I never knew my father’s father. He died a decade before my twin and I were born. But I did know my grandfather on the other side of the family. He was by repute and by my own recollection a sober realist. If memory serves, he also didn’t have a lively sense of humor. However, he did favor an expression that struck me then, as it does now, as both colorful and definitive. His word for something he couldn’t credit was hogwash.
This word came to mind while reading David Reich’s new book on paleogenetics and prehistory, Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past (Pantheon, 2018). I have been writing off and on about the use and misuse of genetics in anthropology and archaeology since the 1970s. For a number of reasons (some of which I want to put on the table for you to consider), I hadn’t assumed Reich’s book would be one I would want to recommend to others. What I didn’t anticipate, however, is that I would find what he and others are now writing about ancient DNA would be so debatable.
Science today knows much more about our genes and how they work than it did in the past. I think this is all to the good. I become skeptical and concerned, however, when I come across anyone claiming they can tell us who we are and how we got here—wherever “here” for them happens to be—simply by cross-examining our genes. Can geneticists do this? Should we let them?
IS YOUR ANCESTRY RECORDED IN YOUR GENES?
I am amazed at how many of my friends have eagerly sent a sample of their own spit, or a tissue smear taken with a cotton swab from the inside of their cheeks, to a for-profit genotyping service such as AncestryDNA, 23andMe, MyHeritage and CRI Genetics. Apparently, the goal is to find out within a few weeks where their biological ancestors hailed from prior to the time when ordinary folks began recording their genealogical history in a family bible or as part of church and government records. \
There may also be a desire to find whom they can claim as living relatives they haven’t heard about before. After all, don’t we all need more cousins? (I cannot resist adding that in his 1976 novel Slapstick, Kurt Vonnegut detailed how loneliness in America could be resolved by giving people new names making them cousins. Modern genotyping services are evidently now giving us an alternative souped-up way of doing so worthy of the 21st century.)
My friends who have gone down this road are not alone. As one of these Web sites says in touting its offerings: “Almost 10 million people have learned more about themselves. Are you next? From discovering their ethnicity to connecting with distant relatives, the largest DNA network in the world is helping more people find the singular story in their DNA.” Or as a satisfied customer at another Web site relates: “The discoveries I made . . . have given me a completely new understanding of my family history. It’s been so exciting to take this journey. I feel like I know myself and my family better now.”
If all this isn’t enough to convince you to join the many millions who have gone down this particular path toward self-discovery, let me add that another of these Web sites I visited recently was offering a Mother’s Day DNA Sale. For only $59 per kit you can “amaze yourself” and “uncover your ethnic origins and find new relatives with our simple DNA test.”
Who can resist a deal like this one? Is it any wonder geneticists nowadays see the future of personal genetics as bright indeed? Don’t we all want to find out so easily and so cheaply “who we are” and “how we got here” merely by consulting the genes we carry inside us as our personal window on the past?
But wait. Before you send off your spittle or swab along with your PayPal information, are our genes really up to the job? Or is all this more commercial hype than good down-to-earth genetics science?
WHAT SANTA KNOWS
Let’s look at it this way. Given his legendary powers, Santa Claus knows more about you than just whether you have been naughty or nice. He also knows that when all of us are asleep, we are unbelievably the same, at least as biological beings. Truth be told, almost everything that makes us different from our peers and from those living elsewhere on Earth is just something that comes into play after we are awake. Our dreams aside, that’s when we start to be the singular individuals we have learned to be through our personal dealings with the world, as well as through our shared experiences with other people since we came out of our mother’s womb to face the world and its challenges.
Therefore, it isn't at all surprising that, like Santa Claus, geneticists, biological anthropologists, statisticians and other experts today are now documenting genetically what Santa has always known: While common sense—not to mention racial prejudice—may lead us to believe we are a wildly diverse animal species, science now knows that regardless how wonderful and unique you may think yourself to be, you are, on average, 99.9 percent identical, genetically speaking, to every other person on Earth. So wow, we are all really, really biologically the same under our skins. This is not just a politically correct slogan.
Said yet more simply, we are all cousins. Although, of course, not necessarily kissing cousins.
My saying this is not meant to belittle the remaining 0.1 percent of our genetic makeup. What’s in this tiny fraction of ourselves is widely seen by doctors, psychologists and other health care specialists as harboring incredibly important clues about the biological underpinnings of a wide variety of medical disabilities and diseases. Speaking personally, for example, I am confident that the genes I inherited from my mother and father are contributing in some way to my lifelong struggle with asthma―an affliction that does not bother my twin sister at all. There is no way, I can assure you, I am going to accept the old saw that asthma is “all in your head.”
But wait again. What I have just been talking about has to do with genes, diseases and disabilities. If the answer to Reich’s “Who We Are” is that we are all biological cousins, then what does this simple truth have to do with “How We Got Here”?
MAKING A LOT OUT OF LITTLE
David Reich and other geneticists are enthusiastic about probing our genetic heritage as a species in the interests of medical science and improved health care for one and all. Yet it also is clear that he is chiefly interested in tapping into the biological information hidden away inside old bones and teeth in museum collections, or dug up around the world by archaeologists, for clues lurking therein about the highways and byways of human history. As an archaeologist, I share his enthusiasm for documenting human history and our species’ biological diversity.
Unlike profiling the living, genetically “reading” individuals who have been dead for hundreds or thousands of years costs more than a Mother’s Day Sale DNA test kit. Why? Because of all the extra care that must be taken when extracting DNA from the dead so that the living don’t contribute their own DNA to the mix. This can screw up the analytical results irreparably. Nonetheless, as Reich repeatedly says in his new book, working with the dead is now both affordable and, when done right, also scientifically credible. So yes, genetics profiling may be able to give you clues to your cousins long dead as well as others still living you can approach to overcome feelings of loneliness and the like.
Therefore, I feel we can take Reich at his word on some of the achievable results of modern genetics profiling of the dead as well as the living, and not simply because he happens to work at Harvard (my old alma mater). He is also by repute a skillful and inventive laboratory wunderkind. And yet, as sound as his genetic science may be, I find what he and others are writing about genetics and history to be more than a little disturbing, at times even infuriating.
One reason is that I take umbrage (such a wonderfully old-fashioned word) when he extols the virtues of using genetic profiling in the interests of medicine and human health without acknowledging also that connecting the dots between genes and diseases/disabilities isn’t the same kind of enterprise as using gene profiling to help determine what possibly happened in the past. I will have more to say about this shortly.
But this isn’t why I am concerned about what he and others are writing about ancient DNA. The practical (and financially profitable) rewards of using genetics to advance medicine and public health largely speak for themselves. However, trying to decipher the history perhaps written in our genes can be a dangerous undertaking—as the sordid history of Nazi Germany and of racial prejudice in the United States (and elsewhere in the world) alike shamefully attests.
It is important, therefore, that I am as up-front with you as I can be about how profiling people in the interests of medicine and health is different from profiling them genetically, living or dead, to write about the history of our species.
GENES AND HEALTH VS. GENES AND HISTORY
Finding connections—the ones called associations―between genes and the symptoms of particular diseases/disabilities is basically a matter of statistical detective work. In simple terms, the challenge is to link observable genes on one side of the analytical equation, so to speak, with observable symptoms on the other side. For example, it is now well-known that abnormal cell division during conception resulting in an extra full or partial copy of chromosome 21 is observably associated with the kinds of developmental changes and physical features of Down syndrome. I hasten to add, however, that even in this instance, the severity of the observable symptoms associated with this syndrome varies among individuals afflicted. Even in such cases, using genes in the advancement of medical science and human health is not as straightforward as popularly believed (Novembre and Barton, 2018). Nonetheless, there is solid evidence to work with on both sides of the equation, so to speak. Genes on one side, symptoms on the other.
In contrast, using genes to write history is a different challenge. Unlike searching for associations between genes and diseases/disabilities, discovering associations between genes and history is largely one-sided. Yes, there are still observable genes to work with―as David Reich and others interested in ancient DNA know well. But brave indeed would be the fool who would claim that history has discernible “symptoms” in any fashion truly comparable, say, to having a fever, runny nose and persistent headache. Of course, it is arguable that history has patterns despite the popular conviction that history is just a story about things and events that are unique, unprecedented and ever changing. But no, history doesn’t have symptoms that can be used robustly to predict the future or reconstruct what happened in the past. Many have tried to do this. Nobody has succeeded beyond the sage words of the ancient Persian adage “This too shall pass.”
Therefore, connecting the dots between genes and history is not just a statistical exercise. As Hamlet says in a famous play by Shakespeare, there’s the rub. When it comes to something as involved and complicated as history, there is almost always more than one way to account for the evidence available. Nobody has to be as talented as Agatha Christie’s famous fictional Belgian detective Hercule Poirot to see the truth of this observation. As any good trial lawyer will tell you, proving what you claim happened at a crime scene, say, “beyond reasonable doubt” calls for more than coming up with a good story. What’s needed is the correct story.
I don’t believe I need to convince you of the truth of what I just said. In any case, even if writing history rarely calls for judgments about what happened in the past that are necessarily a matter of life or death, writing history is hard work. Furthermore, historians are notorious for arguing with one another generation after generation about “what really happened.”
In a nutshell, then, this is why I think experts like Reich may be skilled at coming up with stories about the past using the tea leaves of genetics, but are the stories they are telling us the correct stories?
This is not a silly question. The stories we tell ourselves and others can lead to real consequences. Sometimes to mayhem, murder, inequality, ethnic cleansing, racial genocide.
SCIENCE VS. STORYTELLING
Science has a number of generally accepted procedures. Among these are careful theory development, plausibility analysis, statistical sampling and hypothesis testing. Judging, however, by the research being reported by Reich and others, paleogenetics at the moment favors an alternative strategy when it comes to bringing genes, haplotypes and genome-wide association studies (GWAS) back to life—a strategy that is more a storytelling exercise than a scientific undertaking. Although not widely recognized as such, I call this strategy “plug and play.”
The major characteristic of plug and play research is the willingness to fit (or “plug”) new information (say, genetics data) into a pre-existing explanation (“play”) and doing so (1) without adequately evaluating the historical plausibility of that favored explanation, and (2) without sufficiently weighing the likelihood that alternative explanations may be of similar or even greater plausibility.
I am not an expert on world history (neither is Reich, although he may come across in his book as one). I can claim, however, to know something about Pacific Islands history. Here then is one example of what I see as using plug and play genetics to write misleadingly about the past based on what Reich and others are currently reporting.
THE PREHISTORIC PACIFIC
The story of ancient Pacific history that has been favored by scholars and others for centuries is a tale taking it more or less for granted that the Polynesian-speaking islanders of the central and eastern Pacific must be seen collectively as a biological, cultural and linguistic “race,” “people,” or “population” apart from other islanders in Oceania. According to this traditional interpretation, their ancestors migrated swiftly out into the Pacific long ago more or less already “Polynesian” in their appearance, cultural practices and ways of speaking from a “homeland” located somewhere in Southeast Asia or (nowadays) on Taiwan.
I have been the curator of Pacific anthropology at the Field Museum in Chicago since 1971. I first went to work in the Pacific in 1965 as a Fulbright Fellow at the University of Auckland. I’ve gotten a lot older, but one thing hasn’t changed. Every time I hear someone claiming there was an ancient migration from Southeast Asia or Taiwan out into the South Pacific, my reaction is more or less the same. Almost invariably, I think of something the physicist Wolfgang Pauli supposedly once said: “Das ist nicht nur nicht richtig; es ist nicht einmal falsch!” (That is not only not right, it is not even wrong).
I find it more than a little discouraging, therefore, that Reich and his colleagues would favor using this old migration story as the basis for their paleogenetics interpretations of prehistory in Oceania (e.g., Lipson, et al., 2018; Posth, et al., 2018; Skoglund, et al., 2016). Why?
I am confident that Reich and his team agree with me that science, like writing history, is hard work. I have been around long enough to know, however, that the American physicist, historian and philosopher of science Thomas Kuhn (1962) was right about at least one thing even if you don’t fully embrace Kuhn’s notion that there is something called “normal science.” One of the real pitfalls of doing science is how easy it is to be unknowingly broadsided by the initial assumptions you accept about the world and how it works before the hard work of doing science begins. The influential 20th century evolutionist C. H. (“Wad”) Waddington had a name for such naïve but disabling predispositions. He called them COWDUNG, his almost acronym for “Conventional Wisdom of the Dominant Group” (Waddington 1977).
Call it normal science or call it COWDUNG, I am sure Reich and others are not intentionally favoring the old migration story about the Polynesians over modern understandings and debates about the complexities and uncertainties of Oceanic prehistory (Cochrane and Hunt, 2018; Matisoo-Smith and Gosling, 2018). I suspect the explanation for their evident commitment to this racial reconstruction of the past in the Pacific may simply be that they have been misled by the appeal of conventional wisdom. After all, this part of the world has long been the inspiration for seductive fantasies—an exotic and erotic arena for normal science or COWDUNG (Terrell 2013).
POPULATIONS, MIGRATIONS AND ADMIXTURE
Short of offering to give you a full lecture on Pacific prehistory, what can I do here to show you why I think Reich and others should not be plugging their newly acquired genetics data into such an outdated migration story? I may be too optimistic, but I think it might help to explain some of the misleading words—the danger signs—to look out for when you are reading about people and history in this, or for that matter any other, part of the world. Others may have other cautionary words to offer. Here are three I want to put on the table: populations, migrations and admixture.
Populations. Despite their scientific training and accomplishments, a surprising number of geneticists, anthropologists, archaeologists, linguists and other academics nowadays still seem willing to accept the old-fashioned folk idea that people “belong to” more or less separate and distinct collective “kinds” that can be labeled as “populations.” (These are also sometimes called “groups,” “peoples,” “tribes” and the like.)
Once upon a time, these supposed collectives would have been called “races,” at least in some contexts. Most of us know nowadays, of course, that we need to avoid using this word for politically correct reasons, if for none other. Hence almost nobody nowadays, for example, would write about Polynesian speakers in the central and eastern Pacific as a race. Instead, they are usually referred to as a population.
This may sound better, but let’s be honest. Distinguishing between races and populations is effectively making a distinction without a difference. If this comes across as sounding crazy to you, then tell me this. What is a population? How can you tell whether you are “inside” a population or “outside” it? How many of them are there “out there” in the real world? How many did there used to be? More than today, or fewer? (Now substitute in these simple questions the word “race.” Doesn’t make much difference, right?)
Reich and his colleagues are not alone in neglecting to answer for us basic questions such as these before using this word in what they write about the past. Without knowing the answers they favor, how are we to know what to make of what they are claiming not just about the ancient Pacific, but about ancient history throughout the world? Frankly, whenever I hear someone using this word, I always think of the Emperor and that little child who blurted out “But he hasn't got anything on!”
Migrations. Another word Reich and other geneticists often use when writing about ancient history is migration. Again, it is anybody’s guess what we are to take this word to mean, although it is conventional enough to opine that folks everywhere on earth are capable of moving from Point A to Point B by foot or by crook, so to speak. Even so, it strikes me as astonishing—as one example—that Reich’s colleague Mark Lipson and others, including Reich himself, would ask us to believe that drawing an arrow on a map of the Pacific from the island of Taiwan off the Chinese coast to the small islands of Vanuatu 4,000 miles away in the South Pacific shows us that the ancestors of the Polynesians took 2,000 years to migrate all the way from the former to the latter (Lipson, et al. 2018: graphical abstract).
Drawing arrows on maps is easy to do, but again, let’s be honest. An arrow drawn on a map tells us nothing about what supposedly happened while ancient Polynesians were supposedly traveling along that arrow for the 2,000 years or so it evidently (and supposedly) took them to make the trip. One thought, however, does come to mind. I do hope everyone had packed enough sandwiches in their canoes.
All joking aside, it isn’t fair to write about ancient Polynesians migrating from Taiwan, or anywhere else for that matter, without telling us what might have been involved and why those making the journey were able to get from A to B. Did those hypothetical travelers know they were migrating when they were migrating? How many people did it take to mount this migration, if indeed it was intentional? How far did they have to go, and for how long did they need to travel, for us to call them migrants? Did they know where they were going? Did they encounter anyone along the way? How did they know when it was time to stop? Did somebody suddenly shout “Hey, we’re here! We made it!” Or did everybody just stop when there were no more sandwiches left, so to speak?
Sorry, but it isn’t fair or reasonable for anyone to use a word like “migration” without telling us what they mean by it. This leaves way too much to the imagination. It’s like telling a story that asks you fill in the nouns and the verbs. Maybe the adjectives and adverbs, too. This is not only not science. This is not even good storytelling.
Admixture. A third word that Reich and others use without telling us what they mean is possibly the most revealing one of all. This is the term admixture.
The other day I made a cheese soufflé by mixing together eggs, flour, butter, hot milk, cheese, spices and carefully beaten egg whites. I have no trouble, therefore, understanding what “admixture” means. But does it make any historical sense to say that human beings naturally come in separate kinds (populations) that move around as such (migrate) and then sometimes meet (admix) with one another like eggs and cheese in my soufflé (Terrell and Stewart, 1996)? Or is “admix” just a five-letter word for that four-letter word we aren’t supposed to use in polite company?
Sadly, human genes don’t survive after death for long in the hot and humid climate of the South Pacific. So far Reich and his colleagues have been able to profile genetically only four people in Vanuatu who had been alive during the 100 years or so of pioneering human settlement there around 3,000 years ago. It would be hard to argue that the profiles of just four people tell us in a statistically credible way what the first settlers of Vanuatu were like, biologically speaking. For instance, what if they were all members of one or two families? How representative would one or two families be back then and there in Vanuatu?
Reich’s team recently reported that the genetic profiles of these 4 individuals are admixed (Lipson, et al. 2018: 1158). However you want label them, they were not “pure Taiwanese,” “pure Southeast Asian,” or pure anything else—whatever that might have possibly meant 3,000 years ago. If we add to this biological discovery other sorts of evidence (what archaeologists know about their pottery, the pieces of imported obsidian from New Britain discarded in ancient refuse dumps, and so forth), then the picture does become clearer. The best bet at the moment is that these four people, or their parents or their grandparents, had come from a village community or network of communities located somewhere in the Bismarck Archipelago just east of New Guinea (Terrell, 2018).
Now it is certainly plausible that thousands of years earlier, folks living somewhere in Taiwan, the Philippines, Indonesia and western New Guinea were among their distant ancestors. This is anyone’s guess at the moment. What we do know is that the immediate families of these four had been “admixing” with their neighbors somewhere in the New Guinea area. Perhaps quite openly. If not, then at least on the sly. After all, love knows no bounds.
Whatever the correct story, what does knowing that their families had been admixing with their neighbors tells us? Little if anything about why some people at home in the Bismarck Archipelago of New Guinea around 3,000 years ago decided to sail off and seek their fortunes elsewhere, even as far away as the remote islands now called Vanuatu. Sadly, dead men (and women) tell no tales. Also sadly, we may never know what their motivation was.
DOES IT REALLY MATTER?
Historians love to argue about what history is all about. No single definition of this word is sufficient. Nonetheless, this definition works fairly well: “a continuous, systematic narrative of past events as relating to a particular people, country, period, person, etc., usually written as a chronological account.” Given this definition, saying the first people to reach Vanuatu 3,000 years ago came from Taiwan and took 2,000 years to make the journey does not even begin to qualify as a page out of human history.
Right now, however, I can imagine you may be thinking “So what? Why should I care?” If so, then here in brief is my answer. There are two thoughts I want to leave you with.
My first thought is about scientific responsibility. Pacific Islanders have been dealing with foreigners telling them what to do and how to do it ever since Europeans began sailing around the Pacific in the 16th century. Are we now committed to telling them also what was their history? Why would we want to do this? The days of European colonialism are over, aren’t they? Or are they?
The second thought is this one. Call them “populations” or call them “races,” it makes no difference. As modern molecular genetics has now shown us in remarkable detail, we are all 99.9 percent the same. It may be conventional wisdom to think we humans come in different kinds called races, populations and the like. A statistic like this one, however, ought to be enough to convince anyone willing to listen that we don’t come in kinds whatever you want to call them.
Instead, as two of my colleagues and I wrote in a Scientific American blog several years ago, what we are like as individuals depends critically on how we are linked biologically, socially and emotionally with others in relational networks reaching far and wide. We don’t live in separate populations or races. We engage with one another through our social networks. With consequences that are sometimes good, sometimes bad, and sometimes deadly.
Hence the apparent willingness of more than a few geneticists today to use words like populations, migrations and admixture when they are writing about ancient DNA and the past does more than just misinform the rest of us. As reviews of Reich’s book, both pro and con, have sometimes scoldingly observed, when scientists talk this way, they can sound like they are doing racial profiling. Apparently, it can be hard for some folks to see that what my grandfather called hogwash may not just be something unbelievable. Hogwash can also be words and stories that are socially, politically and, yes, historically misleading. Maybe even dangerous.
I thank Tom Clark, Ethan Cochrane, Helen Dawson, Stacy Drake, Kevin Kelly, Jim Koeppl, Thorsten Lumbsch, Lisa Matisoo-Smith, Lisa Niziolek, Jon Marks, Martin Richards, Esther Schechter, Peter Sheppard, Pat Shipman and Gabriel Terrell for comments and suggestions on how I might say what I want to say better.
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