Reflections of Our Past

How Human History Is Revealed in Our Genes

John H. Relethford, Deborah A. Bolnick

• Publisher: Routledge
• Year: 2018
• ISBN:
  9780429891700
• Edition: 2
• Topic: Social Sciences
• Subtopic: Sociology
• Index: Social Sciences

The rise of the multi-billion dollar ancestry testing industry points to one immutable truth about us as human beings: we want to know where we come from and who our ancestors were. John H. Relethford and Deborah A. Bolnick explore this topic and many more in this second edition of Reflections of Our Past.

Where did modern humans come from and how important are the biological differences among us? Are we descended from Neandertals? How should we understand the connections between genetic ancestry, race, and identity? Were Native Americans the first to inhabit the Americas? Can we see evidence of the Viking invasions of Ireland a millennium ago even in the Irish of today? Through engaging examination of issues such as these, and using non-technical language, Reflections of Our Past shows how anthropologists use genetic information to suggest answers to fundamental questions about human history. By looking at genetic variation in the world today and in the past, we can reconstruct the recent and remote events and processes that have created the variation we see, providing a fascinating reflection of our genetic past.

CONTENTS

Preface

CHAPTER 1 The History in Our Genes

Anthropologists, Genetics, and History: About Us

Genetics and Human History

CHAPTER 2 The Naked Ape

Our Place in Nature

Who Is Our Closest Living Relative?

Genetic Comparisons of Apes and Humans

Dating the Split

Views on Classification

What Makes Us Different?

CHAPTER 3 Out of Africa: Our Genetic Legacy

A Quick Summary of Human Evolution

What Is a Species?

Models of Modern Human Origins

Fossil Evidence for an African Origin

Gene Trees

Most Gene Trees Have African Roots

Genetic Diversity Is Higher in Sub-Saharan African Populations

Genetic Drift, Mutation, and African Diversity

Genetic Diversity Decreases with Distance Out of Africa

Genetic Distance

Global Genetic Distances Correlate with Geographic Distance

What Happened Next?

CHAPTER 4 The Fate of the Neandertals (and Other Archaic Humans)

A Brief History of the Discovery and Interpretation of Neandertals

The Discovery of Neandertal DNA

More Neandertal Mitochondrial DNA

Where Did All the Neandertal Mitochondrial Sequences Go?

The Neandertal Genome Sequence

The Denisovans

What Did We Inherit from Archaic Humans?

The Future of Studies of Neandertals (and Other Archaic Humans)

CHAPTER 5 The First Inhabitants of the Americas

Where Did the First Migrants Come From, and How and When Did They Arrive?

The Genetic Link between Asia and North America

Studies of Mitochondrial DNA

Nuclear DNA Studies

Insights from Ancient Genomes

How Many Migrations?

Past and Present

CHAPTER 6 Genetics and the Spread of Agriculture in Europe

Origins of Agriculture

The Emergence of Agriculture in Europe

Cultural Diffusion versus Demic Diffusion

Genetic Evidence for Demic Diffusion

Insights from Ancient DNA

Other Migrations into Europe

Genetic Adaptation and the Spread of Agriculture: The Case of Lactase Persistence

The Genetic and Cultural History of Europe

CHAPTER 7 Voyagers of the Pacific

Where Did the Polynesians Come From?

Genetic Distances and Polynesia

What Does Mitochondrial DNA Tell Us?

The Evidence from Y Chromosomes

The Evidence from Autosomal DNA

Sex Differences in Polynesian Ancestry

A Final Thought about Expansions

CHAPTER 8 Three Tales from Ireland

English Gene Flow in the Aran Islands

Invasions, Settlements, and Irish History

The Origin of the Irish Travellers

Some Closing Thoughts from Both of Us

CHAPTER 9 Admixture and History

The Genetics of Admixture

Admixture in Mexicans and Native Americans in North America

Admixture in African Americans in the United States

Admixture in Individual African Americans

Thomas Jefferson and Sally Hemings

Genetic Admixture and the Jewish Diaspora

The Cohen Modal Haplotype

The Lemba

Admixture and Identity

CHAPTER 10 Ancestry, Identity, and Race

Genealogical and Genetic Ancestry

Genetic Ancestry Testing

Genetic Ancestry and Cultural Identity

Ancestry and Identity: A Personal Anecdote

Race and Genetic Variation

Ancestry and History

Appendix: Analyzing DNA

Glossary

CHAPTER Notes

References

Index

PREFACE

A lot can happen in two decades.

Almost 20 years ago one of us (John) decided to write a book about how anthropologists and geneticists use genetic data (in the broad sense of the term) to answer questions about human history, origins, and ancestry. John’s goal was to produce a book that would explain in clear terms exactly what anthropologists and geneticists do, something of interest to a general audience and that would be useful in undergraduate classes. He focused on the origins and ancestry of our species and various human populations, as well as the history and ancestry of individuals. In the first edition John described much of the work that had been done using what we call “classical genetic markers,” or variants that affect the biochemistry of blood cells, as well as even older means of assessing human variation, such as cranial measures. The first edition of this book also included a review of how newer DNA analyses were becoming more central to efforts to address questions about human origins and ancestry (both scientific studies and individuals’ quests for genetic data that could shed light on their personal histories).

Since the publication of the first edition in 2003, the fields of anthropological genetics and human population genetics have exploded due to the rapid development of new genetic technologies. These technologies have allowed us to discover more and more about our genetic history, more quickly (and cheaply) than anyone could have imagined only a few years ago. We now have the laboratory methods and analytical tools to sequence the entire human genome (as well as the genomes of other species), and we can reconstruct DNA sequences from the skeletal remains of individuals who lived tens (and even hundreds) of thousands of years ago. The scope and quantity of data available today are truly remarkable: through the 1990s, genetic studies of human populations often looked at several dozen different markers; now it has become commonplace to examine hundreds of thousands of markers (or more) in an analysis, and datasets contain many more individuals than in the past. Indeed, we might now even run the risk of drowning in data.

Several years ago John noticed how much had changed in the field and realized that the book, although useful in some general ways, had become increasingly outdated. Some of the earlier conclusions had changed, and others had been supplemented and expanded by new data and analyses. This is a reflection of how science works. One of the basic rules about science—and scientific knowledge—is that it is always changing, as we test and retest hypotheses and use new approaches to answer questions. Every question that is answered inevitably leads to new questions, and the challenge in writing a book like this is to capture this history of discovery and the dynamic nature of science. Indeed, one of the goals of the first edition was to show how anthropologists and geneticists use genetic data to address anthropological hypotheses through application of the scientific method.

Because the scientific method has yielded such extensive changes in anthropological knowledge in recent years, the book had to be brought up to date to continue showing this in an effective and useful way. In fact, the pace of discovery has been so rapid and has affected so many different areas of research that John felt it would be exceedingly difficult for any single person to have a comprehensive and hands-on understanding of the entire field. He therefore turned to Deborah, a colleague with similar broad views on anthropology, history, and genetics, but with a different background and a different set of research interests, to help update this book. We are of different generations and have different training and skill sets, but we complement each other in providing this basic introduction to the reader. We want to reach the broadest audience, providing a text that is detailed enough for use in a course on anthropological genetics or human variation, but with key concepts clarified so that other interested readers can dive in without any formal prerequisites. It is our shared view that far too much scientific writing is geared only to the professional or the advanced student, and we want our understanding of and passion for this research to be accessible to all.

To make this a widely useful book (both inside and beyond the classroom), we use two basic approaches. First, we have made much of this book personal, outlining our own interests and research, as well as our personal histories. We find this approach preferable to the passive voice employed in some of the scientific literature. We have both found that our students find this personal involvement more appealing, and many appreciate how our own interests and history mirror theirs (such as the roundabout w...

Table of contents

• Cover
• Halftitle Page
• Title Page
• Copyright
• Table of Contents