The Invisible History of the Human Race Read online

  ALSO BY CHRISTINE KENNEALLY

  The First Word:

  The Search for the Origins of Language

  VIKING

  Published by the Penguin Group

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  First published by Viking Penguin, a member of Penguin Group (USA) LLC, 2014

  Copyright © 2014 by Christine Kenneally

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  LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA

  Kenneally, Christine, author.

  The invisible history of the human race: how DNA and history shape our

  identities and our futures / Christine Kenneally.

  p. cm.

  Includes bibliographical references and index.

  eBook ISBN: 9780698176294

  I. Title.

  [DNLM: 1. Genetics—history. 2. Pedigree. 3. DNA—history.

  4. Human Migration—history. QU 11.1]

  RB155

  616'.042—dc23 2014021679

  Version_1

  For J&D

  You know who you are

  CONTENTS

  Also by Christine Keneally

  Title Page

  Copyright

  Dedication

  Author’s Note

  Introduction

  I. Ideas About What Is Passed Down Are Passed Down

  1.Do Not Ask What Gets Passed Down

  2.The History of Family History

  3.The Worst Idea in History

  4.The Reich Genealogical Authority

  II. What Is Passed Down?

  5.Silence

  6.Information

  7.Ideas and Feelings

  8.The Small Grains of History

  9.DNA + Culture

  10.Chunks of DNA

  11.The Politics of DNA

  12.The History of the World

  III. How What Is Passed Down Shapes Bodies and Minds

  13.The Past Is Written on Your Face:

  DNA, Traits, and What We Make of Them

  14.The Past May Not Make You Feel Better:

  DNA, History, and Health

  Epilogue

  Acknowledgments

  Notes

  Index

  AUTHOR’S NOTE

  It was my goal in this book to bring together in a natural way the questions of the general reader about our immediate and historical ancestry and the considerations of the humanities and sciences. The traditional domains have much to offer one another, and this is more true than ever in the age of the personal genome and big DNA data. When I began reporting, I had a memorable conversation with Michael McCormick at Harvard. McCormick is a historian of the Roman Empire and medieval history who has extended his interest in ancient manuscripts to include the Y chromosome, charcoal layers in the soil from ancient fires, and the isotopes in old bones. “What was considered historical evidence in the nineteenth century was only written records; now it’s atomic disorder and genes,” he said. “The distinction between history and prehistory is blurred, if not dissolved.”

  I’ve focused on aspects of inheritance, and our philosophies of it, that either are particularly fresh or have not been paid much attention—their invisibility made them all the more interesting. Herein are studies from psychology, economics, history, and genetics, anecdotes and data from business, science, and the lives of many fascinating individuals. They each exemplify in some way what gets passed down over the generations, and they all provide insights that resonate with one another. As I hope to demonstrate by the end of the book, the concept of ancestry can bring genetics and history together fruitfully; perhaps ancestry will lead us to a place where we can make use of these different kinds of data in a more unified way.

  This book focuses primarily on what genetics and genomics can tell us about the connection between an individual’s genotype and his history and idiosyncratic traits. Inevitably there are fascinating one-off findings and whole fields of inquiry that I could not include for reasons of length. Twin studies and calculations of heredity based on the differences between them are not referenced here. Before we were able to dig into the genome, twin studies were one of the best ways to try to work out what gets passed down. Identical twins have the same genome, so when they end up looking different, having different aptitudes, or developing different diseases, it tells us that the same genome may be expressed in different ways, and it may tell us what aspects of the environment shape a person via their genome. Twins will always be interesting to geneticists, but traditional twin studies used an indirect method for estimating what is passed down.

  Writing a book about DNA presents an inherent challenge, as scientists and scholars of the humanities often think about the subject in different ways while the rest of us may think about it in yet another. Until now there’s been little synthesis between the ways we consider genes and health, genes and culture, genes and history, genes and race, and genes and specific traits. We often treat these aspects of our lives as if they were completely distinct, and when we attempt to understand the role that DNA plays, we do so from only one vantage point. But DNA does what it does without regard to any of the conceptual silos in which we attempt to confine it.

  It’s often the case that when people discuss DNA, they are not talking about DNA at all but rather about the idea of biological determinism, racism, sexism, or the concept of ownership. Or perhaps they’re just experiencing a deep-down, angry resistance to the idea that something we do not control may influence our fate. Sometimes people emphasize that the similarities to be found in our DNA prove we are one big family or, alternatively, that the differences in our DNA reveal much about why we are different. Where appropriate I have endeavored to directly address these concerns, and elsewhere I do my best when I use the word “DNA” to mean only DNA.

  How DNA shapes us physically is a fascinating but still nascent science. The most solid findings are found in the area of physical health and traits, so I focused on findings from these domains. Does DNA contribute to human behavior, decision making, and complex traits like language and intelligence? Of course it does. But probably not in the ways that many people imagine or fear. At present one of the most complex problems in genetics is how DNA contributes to common diseases. Perhaps once we have solutions to these mysteries, the relationship between genetics and behavior will become clearer.

  A note for readers who are scientists, to keep the book accessible, when I talk about locations on the genome, I may talk about “places” or “segments.” When I discuss single nucleotide polymorphisms, I often describe them as “letters.” Sometimes when I use the word “gene,” I am referring to all the possible alleles of that gene. Sometimes I am referring to only one allele, as in “the gene for a particular condition or trait.”

  Introduction

  We follow in the steps of our ancestry, and that cannot be broken.

  —Midn
ight Oil

  One cannot and must not try to erase the past merely because it does not fit the present.

  —Golda Meir

  There’s a moment somewhere between the North Pole and the South when I look out my window and see the top of the Himalayas. At first the shapes are clouds, but then they resolve into immense snow-covered crags, perfectly still in the cumulus sea. It doesn’t matter how many times I’ve seen them before; I am always surprised. They are proof that I am somewhere very high and very strange. At thirty thousand feet light floods the plane. Ahead the night drapes across the earth. We barrel toward the darkness, and then we tunnel quickly through it. In a few hours, when we land, it will be morning.

  I call my boyfriend’s attention to the window. “CB! Look!” He wonders if anyone is over there on the mountains. Perhaps there are a few souls right on the tip. But if so, it’s just us and them and all the other long-distance flying containers up here. We are tracing the outer edge of the human envelope. Below, six billion people inhale. Above, there’s nothing to breathe.

  It’s at about this point, when I am too tired to read, I have consumed too much wine, and all I can do is stare, that the human condition starts to get to me. Half the plane is unconscious, the other half is gingerly stepping over them, and there is a permanent line to the toilets. In addition to this aerial trip, my boyfriend and I were embarking on a few heady metaphorical ones as well. We had met in England and were heading to Melbourne to meet my parents. Maybe at some point we would become parents too. It was momentous to contemplate, and it’s a truism that we didn’t know the half of it, but we didn’t even know what we didn’t know.

  Here’s one thing I didn’t know when I was flying above the Indian Ocean. One of my great-great-grandfathers was called Michael Deegan, and 170 years before we got on our plane, he followed a similar trajectory, from high in the Northern Hemisphere to way down in the Southern. He was only fifteen years old and he crossed the oceans on a bark called the Kinnear. The trip took 105 days. The boat left Dublin with 174 men and arrived in Australia with 172. Deegan had left a country on the edge of a famine in which one million people died and two and a half million people fled within a ten-year period. He had stolen a handkerchief and was now a convict on his way to Van Diemen’s Land. Even if he survived his sentence, he was forbidden to return home. All the Kinnear’s passengers boarded as criminals, but many of them disembarked compliant. At the end of the journey, the ship’s surgeon entered a report on the character of each of the survivors: “good,” “orderly,” or even “very good.” Yet somehow Deegan remained “troublesome.”

  In the twenty-first century we move through space in these high-speed vessels and through our lives inside little envelopes of time. Usually we know people from the generation or two that come before us, and probably the generation or two that come after, but mortality draws a thick line across the horizon ahead, and existence—or the lack of it—marks the line behind us. It’s not common in the West to have met, or even know much about, anyone born three generations before us. Do these people shape us anyway, whether we know about them or not?

  • • •

  Humanity has been making some consequential moves for a long time now. Over the course of hundreds of thousands of years, we populated Africa; then we left the continent in waves and spread across the world. The global travel that began more than sixty thousand years ago continued for the next forty-five thousand years before we settled every habitable continent on earth.

  From the ninth century, when Vikings set out to sea in longboats, through the ages of expansion, slavery, the spice trade, and the colonialism that ended in the twentieth century, thousands of ships crossed the oceans. The vessels carried explorers, prisoners, slaves, and immigrants far away from the places where they were born, in most cases never to return. In the second half of the nineteenth century, now known as the age of mass migration, the movement peaked, with more than fifty-five million emigrants embarking from the Old World and heading to the Americas and Australia. On the human scale the ships marked crucial chapters in the lives of many individuals—and in the lives of everyone who descended from them. Culturally they changed the stories of families forever. Biologically the ships delivered mixed samples of human genomes. Everywhere they went they transformed the human landscape, releasing new variants into the local gene pool, creating never-before-seen mixes of human material, and founding novel lineages that branched and then branched again.

  I wonder if my convict ancestor thought about whether he would have descendants who might one day look back on his life or who would know him only as a wisp in a cloud of long-dead family. He lived for many, many years after his terrible journey, and though he died long before I was born, I’ve spoken to people who have spoken to people who once spoke to him. Oh look, here comes the human condition again: He and I have physically touched people who have physically touched each other. But although we will never speak, and I will never see him or hear his voice, he is here with me, and not just in my thoughts. This isn’t a metaphor but a fact, as real as the Himalayas. There is information within me that came from him, and if my boyfriend and I have children, some of that information will be inside them too.

  We are ourselves vessels. Inside each cell that is inside each person is a massive library of DNA, three billion base pairs that have been passed down to us. I think about this while I sit on the plane; the principle is true for all 466 of my fellow passengers, no matter what class they’re in or their reasons for travel. They all carry their great-great-grandparents inside, and they carry traces of their grandparents’ ancestors too. Here in this plane are multitudes, 1.4 trillion base pairs that have been passed down through history by millions of people. It’s a miracle we ever got off the ground.

  • • •

  In second grade our teacher gave the class a project: We were to go home and interview our parents and then draw a family tree. That afternoon I explained the project to my parents. I would write my name and birth date, and then I would draw a branch growing up out of my name. At the end of that branch I would write their names and what they did for a living, and then I would add their parents’ names and birth dates, and I would then draw lines stretching up to them.

  I had never before thought much about my forebears. My parents had told me that my father’s parents had died before I was born, and my mother’s parents lived in another country. And yet here, in the tree I was carefully drawing, I could see that these people had once existed, and they were connected to me.

  If I was lucky, my teacher said, my parents would be able to name their grandparents—my great-grandparents—and say when they lived and what they did.

  But I was not so lucky. It turned out that my parents were interested in the project, but they were upset about it too: Why is your teacher asking you these questions? This is homework? What business is it of hers?

  In the end my parents made a few suggestions and, naturally, I wrote them down. They could have kept a lid on their ire and lied to me right then and there, but that wasn’t something they did, and they were too indignant to conceal it. So I learned early that the past can bother people in surprising ways and that memory is meaningful but odd. That incident gave rise to a lifelong interest in why family matters, how it shapes you, and especially why people who are long dead still matter so much to you, who are alive.

  Pretty much everyone alive today has been asked some form of the question “Who are you?” and the ancient and universal impulse has been to respond by talking about our family. For many years I did a good job of squashing that ancient and universal impulse, studying biology and history in high school and starting a degree and acquiring all sorts of research skills. Occasionally I prodded my mother about my grandparents, but for the most part a thick mist hung in the part of my brain that stores all the questions about family and history and identity. That changed one day in 1990 when my parents and my four siblings were a
ssembled in my parents’ kitchen, and my father announced that it was time to tell us that the man we thought was his father wasn’t actually his father. The man who raised him, who we thought was our long-dead grandfather, was actually our dad’s long-dead grandfather. Our father’s mother was our great-grandfather’s daughter.

  For my father this was an awful admission. He had trouble speaking, and I can still see his crooked right arm and hand supporting his forehead. My mother had her hand on his shoulder, and we five children sat there watching. Their distress was extraordinary, yet none of us shared it, not then and not since. The world has galloped on since my father was born, and at least in our part of it, few people today are concerned with matters of paternity in the way they were in the 1930s. By some mysterious process, even though my conservative parents raised us to be like them, neither did we.

  Which is not to say that we weren’t disoriented. A truth that none of us had questioned—what is reasonable to call a small foundation stone of our identity—had cracked. Humans tend not to act well when things like that happen, and I still cringe at my first response, which was to exclaim, “I knew there was something going on!” only to realize that my father, who never cried, was choking back tears.

  What then? My father didn’t want to talk more about it. But I did: What was his name, this man, my actual paternal grandfather, and shouldn’t his last name be my last name? Who was he, anyway? Did my father look like him? Wait, did I? Like all normal children, I had spent a considerable amount of time imagining the sudden death of both my parents and my ensuing survival adventure. (My knapsack was packed and ready, just in case.) For half a minute the old daydream stirred, I was long lost to someone else, and here was a truly unknown unknown, a story that hadn’t been told.

  But my father shut it down again. He had once heard a name, he said, but he had no documentary evidence to prove the connection, so he wouldn’t tell us what it was.