relevant Units of Analysis
Lastly, in some cases, the definition of the relevant units of analysis may
still retain some conceptual uncertainty. This is not an unsurmountable
obstacle, provided that this uncertainty is clearly defined itself. For example,
many human diseases lack a precise definition (Tibayrenc, 2016b). This is
especially true where the so-called autoimmune diseases are concerned. We
still do not know precisely what multiple sclerosis is, nor what causes it.
Perhaps we will never know. Moreover, there are transition forms between
sclerosis and other autoimmune diseases. However, patients urgently need
treatment. The situation is even worse when mental disorders are considered,
as illustrated by the many successive versions of the Diagnostic and
Statistical Manual of Mental Disorders (Hyman, 2014). As an example, no
satisfactory definition of schizophrenia can be proposed. However, the worst
attitude with medical or scientific inquiry is an acknowledgment of failure:
“I can’t define perfect units of analysis, therefore I do nothing.” Perfect,
essential entities are only good for mathematical or philosophical
abstractions.
Safety and Controversial Levels of Definition
When it is difficult to define and delineate an uncertain entity, it may be
wise to go up to some “safety level of definition” (SLD), if need be by a sort
of reasoning to the absurd (reductio ad absurdum), then to go down step by
step until one reaches the “controversial level of definition” (CLD). This
way, even if it is impossible to sharply define what an entity is, one knows
better what it is not. For example, the highly pathogenic bacterium Shigella
spp. obviously is not a mammal. Less absurd an example, it is not a
protozoan either: It has no nucleus. It is not Mycobacterium tuberculosis, the
Michel Tibayrenc and Francisco J. Ayala
6
bacterium responsible for tuberculosis (note that we are approaching the
CLD): Its morphology is quite different from that of M. tuberculosis; its
properties in culture have nothing to do with it, and it causes quite different
symptoms. It is not E. coli? Well, although we have different genus names
here, which misleadingly suggest substantial differences, we are right in the
controversial zone. Shigella spp. actually are part of the taxon E. coli.
Shigella spp. are no more than a bunch of strains of E. coli that have been
defined by specific pathogenic properties, due to the presence of so-called
pathogenicity islands (sets of genes* that lead to virulence). When one
constructs a phylogenetic* tree of the whole E. coli taxon, Shigella spp.
strains are found within this tree. On the way, we have seen that the Shigella
and E. coli entities are based on concepts that are significantly different. The
former is a patho-entity, defined by the specific pathology (it causes
dysentery), while the latter can be defined as an (imperfectly discrete)
evolutionary line.
In conclusion, when analyzing a given scientific problem, the first
question is: What is the goal of the study? The second is: What are the most
relevant units of analysis to answer the question? Many scientists neglect to
clearly answer these two questions and get lost on “fishing expeditions.”
After this long, but indispensable conceptual detour, let us now address
our specific problem: What is Homo sapiens and how should hominin paleo-
species be identified and defined? A brief reminder of the specific case of
the species concept will be enlightening.
The
Taxonomical System: Like Russian Dolls
The taxonomic category “species” is the lower level of a hierarchized
classification system called KPCOFGS (from top to bottom: kingdom,
phylum, class, order, family, genus, species). In this system, class, order,
family, and genus have no biological definition other than their rank:
Kingdom is at the top, class is above order, etc. According to the zoological
or botanical category considered, taxonomists may introduce additional
Origins of Mankind
7
subdivisions: subfamily below family, tribe below family, etc. The lowest
rank is the species.
Species and Their Latin Names
Species are named with a Latin biname, a rule established by the
Swedish naturalist Carl Linnaeus (1707–1778). The biname is composed of
the name of the genus, followed by the name of the species. We are the
species Homo (name of the genus) sapiens (name of the species), the only
living species of the genus. The binominal system is both a blessing and a
curse. It is a blessing because it is indispensable for scientists to
communicate throughout the world. It is a curse, because Latin names have
a kind of magic, resulting in many scientists being eager to describe “their”
species. In addition, when a species has been baptized with the prestigious
Latin name, this tends to fossilize scientific thought: It is extremely difficult
to back out. These remarks are especially true for human fossils.
The (Many) Biological Definitions of the Species
Species is the only taxonomical rank for which there have been many
attempts to give a precise biological definition—this has proved to be
troublesome. This uncertainty about the concept of species is illustrated by
the fact that a specialist (Hey, 2001) counted no fewer than 24 different
definitions of what a species is. Nevertheless, three main definitions can be
put forward.
The most successful one is the biological species concept (BSC), or
mixiologic species concept, formulated first by one of the fathers of the
“synthetic theory of evolution,” Theodozius Dobzhansky (1937): A
biological species is a group of individuals that can freely breed together,
but physical obstacles (time, space). However, they cannot breed with other
groups. In addition, if these individuals breed together, their offspring should
be fully fertile. Horses and donkeys are different species, since, even if they
Michel Tibayrenc and Francisco J. Ayala
8
mate, their kids (mules and hinnies) are unfertile. The central concept of the
BSC is genetic isolation. But what about polar bears, for example?
Polar bears are classified as a species (Ursus maritimus) that is distinct
from the brown bear (Ursus arctos). Now, because of global warning, the
ecological niche of the two species is beginning to overlap. They easily
mate, and the offspring (pizzly, the child of a polar bear and of a grizzly, or
North American brown bear) is fertile. This results in the fact that polar bears
do not meet the criteria of a biological species. They are a phenotypic*
species, that is, a species that is not defined by genetic criteria, but according
to the overall similarity of its phenotype* among the individuals that
compose it. This is the second species concept, the phenotypic* species
concept. Since polar bears are distinguished from brown bears only by their
phenotype* (in this case, mainly their appearance), they could also be
considered as a mere subspecies*, or geographical race of the brown bear,
that is, a geographical population of the species brown bear that exhibits
distinct, genetically based, phenotypic* traits making it possible to
distinguish most individuals of the polar bear population from most
individuals of the brown bear population. Distinct subspecies* remain
interfertile, which, we have seen, is the case between polar and brown bears.
It is traditionally admitted that the North American brown bear (grizzly) and
its European cousins are distinct subspecies* of the same species Ursus
arctos. Tradition matters much in taxonomy and you cannot argue with
tradition. Polar and brown bears are still considered a distinct species, not
trivial subspecies*, possibly because the polar bear is the darling number
one of nature lovers, ex aequo with the giant panda.
The third species concept is the phylogenetic* species concept (PSC;
Cracraft, 1983). Phylogenetics* is the science that aims at reconstructing the
remote history of present or past living organisms and at identifying distinct
evolutionary lineages or phyla. It is based on various means, including
phenotyping* characters inferred to be evolutionarily meaningful and,
increasingly, genetic characters such as DNA sequences*. According to the
PSC, all species should correspond to separate evolutionary lineages.
