Levi FoxPage 111/15/2018
Languages, Teeth, DNA, Boats, Beringia, and Controversy:
An Examination of the Debate Over Various Aspects of the Initial Peopling of the Americas
Ever since the first arrival of Europeans on the North American continent people have been curious about the origins of the Native Americans. Over the past few centuries, and especially in the past one hundred or so years with the advent of professional archeology, a good many questions surrounding the origins of these people have been asked and answered. However, even as older questions, such as whether the Clovis settlement represents the earliest group of Native Americans, appear to be answered, even more questions spring forth. While today it is generally accepted that the Native Americans are descended from people who originally came from Asia, a number of questions over the specifics of their ancestors have arisen. Questions such as whether there were multiple migrations of people, whether such migrations were made up of different populations and gave rise to different groups of Indians, where exactly in Asia these people came from, whether they crossed by land or water, and even whether the first inhabitants of the Americas are the same people whose descendents inhabited the continents in 1492, are continually posited. To try to answer such questions, archeologists today make use of various types of evidence and some of the very latest in scientific techniques. Linguistic evidence may agree with dental evidence yet come into conflict with the findings of researchers that examine mitochondrial DNA. As this controversy continues, new studies are constantly being done, old research reexamined, and paper after paper presented, published, and argued about.
One of the major bones of contention today is over the exact number of migrations that took place from Asia. A related question, and one which has often been examined in an attempt to answer the migration question, is how many distinct populations the Native Americans should be grouped into. A variety of approaches have been taken in order to try to answer these questions, including examinations of linguistic, dental, and genetic evidence. Regardless of how many migrations various archeologists believe have taken place, they have often assumed that all of these people simply crossed the Bering land bridge, or Beringia, during the last ice age, and then moved down into continental North America when the ice sheets receded. This model of New World immigration was generally accepted, and is still accepted by many, in part because it worked well with certain other theories about paleoindians, such as that of Clovis. However, with the mounting evidence against Clovis as the earliest spot of occupation, and with mounting evidence that areas of the Pacific Coast may have been the earliest places of settlement, proposals for an initial migration by water instead of land have been advanced. This controversy, though less written about so far, is also an important one that must be examined and resolved in order for a complete model of the initial peopling of the Americas to ever be constructed and agreed upon.
A landmark in the controversy over the number of migrations, as well as an excellent case study in the use of a variety of scientific disciplines to answer archeological questions, is a 1986 article by Joseph Greenberg, Christy Turner, and Stephen Zegura entitled “The Settlement of the Americas: A Comparison of the Linguistic, Dental, and Genetic Evidence.” This article set forth the so-called Greenberg Hypothesis, which states that three separate lines of evidence all point to the conclusion that the Americas were initially settled by three migratory waves, which developed into three distinct groups, namely the Amerind, Na-Dene, and Aleut-Eskimo. The article itself briefly outlines the ways in which the evidences were used to create and support a three-migration model. Attached to the article are a number of comments from various scholars which question and even attack the hypothesis as well as a reply from the three authors. Together the article, commentary, and reply are an excellent illustration of the debate that has raged on in recent years over this and other questions about the initial peopling of the Americas, as well as demonstrating the controversy over the Greenberg Hypothesis itself.
The Greenberg Hypothesis, while using genetics and dental data as support, rests largely upon the linguistic evidence. Greenberg, the linguist of the group, begins his argument by citing his own research on the classification of indigenous American languages, which he says leads to the unmistakable conclusion that there are three and only three linguistic groups in the Americas. He argues that “the oldest is probably Amerind, since it centers farther to the south and shows greater internal division”. Additionally, he cites less differentiation in the north as evidence for a “relatively rapid spread” from that area. The article argues that the Na-Dene grouping is the next oldest since it “has deeper internal divisions and is geographically less peripheral than Aleut-Eskimo,” which is viewed as the last group that arose from a third, later migration. Greenberg subsequently restates his thesis and argues that the language groups are too different to come from a single linguistic stock.
The dental evidence, Turner’s contribution, is the next to be presented, and is utilized so as to lend support to the hypothesis which was constructed on linguistic grounds. Turner begins by presenting four observations, the last of which suggests that the Na-Dene, Aleut-Eskimos, and “all other Indians form three New World dental clusters.” From this and other evidence he creates a dental hypothesis that, like the linguistic one, “envisions three distinct late Pleistocene migrations from Siberia.” Turner also suggests that since dental variation is greater in the North than in the South, that population movement “proceeded from Alaska southward.” To his credit then, but not so now, Turner then argues that his evidence “corresponds well with the widely held view that the first Americans were the Clovis culture”, basing this statement on the agreement on his own dental divergence rates and mainstream archeological evidence. Turner also discusses the ways in which his dental evidence agrees with Greenberg’s linguistic evidence. He states that there is “a good fit between Greenberg’s Macro-Indian (Amerind) and Aleut-Eskimo linguistic divisions and the dental clusters” but that there is less agreement between the two types of evidence when it comes to the Na-Dene. He then proceeds to offer some possible explanations for this disagreement, as well as restating that regardless of it, the dental evidence also points to three separate migrations.
Zegura next discusses the genetic evidence, based upon the examination of mitochondrial DNA, as it relates to the Greenberg hypothesis. It is stated that the three authors “view the interpretation of the genetic data as secondary support for the primary inferences based upon linguistic and dental data.” While the lack of development of DNA technology in the mid 1980’s is one reason for this qualifier, another is that the genetic evidence does not lend strong support to the Greenberg Hypothesis. The article itself discusses other possible interpretations of the genetic evidence and even states that “from a genetic perspective the hypothesis of three separate migrations leading to a tripartite division of modern Native Americans is still without strong confirmation.” Thus, while the linguistic and dental evidence, despite some minor disagreement, tend to lend strong support to the Greenberg Hypothesis, the genetic evidence presented in the article is significantly weaker.
The Greenberg Hypothesis created controversy immediately after it was published. A number of commentaries published with the article itself question the evidence as well as the authors’ interpretation of that evidence. Lyle Campbell argues that “Amerind is discounted by nearly all specialists” and that the dental and genetic evidence used to support the linguistic hypothesis are unconvincing and open to alternate interpretation. He views the entire hypothesis as a sort of house of cards, and even chastises Greenberg for his use Amerind classifications. James Fox grants the three groups, but points out that Greenberg use the absence of variation while Turner uses large variation in the North in order to support views of rapid migration. W. S. Laughlin argues that, contrary to the conclusions of Greenberg, Turner, and Zegura the “differences between American populations are not large enough to postulate more than one migration.” Szathmary questions the interpretation of the genetic evidence, while Weiss and Woolford are concerned with the validity of some of the methods used in the study, as well as why the dental data, which is ultimately based upon genetics, is weighed more heavily than the DNA evidence. The authors of the article responded to these criticisms, accepting some as valid, while flatly disagreeing with others. They pointed out that nearly all the commentators agreed on one to three waves being necessary to explain the variation and then went on to state that Turner had “evaluated models of one to four migrations” but had come to the conclusion that only the “three-wave scenario stands up” to scrutiny. Despite the immediate criticisms the authors stuck by their hypothesis, but the controversy present within the debate over this one article was only an indication of what was to come.
A number of later articles, many of them making use of more modern genetic and other biological technologies and the evidence derived from the use of such techniques, have challenged the Greenberg Hypothesis. A 1992 article by Steele and Powell concluded that “the number of founding populations [could not] be discerned” from an examination of fossil remains. A 1996 article by Ann Gibbons goes much further. She presents genetic evidence which creates a model whereby the ancestors of Native Americans migrated to North America in either one or two waves, but not three, thus contradicting the Greenberg Hypothesis. The article spends a great deal of time discussing the merits and the legacy of the Greenberg Hypothesis, outlining the history of controversy surrounding it and stating that genetic evidence of the early nineties had lent further support to it. The new genetic evidence presented in the article, based on new DNA findings and heightened technology, undercuts the Greenberg model, however. In the article geneticist Ryk Ward argues that new genetic evidence illustrates that “there isn’t a relationship between genetic signatures of migrations and language" which further calls into question the Greenberg Hypothesis. According to geneticist D. Andrew Merriweather, who also appears in the article, the presence of certain genetic markers in all three of the proposed linguistic groups “makes it unlikely that the groups’ ancestors came in different migrations.” A new model put forth in this article proposes that one population gave rise to all three linguistic groups. This model argues that the ancestors of the Amerinds moved south first, while the ancestors of the Na-Dene and Eskimo-Aleuts stayed back and lost some of their genetic diversity due to population decreases. Later these groups rebounded, spread out, and gave rise to the linguistic groups of today. This model has alternately been called both a one or two migration model but is called by its proponents one of a single migration followed by “a re-expansion.” The Gibbons article also points out that linguists, stemming back all the way to Campbell, have questioned the validity of the Amerind grouping. Thus in 1996, this new model, based upon genetic evidence, was only one of a series of challenges to the Greenberg Hypothesis.
More recent genetic evidence also supports a single migration hypothesis. A 1997 article by Bonatto and Salzano utilizes mitochondrial DNA evidence as well as geologic data to propose a model similar to that which appears in the Gibbons article. In this model the Amerind groups arose out of the larger Native American population occupying Beringia over 20,000 years ago. Between 20,000, and 14,000 years ago part of the population was isolated in the South by the collapse of the ice-free corridor they had used to move southward. The groups that remained gave rise to the Na-Dene and Aleut-Eskimo. Recent articles by Mark Stoneking and others have also proposed a single migration model. A February 1998 article authored in part by Stoneking presented three genetic groups for the Americas which were divided largely by geography, rather than by linguistic or dental variation. This article argues for one of two interpretations; both of which include the provision that there was only one founding population. Either the various genetic differences among groups of Indians arose due to “a single migration to the New World followed by partial isolation and genetic drift” or “instead of a single migration wave, several migration waves from the same source population took place.” In another 1997 article, co-authored with Anne Stone, Stoneking again reasserts that “a single migration of a population with significant mtDNA diversity” is suggested by the mitochondrial DNA evidence, while the Greenberg Hypothesis of three migrations has no such support. A 1999 article by Stuart Fiedal argues that the sum of the genetic evidence goes against the Greenberg Hypothesis while stating that new, earlier dates for the initial peopling of the Americas mean that, contrary to Greenberg’s earlier conclusions, the linguistic differences between the Amerind, Na-Dene, and Aleut-Eskimo groups need not indicate three separate migrations.
Another theory concerning the initial peopling of the America’s was put forth not long after the Greenberg Hypothesis, though it is not necessarily in conflict with the earlier theory. In 1988 Ruth Gruhn put forth evidence supporting a model whereby the initial migration to the Americas would have taken place by sea rather than by land over Beringia. Like Greenberg, Gruhn uses largely linguistic data. She cites research by Richard Rogers, which suggested that the great linguistic diversity found in the Pacific Coast area of North America indicates that the peopling of the Americas followed “an initial coastal entry route, and only secondary occupation of the interior.” Gruhn states that her scenario, in which the first settlers of the Americas moved south along the Pacific coast, is “hypothesized on the basis of the linguistic evidence,” but she also uses evidence of early coastal area occupation, such as Monte Verde, to support her model. She points out that, with the Clovis model faltering, her hypothesis could be used to explain how people had arrived in the Americas at a time when the ice sheets were still blocking land entry. In the time since this model was proposed it has received both some support and some opposition.
One example of the opposition that this model has provoked comes from a 1996 American Antiquity review by Robert Kelly of a volume of essays on various aspects of the peopling of the Americas. Kelley’s criticisms of Gruhn specifically center around her interpretation of some data and her “premise that geographical areas occupied longer will show greater language diversification.” He points out that those who use linguistic data tend to ignore the fact that “language is behavior and behavior is adaptive,” and that linguistic change over time may thus not be a good indicator of when certain things, such as migrations, took place. He also points out that Goddard and Campbell do not feel that “linguistic diversity on the coast necessarily indicates” longer term occupation and that Gruhn's demonstration of the possibility of a seaward migration “in no way proves the claim.” A 1996 article by Carles Fox does lend support to Gruhn’s model, however. Along with supporting a multiple migration model, this article also postulates that “a coastal route along the Pacific Ocean” could have given rise to certain tribes, while others may have arrived by land. However, it should be noted that nearly all of the migration models which were presented earlier, whether agreeing with or disputing the Greenberg Hypothesis, tend to take a land based initial migration forgranted.
Having presented the evidence and arguments on both sides of these controversies, the question of what to conclude comes to the fore. What model, or combination of models, of the initial peopling of the Americas can be supported by the greater weight of the available evidence? In short, what, if any, conclusions can be reached about the number of migrations that it took to populate the New World and whether these any of these migrations could have been by boat rather than across Beringia and through the ice free corridor into central North America? I will turn first to the Greenberg Hypothesis and the controversy over the number of migrations and then quickly attempt to draw a conclusion about Ruth Gruhn’s ideas concerning a possible water based initial migration.